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Sample records for pyrethroid-treated bed nets

  1. Loss of protection with insecticide-treated nets against pyrethroid-resistant Culex quinquefasciatus mosquitoes once nets become holed: an experimental hut study

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    Irish SR

    2008-06-01

    Full Text Available Abstract Background An important advantage of pyrethroid-treated nets over untreated nets is that once nets become worn or holed a pyrethroid treatment will normally restore protection. The capacity of pyrethroids to kill or irritate any mosquito that comes into contact with the net and prevent penetration of holes or feeding through the sides are the main reasons why treated nets continue to provide protection despite their condition deteriorating over time. Pyrethroid resistance is a growing problem among Anopheline and Culicine mosquitoes in many parts of Africa. When mosquitoes become resistant the capacity of treated nets to provide protection might be diminished, particularly when holed. An experimental hut trial against pyrethroid-resistant Culex quinquefasciatus was therefore undertaken in southern Benin using a series of intact and holed nets, both untreated and treated, to assess any loss of protection as nets deteriorate with use and time. Results There was loss of protection when untreated nets became holed; the proportion of mosquitoes blood feeding increased from 36.2% when nets were intact to between 59.7% and 68.5% when nets were holed to differing extents. The proportion of mosquitoes blood feeding when treated nets were intact was 29.4% which increased to 43.6–57.4% when nets were holed. The greater the number of holes the greater the loss of protection regardless of whether nets were untreated or treated. Mosquito mortality in huts with untreated nets was 12.9–13.6%; treatment induced mortality was less than 12%. The exiting rate of mosquitoes into the verandas was higher in huts with intact nets. Conclusion As nets deteriorate with use and become increasingly holed the capacity of pyrethroid treatments to restore protection is greatly diminished against resistant Culex quinquefasciatus mosquitoes.

  2. Synergistic insecticidal and repellent effects of combined pyrethroid and repellent-impregnated bed nets using a novel long-lasting polymer-coating multi-layer technique.

    Science.gov (United States)

    Faulde, Michael K; Nehring, Oliver

    2012-08-01

    New and improved strategies for malaria control and prevention are urgently needed. As a contribution to an optimized personal protection strategy, a novel long-lasting insecticide and repellent-treated net (LLIRN) has been designed by binding combinations of permethrin plus N,N-diethyl-m-toluamide (DEET), or insect repellent 3535 (IR3535), and etofenprox plus DEET, onto fibres of bed net fabric employing a new multi-layer polymer-coating technique. Protective repellent efficacy, toxicological effectiveness and residual activity of 12 LLIRN types have been evaluated by laboratory testing against adult Aedes aegypti. The novel multi-layer LLIRN design allowed simultaneous embedding at concentrations up to 5,930 mg/m(2) for DEET, 3,408 mg/m(2) for IR3535, 2,296 mg/m(2) for permethrin and 2,349 mg/m(2) for etofenprox, respectively. IR3535 layers prevented co-binding of additional pyrethroid-containing polymer layers, thus making pyrethroids plus DEET LLIRNs an ideal combination. All LLIRNs revealed synergistic insecticidal effects which, when measured against concentration controls of the isolated compounds, were significant in all LLIRN types designed. DEET in DEET plus permethrin LLIRNs significantly (p time from 55 to 75 %, the corresponding 100 % kill time (p time of etofenprox from 42 to 50 % (p = 0.004), the 100 % kill time from 25 to 38 % (p biting protection, even at low concentrations. One hundred percent biting and probing protection of stored LLIRNs was preserved for 83 weeks with the 5,930 mg/m(2) DEET and 2,139 mg/m(2) etofenprox LLIRN, for 72 weeks with the 5,002 mg/m(2) DEET and 2,349 mg/m(2) etofenprox LLIRN, for 63 weeks with the 3,590 mg/m(2) DEET and 1,208 mg/m(2) permethrin LLRN, and for 61 weeks with the 4,711 mg/m(2) DEET and 702 mg/m(2) etofenprox LLIRN. Because 100 % bite protection with up to 75 % quicker contact toxicity of pyrethroids were documented, synergistic toxicological and repellent effects of multi-layer polymer

  3. Effect of insecticide-treated bed nets on house-entry by malaria mosquitoes: The flight response recorded in a semi-field study in Kenya.

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    Spitzen, Jeroen; Koelewijn, Teun; Mukabana, W Richard; Takken, Willem

    2017-08-01

    Insecticide-treated nets are currently a major tool to reduce malaria transmission. Their level of repellency affects contact of the mosquito with the net, but may also influence the mosquito's entry into the house. The response of host-seeking malaria mosquitoes approaching the eave of an experimental house was recorded within a large screen house. We compared entry- and exit rates in relation to the presence in the house of different insecticide-treated bed nets (ITNs) with an untreated net. Mosquitoes were lured towards the house by dispensing a synthetic host-odour blend from within the net in the house. Complementary WHO bioassays revealed that the treated nets caused high knock-down- and mortality responses to the Anopheles gambiae sensu stricto strain tested. The proportion of mosquitoes that came into view of the cameras and subsequently entered the house did not differ between treated nets and the untreated net. Treated nets did not affect proportions of mosquitoes that exited the house and departed from view around the eave. However, the percentage of house-leaving and re-entering mosquitoes when an insecticide- treated net was present, was lower than in the presence of an untreated net. Our results indicated that there was no spatial repellent effect from pyrethroid-treated nets that influences house-entry at eave level. It is argued that the toxic effect of treated bed nets resulted in a reduced number of mosquitoes re-entering the house, which could thereby affect malaria transmission in neighbouring, unprotected houses. Copyright © 2017 The Authors. Published by Elsevier B.V. All rights reserved.

  4. Efficacy of mosquito nets treated with a pyrethroid-organophosphorous mixture against Kdr- and Kdr+ malaria vectors (Anopheles gambiae

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    Darriet F.

    2003-12-01

    Full Text Available In order to prevent the resistance of Anopheles gambiae s.l. to pyrethroids from spreading too quickly and to lengthen the effectiveness of insecticide impregnated mosquito nets, it has recently been suggested to use mixtures of insecticides that have different modes of action. This study presents the results obtained with tulle mosquito nets treated with bifenthrin (a pyrethroid] and chlorpyrifos-methyl (an organophosphorous both separately and in mixture on two strains of An. gambiae, one sensitive to all insecticides, and the other resistant to pyrethroids. The values of KDt50 and KDt95 and the mortality induced with the mixture of bifenthrin (25 mg/m2 and chlorpyrifos-methyl (4.5 mg/m2 show a significant synergistic effect on the strain of An. gambiae susceptible to insecticides. However, the tested combination does not induce any synergistic effect on the VKPR strain selected with permethrin, but only enhances the effectiveness of the two insecticides taken separately.

  5. The effect of insecticide-treated bed net on malarial parasitaemia ...

    African Journals Online (AJOL)

    AFRICAN JOURNALS ONLINE (AJOL) · Journals · Advanced Search ... nets sold by a social marketing project were used as the intervention group. ... Keywords: Insecticide-treated bed net, Effectiveness, Malaria control, South-South Nigeria.

  6. Alternative treatments for indoor residual spraying for malaria control in a village with pyrethroid- and DDT-resistant vectors in The Gambia

    NARCIS (Netherlands)

    Tangena, J.A.A.; Adiamoh, M.; Alessandro, D' U.; Jarju, L.; Jawara, M.; Jeffries, D.; Malik, N.; Nwakanma, D.; Kaur, H.; Takken, W.; Lindsay, S.W.; Pinder, M.

    2013-01-01

    Background: Malaria vector control is threatened by resistance to pyrethroids, the only class of insecticides used for treating bed nets. The second major vector control method is indoor residual spraying with pyrethroids or the organochloride DDT. However, resistance to pyrethroids frequently

  7. Social marketing of insecticide-treated bed net for malaria control ...

    African Journals Online (AJOL)

    Background: The effectiveness of the insecticide-treated bed net in reducing the morbidity and mortality associated with malaria has been proved at all levels of malaria transmission. Several models on how to achieve massive coverage have been suggested, but social marketing of the nets is highly favoured for its ...

  8. Infestation by pyrethroids resistant bed bugs in the suburb of Paris, France

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    Durand R.

    2012-11-01

    Full Text Available Bed bugs are hematophagous insects responsible for a re-emerging and challenging indoor pest in many countries. Bed bugs infestations may have health consequences including nuisance biting, cutaneous and systemic reactions. This resurgence can probably be attributed to factors such as increased international travel and development of resistance against insecticides. Resistance against pyrethroids has been reported several times from the USA and rarely in Europe. In France, very few data on bed bugs are available. The present study aimed to assess the infestation by bed bugs of a complex of two high-rise apartment buildings in the suburb of Paris and to evaluate their susceptibility to pyrethroid insecticides. We inspected for bed bugs 192 out of 198 apartments units (97% and interviewed their residents. 76 (39.6% apartments were infested. Among the 97 residents living in infested apartments, 53 (54.6% reported bed bug bites. A total of 564 bed bugs were collected in the infested units. Bioassays showed that 54 out of 143 bed bugs were resistant to pyrethroids (37.8%; 95% confidence interval: 29.9-45.7%. DNA sequencing showed that all bed bugs tested (n = 124 had homozygous L925I kdr-like gene mutation. The level of pyrethroid resistance found indicates that this phenomenon was already established in the site and prompts the need to reevaluate the wide use of pyrethroids to control bed bugs.

  9. Entomological determinants of insecticide-treated bed net effectiveness in Western Myanmar

    NARCIS (Netherlands)

    Smithuis, Frank M.; Kyaw, Moe Kyaw; Phe, U. Ohn; van der Broek, Ingrid; Katterman, Nina; Rogers, Colin; Almeida, Patrick; Kager, Piet A.; Stepniewska, Kasia; Lubell, Yoel; Simpson, Julie A.; White, Nicholas J.

    2013-01-01

    In a large cluster randomized control trial of insecticide-treated bed nets (ITN) in Western Myanmar the malaria protective effect of ITN was found to be highly variable and, in aggregate, the effect was not statistically significant. A coincident entomological investigation measured malaria vector

  10. Use of bed nets and factors that influence bed net use among Jinuo Ethnic Minority in southern China.

    Science.gov (United States)

    Xu, Jian-wei; Liao, Yuan-mei; Liu, Hui; Nie, Ren-hua; Havumaki, Joshua

    2014-01-01

    Insecticide-treated nets (ITNs) are an integral part of vector control recommendations for malaria elimination in China. This study investigated the extent to which bed nets were used and which factors influence bed net use among Jinuo Ethnic Minority in China-Myanmar-Laos border areas. This study combined a quantitative household questionnaire survey and qualitative semi-structured in-depth interviews (SDI). Questionnaires were administered to 352 heads of households. SDIs were given to 20 key informants. The bed net to person ratio was 1∶2.1 (i.e., nearly one net for every two people), however only 169 (48.0%) households owned at least one net and 623 (47.2%) residents slept under bed nets the prior night. The percentages of residents who regularly slept under nets (RSUN) and slept under nets the prior night (SUNPN) were similar (48.0% vs. 47.2%, P>0.05), however the percentage correct use of nets (CUN) was significantly lower (34.5%, Pcash income per person (ACIP) was an independent factor that influenced bed net use (PHigh bed net availability does not necessarily mean higher coverage or bed net use. Household income, house type and knowledge of the ability of bed nets to prevent malaria are all independent factors that influence bed net use among Jinuo Ethnic Minority.

  11. LABORATORY PROTECTION RATE OF TORN BEDNETS TREATED WITH THREE DOSAGES OF PYRETHROIDE AGAINST ANOPHELES CULICIFACIES

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    G. Babaee

    2007-05-01

    Full Text Available Evaluated under laboratory condition. The objective of the present study was to observe the effect of impregnated torn bednets on the number of bites by An. culicifacies A glass made tunnel test was designed to The effect of torn bednets treated with three dosages of cyfluthrin 5% EW, were induce hungry female mosquitoes to pass through holes cut in the pyrethroid treated nets. A guinea pig used as bait to attract mosquitoes through circular holes in the netting. With untreated netting, 72-87% of laboratory-reared females passed through the holes overnight, 64-92% blood-fed successfully and 0.3/9-4/3% died. When the netting was treated with cyfluthrin at doses of 25, 50 and 100 mg a.i./m2, the entry Index (the proportions that passed through the holes overnight were 43.37%, 42.82% and 24.72%; mortality rates were 66.31%, 81.45% and 95.99%; and the feeding rate were 45%, 27% and 3%. In conclusion it should be stressed that efficacy of pyrethroid impregnated bednets using “Tunnel Tests” showing acceptable protection rate both in lower and higher dosages as well as cause dead in the blood-fed mosquitoes. In addition, the higher dosages of these three dosages pyrethroid provided good levels of protection against An. culicifacies.

  12. Olyset Duo® (a pyriproxyfen and permethrin mixture net: an experimental hut trial against pyrethroid resistant Anopheles gambiae and Culex quinquefasciatus in Southern Benin.

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    Corine Ngufor

    Full Text Available Alternative compounds which can complement pyrethroids on long-lasting insecticidal nets (LN in the control of pyrethroid resistant malaria vectors are urgently needed. Pyriproxyfen (PPF, an insect growth regulator, reduces the fecundity and fertility of adult female mosquitoes. LNs containing a mixture of pyriproxyfen and pyrethroid could provide personal protection through the pyrethroid component and reduce vector abundance in the next generation through the sterilizing effect of pyriproxyfen.The efficacy of Olyset Duo, a newly developed mixture LN containing pyriproxyfen and permethrin, was evaluated in experimental huts in southern Benin against pyrethroid resistant Anopheles gambiae and Culex quinquefasciatus. Comparison was made with Olyset Net® (permethrin alone and a LN with pyriproxyfen alone (PPF LN. Laboratory tunnel tests were performed to substantiate the findings in the experimental huts.Overall mortality of wild pyrethroid resistant An. gambiae s.s. was significantly higher with Olyset Duo than with Olyset Net (50% vs. 27%, P = 0.01. Olyset DUO was more protective than Olyset Net (71% vs. 3%, P<0.001. The oviposition rate of surviving blood-fed An. gambiae from the control hut was 37% whereas none of those from Olyset Duo and PPF LN huts laid eggs. The tunnel test results were consistent with the experimental hut results. Olyset Duo was more protective than Olyset Net in the huts against wild pyrethroid resistant Cx. quinquefasciatus although mortality rates of this species did not differ significantly between Olyset Net and Olyset Duo. There was no sterilizing effect on surviving blood-fed Cx. quinquefasciatus with the PPF-treated nets.Olyset Duo was superior to Olyset Net in terms of personal protection and killing of pyrethroid resistant An. gambiae, and sterilized surviving blood-fed mosquitoes. Mixing pyrethroid and pyriproxyfen on a LN shows potential for malaria control and management of pyrethroid resistant vectors by

  13. The impact of pyrethroid resistance on the efficacy of insecticide-treated bed nets against African anopheline mosquitoes: systematic review and meta-analysis.

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    Clare Strode

    2014-03-01

    Full Text Available Pyrethroid insecticide-treated bed nets (ITNs help contribute to reducing malaria deaths in Africa, but their efficacy is threatened by insecticide resistance in some malaria mosquito vectors. We therefore assessed the evidence that resistance is attenuating the effect of ITNs on entomological outcomes.We included laboratory and field studies of African malaria vectors that measured resistance at the time of the study and used World Health Organization-recommended impregnation regimens. We reported mosquito mortality, blood feeding, induced exophily (premature exit of mosquitoes from the hut, deterrence, time to 50% or 95% knock-down, and percentage knock-down at 60 min. Publications were searched from 1 January 1980 to 31 December 2013 using MEDLINE, Cochrane Central Register of Controlled Trials, Science Citation Index Expanded, Social Sciences Citation Index, African Index Medicus, and CAB Abstracts. We stratified studies into three levels of insecticide resistance, and ITNs were compared with untreated bed nets (UTNs using the risk difference (RD. Heterogeneity was explored visually and statistically. Included were 36 laboratory and 24 field studies, reported in 25 records. Studies tested and reported resistance inconsistently. Based on the meta-analytic results, the difference in mosquito mortality risk for ITNs compared to UTNs was lower in higher resistance categories. However, mortality risk was significantly higher for ITNs compared to UTNs regardless of resistance. For cone tests: low resistance, risk difference (RD 0.86 (95% CI 0.72 to 1.01; moderate resistance, RD 0.71 (95% CI 0.53 to 0.88; high resistance, RD 0.56 (95% CI 0.17 to 0.95. For tunnel tests: low resistance, RD 0.74 (95% CI 0.61 to 0.87; moderate resistance, RD 0.50 (95% CI 0.40 to 0.60; high resistance, RD 0.39 (95% CI 0.24 to 0.54. For hut studies: low resistance, RD 0.56 (95% CI 0.43 to 0.68; moderate resistance, RD 0.39 (95% CI 0.16 to 0.61; high resistance, RD 0

  14. Bed net ownership in Kenya: the impact of 3.4 million free bed nets

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    Vulule John

    2010-06-01

    Full Text Available Abstract Background In July and September 2006, 3.4 million long-lasting insecticide-treated bed nets (LLINs were distributed free in a campaign targeting children 0-59 months old (CU5s in the 46 districts with malaria in Kenya. A survey was conducted one month after the distribution to evaluate who received campaign LLINs, who owned insecticide-treated bed nets and other bed nets received through other channels, and how these nets were being used. The feasibility of a distribution strategy aimed at a high-risk target group to meet bed net ownership and usage targets is evaluated. Methods A stratified, two-stage cluster survey sampled districts and enumeration areas with probability proportional to size. Handheld computers (PDAs with attached global positioning systems (GPS were used to develop the sampling frame, guide interviewers back to chosen households, and collect survey data. Results In targeted areas, 67.5% (95% CI: 64.6, 70.3% of all households with CU5s received campaign LLINs. Including previously owned nets, 74.4% (95% CI: 71.8, 77.0% of all households with CU5s had an ITN. Over half of CU5s (51.7%, 95% CI: 48.8, 54.7% slept under an ITN during the previous evening. Nearly forty percent (39.1% of all households received a campaign net, elevating overall household ownership of ITNs to 50.7% (95% CI: 48.4, 52.9%. Conclusions The campaign was successful in reaching the target population, families with CU5s, the risk group most vulnerable to malaria. Targeted distribution strategies will help Kenya approach indicator targets, but will need to be combined with other strategies to achieve desired population coverage levels.

  15. Predicting the impact of insecticide-treated bed nets on malaria transmission: the devil is in the detail

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    Novak Robert J

    2009-11-01

    Full Text Available Abstract Background Insecticide-treated bed nets (ITNs, including long-lasting insecticidal nets (LLINs, play a primary role in global campaigns to roll back malaria in tropical Africa. Effectiveness of treated nets depends on direct impacts on individual mosquitoes including killing and excite-repellency, which vary considerably among vector species due to variations in host-seeking behaviours. While monitoring and evaluation programmes of ITNs have focuses on morbidity and all-cause mortality in humans, local entomological context receives little attention. Without knowing the dynamics of local vector species and their responses to treated nets, it is difficult to predict clinical outcomes when ITN applications are scaled up across African continent. Sound model frameworks incorporating intricate interactions between mosquitoes and treated nets are needed to develop the predictive capacity for scale-up applications of ITNs. Methods An established agent-based model was extended to incorporate the direct outcomes, e.g. killing and avoidance, of individual mosquitoes exposing to ITNs in a hypothetical village setting with 50 houses and 90 aquatic habitats. Individual mosquitoes were tracked throughout the life cycle across the landscape. Four levels of coverage, i.e. 40, 60, 80 and 100%, were applied at the household level with treated houses having only one bed net. By using Latin hypercube sampling scheme, parameters governing killing, diverting and personal protection of net users were evaluated for their relative roles in containing mosquito populations, entomological inoculation rates (EIRs and malaria incidence. Results There were substantial gaps in coverage between households and individual persons, and 100% household coverage resulted in circa 50% coverage of the population. The results show that applications of ITNs could give rise to varying impacts on population-level metrics depending on values of parameters governing interactions of

  16. Predicting the impact of insecticide-treated bed nets on malaria transmission: the devil is in the detail.

    Science.gov (United States)

    Gu, Weidong; Novak, Robert J

    2009-11-16

    Insecticide-treated bed nets (ITNs), including long-lasting insecticidal nets (LLINs), play a primary role in global campaigns to roll back malaria in tropical Africa. Effectiveness of treated nets depends on direct impacts on individual mosquitoes including killing and excite-repellency, which vary considerably among vector species due to variations in host-seeking behaviours. While monitoring and evaluation programmes of ITNs have focuses on morbidity and all-cause mortality in humans, local entomological context receives little attention. Without knowing the dynamics of local vector species and their responses to treated nets, it is difficult to predict clinical outcomes when ITN applications are scaled up across African continent. Sound model frameworks incorporating intricate interactions between mosquitoes and treated nets are needed to develop the predictive capacity for scale-up applications of ITNs. An established agent-based model was extended to incorporate the direct outcomes, e.g. killing and avoidance, of individual mosquitoes exposing to ITNs in a hypothetical village setting with 50 houses and 90 aquatic habitats. Individual mosquitoes were tracked throughout the life cycle across the landscape. Four levels of coverage, i.e. 40, 60, 80 and 100%, were applied at the household level with treated houses having only one bed net. By using Latin hypercube sampling scheme, parameters governing killing, diverting and personal protection of net users were evaluated for their relative roles in containing mosquito populations, entomological inoculation rates (EIRs) and malaria incidence. There were substantial gaps in coverage between households and individual persons, and 100% household coverage resulted in circa 50% coverage of the population. The results show that applications of ITNs could give rise to varying impacts on population-level metrics depending on values of parameters governing interactions of mosquitoes and treated nets at the individual level

  17. Impact of permethrin-treated bed nets on entomologic indices in an area of intense year-round malaria transmission.

    Science.gov (United States)

    Gimnig, John E; Vulule, John M; Lo, Terrence Q; Kamau, Luna; Kolczak, Margarette S; Phillips-Howard, Penelope A; Mathenge, Evan M; ter Kuile, Feiko O; Nahlen, Bernard L; Hightower, Allen W; Hawley, William A

    2003-04-01

    The effect of permethrin-treated bed nets (ITNs) on malaria vectors was studied as part of a large-scale, randomized, controlled trial in western Kenya. Indoor resting densities of fed Anopheles gambiae s.l. and An. funestus in intervention houses were 58.5% (P = 0.010) and 94.5% (P = 0.001) lower, respectively, compared with control houses. The sporozoite infection rate in An. gambiae s.l. was 0.8% in intervention areas compared with 3.4% (P = 0.026) in control areas, while the sporozoite infection rates in An. funestus were not significantly different between the two areas. We estimated the overall transmission of Plasmodium falciparum in intervention areas to be 90% lower than in control areas. Permethrin resistance was not detected during the study period. As measured by densities of An. gambiae s.l., the efficacy of bed nets decreased if one or more residents did not sleep under a net or if bed nets had not been re-treated within six months. These results indicate that ITNs are optimally effective if used every night and if permethrin is reapplied at least biannually.

  18. Cost and cost effectiveness of long-lasting insecticide-treated bed nets - a model-based analysis

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    Pulkki-Brännström Anni-Maria

    2012-04-01

    Full Text Available Abstract Background The World Health Organization recommends that national malaria programmes universally distribute long-lasting insecticide-treated bed nets (LLINs. LLINs provide effective insecticide protection for at least three years while conventional nets must be retreated every 6-12 months. LLINs may also promise longer physical durability (lifespan, but at a higher unit price. No prospective data currently available is sufficient to calculate the comparative cost effectiveness of different net types. We thus constructed a model to explore the cost effectiveness of LLINs, asking how a longer lifespan affects the relative cost effectiveness of nets, and if, when and why LLINs might be preferred to conventional insecticide-treated nets. An innovation of our model is that we also considered the replenishment need i.e. loss of nets over time. Methods We modelled the choice of net over a 10-year period to facilitate the comparison of nets with different lifespan (and/or price and replenishment need over time. Our base case represents a large-scale programme which achieves high coverage and usage throughout the population by distributing either LLINs or conventional nets through existing health services, and retreats a large proportion of conventional nets regularly at low cost. We identified the determinants of bed net programme cost effectiveness and parameter values for usage rate, delivery and retreatment cost from the literature. One-way sensitivity analysis was conducted to explicitly compare the differential effect of changing parameters such as price, lifespan, usage and replenishment need. Results If conventional and long-lasting bed nets have the same physical lifespan (3 years, LLINs are more cost effective unless they are priced at more than USD 1.5 above the price of conventional nets. Because a longer lifespan brings delivery cost savings, each one year increase in lifespan can be accompanied by a USD 1 or more increase in price

  19. Effect of permethrin-treated bed nets on the spatial distribution of malaria vectors in western Kenya

    NARCIS (Netherlands)

    Gimnig, John E.; Kolczak, Margarette S.; Hightower, Allen W.; Vulule, John M.; Schoute, Erik; Kamau, Luna; Phillips-Howard, Penelope A.; ter Kuile, Feiko O.; Nahlen, Bernard L.; Hawley, William A.

    2003-01-01

    The effect of insecticide (permethrin)-treated bed nets (ITNs) on the spatial distribution of malaria vectors in neighboring villages lacking ITNs was studied during a randomized controlled trial of ITNs in western Kenya. There was a trend of decreased abundance of Anopheles gambiae with decreasing

  20. Host-seeking activity of a Tanzanian population of Anopheles arabiensis at an insecticide treated bed net.

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    Parker, Josephine E A; Angarita Jaimes, Natalia C; Gleave, Katherine; Mashauri, Fabian; Abe, Mayumi; Martine, Jackline; Towers, Catherine E; Towers, David; McCall, Philip J

    2017-07-04

    Understanding how mosquitoes respond to long lasting insecticide treated nets (LLINs) is fundamental to sustaining the effectiveness of this essential control tool. We report on studies with a tracking system to investigate behaviour of wild anophelines at an LLIN, in an experimental hut at a rural site in Mwanza, Tanzania. Groups of adult female mosquitoes (n = 10 per replicate) reared from larvae of a local population, identified as predominantly (95%) Anopheles arabiensis, were released in the hut. An infrared video tracking system recorded flight and net contact activity over 1 h as the mosquitoes attempted to reach a supine human volunteer within a bed net (either a deltamethrin-treated LLIN or an untreated control net). A range of activities, including flight path, position in relation to the bed net and duration of net contact, were quantified and compared between treatments. The total time that female An. arabiensis spent in flight around LLINs was significantly lower than at untreated nets [F(1,10) = 9.26, p = 0.012], primarily due to a substantial reduction in the time mosquitoes spent in persistent 'bouncing' flight [F(1,10) = 18.48, p = 0.002]. Most activity occurred at the net roof but significantly less so with LLINs (56.8% of total) than untreated nets [85.0%; Χ 2 (15) = 234.69, p Activity levels at the bed net directly above the host torso were significantly higher with untreated nets (74.2%) than LLINs [38.4%; Χ 2 (15) = 33.54, p = 0.004]. 'Visiting' and 'bouncing' rates were highest above the volunteer's chest in untreated nets (39.9 and 50.4%, respectively) and LLINs [29.9 and 42.4%; Χ 2 (13) = 89.91, p activity over 60 min was significantly more rapid for LLINs [F(1,10) = 6.81, p = 0.026], reiterating an 'attract and kill' rather than a repellent mode of action. The study has demonstrated the potential for detailed investigations of behaviour of wild mosquito populations under field conditions. The results validate

  1. Malaria in pregnant women in an area with sustained high coverage of insecticide-treated bed nets

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    Mshinda Hassan

    2008-07-01

    Full Text Available Abstract Background Since 2000, the World Health Organization has recommended a package of interventions to prevent malaria during pregnancy and its sequelae that includes the promotion of insecticide-treated bed nets (ITNs, intermittent preventive treatment in pregnancy (IPTp, and effective case management of malarial illness. It is recommended that pregnant women in malaria-endemic areas receive at least two doses of sulphadoxine-pyrimethamine in the second and third trimesters of pregnancy. This study assessed the prevalence of placental malaria at delivery in women during 1st or 2nd pregnancy, who did not receive intermittent preventive treatment for malaria (IPTp in a malaria-endemic area with high bed net coverage. Methods A hospital-based cross-sectional study was done in Ifakara, Tanzania, where bed net coverage is high. Primi- and secundigravid women, who presented to the labour ward and who reported not using IPTp were included in the study. Self-report data were collected by questionnaire; whereas neonatal birth weight and placenta parasitaemia were measured directly at the time of delivery. Results Overall, 413 pregnant women were enrolled of which 91% reported to have slept under a bed net at home the previous night, 43% reported history of fever and 62% were primigravid. Malaria parasites were detected in 8% of the placenta samples; the geometric mean (95%CI placental parasite density was 3,457 (1,060–11,271 parasites/μl in primigravid women and 2,178 (881–5,383 parasites/μl in secundigravid women. Fifteen percent of newborns weighed Conclusion The observed incidence of LBW and prevalence of placental parasitaemia at delivery suggests that malaria remains a problem in pregnancy in this area with high bed net coverage when eligible women do not receive IPTp. Delivery of IPTp should be emphasized at all levels of implementation to achieve maximum community coverage.

  2. Factors affecting use of permethrin-treated bed nets during a randomized controlled trial in western Kenya

    NARCIS (Netherlands)

    Alaii, Jane A.; Hawley, William A.; Kolczak, Margarette S.; ter Kuile, Feiko O.; Gimnig, John E.; Vulule, John M.; Odhacha, Amos; Oloo, Aggrey J.; Nahlen, Bernard L.; Phillips-Howard, Penelope A.

    2003-01-01

    Adherence with permethrin-treated bed net (ITN) use and their proper deployment was directly observed in 2,178 individuals (784 households) participating in a large-scale trial of ITNs on child mortality in western Kenya. The ITNs were distributed free of charge to ensure high coverage, resulting in

  3. Implications of the western Kenya permethrin-treated bed net study for policy, program implementation, and future research

    NARCIS (Netherlands)

    Hawley, William A.; ter Kuile, Feiko O.; Steketee, Richard S.; Nahlen, Bernard L.; Terlouw, Dianne J.; Gimnig, John E.; Shi, Ya Ping; Vulule, John M.; Alaii, Jane A.; Hightower, Allen W.; Kolczak, Margarette S.; Kariuki, Simon K.; Phillips-Howard, Penelope A.

    2003-01-01

    The fifth, and probably last, large-scale, group-randomized, controlled trial of insecticide (permethrin)-treated bed nets (ITNs) showed that ITNs are efficacious in reducing all-cause post-neonatal mortality in an area of intense, perennial malaria transmission. The trial helped to define pregnant

  4. Community-wide effects of permethrin-treated bed nets on child mortality and malaria morbidity in western Kenya

    NARCIS (Netherlands)

    Hawley, William A.; Phillips-Howard, Penelope A.; ter Kuile, Feiko O.; Terlouw, Dianne J.; Vulule, John M.; Ombok, Maurice; Nahlen, Bernard L.; Gimnig, John E.; Kariuki, Simon K.; Kolczak, Margarette S.; Hightower, Allen W.

    2003-01-01

    Spatial analyses of the effect of insecticide (permethrin)-treated bed nets (ITNs) on nearby households both with and without ITNs was performed in the context of a large-scale, group-randomized, controlled mortality trial in Asembo, western Kenya. Results illustrate a protective effect of ITNs on

  5. Control of pyrethroid and DDT-resistant Anopheles gambiae by application of indoor residual spraying or mosquito nets treated with a long-lasting organophosphate insecticide, chlorpyrifos-methyl

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    Chabi Joseph

    2010-02-01

    Full Text Available Abstract Background Scaling up of long-lasting insecticidal nets (LLINs and indoor residual spraying (IRS with support from the Global Fund and President's Malaria Initiative is providing increased opportunities for malaria control in Africa. The most cost-effective and longest-lasting residual insecticide DDT is also the most environmentally persistent. Alternative residual insecticides exist, but are too short-lived or too expensive to sustain. Dow Agrosciences have developed a microencapsulated formulation (CS of the organophosphate chlorpyrifos methyl as a cost-effective, long-lasting alternative to DDT. Methods Chlorpyrifos methyl CS was tested as an IRS or ITN treatment in experimental huts in an area of Benin where Anopheles gambiae and Culex quinquefasiactus are resistant to pyrethroids, but susceptible to organophosphates. Efficacy and residual activity was compared to that of DDT and the pyrethroid lambdacyalothrin. Results IRS with chlorpyrifos methyl killed 95% of An. gambiae that entered the hut as compared to 31% with lambdacyhalothrin and 50% with DDT. Control of Cx. quinquefasciatus showed a similar trend; although the level of mortality with chlorpyrifos methyl was lower (66% it was still much higher than for DDT (14% or pyrethroid (15% treatments. Nets impregnated with lambdacyhalothrin were compromized by resistance, killing only 30% of An. gambiae and 8% of Cx. quinquefasciatus. Nets impregnated with chlorpyrifos methyl killed more (45% of An gambiae and 15% of Cx. quinquefasciatus, but its activity on netting was of short duration. Contact bioassays on the sprayed cement-sand walls over the nine months of monitoring showed no loss of activity of chlorpyrifos methyl, whereas lambdacyhalothrin and DDT lost activity within a few months of spraying. Conclusion As an IRS treatment against pyrethroid resistant mosquitoes chlorpyrifos methyl CS outperformed DDT and lambdacyhalothrin. In IRS campaigns, chlorpyrifos methyl CS should

  6. Equity and coverage of insecticide-treated bed nets in an area of intense transmission of Plasmodium falciparum in Tanzania

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    Mtei Frank

    2009-04-01

    Full Text Available Abstract Background There is no clear consensus on the most sustainable and effective distribution strategy for insecticide treated bed nets (ITNs. Tanzania has been a leader in social marketing but it is still not clear if this can result in high and equitable levels of coverage. Methods A cluster-randomized survey of ITN and bed net ownership and use was conducted in a rural area exposed to intense Plasmodium falciparum transmission in NE Tanzania where ITN distribution had been subject to routine delivery of national strategies and episodic free distribution through local clinics. Data were collected on household assets to assess equity of ITN coverage and a rapid diagnostic test for malaria (RDT was performed in all ages. Results Among 598 households in four villages the use of any or insecticidal bed nets in children less than five years of age was 71% and 54% respectively. However there was a 19.8% increase in the number of bed nets per person (p Conclusion Marked inequity persists with the poorest households still experiencing the highest risk of malaria and the lowest ITN coverage. Abolition of this inequity within the foreseeable future is likely to require mass or targeted free distribution, but risks damaging what is otherwise an effective commercial market.

  7. Impact of permethrin-treated bed nets on entomologic indices in an area of intense year-round malaria transmission

    NARCIS (Netherlands)

    Gimnig, John E.; Vulule, John M.; Lo, Terrence Q.; Kamau, Luna; Kolczak, Margarette S.; Phillips-Howard, Penelope A.; Mathenge, Evan M.; ter Kuile, Feiko O.; Nahlen, Bernard L.; Hightower, Allen W.; Hawley, William A.

    2003-01-01

    The effect of permethrin-treated bed nets (ITNs) on malaria vectors was studied as part of a large-scale, randomized, controlled trial in western Kenya. Indoor resting densities of fed Anopheles gambiae s.l. and An. funestus in intervention houses were 58.5% (P = 0.010) and 94.5% (P = 0.001) lower,

  8. Modelling the impact of the long-term use of insecticide-treated bed nets on Anopheles mosquito biting time.

    Science.gov (United States)

    Ferreira, Claudia P; Lyra, Silas P; Azevedo, Franciane; Greenhalgh, David; Massad, Eduardo

    2017-09-15

    Evidence of changing in biting and resting behaviour of the main malaria vectors has been mounting up in recent years as a result of selective pressure by the widespread and long-term use of insecticide-treated bed nets (ITNs), and indoor residual spraying. The impact of resistance behaviour on malaria intervention efficacy has important implications for the epidemiology and malaria control programmes. In this context, a theoretical framework is presented to understand the mechanisms determining the evolution of feeding behaviour under the pressure of use of ITNs. An agent-based stochastic model simulates the impact of insecticide-treated bed nets on mosquito fitness by reducing the biting rates, as well as increasing mortality rates. The model also incorporates a heritability function that provides the necessary genetic plasticity upon which natural selection would act to maximize the fitness under the pressure of the control strategy. The asymptotic equilibrium distribution of mosquito population versus biting time is shown for several daily uses of ITNs, and the expected disruptive selection on this mosquito trait is observed in the simulations. The relative fitness of strains that bite at much earlier time with respect to the wild strains, when a threshold of about 50% of ITNs coverage highlights the hypothesis of a behaviour selection. A sensitivity analysis has shown that the top three parameters that play a dominant role on the mosquito fitness are the proportion of individuals using bed nets and its effectiveness, the impact of bed nets on mosquito oviposition, and the mosquito genetic plasticity related to changing in biting time. By taking the evolutionary aspect into account, the model was able to show that the long-term use of ITNs, although representing an undisputed success in reducing malaria incidence and mortality in many affected areas, is not free of undesirable side effects. From the evolutionary point of view of the parasite virulence, it

  9. The efficacy of permethrin-treated bed nets on child mortality and morbidity in western Kenya II. Study design and methods

    NARCIS (Netherlands)

    Phillips-Howard, Penelope A.; ter Kuile, Feiko O.; Nahlen, Bernard L.; Alaii, Jane A.; Gimnig, John E.; Kolczak, Margarette S.; Terlouw, Dianne J.; Kariuki, Simon K.; Shi, Ya Ping; Kachur, S. Patrick; Hightower, Allen W.; Vulule, John M.; Hawley, William A.

    2003-01-01

    This paper describes the study design and methods used in a large community-based, group-randomized, controlled trial of permethrin-treated bed nets (ITNs) in an area with intense, perennial malaria transmission in western Kenya conducted between 1996 and 1999. A multi-disciplinary framework was

  10. Experimental hut evaluation of bednets treated with an organophosphate (chlorpyrifos-methyl or a pyrethroid (lambdacyhalothrin alone and in combination against insecticide-resistant Anopheles gambiae and Culex quinquefasciatus mosquitoes

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    Corbel Vincent

    2005-05-01

    Full Text Available Abstract Background Pyrethroid resistant mosquitoes are becoming increasingly common in parts of Africa. It is important to identify alternative insecticides which, if necessary, could be used to replace or supplement the pyrethroids for use on treated nets. Certain compounds of an earlier generation of insecticides, the organophosphates may have potential as net treatments. Methods Comparative studies of chlorpyrifos-methyl (CM, an organophosphate with low mammalian toxicity, and lambdacyhalothrin (L, a pyrethroid, were conducted in experimental huts in Côte d'Ivoire, West Africa. Anopheles gambiae and Culex quinquefasciatus mosquitoes from the area are resistant to pyrethroids and organophosphates (kdr and insensitive acetylcholinesterase Ace.1R. Several treatments and application rates on intact or holed nets were evaluated, including single treatments, mixtures, and differential wall/ceiling treatments. Results and Conclusion All of the treatments were effective in reducing blood feeding from sleepers under the nets and in killing both species of mosquito, despite the presence of the kdr and Ace.1R genes at high frequency. In most cases, the effects of the various treatments did not differ significantly. Five washes of the nets in soap solution did not reduce the impact of the insecticides on A. gambiae mortality, but did lead to an increase in blood feeding. The three combinations performed no differently from the single insecticide treatments, but the low dose mixture performed encouragingly well indicating that such combinations might be used for controlling insecticide resistant mosquitoes. Mortality of mosquitoes that carried both Ace.1R and Ace.1S genes did not differ significantly from mosquitoes that carried only Ace.1S genes on any of the treated nets, indicating that the Ace.1R allele does not confer effective resistance to chlorpyrifos-methyl under the realistic conditions of an experimental hut.

  11. Use of the RISK21 roadmap and matrix: human health risk assessment of the use of a pyrethroid in bed netting.

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    Doe, John E; Lander, Deborah R; Doerrer, Nancy G; Heard, Nina; Hines, Ronald N; Lowit, Anna B; Pastoor, Timothy; Phillips, Richard D; Sargent, Dana; Sherman, James H; Young Tanir, Jennifer; Embry, Michelle R

    2016-01-01

    The HESI-coordinated RISK21 roadmap and matrix are tools that provide a transparent method to compare exposure and toxicity information and assess whether additional refinement is required to obtain the necessary precision level for a decision regarding safety. A case study of the use of a pyrethroid, "pseudomethrin," in bed netting to control malaria is presented to demonstrate the application of the roadmap and matrix. The evaluation began with a problem formulation step. The first assessment utilized existing information pertaining to the use and the class of chemistry. At each stage of the step-wise approach, the precision of the toxicity and exposure estimates were refined as necessary by obtaining key data which enabled a decision on safety to be made efficiently and with confidence. The evaluation demonstrated the concept of using existing information within the RISK21 matrix to drive the generation of additional data using a value-of-information approach. The use of the matrix highlighted whether exposure or toxicity required further investigation and emphasized the need to address the default uncertainty factor of 100 at the highest tier of the evaluation. It also showed how new methodology such as the use of in vitro studies and assays could be used to answer the specific questions which arise through the use of the matrix. The matrix also serves as a useful means to communicate progress to stakeholders during an assessment of chemical use.

  12. Household bed net ownership and use among under-5 children in Nigeria

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    Osuorah DC

    2013-07-01

    Full Text Available D Chidiebere Osuorah,1,2 Chijioke Elias Ezeudu,2 Stanley Kenechi Onah,2 Obinna Tochukwu Anyabolu31Child Survival Unit, Medical Research Council UK, The Gambia Unit, Banjul, The Gambia; 2Department of Pediatrics, Nnamdi Azikiwe University Teaching Hospital, Nnewi, Anambra, Nigeria; 3School of Health and Social Care, Oxford Brookes University, Oxford, UKBackground: Malaria remains the leading cause of morbidity and mortality in sub-Saharan Africa, with children under 5 years accounting for 86% of all malaria deaths. For effective control of malaria, WHO recommends rapid diagnosis and effective treatment, insecticide-treated bed nets, and indoor residual spraying. The use of insecticide-treated bed nets has been shown to be the most cost-effective strategy in preventing this infection. However, despite the Roll Back Malaria subsidized and free bed net distribution initiatives in some Africa countries, bed net uptake and usage still remains low in many households.Aim: This study aimed to investigate household characteristics and child factors that determine bed net ownership and use amongst under-5 children and the effect of its usage on malaria parasitemia in under-5 children in Nigeria.Methods: Data from a nationally representative sample of 5895 households was obtained from the 36 states and the Federal Capital Territory in the 2010 Nigeria demographic and health survey, with a minimum of 67 households enrolled per state. Appropriate statistical tools were used to identify the characteristics of households that owned a bed net and to examine the association between the households and child-level factors that predict the use of bed net and malaria prevalence among under-5 children within these households.Results: The rate of households bed net ownership in Nigeria is about 45.5%. About 48.5% of under-5 children in 33.9% of households surveyed, use a bed net during sleep. There was a strong correlation between households ownership and child

  13. Insecticidal, acaricidal and repellent effects of DEET- and IR3535-impregnated bed nets using a novel long-lasting polymer-coating technique.

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    Faulde, Michael K; Albiez, Gunther; Nehring, Oliver

    2010-03-01

    A novel long-lasting repellent-treated net (LLRTN) has been designed by binding the skin repellents N,N-diethyl-m-toluamide (DEET), or IR3535, onto the fibres of bed net fabric using a new polymer-coating technique. The repellent toxicological effectiveness and residual activity of a factory-based repellent-impregnated fabric has been evaluated by laboratory testing against adult Aedes aegypti mosquitoes and nymphal Ixodes ricinus ticks. By using this repellent-embedding impregnation technique, concentrations exceeding 10 g/m(2) could be achieved with one single polymer layer. Both DEET- and IR3535-impregnated fabrics revealed a dose-dependent insecticidal as well as acaricidal activity. One hundred percent knockdown times of DEET-treated bed nets ranged from 187.5 +/- 31.8 to 27.5 +/- 3.5 min against A. aegypti, and between 214 +/- 47 and 22.6 +/- 5 min against nymphal I. ricinus, linked to a DEET concentration of 1.08 and 10.58 g/m(2), respectively. With IR3535, A. aegypti produced dose-dependent 100% knockdown times varying from 87.5 +/- 10.6 to 57.5 +/- 3.5 min and between 131.4 +/- 6.5 and 33.8 +/- 5 min against nymphal I. ricinus, respectively, linked to concentrations between 1.59 and 10.02 g/m(2). One hundred percent repellency measured by complete landing and biting protection of impregnated fabric by using the arm-in-cage test could be achieved at DEET concentrations exceeding 3.7 to 3.9 g/m(2), and for IR3535 concentrations over 10 g/m(2). One hundred percent landing and biting protection could be preserved with DEET-treated fabrics for 29 weeks at an initial concentration of 4.66 g/m(2), 54 weeks at 8.8 g/m(2), 58 weeks at 9.96 g/m(2) and 61 weeks at 10.48 g/m(2) for DEET, and 23 weeks for IR3535-treated fabric at a concentration of 10.02 g/m(2). Unlike repellent-treated fabric, a brand of a commercially available long-lasting insecticide-treated net tested containing 500 mg permethrin/m(2) did not protect from mosquito bites. First results on

  14. Comparing insecticide-treated bed net use to Plasmodium falciparum infection among schoolchildren living near Lake Victoria, Kenya.

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    Okoyo, Collins; Mwandawiro, Charles; Kihara, Jimmy; Simiyu, Elses; Gitonga, Caroline W; Noor, Abdisalan M; Njenga, Sammy M; Snow, Robert W

    2015-12-22

    Under trial conditions insecticide-treated nets have been shown to provide significant clinical and mortality protection under a range of malaria transmission intensity conditions. There are, however, few operational impact data, notably in very intense transmission conditions. This study, reports on malaria infection among Kenyan schoolchildren living in areas of intense malaria transmission and their reported use of insecticide-treated bed nets. 5188 children in 54 schools were randomly sampled from seven counties surrounding Lake Victoria between May and June 2014. A questionnaire was administered to schoolchildren in classes 2-6 on the use of a long-lasting, insecticide-treated net (LLIN) the night before the survey and provided a single blood sample for a rapid diagnostic test for malaria infection. Analysis of the impact of insecticide-treated net use on malaria prevalence was undertaken using a multivariable, mixed effects, logistic regression at 95% confidence interval (CI), taking into account hierarchical nature of the data and results adjusted for school clusters. The overall prevalence of malaria infection was 48.7%, two-thirds (67.9%) of the children reported using LLIN, 91.3% of the children reported that their households own at least one LLIN and the household LLIN coverage was 2.5 persons per one LLIN. The prevalence of infection showed variation across the counties, with prevalence being highest in Busia (66.9%) and Homabay (51.8%) counties, and lowest in Migori County (29.6%). Generally, malaria parasite prevalence differed between age groups and gender with the highest prevalence occurring in children below 7 years (50.6%) and males (52.2%). Adjusting for county and school, there was a significant reduction in odds of malaria infection among the schoolchildren who reported LLIN use the previous night by 14 % (aOR 0.86, 95% CI 0.74-0.98, P provide protection against infection among school-aged children.

  15. The Effect of Mass Media Campaign on the Use of Insecticide-Treated Bed Nets among Pregnant Women in Nigeria

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    A. Ankomah

    2014-01-01

    Full Text Available Background. Malaria during pregnancy is a major public health problem in Nigeria especially in malaria-endemic areas. It increases the risk of low birth weight and child/maternal morbidity/mortality. This paper addresses the impact of radio campaigns on the use of insecticide-treated bed nets among pregnant women in Nigeria. Methods. A total of 2,348 pregnant women were interviewed during the survey across 21 of Nigeria’s 36 states. Respondents were selected through a multistage sampling technique. Analysis was based on multivariate logistic regression. Results. Respondents who knew that sleeping under ITN prevents malaria were 3.2 times more likely to sleep under net (OR: 3.15; 95% CI: 2.28 to 4.33; P<0.0001. Those who listened to radio are also about 1.6 times more likely to use ITN (OR: 1.56; 95% CI: 1.07 to 2.28; P=0.020, while respondents who had heard of a specific sponsored radio campaign on ITN are 1.53 times more likely to use a bed net (P=0.019. Conclusion. Pregnant women who listened to mass media campaigns were more likely to adopt strategies to protect themselves from malaria. Therefore, behavior change communication messages that are aimed at promoting net use and antenatal attendance are necessary in combating malaria.

  16. Efficacy of PermaNet® 2.0 and PermaNet® 3.0 against insecticide-resistant Anopheles gambiae in experimental huts in Côte d'Ivoire

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    Koffi Alphonsine A

    2011-06-01

    Full Text Available Abstract Background Pyrethroid resistance in vectors could limit the efficacy of long-lasting insecticidal nets (LLINs because all LLINs are currently treated with pyrethroids. The goal of this study was to evaluate the efficacy and wash resistance of PermaNet® 3.0 compared to PermaNet® 2.0 in an area of high pyrethroid in Côte d'Ivoire. PermaNet® 3.0 is impregnated with deltamethrin at 85 mg/m2 on the sides of the net and with deltamethrin and piperonyl butoxide on the roof. PermaNet® 2.0 is impregnated with deltamethrin at 55 mg/m2 across the entire net. Methods The study was conducted in the station of Yaokoffikro, in central Côte d'Ivoire. The efficacy of intact unwashed and washed LLINs was compared over a 12-week period with a conventionally-treated net (CTN washed to just before exhaustion. WHO cone bioassays were performed on sub-sections of the nets, using wild-resistant An. gambiae and Kisumu strains. Mosquitoes were collected five days per week and were identified to genus and species level and classified as dead or alive, then unfed or blood-fed. Results Mortality rates of over 80% from cone bioassays with wild-caught pyrethroid-resistant An. gambiae s.s were recorded only with unwashed PermaNet® 3.0. Over 12 weeks, a total of 7,291 mosquitoes were collected. There were significantly more An. gambiae s.s. and Culex spp. caught in control huts than with other treatments (P An. gambiae s.s and Culex spp, were lower for the control than for other treatments (P 0.05 except for unwashed PermaNet® 3.0 (P Conclusions This study showed that unwashed PermaNet® 3.0 caused significantly higher mortality against pyrethroid resistant An. gambiae s.s and Culex spp than PermaNet® 2.0 and the CTN. The increased efficacy with unwashed PermaNet® 3.0 over PermaNet® 2.0 and the CTN was also demonstrated by higher KD and mortality rates (KD > 95% and mortality rate > 80% in cone bioassays performed with wild pyrethroid-resistant An. gambiae s

  17. Insecticide mixtures for mosquito net impregnation against malaria vectors

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    Corbel V.

    2002-09-01

    Full Text Available Insecticides belonging to the pyrethroid family are the only compounds currently available for the treatment of mosquito nets. Unfortunately, some malaria vector species have developed resistance to pyrethroids and the lack of alternative chemical categories is a great concern. One strategy for resistance management would be to treat mosquito nets with a mixture associating two insecticides having different modes of action. This study presents the results obtained with insecticide mixtures containing several proportions of bifenthrin (a pyrethroid insecticide and carbosulfan (a carbamate insecticide. The mixtures were sprayed on mosquito net samples and their efficacy were tested against a susceptible strain of Anopheles gambiae, the major malaria vector in Africa. A significant synergism was observed with a mixture containing 25 mg/m2 of bifenthrin (half the recommended dosage for treated nets and 6.25 mg/m2 of carbosulfan (about 2 % of the recommended dosage. The observed mortality was significantly more than expected in the absence of any interaction (80 % vs 41 % and the knock-down effect was maintained, providing an effective barrier against susceptible mosquitoes.

  18. The efficacy of permethrin-treated bed nets on child mortality and morbidity in western Kenya I. Development of infrastructure and description of study site

    NARCIS (Netherlands)

    Phillips-Howard, Penelope A.; Nahlen, Bernard L.; Alaii, Jane A.; ter Kuile, Feiko O.; Gimnig, John E.; Terlouw, Dianne J.; Kachur, S. Patrick; Hightower, Allen W.; Lal, Altaf A.; Schoute, Erik; Oloo, Aggrey J.; Hawley, William A.

    2003-01-01

    Randomized controlled trials in sub-Saharan Africa have shown that permethrin-treated bed nets and curtains reduce all-cause child mortality by 15-33% in areas with low or high but seasonal malaria transmission. This report describes the study site for a community-based, group-randomized, controlled

  19. Determinants of household demand for bed nets in a rural area of southern Mozambique.

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    Chase, Claire; Sicuri, Elisa; Sacoor, Charfudin; Nhalungo, Delino; Nhacolo, Ariel; Alonso, Pedro L; Menéndez, Clara

    2009-06-15

    A key to making insecticide-treated nets (ITNs) a long-term, sustainable solution to the spread of malaria is understanding what drives their purchase and use. Few studies have analysed the determinants of demand for bed nets for malaria prevention at the household level, and in particular, how demand for nets compares with demand for other mosquito prevention methods. This study uses a household survey to assess the determinants of demand for bed nets in an area of endemic malaria transmission in rural, southern Mozambique. The study looks at willingness to pay (WTP) for bed nets, net ownership, usage, and past purchase behaviour, alongside expenditure and frequency of use of alternate methods for malaria prevention. While overall net ownership in the sample is low, the evidence fails to suggest that poorer households are less likely to own bed nets, when controlling for covariates, nor does the likelihood of receiving a free net depend on socioeconomic status (SES). Formal schooling and market knowledge seem to indicate higher average willingness to pay, while use of alternate methods for malaria prevention, and receipt of Indoor Residual Spraying (IRS) are found to decrease demand for bed nets. For long-term sustainability of ITNs to be realized, results suggest that either full or partial subsidies may be necessary in some contexts to encourage households to obtain and use nets. Given the possible substitution effects of combined malaria control interventions, and the danger of not taking into consideration household preferences for malaria prevention, successful malaria control campaigns should invest a portion of their funds towards educating recipients of IRS and users of other preventive methods on the importance of net use even in the absence of mosquitoes.

  20. Determinants of household demand for bed nets in a rural area of southern Mozambique

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    Nhacolo Ariel

    2009-06-01

    Full Text Available Abstract Background A key to making insecticide-treated nets (ITNs a long-term, sustainable solution to the spread of malaria is understanding what drives their purchase and use. Few studies have analysed the determinants of demand for bed nets for malaria prevention at the household level, and in particular, how demand for nets compares with demand for other mosquito prevention methods. Methods This study uses a household survey to assess the determinants of demand for bed nets in an area of endemic malaria transmission in rural, southern Mozambique. The study looks at willingness to pay (WTP for bed nets, net ownership, usage, and past purchase behaviour, alongside expenditure and frequency of use of alternate methods for malaria prevention. Results While overall net ownership in the sample is low, the evidence fails to suggest that poorer households are less likely to own bed nets, when controlling for covariates, nor does the likelihood of receiving a free net depend on socioeconomic status (SES. Formal schooling and market knowledge seem to indicate higher average willingness to pay, while use of alternate methods for malaria prevention, and receipt of Indoor Residual Spraying (IRS are found to decrease demand for bed nets. Conclusion For long-term sustainability of ITNs to be realized, results suggest that either full or partial subsidies may be necessary in some contexts to encourage households to obtain and use nets. Given the possible substitution effects of combined malaria control interventions, and the danger of not taking into consideration household preferences for malaria prevention, successful malaria control campaigns should invest a portion of their funds towards educating recipients of IRS and users of other preventive methods on the importance of net use even in the absence of mosquitoes.

  1. Impact of permethrin-treated bed nets on malaria, anemia, and growth in infants in an area of intense perennial malaria transmission in western Kenya

    NARCIS (Netherlands)

    ter Kuile, Feiko O.; Terlouw, Dianne J.; Kariuki, Simon K.; Phillips-Howard, Penelope A.; Mirel, Lisa B.; Hawley, William A.; Friedman, Jennifer F.; Shi, Ya Ping; Kolczak, Margarette S.; Lal, Altaf A.; Vulule, John M.; Nahlen, Bernard L.

    2003-01-01

    As part of a community-based, group-randomized, controlled trial of insecticide-treated bed nets (ITNs) in an area with intense malaria transmission in western Kenya, a birth cohort (n = 833) was followed monthly until the age of 24 months to determine the potential beneficial and adverse effects of

  2. Resistance to DDT and pyrethroids and increased kdr mutation frequency in An. gambiae after the implementation of permethrin-treated nets in Senegal.

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    Mamadou O Ndiath

    Full Text Available The aim of this study was to evaluate the susceptibility to insecticides of An. gambiae mosquitoes sampled in Dielmo (Senegal, in 2010, 2 years after the implementation of Long Lasting Insecticide-treated Nets (LLINs and to report the evolution of kdr mutation frequency from 2006 to 2010.WHO bioassay susceptibility tests to 6 insecticides were performed on adults F0, issuing from immature stages of An. gambiae s.l., sampled in August 2010. Species and molecular forms as well as the presence of L1014F and L1014S kdr mutations were assessed by PCR. Longitudinal study of kdr mutations was performed on adult mosquitoes sampled monthly by night landing catches from 2006 to 2010.No specimen studied presented the L1014S mutation. During the longitudinal study, L1014F allelic frequency rose from 2.4% in year before the implementation of LLINs to 4.6% 0-12 months after and 18.7% 13-30 months after. In 2010, An. gambiae were resistant to DDT, Lambda-cyhalothrin, Deltamethrin and Permethrin (mortality rates ranging from 46 to 63% but highly susceptible to Fenitrothion and Bendiocarb (100% mortality. There was significantly more RR genotype among An. gambiae surviving exposure to DDT or Pyrethroids. An. arabiensis represented 3.7% of the sampled mosquitoes (11/300 with no kdr resistance allele detected. An. gambiae molecular form M represented 29.7% of the mosquitoes with, among them, kdr genotypes SR (18% and SS (82%. An. gambiae molecular form S represented 66% of the population with, among them, kdr genotype SS (33.3%, SR (55.6% and RR (11.1%. Only 2 MS hybrid mosquitoes were sampled and presented SS kdr genotype.Biological evidence of resistance to DDT and pyrethroids was detected among An. gambiae mosquitoes in Dielmo (Senegal within 24 months of community use of LLINs. Molecular identification of L1014F mutation indicated that target site resistance increased after the implementation of LLINs.

  3. Efficacy of permethrin-treated bed nets in the prevention of mortality in young children in an area of high perennial malaria transmission in western Kenya

    NARCIS (Netherlands)

    Phillips-Howard, Penelope A.; Nahlen, Bernard L.; Kolczak, Margarette S.; Hightower, Allen W.; ter Kuile, Feiko O.; Alaii, Jane A.; Gimnig, John E.; Arudo, John; Vulule, John M.; Odhacha, Amos; Kachur, S. Patrick; Schoute, Erik; Rosen, Daniel H.; Sexton, John D.; Oloo, Aggrey J.; Hawley, William A.

    2003-01-01

    A group-randomized controlled trial of insecticide (permethrin)-treated bed nets (ITNs) was conducted in an area of high perennial malaria transmission in western Kenya to test the effect of ITNs on all-cause mortality in children 1-59 months of age. Child deaths were monitored over a two-year

  4. Determinants of Ownership and Utilization of Insecticide-Treated Bed Nets for Malaria Control in Eastern Ethiopia

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    Sibhatu Biadgilign

    2012-01-01

    Full Text Available Background. Malaria remains a major cause of mortality and morbidity in the world, and particularly in sub-Saharan Africa. Objectives. The aim of this study was to determine ownership and utilization of ITNs among households with children under five in the previous night. Methods. A community based cross-sectional study was conducted in Gursum district in Eastern Ethiopia. A total of 335 households were surveyed using a pretested structured questionnaire administered though house-to-house interviews. Results. Household ownership for at least one mosquito net and use of nets were 62.4% (95% CI 57.2–67.6% and 21.5% (95% CI 17.1–25.9%, respectively. Households who received or were told about ITN in the last 6 months were three times more likely to have used it than those who were not (OR 3.25; 95% CI 1.5–7.10. Households whose heads were engaged as a farmer (adjusted OR 0.137; 95% CI: 0.04–0.50 and housewife (OR 0.26; 95% CI: 0.08–0.82 were less likely to use ITN than those of other occupations. Conclusion. The findings indicate low ITN ownership and utilization among the households. Intensive health education and community mobilization effort should be employed to increase the possession and proper utilization of insecticide treated bed nets.

  5. The importance of education to increase the use of bed nets in villages outside of Kinshasa, Democratic Republic of the Congo

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    Ndjinga Julie K

    2010-10-01

    Full Text Available Abstract Background Malaria is the most prominent disease in the Democratic Republic of the Congo (DRC, and long-lasting insecticide-treated nets (LLINs have been distributed free of charge since 2006 to combat the disease. However, the success of this bed net campaign depends on sufficient bed net use in all age groups. This study was designed to examine the factors affecting bed net use in villages outside of Kinshasa. Methods Two villages along the Congo River, totalling 142 households with 640 residents, were surveyed using a standard questionnaire. The interview determined the number, ages, and sexes of family members; the education level of the family head; the number, colour, and type of nets owned; and the number of nets used in the previous night. The size of house was also measured, and numbers of rooms and beds were recorded. These variables were examined to reveal important factors that affect bed net use. Results A total of 469 nets were counted, and nearly all nets were white LLINs. Of these nets, 229 (48.8% nets were used by 284 (44.4% residents. Bed nets were used by over 90% of children 5 to 15 years of age, whereas less than 50% of the residents in other age groups used bed nets. The important variables affecting bed net use were numbers of beds and rooms in the house and the education level of the family head of household. Conclusion Education was the most important factor affecting bed net use in the villages outside Kinshasa. Development of an educational programme, particularly one directed toward parents, is necessary to reduce misconceptions and increase prevalence of bed net use among all age groups.

  6. Efficacy of PermaNet® 3.0 and PermaNet® 2.0 nets against laboratory-reared and wild Anopheles gambiae sensu lato populations in northern Tanzania.

    Science.gov (United States)

    Kweka, Eliningaya J; Lyaruu, Lucile J; Mahande, Aneth M

    2017-01-18

    Mosquitoes have developed resistance against pyrethroids, the only class of insecticides approved for use on long-lasting insecticidal nets (LLINs). The present study sought to evaluate the efficacy of the pyrethroid synergist PermaNet® 3.0 LLIN versus the pyrethroid-only PermaNet® 2.0 LLIN, in an East African hut design in Lower Moshi, northern Tanzania. In this setting, resistance to pyrethroid insecticides has been identified in Anopheles gambiae mosquitoes. Standard World Health Organization bioefficacy evaluations were conducted in both laboratory and experimental huts. Experimental hut evaluations were conducted in an area where there was presence of a population of highly pyrethroid-resistant An. arabiensis mosquitoes. All nets used were subjected to cone bioassays and then to experimental hut trials. Mosquito mortality, blood-feeding inhibition and personal protection rate were compared between untreated nets, unwashed LLINs and LLINs that were washed 20 times. Both washed and unwashed PermaNet® 2.0 and PermaNet® 3.0 LLINs had knockdown and mortality rates of 100% against a susceptible strain of An. gambiae sensu stricto. The adjusted mortality rate of the wild mosquito population after use of the unwashed PermaNet® 3.0 and PermaNet® 2.0 nets was found to be higher than after use of the washed PermaNet® 2.0 and PermaNet® 3.0 nets. Given the increasing incidence of pyrethroid resistance in An. gambiae mosquitoes in Tanzania, we recommend that consideration is given to its distribution in areas with pyrethroid-resistant malaria vectors within the framework of a national insecticide-resistance management plan.

  7. The underlying reasons for very high levels of bed net use, and higher malaria infection prevalence among bed net users than non-users in the Tanzanian city of Dar es Salaam: a qualitative study.

    Science.gov (United States)

    Msellemu, Daniel; Shemdoe, Aloysia; Makungu, Christina; Mlacha, Yeromini; Kannady, Khadija; Dongus, Stefan; Killeen, Gerry F; Dillip, Angel

    2017-10-23

    Bed nets reduce malaria-related illness and deaths, by forming a protective barrier around people sleeping under them. When impregnated with long-lasting insecticide formulations they also repel or kill mosquitoes attempting to feed upon sleeping humans, and can even suppress entire populations of malaria vectors that feed predominantly upon humans. Nevertheless, an epidemiological study in 2012 demonstrated higher malaria prevalence among bed net users than non-users in urban Dar es Salaam, Tanzania. Focus group discussions were conducted with women from four selected wards of Dar es Salaam city, focusing on four major themes relating to bed net use behaviours: (1) reasons for bed net use, (2) reasons for not using bed nets, (3) stimuli or reminders for people to use a bed net (4) perceived reasons for catching malaria while using a bed net. An analytical method by framework grouping of relevant themes was used address key issues of relevance to the study objectives. Codes were reviewed and grouped into categories and themes. All groups said the main reason for bed net use was protection against malaria. Houses with well-screened windows, with doors that shut properly, and that use insecticidal sprays against mosquitoes, were said not to use bed nets, while frequent attacks from malaria was the main stimulus for people to use bed nets. Various reasons were mentioned as potential reasons that compromise bed net efficacy, the most common of which were: (1) bed net sharing by two or more people, especially if one occupant tends to come to bed late at night, and does not tuck in the net 71%; (2) one person shares the bed but does not use the net, moving it away from the side on which s/he sleeps 68%; (3) ineffective usage habits, called ulalavi, in which a sprawling sleeper either touches the net while sleeping up against it or leaves a limb hanging outside of it 68%. Less common reasons mentioned included: (1) Small bed nets which become un-tucked at night (31%); (2

  8. Increasing coverage and decreasing inequity in insecticide-treated bed net use among rural Kenyan children.

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    Abdisalan M Noor

    2007-08-01

    Full Text Available Inexpensive and efficacious interventions that avert childhood deaths in sub-Saharan Africa have failed to reach effective coverage, especially among the poorest rural sectors. One particular example is insecticide-treated bed nets (ITNs. In this study, we present repeat observations of ITN coverage among rural Kenyan homesteads exposed at different times to a range of delivery models, and assess changes in coverage across socioeconomic groups.We undertook a study of annual changes in ITN coverage among a cohort of 3,700 children aged 0-4 y in four districts of Kenya (Bondo, Greater Kisii, Kwale, and Makueni annually between 2004 and 2006. Cross-sectional surveys of ITN coverage were undertaken coincidentally with the incremental availability of commercial sector nets (2004, the introduction of heavily subsidized nets through clinics (2005, and the introduction of free mass distributed ITNs (2006. The changing prevalence of ITN coverage was examined with special reference to the degree of equity in each delivery approach. ITN coverage was only 7.1% in 2004 when the predominant source of nets was the commercial retail sector. By the end of 2005, following the expansion of heavily subsidized clinic distribution system, ITN coverage rose to 23.5%. In 2006 a large-scale mass distribution of ITNs was mounted providing nets free of charge to children, resulting in a dramatic increase in ITN coverage to 67.3%. With each subsequent survey socioeconomic inequity in net coverage sequentially decreased: 2004 (most poor [2.9%] versus least poor [15.6%]; concentration index 0.281; 2005 (most poor [17.5%] versus least poor [37.9%]; concentration index 0.131, and 2006 with near-perfect equality (most poor [66.3%] versus least poor [66.6%]; concentration index 0.000. The free mass distribution method achieved highest coverage among the poorest children, the highly subsidised clinic nets programme was marginally in favour of the least poor, and the commercial

  9. Bed net use and associated factors in a rice farming community in Central Kenya

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    Kabuage Lucy

    2009-04-01

    Full Text Available Abstract Background Use of insecticide-treated nets (ITNs continues to offer potential strategy for malaria prevention in endemic areas. However their effectiveness, sustainability and massive scale up remain a factor of socio-economic and cultural variables of the local community which are indispensable during design and implementation stages. Methods An ethnographic household survey was conducted in four study villages which were purposefully selected to represent socio-economic and geographical diversity. In total, 400 households were randomly selected from the four study villages. Quantitative and qualitative information of the respondents were collected by use of semi-structured questionnaires and focus group discussions. Results Malaria was reported the most frequently occurring disease in the area (93% and its aetiology was attributed to other non-biomedical causes like stagnant water (16%, and long rains (13%. Factors which significantly caused variation in bed net use were occupant relationship to household head (χ2 = 105.705; df 14; P = 0.000, Age (χ2 = 74.483; df 14; P = 0.000, village (χ2 = 150.325; df 6; P = 0.000, occupation (χ2 = 7.955; df 3; P = 0.047, gender (χ2 = 4.254; df 1; P = 0.039 and education levels of the household head or spouse (χ2 = 33.622; df 6; P = 0.000. The same variables determined access and conditions of bed nets at household level. Protection against mosquito bite (95% was the main reason cited for using bed nets in most households while protection against malaria came second (54%. Colour, shape and affordability were some of the key potential factors which determined choice, use and acceptance of bed nets in the study area. Conclusion The study highlights potential social and economic variables important for effective and sustainable implementation of bed nets-related programmes in Sub-Saharan Africa.

  10. Pyrethroid Resistance Alters the Blood-Feeding Behavior in Puerto Rican Aedes aegypti Mosquitoes Exposed to Treated Fabric

    Science.gov (United States)

    Emerging insecticide resistance is a major issue for vector control; it decreases effectiveness of insecticides, thereby requiring greater quantities for comparable control with a net increase in risk of disease resurgence, product cost, and damage risk to the ecosystem. Pyrethroid resistance has b...

  11. Insecticide-treated bed nets reduce plasma antibody levels and limit the repertoire of antibodies to Plasmodium falciparum variant surface antigens

    DEFF Research Database (Denmark)

    Askjaer, N; Maxwell, C; Chambo, W

    2001-01-01

    The use of insecticide-treated bed nets (ITN) has been documented to reduce malaria morbidity and mortality in areas with endemic malaria, but concerns have been raised that ITN usage could affect the acquisition of malaria immunity. Several lines of evidence have indicated that antibodies against...... variant surface antigens (VSA) are important in the development of naturally acquired immunity to Plasmodium falciparum malaria and may thus be good indicators of immune status. We have compared the levels of VSA antibodies in plasma from children who have used ITN for 4 years to levels in plasma from...

  12. The phenomenon of diminishing –returns in the use of bed nets and ...

    African Journals Online (AJOL)

    2014-03-01

    Mar 1, 2014 ... treated bed nets and prompt malaria therapy in Tororo. Uganda, concluded the .... namely vaccination, cure and quarantine and yet cure for malaria actually ..... It is therefore the anti-malarial medicines given to their children that are .... his great assistance in the preparation of the electronic version of this ...

  13. Airflow attenuation and bed net utilization: observations from Africa and Asia

    DEFF Research Database (Denmark)

    von Seidlein, Lorenz; Ikonomidis, Konstantin; Bruun, Rasmus

    2012-01-01

    Background/Methods Qualitative studies suggest that bed nets affect the thermal comfort of users. To understand and reduce this discomfort the effect of bed nets on temperature, humidity, and airflow was measured in rural homes in Asia and Africa, as well as in an experimental wind tunnel. Two...... discomfort is a factor limiting bed net use and open a range of architectural possibilities to overcome this limitation. Keywords: Malaria; Bed nets; Africa; Tanzania; The Gambia; Asia; Thailand; Philippines; Airflow; Temperature; Humidity; Climate...... investigators with architectural training selected 60 houses in The Gambia, Tanzania, Philippines, and Thailand. Data-loggers were used to measure indoor temperatures in hourly intervals over a 12 months period. In a subgroup of 20 houses airflow, temperature and humidity were measured at five-minute intervals...

  14. New Introductions, Spread of Existing Matrilines, and High Rates of Pyrethroid Resistance Result in Chronic Infestations of Bed Bugs (Cimex lectularius L. in Lower-Income Housing.

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    Ronald W Raab

    Full Text Available Infestations of the common bed bug (Cimex lectularius L. have increased substantially in the United States in the past 10-15 years. The housing authority in Harrisonburg, Virginia, conducts heat-treatments after bed bugs are detected in a lower-income housing complex, by treating each infested unit at 60°C for 4-6 hours. However, a high frequency of recurrent infestations called into question the efficacy of this strategy. Genetic analysis using Bayesian clustering of polymorphic microsatellite loci from 123 bed bugs collected from 23 units from May 2012 to April 2013 in one building indicated that (a 16/21 (73% infestations were genetically similar, suggesting ineffective heat-treatments or reintroductions from within the building or from a common external source, followed by local spread of existing populations; and (b up to 5 of the infestations represented new genotypes, indicating that 5 new populations were introduced into this building in one year, assuming they were not missed in earlier screens. There was little to no gene flow among the 8 genetic clusters identified in the building. Bed bugs in the U.S. often possess one or both point mutations in the voltage-gated sodium channel, termed knockdown resistance (kdr, from valine to leucine (V419L and leucine to isoleucine (L925I that confer target-site resistance against pyrethroid insecticides. We found that 48/121 (40% bed bugs were homozygous for both kdr mutations (L419/I925, and a further 59% possessed at least one of the kdr mutations. We conclude that ineffective heat treatments, new introductions, reintroductions and local spread, and an exceptionally high frequency of pyrethroid resistance are responsible for chronic infestations in lower-income housing. Because heat treatments fail to protect from reintroductions, and pesticide use has not decreased the frequency of infestations, preventing new introductions and early detection are the most effective strategies to avoid bed bug

  15. Bed nets for the prevention of malaria and anaemia in pregnancy

    NARCIS (Netherlands)

    Dolan, G.; ter Kuile, F. O.; Jacoutot, V.; White, N. J.; Luxemburger, C.; Malankirii, L.; Chongsuphajaisiddhi, T.; Nosten, F.

    1993-01-01

    A prospective comparison of the antimalarial efficacy of bed nets was conducted with 341 pregnant women living in a mesoendemic malarious area of the Thai-Burmese border. Women in 3 adjacent study sites were allocated at random to receive either a single size permethrin-impregnated bed net (PIB), a

  16. Comparing ownership and use of bed nets at two sites with differential malaria transmission in western Kenya.

    Science.gov (United States)

    Ernst, Kacey C; Hayden, Mary H; Olsen, Heather; Cavanaugh, Jamie L; Ruberto, Irene; Agawo, Maurice; Munga, Stephen

    2016-04-14

    Challenges persist in ensuring access to and optimal use of long-lasting, insecticidal bed nets (LLINs). Factors associated with ownership and use may differ depending on the history of malaria and prevention control efforts in a specific region. Understanding how the cultural and social-environmental context of bed net use may differ between high- and low-risk regions is important when identifying solutions to improve uptake and appropriate use. Community forums and a household, cross-sectional survey were used to collect information on factors related to bed net ownership and use in western Kenya. Sites with disparate levels of transmission were selected, including an endemic lowland area, Miwani, and a highland epidemic-prone area, Kapkangani. Analysis of ownership was stratified by site. A combined site analysis was conducted to examine factors associated with use of all available bed nets. Logistic regression modelling was used to determine factors associated with ownership and use of owned bed nets. Access to bed nets as the leading barrier to their use was identified in community forums and cross-sectional surveys. While disuse of available bed nets was discussed in the forums, it was a relatively rare occurrence in both sites. Factors associated with ownership varied by site. Education, perceived risk of malaria and knowledge of individuals who had died of malaria were associated with higher bed net ownership in the highlands, while in the lowlands individuals reporting it was easy to get a bed net were more likely to own one. A combined site analysis indicated that not using an available bed net was associated with the attitudes that taking malaria drugs is easier than using a bed net and that use of a bed net will not prevent malaria. In addition, individuals with an unused bed net in the household were more likely to indicate that bed nets are difficult to use, that purchased bed nets are better than freely distributed ones, and that bed nets should only

  17. Knowledge, access and utilization of bed-nets among stable and seasonal migrants in an artemisinin resistance containment area of Myanmar.

    Science.gov (United States)

    Phyo Than, Wint; Oo, Tin; Wai, Khin Thet; Thi, Aung; Owiti, Philip; Kumar, Binay; Deepak Shewade, Hemant; Zachariah, Rony

    2017-09-14

    Myanmar lies in the Greater Mekong sub-region of South-East Asia faced with the challenge of emerging resistance to artemisinin combination therapies (ACT). Migrant populations are more likely than others to spread ACT resistance. A vital intervention to reduce malaria transmission, resistance spread and eliminate malaria is the use of bed nets. Among seasonal and stable migrants in an artemisinin resistance containment region of Myanmar, we compared a) their household characteristics, b) contact with health workers and information material, and c) household knowledge, access and utilization of bed nets. Secondary data from community-based surveys on 2484 migrant workers (2013 and 2014, Bago Region) were analyzed of which 37% were seasonal migrants. Bed net access and utilization were assessed using a) availability of at least one bed net per household, and b) one bed net per two persons, and c) proportion of household members who slept under abed net during the previous night (Indicator targets = 100%). Over 70% of all migrants were from unstable work settings with short transitory stays. Average household size was five (range 1-25) and almost half of all households had children under-five years. Roughly 10 % of migrants were night-time workers. Less than 40% of households had contact with health workers and less than 30% had exposure to information education and communication (IEC) materials, the latter being significantly lower among seasonal migrants. About 70% of households were aware of the importance of insecticide-treated bed-nets/long-lasting insecticidal nets (ITNs/LLINs), but knowledge on insecticide impregnation and retreatment of ITNs was poor (Myanmar. Possible ways forward include frequent distribution campaigns to compensate for short transitory stays, matching household distributions to household size, enhanced information campaigns and introducing legislation to make mosquito repellents available for night-time workers at plantations and farms

  18. Bed net ownership, use and perceptions among women seeking antenatal care in Kinshasa, Democratic Republic of the Congo (DRC: Opportunities for improved maternal and child health

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    Tabala Martine

    2008-09-01

    Full Text Available Abstract Background To describe malaria knowledge, attitudes toward malaria and bed net use, levels of ownership and use of bed nets, and factors associated with ownership and use among pregnant women attending their first antenatal care (ANC visit in Kinshasa, DRC. Methods Women attending their first ANC visit at one maternity in Kinshasa were recruited to take part in a study where they were given free insecticide treated bed nets (ITNs and then followed up at delivery and 6 months post delivery to assess ITN use. This study describes the baseline levels of bed net ownership and use, attitudes towards net use and factors associated with net use Results Among 351 women interviewed at baseline, 115 (33% already owned a bed net and 86 (25% reported to have slept under the net the previous night. Cost was reported as the reason for not owning a net by 48% of the 236 women who did not own one. In multivariable analyses, women who had secondary school or higher education were 3.4 times more likely to own a net (95% CI 1.6–7.3 and 2.8 times more likely to have used a net (95% CI 1.3–6.0 compared to women with less education Conclusion Distribution of ITNs in antenatal clinics in this setting is needed and feasible. The potential for ITN use by this target population is high.

  19. How many holes is too many? A prototype tool for estimating mosquito entry risk into damaged bed nets.

    Science.gov (United States)

    Sutcliffe, James; Ji, Xin; Yin, Shaoman

    2017-08-01

    Insecticide-treated bed nets (ITNs) have played an integral role in malaria reduction but how insecticide depletion and accumulating physical damage affect ITN performance is poorly understood. More accurate methods are needed to assess damage to bed nets so that they can be designed, deployed and replaced optimally. Video recordings of female Anopheles gambiae in near approach (1-½ cm) to occupied untreated rectangular bed nets in a laboratory study were used to quantify the amount of mosquito activity (appearances over time) around different parts of the net, the per-appearance probability of a mosquito coming close to holes of different sizes (hole encounter) and the per-encounter probability of mosquitoes passing through holes of different sizes (hole passage). Appearance frequency on different parts of the net reflected previously reported patterns: the area of the net under greatest mosquito pressure was the roof, followed by the bottom 30 cm of the sides, followed by the 30 cm area immediately above this, followed by the upper two-thirds of the sides. The ratio of activity in these areas was (respectively) 250:33:5:1. Per-appearance probability of hole encounter on all parts of the net was strongly predicted by a factor combining hole perimeter and area. Per-encounter probability of hole passage, in turn, was strongly predicted by hole width. For a given width, there was a 20% greater risk of passage through holes on the roof than holes on the sides. Appearance, encounter and passage predictors correspond to various mosquito behaviours that have previously been described and are combined into a prototype mosquito entry risk tool that predicts mosquito entry rates for nets with various amounts of damage. Scenarios that use the entry risk tool to test the recommendations of the WHOPES proportionate hole index (pHI) suggest that the pHI hole size categories and failure to account for hole location likely sometimes lead to incorrect conclusions about net

  20. Impact of malaria related messages on insecticide-treated net (ITN) use for malaria prevention in Ghana

    OpenAIRE

    Owusu Adjah, Ebenezer S; Panayiotou, Andrie G

    2014-01-01

    Background: Media messages have been used in Ghana to promote insecticide-treated net (ITN)/bed net usage in an effort to impact on malaria prevention. The aim of this study was to assess the effect of such malaria-related messages delivered through electronic/print media and by volunteers/health workers on the use of ITNs by children living in a household. Methods: Data was collected from September to November of 2008 using a structured, interviewer-administered questionnaire by the Ghana St...

  1. Impact of PermaNet 3.0 on entomological indices in an area of pyrethroid resistant Anopheles gambiae in south-western Nigeria

    Science.gov (United States)

    2014-01-01

    Background PermaNet® 3.0 is an insecticide synergist-combination long-lasting insecticidal net designed to have increased efficacy against malaria vectors with metabolic resistance, even when combined with kdr. The current study reports on the impact of this improved tool on entomological indices in an area with pyrethroid-resistant malaria vectors in Nigeria. Methods Baseline entomological indices across eight villages in Remo North LGA of Ogun State provided the basis for selection of three villages (Ilara, Irolu and Ijesa) for comparing the efficacy of PermaNet® 3.0 (PN3.0), PermaNet® 2.0 (PN2.0) and untreated polyester nets as a control (UTC). In each case, nets were distributed to cover all sleeping spaces and were evaluated for insecticidal activity on a 3-monthly basis. Collection of mosquitoes was conducted monthly via window traps and indoor resting catches. The arithmetic means of mosquito catches per house, entomological inoculation rates before and during the intervention were compared as well as three other outcome parameters: the mean mosquito blood feeding rate, mean mortality and mean parity rates. Results Anopheles gambiae s.l. was the main malaria vector in the three villages, accounting for >98% of the Anopheles population and found in appreciable numbers for 6–7 months. Deltamethrin, permethrin and lambdacyhalothrin resistance were confirmed at Ilara, Irolu and Ijesa. The kdr mutation was the sole resistance mechanism at Ilara, whereas kdr plus P450-based metabolic mechanisms were detected at Irolu and Ijesa. Bioassays repeated on domestically used PN 2.0 and PN 3.0 showed persistent optimal (100%) bio-efficacy for both net types after the 3rd, 6th, 9th and 12th month following net distribution. The use of PN 3.0 significantly reduced mosquito densities with a ‘mass killing’ effect inside houses. Households with PN 3.0 also showed reduced blood feeding as well as lower mosquito parity and sporozoite rates compared to the PN 2.0 and the

  2. Mass distribution of free insecticide-treated nets do not interfere with continuous net distribution in Tanzania.

    Science.gov (United States)

    Eze, Ikenna C; Kramer, Karen; Msengwa, Amina; Mandike, Renata; Lengeler, Christian

    2014-05-27

    To protect the most vulnerable groups from malaria (pregnant women and infants) the Tanzanian Government introduced a subsidy (voucher) scheme in 2004, on the basis of a public-private partnership. These vouchers are provided to pregnant women at their first antenatal care visit and mothers of infants at first vaccination. The vouchers are redeemed at registered retailers for a long-lasting insecticidal net against the payment of a modest top-up price. The present work analysed a large body of data from the Tanzanian National Voucher Scheme, focusing on interactions with concurrent mass distribution campaigns of free nets. In an ecologic study involving all regions of Tanzania, voucher redemption data for the period 2007-2011, as well as data on potential determinants of voucher redemption were analysed. The four outcome variables were: pregnant woman and infant voucher redemption rates, use of treated bed nets by all household members and by under- five children. Each of the outcomes was regressed with selected determinants, using a generalized estimating equation model and accounting for regional data clustering. There was a consistent improvement in voucher redemption rates over the selected time period, with rates >80% in 2011. The major determinants of redemption rates were the top-up price paid by the voucher beneficiary, the retailer- clinic ratio, and socio-economic status. Improved redemption rates after 2009 were most likely due to reduced top-up prices (following a change in policy). Redemption rates were not affected by two major free net distribution campaigns. During this period, there was a consistent improvement in net use across all the regions, with rates of up to 75% in 2011. The key components of the National Treated Nets Programme (NATNETS) seem to work harmoniously, leading to a high level of net use in the entire population. This calls for the continuation of this effort in Tanzania and for emulation by other countries with endemic malaria.

  3. An exploratory qualitative study on perceptions about mosquito bed nets in the Niger Delta: what are the barriers to sustained use?

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    Galvin KT

    2011-04-01

    Full Text Available Kathleen T Galvin1, Nick Petford2, Frances Ajose3, Dai Davies41Bournemouth University, Talbot Campus, Fern Barrow, Poole, Dorset, UK; 2University of Northampton, Northampton, UK; 3Department of Medicine, Lagos State University and The Lagos State University Teaching Hospital, Ikeja, Lagos, Nigeria; 4Niger Delta Development Initiative, Poole, Dorset, UKBackground: The effectiveness of malaria control programs is determined by an array of complex factors, including the acceptability and sustained use of preventative measures such as the bed net. A small-scale exploratory study was conducted in several locations in the Niger Delta region, Nigeria, to discover barriers against the use of bed nets, in the context of a current drive to scale up net use in Nigeria.Methods: A qualitative approach with a convenience sample was used. One to one interviews with mostly male adult volunteers were undertaken which explored typical living and sleeping arrangements, and perceptions about and barriers against the use of the mosquito prevention bed net.Results: Several key issues emerged from the qualitative data. Bed nets were not reported as widely used in this small sample. The reasons reported for lack of use included issues of convenience, especially net set up and dismantling; potential hazard and safety concerns; issues related to typical family composition and nature of accommodation; humid weather conditions; and perceptions of cost and effectiveness. Most barriers to net use concerned issues about everyday practical living and sleeping arrangements and perceptions about comfort. Interviewees identified were aware of malaria infection risks, but several also indicated certain beliefs that were barriers to net use.Conclusions: Successful control of malaria and scale up of insecticide-treated net coverage relies on community perceptions and practice. This small study has illuminated a number of important everyday life issues, which remain barriers to

  4. Indoor application of attractive toxic sugar bait (ATSB in combination with mosquito nets for control of pyrethroid-resistant mosquitoes.

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    Zachary P Stewart

    Full Text Available BACKGROUND: Attractive toxic sugar bait (ATSB sprayed onto vegetation has been successful in controlling Anopheles mosquitoes outdoors. Indoor application of ATSB has yet to be explored. The purpose of this study was to determine whether ATSB stations positioned indoors have the potential to kill host-seeking mosquitoes and constitute a new approach to control of mosquito-borne diseases. METHODS: Insecticides were mixed with dyed sugar solution and tested as toxic baits against Anopheles arabiensis, An. Gambiae s.s. and Culex quinquefasciatus in feeding bioassay tests to identify suitable attractant-insecticide combinations. The most promising ATSB candidates were then trialed in experimental huts in Moshi, Tanzania. ATSB stations were hung in huts next to untreated mosquito nets occupied by human volunteers. The proportions of mosquitoes killed in huts with ATSB treatments relative to huts with non-insecticide control treatments huts were recorded, noting evidence of dye in mosquito abdomens. RESULTS: In feeding bioassays, chlorfenapyr 0.5% v/v, boric acid 2% w/v, and tolfenpyrad 1% v/v, mixed in a guava juice-based bait, each killed more than 90% of pyrethroid-susceptible An. Gambiae s.s. and pyrethroid-resistant An. arabiensis and Cx. quinquefasciatus. In the hut trial, mortality rates of the three ATSB treatments ranged from 41-48% against An. arabiensis and 36-43% against Cx. quinquefasciatus and all were significantly greater than the control mortalities: 18% for An. arabiensis, 7% for Cx. quinquefasciatus (p<0.05. Mortality rates with ATSB were comparable to those with long lasting insecticidal nets previously tested against the same species in this area. CONCLUSIONS: Indoor ATSB shows promise as a supplement to mosquito nets for controlling mosquitoes. Indoor ATSB constitute a novel application method for insecticide classes that act as stomach poisons and have not hitherto been exploited for mosquito control. Combined with LLIN, indoor

  5. Mathematical evaluation of community level impact of combining bed nets and indoor residual spraying upon malaria transmission in areas where the main vectors are Anopheles arabiensis mosquitoes

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    Okumu Fredros O

    2013-01-01

    Full Text Available Abstract Background Indoor residual insecticide spraying (IRS and long-lasting insecticide treated nets (LLINs are commonly used together even though evidence that such combinations confer greater protection against malaria than either method alone is inconsistent. Methods A deterministic model of mosquito life cycle processes was adapted to allow parameterization with results from experimental hut trials of various combinations of untreated nets or LLINs (Olyset®, PermaNet 2.0®, Icon Life® nets with IRS (pirimiphos methyl, lambda cyhalothrin, DDT, in a setting where vector populations are dominated by Anopheles arabiensis, so that community level impact upon malaria transmission at high coverage could be predicted. Results Intact untreated nets alone provide equivalent personal protection to all three LLINs. Relative to IRS plus untreated nets, community level protection is slightly higher when Olyset® or PermaNet 2.0® nets are added onto IRS with pirimiphos methyl or lambda cyhalothrin but not DDT, and when Icon Life® nets supplement any of the IRS insecticides. Adding IRS onto any net modestly enhances communal protection when pirimiphos methyl is sprayed, while spraying lambda cyhalothrin enhances protection for untreated nets but not LLINs. Addition of DDT reduces communal protection when added to LLINs. Conclusions Where transmission is mediated primarily by An. arabiensis, adding IRS to high LLIN coverage provides only modest incremental benefit (e.g. when an organophosphate like pirimiphos methyl is used, but can be redundant (e.g. when a pyrethroid like lambda cyhalothin is used or even regressive (e.g. when DDT is used for the IRS. Relative to IRS plus untreated nets, supplementing IRS with LLINs will only modestly improve community protection. Beyond the physical protection that intact nets provide, additional protection against transmission by An. arabiensis conferred by insecticides will be remarkably small, regardless of

  6. An exploratory study of treated-bed nets in Timor-Leste: patterns of intended and alternative usage

    Directory of Open Access Journals (Sweden)

    Wilder-Smith Annelies

    2011-07-01

    Full Text Available Abstract Background The Timor-Leste Ministry of Health has recently finalized the National Malaria Control Strategy for 2010-2020. A key component of this roadmap is to provide universal national coverage with long-lasting insecticide-treated nets (LLINs in support of achieving the primary goal of reducing both morbidity and mortality from malaria by 30% in the first three years, followed by a further reduction of 20% by end of the programme cycle in 2020 1. The strategic plan calls for this target to be supported by a comprehensive information, education and communication (IEC programme; however, there is limited prior research into household and personal usage patterns to assist in the creation of targeted, effective, and socio-culturally specific behaviour change materials. Methods Nine separate focus group discussions (FGDs were carried out in Dili, Manatuto, and Covalima districts, Democratic Republic of Timor-Leste, in July 2010. These focus groups primarily explored themes of perceived malaria risk, causes of malaria, net usage patterns within families, barriers to correct and consistent usage, and the daily experience of users (both male and female in households with at least one net. Comprehensive qualitative analysis utilized open source analysis software. Results The primary determinants of net usage were a widespread perception that nets could or should only be used by pregnant women and young children, and the availability of sufficient sleeping space under a limited number of nets within households. Both nuisance biting and disease prevention were commonly cited as primary motivations for usage, while seasonality was not a significant factor. Long-term net durability and ease of hanging were seen as key attributes in net design preference. Very frequent washing cycles were common, potentially degrading net effectiveness. Finally, extensive re-purposing of nets (fishing, protecting crops was both reported and observed, and may

  7. The cytochrome P450 CYP6P4 is responsible for the high pyrethroid resistance in knockdown resistance-free Anopheles arabiensis.

    Science.gov (United States)

    Ibrahim, Sulaiman S; Riveron, Jacob M; Stott, Robert; Irving, Helen; Wondji, Charles S

    2016-01-01

    Pyrethroid insecticides are the front line vector control tools used in bed nets to reduce malaria transmission and its burden. However, resistance in major vectors such as Anopheles arabiensis is posing a serious challenge to the success of malaria control. Herein, we elucidated the molecular and biochemical basis of pyrethroid resistance in a knockdown resistance-free Anopheles arabiensis population from Chad, Central Africa. Using heterologous expression of P450s in Escherichia coli coupled with metabolism assays we established that the over-expressed P450 CYP6P4, located in the major pyrethroid resistance (rp1) quantitative trait locus (QTL), is responsible for resistance to Type I and Type II pyrethroid insecticides, with the exception of deltamethrin, in correlation with field resistance profile. However, CYP6P4 exhibited no metabolic activity towards non-pyrethroid insecticides, including DDT, bendiocarb, propoxur and malathion. Combining fluorescent probes inhibition assays with molecular docking simulation, we established that CYP6P4 can bind deltamethrin but cannot metabolise it. This is possibly due to steric hindrance because of the large vdW radius of bromine atoms of the dihalovinyl group of deltamethrin which docks into the heme catalytic centre. The establishment of CYP6P4 as a partial pyrethroid resistance gene explained the observed field resistance to permethrin, and its inability to metabolise deltamethrin probably explained the high mortality from deltamethrin exposure in the field populations of this Sudano-Sahelian An. arabiensis. These findings describe the heterogeneity in resistance towards insecticides, even from the same class, highlighting the need to thoroughly understand the molecular basis of resistance before implementing resistance management/control tools. Copyright © 2015 The Authors. Published by Elsevier Ltd.. All rights reserved.

  8. Field Study of the Comparative Efficacy of Three Pyrethroid/Neonicotinoid Mixture Products for the Control of the Common Bed Bug, Cimex lectularius

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    Changlu Wang

    2015-03-01

    Full Text Available Three insecticide mixtures that contain two classes of insecticides (pyrethroid and neonicotinoid were recently developed to control bed bugs. We evaluated three integrated bed bug management strategies in apartments, each using the same non-chemical control methods and one of the three insecticide mixture products: Tandem (lambda-cyhalothrin + thiamethoxam, Temprid SC (beta-cyfluthrin + imidacloprid, and Transport Mikron (bifenthrin + acetamiprid. No insecticides were applied in the Control apartments. In all apartments, we installed vinyl mattress encasements (if not already present and applied steam to beds and other infested upholstered furniture. Insecticide sprays were applied in the three treatments. Each treatment and the Control included 8–10 occupied apartments. Re-treatment was conducted during biweekly inspections if necessary. After eight weeks, the mean (± SEM bed bug count reduction in the Tandem, Temprid SC, Transport Mikron, and Control was 89 ± 9, 87 ± 6, 98 ± 1, and 23 ± 54%, respectively. Only Tandem and Transport Mikron treatments resulted in significantly higher population reduction than the Control at eight weeks. There were no significant differences in mean percent reduction among the three treatments (Tandem, Temprid SC, Transport Mikron at eight weeks. Tandem spray caused significantly faster bed bug reduction than Temprid SC spray and Transport Mikron spray.

  9. Mixture for Controlling Insecticide-Resistant Malaria Vectors

    OpenAIRE

    Pennetier, Cédric; Costantini, Carlo; Corbel, Vincent; Licciardi, Séverine; Dabire, R. K.; Lapied, B.; Chandre, Fabrice; Hougard, Jean-Marc

    2008-01-01

    The spread of resistance to pyrethroids in the major Afrotropical malaria vectors Anopheles gambiae s.s. necessitates the development of new strategies to control resistant mosquito populations. To test the efficacy of nets treated with repellent and insecticide against susceptible and insecticide-resistant An. gambiae mosquito populations, we impregnated mosquito bed nets with an insect repellent mixed with a low dose of organophosphorous insecticide and tested them in a rice-growing area ne...

  10. Environmental modeling and exposure assessment of sediment-associated pyrethroids in an agricultural watershed.

    Directory of Open Access Journals (Sweden)

    Yuzhou Luo

    Full Text Available Synthetic pyrethroid insecticides have generated public concerns due to their increasing use and potential effects on aquatic ecosystems. A modeling system was developed in this study for simulating the transport processes and associated sediment toxicity of pyrethroids at coupled field/watershed scales. The model was tested in the Orestimba Creek watershed, an agriculturally intensive area in California' Central Valley. Model predictions were satisfactory when compared with measured suspended solid concentration (R(2 = 0.536, pyrethroid toxic unit (0.576, and cumulative mortality of Hyalella azteca (0.570. The results indicated that sediment toxicity in the study area was strongly related to the concentration of pyrethroids in bed sediment. Bifenthrin was identified as the dominant contributor to the sediment toxicity in recent years, accounting for 50-85% of predicted toxicity units. In addition, more than 90% of the variation on the annual maximum toxic unit of pyrethroids was attributed to precipitation and prior application of bifenthrin in the late irrigation season. As one of the first studies simulating the dynamics and spatial variability of pyrethroids in fields and instreams, the modeling results provided useful information on new policies to be considered with respect to pyrethroid regulation. This study suggested two potential measures to efficiently reduce sediment toxicity by pyrethroids in the study area: [1] limiting bifenthrin use immediately before rainfall season; and [2] implementing conservation practices to retain soil on cropland.

  11. Low Utilization of Insecticide-Treated Bed Net among Pregnant Women in the Middle Belt of Ghana

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    Grace Manu

    2017-01-01

    Full Text Available Background. Malaria in pregnancy leads to low birth weight, premature birth, anaemia, and maternal and neonatal mortality. Use of insecticide-treated nets (ITNs during pregnancy is one of the proven interventions to reduce the malaria burden. However, Ghana has not achieved its target for ITN use among pregnant women. Methods. A qualitative study was conducted in seven communities purposively selected from the middle belt of Ghana. Participants who had delivered in the six months prior to this study were selected. In all, seven focus group discussions and twenty-four in-depth interviews were conducted between June and August 2010. Results. Respondents knew of the importance of ITNs and other malaria-preventive strategies. Factors such as financial access and missed opportunities of free distribution denied some pregnant women the opportunity to own or use an ITN. Reasons for not using ITNs during pregnancy included discomfort resulting from heat, smell of the net, and difficulty in hanging the net. Participants maintained their ITNs by preventing holes in the nets, retreatment, and infrequent washing. Conclusion. Pregnant women know about the causes and prevention of malaria. However, this knowledge is not transformed into practice due to lack of access to ITNs and sleeping discomforts among other logistical constraints.

  12. Targeted application of an organophosphate-based paint applied on windows and doors against Anopheles coluzzii resistant to pyrethroids under real life conditions in Vallée du Kou, Burkina Faso (West Africa).

    Science.gov (United States)

    Poda, Serge B; Soma, Dieudonné D; Hien, Aristide; Namountougou, Moussa; Gnankiné, Olivier; Diabaté, Abdoulaye; Fournet, Florence; Baldet, Thierry; Mas-Coma, Santiago; Mosqueira, Beatriz; Dabiré, Roch K

    2018-04-02

    A novel strategy applying an organophosphate-based insecticide paint on doors and windows in combination with long-lasting insecticide-treated nets (LLINs) was tested for the control of pyrethroid-resistant malaria vectors in a village setting in Vallée du Kou, a rice-growing area west of Burkina Faso. Insecticide Paint Inesfly 5A IGR™, comprised of two organophosphates and an insect growth regulator, was applied to doors and windows and tested in combination with pyrethroid-treated LLINs. The killing effect was monitored for 5 months by early morning collections of anophelines and other culicids. The residual efficacy was evaluated monthly by WHO bioassays using Anopheles gambiae 'Kisumu' and local populations of Anopheles coluzzii resistant to pyrethroids. The spatial mortality efficacy (SME) at distances of 1 m was also assessed against pyrethroid-susceptible and -resistant malaria vectors. The frequency of L1014F kdr and Ace-1 R G119S mutations was, respectively, reported throughout the study. The Insecticide Paint Inesfly 5A IGR had been tested in past studies yielding a long-term mortality rate of 80% over 12 months against An. coluzzii, the local pyrethroid-resistant malaria vector. The purpose of the present study is to test if treating smaller, targeted surfaces (e.g. doors and windows) was also efficient in killing malaria vectors. Treating windows and doors alone yielded a killing efficacy of 100% for 1 month against An. coluzzii resistant to pyrethroids, but efficacy reduced quickly afterwards. Likewise, WHO cone bioassays yielded mortalities of 80-100% for 2 months but declined to 90 and 40% 2 and 3 months after treatment, respectively. Mosquitoes exposed to insecticide paint-treated surfaces at distances of 1 m, yielded mortality rates of about 90-80% against local pyrethroids-resistant An. coluzzii during the first 2 months, but decreased to 30% afterwards. Anopheles coluzzii was reported to be exclusively the local malaria vector and

  13. Insecticidal and sterilizing effect of Olyset Duo (R), a permethrin and pyriproxyfen mixture net against pyrethroid-susceptible and -resistant strains of Anopheles gambiae s.s. : a release-recapture assay in experimental huts

    OpenAIRE

    Djènontin, A.; Alou, L. P. A.; Koffi, A.; Zogo, B.; Duarte, E.; N'Guessan, R.; Moiroux, Nicolas; Pennetier, Cédric

    2015-01-01

    In the context of the widespread distribution of pyrethroid resistance among malaria vectors, we did a release-recapture trial in experimental huts to investigate the insecticidal and sterilizing effects of a novel long-lasting net (LN), Olyset (R) Duo, incorporating a mixture of permethrin (PER) and the insect growth regulator (IGR), pyriproxyfen (PPF). An LN containing PPF alone and a classic Olyset (R) Net were tested in parallel as positive controls. The effect of progressive number of ho...

  14. The effect of deltamethrin-treated net fencing around cattle enclosures on outdoor-biting mosquitoes in Kumasi, Ghana.

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    Marta Ferreira Maia

    Full Text Available Classic vector control strategies target mosquitoes indoors as the main transmitters of malaria are indoor-biting and -resting mosquitoes. However, the intensive use of insecticide-treated bed-nets (ITNs and indoor residual spraying have put selective pressure on mosquitoes to adapt in order to obtain human blood meals. Thus, early-evening and outdoor vector activity is becoming an increasing concern. This study assessed the effect of a deltamethrin-treated net (100 mg/m(2 attached to a one-meter high fence around outdoor cattle enclosures on the number of mosquitoes landing on humans. Mosquitoes were collected from four cattle enclosures: Pen A - with cattle and no net; B - with cattle and protected by an untreated net; C - with cattle and protected by a deltamethrin-treated net; D - no cattle and no net. A total of 3217 culicines and 1017 anophelines were collected, of which 388 were Anopheles gambiae and 629 An. ziemanni. In the absence of cattle nearly 3 times more An. gambiae (p<0.0001 landed on humans. The deltamethrin-treated net significantly reduced (nearly three-fold, p<0.0001 culicine landings inside enclosures. The sporozoite rate of the zoophilic An. ziemanni, known to be a secondary malaria vector, was as high as that of the most competent vector An. gambiae; raising the potential of zoophilic species as secondary malaria vectors. After deployment of the ITNs a deltamethrin persistence of 9 months was observed despite exposure to African weather conditions. The outdoor use of ITNs resulted in a significant reduction of host-seeking culicines inside enclosures. Further studies investigating the effectiveness and spatial repellence of ITNs around other outdoor sites, such as bars and cooking areas, as well as their direct effect on vector-borne disease transmission are needed to evaluate its potential as an appropriate outdoor vector control tool for rural Africa.

  15. Health impact and cost-effectiveness of a private sector bed net distribution: experimental evidence from Zambia.

    Science.gov (United States)

    Sedlmayr, Richard; Fink, Günther; Miller, John M; Earle, Duncan; Steketee, Richard W

    2013-03-18

    Relatively few programmes have attempted to actively engage the private sector in national malaria control efforts. This paper evaluates the health impact of a large-scale distribution of insecticide-treated nets (ITNs) conducted in partnership with a Zambian agribusiness, and its cost-effectiveness from the perspective of the National Malaria Control Programme (NMCP). The study was designed as a cluster-randomized controlled trial. A list of 81,597 cotton farmers was obtained from Dunavant, a contract farming company in Zambia's cotton sector, in December 2010. 39,963 (49%) were randomly selected to obtain one ITN each. Follow-up interviews were conducted with 438 farmers in the treatment and 458 farmers in the control group in June and July 2011. Treatment and control households were compared with respect to bed net ownership, bed net usage, self-reported fever, and self-reported confirmed malaria. Cost data was collected throughout the programme. The distribution effectively reached target beneficiaries, with approximately 95% of households in the treatment group reporting that they had received an ITN through the programme. The average increase in the fraction of household members sleeping under an ITN the night prior to the interview was 14.6 percentage points (p-value US$ per ITN to Zambia's NMCP. The results illustrate that existing private sector networks can efficiently control malaria in remote rural regions. The intra-household allocation of ITNs distributed through this channel was comparable to that of ITNs received from other sources, and the health impact remained substantial.

  16. Insecticidal and sterilizing effect of Olyset Duo®, a permethrin and pyriproxyfen mixture net against pyrethroid-susceptible and -resistant strains of Anopheles gambiae s.s.: a release-recapture assay in experimental huts

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    Djènontin Armel

    2015-01-01

    Full Text Available In the context of the widespread distribution of pyrethroid resistance among malaria vectors, we did a release-recapture trial in experimental huts to investigate the insecticidal and sterilizing effects of a novel long-lasting net (LN, Olyset® Duo, incorporating a mixture of permethrin (PER and the insect growth regulator (IGR, pyri-proxyfen (PPF. An LN containing PPF alone and a classic Olyset® Net were tested in parallel as positive controls. The effect of progressive number of holes (6, 30, or 150 that may accrue in nets over time was simulated. We used two laboratory Anopheles gambiae s.s. strains: the susceptible Kisumu strain and the pyrethroid-resistant VK-Per strain having solely kdr as resistance mechanism. The effect of these nets on the reproductive success of blood-fed females that survived the different LNs conditions was recorded. Regardless of the mosquito strain, the LNs containing PPF alone with as many as 30 holes drastically reduced the number of eggs laid by females succeeding in feeding, i.e. fecundity by 98% and egg hatching rate (fertility by 93% relative to untreated control net. Very few of the resistant females blood fed and survived under the Olyset® Duo with similar number of holes (up to 30 but of these few, the inhibition of reproductive success was 100%. There was no evidence that the Olyset® Duo LN with 150 holes impacted fecundity or fertility of the resistant colony. The efficacy of Olyset® Duo is encouraging and clearly illustrates that this new net might be a promising tool for malaria transmission control and resistance management.

  17. Insecticidal and sterilizing effect of Olyset Duo®, a permethrin and pyriproxyfen mixture net against pyrethroid-susceptible and -resistant strains of Anopheles gambiae s.s.: a release-recapture assay in experimental huts.

    Science.gov (United States)

    Djènontin, Armel; Ahoua Alou, Ludovic P; Koffi, Alphonsine; Zogo, Barnabas; Duarte, Elves; N'Guessan, Raphael; Moiroux, Nicolas; Pennetier, Cédric

    2015-01-01

    In the context of the widespread distribution of pyrethroid resistance among malaria vectors, we did a release-recapture trial in experimental huts to investigate the insecticidal and sterilizing effects of a novel long-lasting net (LN), Olyset® Duo, incorporating a mixture of permethrin (PER) and the insect growth regulator (IGR), pyri-proxyfen (PPF). An LN containing PPF alone and a classic Olyset® Net were tested in parallel as positive controls. The effect of progressive number of holes (6, 30, or 150) that may accrue in nets over time was simulated. We used two laboratory Anopheles gambiae s.s. strains: the susceptible Kisumu strain and the pyrethroid-resistant VK-Per strain having solely kdr as resistance mechanism. The effect of these nets on the reproductive success of blood-fed females that survived the different LNs conditions was recorded. Regardless of the mosquito strain, the LNs containing PPF alone with as many as 30 holes drastically reduced the number of eggs laid by females succeeding in feeding, i.e. fecundity by 98% and egg hatching rate (fertility) by 93% relative to untreated control net. Very few of the resistant females blood fed and survived under the Olyset® Duo with similar number of holes (up to 30) but of these few, the inhibition of reproductive success was 100%. There was no evidence that the Olyset® Duo LN with 150 holes impacted fecundity or fertility of the resistant colony. The efficacy of Olyset® Duo is encouraging and clearly illustrates that this new net might be a promising tool for malaria transmission control and resistance management. © A. Djènontin et al., published by EDP Sciences, 2015.

  18. Perceptions on the effect of small electric fans on comfort inside bed nets in southern Ghana: a qualitative study.

    Science.gov (United States)

    Jaeger, Mulako S; Briët, Olivier J T; Keating, Joseph; Ahorlu, Collins K; Yukich, Joshua O; Oppong, Samuel; Nardini, Peter; Pfeiffer, Constanze

    2016-12-01

    Long-lasting insecticidal nets (LLINs) are known to be highly effective in reducing malaria transmission, morbidity and mortality. However, among those owning an LLIN, use rates are often suboptimal. A reported barrier to bed net use is discomfort due to heat. This qualitative study was part of a larger evaluation conducted in communities without electricity in rural Ghana to assess whether 0.8 W solar powered net fans can increase net use. Twenty-three key informant interviews with household heads in the study communities in Shai-Osudoku District, southern Ghana, were conducted from July to August 2015. The purpose of the interviews was to obtain insight into perceptions of participants about the net fan system in relation to LLIN use. While all study participants reported using LLINs, with mosquito nuisance prevention as the prime motivation, heat was also mentioned as a key barrier to net use. Respondents appreciated the net fans because they improved comfort inside bed nets. The LED light on the fan stand became the main source of light at night and positively influenced the perception of the intervention as a whole. The general acceptance of the net fan system by the study participants highlights the potential of the intervention to improve comfort inside mosquito nets. This, therefore, has a potential to increase bed net use in areas with low access to electricity.

  19. Video studies of passage by Anopheles gambiae mosquitoes through holes in a simulated bed net: effects of hole size, hole orientation and net environment.

    Science.gov (United States)

    Sutcliffe, James; Colborn, Kathryn L

    2015-05-13

    Holes in netting provide potential routes for mosquitoes to enter ITNs. Despite this, there is little information on how mosquitoes respond to holes in bed nets and how their responses are affected by hole size, shape and orientation or by ambient conditions around the net. Female Anopheles gambiae (G3) were recorded in a simulated bed net consisting of two sizes of untreated netting-covered behavioural arenas placed above and beside (to simulate the bed net roof and sides respectively) the experimenter who was a source of host cues from 'inside' the net. A round hole of 9 mm or 13 mm diameter was cut into the centre of the netting of each arena. Videos of unfed female mosquitoes in arenas were analysed for time spent flying, walking and standing still and for exit through the hole. The effects of the experimenter on temperature and relative humidity around the simulated net were also measured. Mosquitoes were significantly more active in overhead arenas than in arenas to the side. Hole passage was significantly more likely in smaller arenas than larger ones and for larger holes than smaller ones. In arenas to the side, hole passage rate through small holes was about 50% less likely than what could be explained by area alone. Passage rate through holes in overhead arenas was consistent with hole area. Temperature in arenas did not strongly reflect the experimenter's presence in the simulated net. Relative humidity and absolute humidity in overhead arenas, but not in arenas to the side, were immediately affected by experimenter presence. Higher levels of activity in overhead arenas than in arenas to the side were likely due to the rising heat and humidity plume from the experimenter. Lower than expected passage rates through smaller vertically oriented holes may have been be due to an edge effect that does not apply to horizontally oriented holes. Results suggest that current methods of assessing the importance of physical damage to ITNs may not accurately reflect

  20. Low Utilization of Insecticide-Treated Bed Net among Pregnant Women in the Middle Belt of Ghana

    OpenAIRE

    Grace Manu; Ellen Abrafi Boamah-Kaali; Lawrence Gyabaa Febir; Emmanuel Ayipah; Seth Owusu-Agyei; Kwaku Poku Asante

    2017-01-01

    Background. Malaria in pregnancy leads to low birth weight, premature birth, anaemia, and maternal and neonatal mortality. Use of insecticide-treated nets (ITNs) during pregnancy is one of the proven interventions to reduce the malaria burden. However, Ghana has not achieved its target for ITN use among pregnant women. Methods. A qualitative study was conducted in seven communities purposively selected from the middle belt of Ghana. Participants who had delivered in the six months prior to th...

  1. Essential oils as fumigants for bed bugs (Hemiptera: Cimicidae)

    Science.gov (United States)

    In Petri dish assays, fumigation of a pyrethroid-susceptible strain of bed bugs Cimex lectularius L. (Hemiptera: Cimicidae) with various essential oils resulted in mortality that approached or equaled 100%, after 5 days. However, when bed bugs were exposed to the same essential oils in sealed, comme...

  2. Rapid selection of a pyrethroid metabolic enzyme CYP9K1 by operational malaria control activities.

    Science.gov (United States)

    Vontas, John; Grigoraki, Linda; Morgan, John; Tsakireli, Dimitra; Fuseini, Godwin; Segura, Luis; Niemczura de Carvalho, Julie; Nguema, Raul; Weetman, David; Slotman, Michel A; Hemingway, Janet

    2018-05-01

    Since 2004, indoor residual spraying (IRS) and long-lasting insecticide-impregnated bednets (LLINs) have reduced the malaria parasite prevalence in children on Bioko Island, Equatorial Guinea, from 45% to 12%. After target site-based (knockdown resistance; kdr ) pyrethroid resistance was detected in 2004 in Anopheles coluzzii (formerly known as the M form of the Anopheles gambiae complex), the carbamate bendiocarb was introduced. Subsequent analysis showed that kdr alone was not operationally significant, so pyrethroid-based IRS was successfully reintroduced in 2012. In 2007 and 2014-2015, mass distribution of new pyrethroid LLINs was undertaken to increase the net coverage levels. The combined selection pressure of IRS and LLINs resulted in an increase in the frequency of pyrethroid resistance in 2015. In addition to a significant increase in kd r frequency, an additional metabolic pyrethroid resistance mechanism had been selected. Increased metabolism of the pyrethroid deltamethrin was linked with up-regulation of the cytochrome P450 CYP9K1. The increase in resistance prompted a reversion to bendiocarb IRS in 2016 to avoid a resurgence of malaria, in line with the national Malaria Control Program plan. Copyright © 2018 the Author(s). Published by PNAS.

  3. Neurobehavioral toxicology of pyrethroid insecticides

    International Nuclear Information System (INIS)

    Crofton, K.M.

    1986-01-01

    Pyrethroid insecticides are classified as either Type I or Type II based upon in vivo toxic signs, and neurophysiological and biochemical data. Both axonal sodium channels and the γ-aminobutyric acid (GABA) receptor complex have been proposed as the major site of action of the Type II pyrethroids. This investigation characterized the behavior and biochemical effects of low dosages of pyrethroids in rats. Type I and II pyrethroids were tested for effects on figure-eight maze activity and the acoustic startle response (ASR). All compounds decreased figure-eight maze activity. Interactions of Type I and II pyrethroids with the three major binding sites on the GABA complex were determined in vivo. Radioligand binding experiments assessed in vitro interactions of pyrethroids with the three major GABA-complex binding sites. None of the pyrethroids competed for [ 3 H]-muscimol or [ 3 H]-flunitrazepam binding. Only Type II pyrethroids inhibited binding of [ 35 S]-t-butylbicyclophosphorothionate (TBPS) in cortical synaptosome preparations with K/sub i/ values of 5 to 10 μM. The [ 35 S]-TBPS data implicate the TBPS/picrotoxinin binding site in the mechanism of Type II pyrethroid toxicity. The results of these experiments support the classification of pyrethroids into two classes, and demonstrate the utility of the figure-eight maze and the ASR in studies to elucidate neurotoxic mechanisms. The interaction of the Type II pyrethroids is probably restricted to the TBPS/picrotoxinin binding domain on the GABA complex as shown by both the in vivo and in vitro studies

  4. Environmentally relevant pyrethroid mixtures: A study on the correlation of blood and brain concentrations of a mixture of pyrethroid insecticides to motor activity in the rat.

    Science.gov (United States)

    Hughes, Michael F; Ross, David G; Starr, James M; Scollon, Edward J; Wolansky, Marcelo J; Crofton, Kevin M; DeVito, Michael J

    2016-06-01

    Human exposure to multiple pyrethroid insecticides may occur because of their broad use on crops and for residential pest control. To address the potential health risk from co-exposure to pyrethroids, it is important to understand their disposition and toxicity in target organs such as the brain, and surrogates such as the blood when administered as a mixture. The objective of this study was to assess the correlation between blood and brain concentrations of pyrethroids and neurobehavioral effects in the rat following an acute oral administration of the pyrethroids as a mixture. Male Long-Evans rats were administered a mixture of β-cyfluthrin, cypermethrin, deltamethrin, esfenvalerate and cis- and trans-permethrin in corn oil at seven dose levels. The pyrethroid with the highest percentage in the dosing solution was trans-permethrin (31% of total mixture dose) while deltamethrin and esfenvalerate had the lowest percentage (3%). Motor activity of the rats was then monitored for 1h. At 3.5h post-dosing, the animals were euthanized and blood and brain were collected. These tissues were extracted and analyzed for parent pyrethroid using HPLC-tandem mass spectrometry. Cypermethrin and cis-permethrin were the predominate pyrethroids detected in blood and brain, respectively, at all dosage levels. The relationship of total pyrethroid concentration between blood and brain was linear (r=0.93). The pyrethroids with the lowest fraction in blood were trans-permethrin and β-cyfluthrin and in brain were deltamethrin and esfenvalerate. The relationship between motor activity of the treated rats and summed pyrethroid blood and brain concentration was described using a sigmoidal Emax model with the Effective Concentration50 being more sensitive for brain than blood. The data suggests summed pyrethroid rat blood concentration could be used as a surrogate for brain concentration as an aid to study the neurotoxic effects of pyrethroids administered as a mixture under the conditions

  5. Gender and willingness to pay for insecticides treated bed nets in a poor rural area in Tanzania.

    Science.gov (United States)

    Mujinja, P G M; Makwaya, C K; Sauerborn, R

    2004-12-01

    To examine socio-economic and malaria related differences between males and females that may cause gender differences in willingness to pay (WTP) for insecticide treated bed nets in a poor rural area. A two-week-interval (test re-test) cross-sectional study. Kisarawe District in coastal Tanzania. Two hundred and fifty one males and two hundred dollars females were interviewed. Females had about 50% of the males' income. The monthly average income was about US dollars 10.50 for females and US dollars 20.20 for males. The proportion of respondents willing to pay for an ITN, for both males and females, declined as the ITN prices increased (Pdifference between men and women, between both rounds were not statistically significant (p>0.05). Male respondents reported a higher mean number of own underfives living in the household compared to women, the difference was not statistically significant (P>0.8). Willingness to pay for ITN was found to be independent of having an under five child with recent history of malaria. Among both males and females, there was an association between a recent experience with malaria episode and WTP, p=0.05 and p=0.02 respectively. Among females, the proportion of those willing to pay for another person, at the lowest ITN price, was significantly higher in those with under five children in their households than in those with no underfives. This was not the case among the male respondents as the association was not statistically significant. Contrary to expectations were was no statistically significant difference in WTP for an ITN between females and males. Further studies that link willingness and ability to pay are required in rural poor population, such studies may be valuable inputs to government policy on and planning of ITN interventions in the public and private sector.

  6. Markets, voucher subsidies and free nets combine to achieve high bed net coverage in rural Tanzania

    Directory of Open Access Journals (Sweden)

    Gerrets Rene PM

    2008-06-01

    Full Text Available Abstract Background Tanzania has a well-developed network of commercial ITN retailers. In 2004, the government introduced a voucher subsidy for pregnant women and, in mid 2005, helped distribute free nets to under-fives in small number of districts, including Rufiji on the southern coast, during a child health campaign. Contributions of these multiple insecticide-treated net delivery strategies existing at the same time and place to coverage in a poor rural community were assessed. Methods Cross-sectional household survey in 6,331 members of randomly selected 1,752 households of 31 rural villages of Demographic Surveillance System in Rufiji district, Southern Tanzania was conducted in 2006. A questionnaire was administered to every consenting respondent about net use, treatment status and delivery mechanism. Findings Net use was 62.7% overall, 87.2% amongst infants (0 to1 year, 81.8% amongst young children (>1 to 5 years, 54.5% amongst older children (6 to 15 years and 59.6% amongst adults (>15 years. 30.2% of all nets had been treated six months prior to interview. The biggest source of nets used by infants was purchase from the private sector with a voucher subsidy (41.8%. Half of nets used by young children (50.0% and over a third of those used by older children (37.2% were obtained free of charge through the vaccination campaign. The largest source of nets amongst the population overall was commercial purchase (45.1% use and was the primary means for protecting adults (60.2% use. All delivery mechanisms, especially sale of nets at full market price, under-served the poorest but no difference in equity was observed between voucher-subsidized and freely distributed nets. Conclusion All three delivery strategies enabled a poor rural community to achieve net coverage high enough to yield both personal and community level protection for the entire population. Each of them reached their relevant target group and free nets only temporarily

  7. Population preference of net texture prior to bed net trial in Kala-Azar-endemic areas.

    Directory of Open Access Journals (Sweden)

    Murari L Das

    Full Text Available Prior to a community-based efficacy trial of long-lasting insecticidal nets (LLINs in the prevention of visceral leishmaniasis (VL; also called kala-azar, a pilot study on preference of tools was held in endemic areas of India and Nepal in September 2005.LLINs made of polyester and polyethylene were distributed to 60 participants, who used the nets sequentially for 7 d. Acceptability and preference were evaluated via indirect indicators through questionnaires at three defined time points before and after use of the LLINs and through focus group discussions (FGDs. In the latter, preferences for color and size were also assessed. Untreated bed nets were owned by 87% of the households prior to the study. All users liked textures of both LLIN types after 7 d of use, but had a slight preference for those made of polyester if they were to recommend a LLIN to relatives or friends (p<0.05, mainly because of their relatively greater softness in comparison to polyethylene LLINs. Users reported that both net types reduced mosquito bites and number of insects, including sand fly (bhusana; genus Phlebotomus, inside the house. Side effects were minor and disappeared quickly.The large-scale intervention trial considered the preferences of the study population to decide on the best tool of intervention--light-blue, rectangular, polyester LLINs of different sizes.

  8. "Tazomoka Is Not a Problem". Local Perspectives on Malaria, Fever Case Management and Bed Net Use in Madagascar.

    Science.gov (United States)

    Mattern, Chiarella; Pourette, Dolorès; Raboanary, Emma; Kesteman, Thomas; Piola, Patrice; Randrianarivelojosia, Milijaona; Rogier, Christophe

    2016-01-01

    Although its incidence has been decreasing during the last decade, malaria is still a major public health issue in Madagascar. The use of Long Lasting Insecticidal Nets (LLIN) remains a key malaria control intervention strategy in Madagascar, however, it encounters some obstacles. The present study aimed to explore the local terminology related to malaria, information channels about malaria, attitude towards bed nets, and health care seeking practices in case of fever. This article presents novel qualitative findings about malaria. Until now, no such data has been published for Madagascar. A comparative qualitative study was carried out at four sites in Madagascar, each differing by malaria epidemiology and socio-cultural background of the populations. Seventy-one semi-structured interviews were conducted with biomedical and traditional caregivers, and members of the local population. In addition, observations of the living conditions and the uses of bed net were conducted. Due to the differences between local and biomedical perspectives on malaria, official messages did not have the expected impact on population in terms of prevention and care seeking behaviors. Rather, most information retained about malaria was spread through informal information circulation channels. Most interviewees perceived malaria as a disease that is simple to treat. Tazomoka ("mosquito fever"), the Malagasy biomedical word for malaria, was not used by populations. Tazo ("fever") and tazomahery ("strong fever") were the terms more commonly used by members of the local population to refer to malaria related symptoms. According to local perceptions in all areas, tazo and tazomahery were not caused by mosquitos. Each of these symptoms required specific health recourse. The usual fever management strategies consisted of self-medication or recourse to traditional and biomedical caregivers. Usage of bed nets was intermittent and was not directly linked to protection against malaria in the eyes

  9. Control of pyrethroid-resistant Anopheles gambiae and Culex quinquefasciatus mosquitoes with chlorfenapyr in Benin

    NARCIS (Netherlands)

    N'Guessan, R.; Boko, P.; Odjo, A.; Knols, B.G.J.; Akogbeto, M.; Rowland, M.

    2009-01-01

    Objective To compare the efficacy of chlorfenapyr applied on mosquito nets and as an indoor residual spray against populations of Anopheles gambiae and Culex quinquefasciatus in an area of Benin that shows problematic levels of pyrethroid resistance. Method Eight-week trial conducted in experimental

  10. Effectiveness of insecticide-treated and untreated nets to prevent malaria in India.

    Science.gov (United States)

    Van Remoortel, Hans; De Buck, Emmy; Singhal, Maneesh; Vandekerckhove, Philippe; Agarwal, Satya P

    2015-08-01

    India is the most malaria-endemic country in South-East Asia, resulting in a high socio-economic burden. Insecticide-treated or untreated nets are effective interventions to prevent malaria. As part of an Indian first-aid guideline project, we aimed to investigate the magnitude of this effect in India. We searched MEDLINE, Embase and Central to systematically review Indian studies on the effectiveness of treated or untreated vs. no nets. Parasite prevalence and annual parasite incidence served as malaria outcomes. The overall effect was investigated by performing meta-analyses and calculating the pooled risk ratios (RR) and incidence rate ratios. Of 479 articles, we finally retained 16 Indian studies. Untreated nets decreased the risk of parasite prevalence compared to no nets [RR 0.69 (95% CI; 0.55, 0.87) in high-endemic areas, RR 0.49 (95% CI; 0.28, 0.84) in low-endemic areas], as was the case but more pronounced for treated nets [RR 0.35 (95% CI; 0.26, 0.47) in high-endemic areas, risk ratio 0.16 (95% CI; 0.06, 0.44) in low-endemic areas]. Incidence rate ratios showed a similar observation: a significantly reduced rate of parasites in the blood for untreated nets vs. no nets, which was more pronounced in low-endemic areas and for those who used treated nets. The average effect of treated nets (vs. no nets) on parasite prevalence was higher in Indian studies (RR 0.16-0.35) than in non-Indian studies (data derived from a Cochrane systematic review; RR 0.58-0.87). Both treated and untreated nets have a clear protective effect against malaria in the Indian context. This effect is more pronounced there than in other countries. © 2015 John Wiley & Sons Ltd.

  11. Enhanced protection against malaria by indoor residual spraying in addition to insecticide treated nets: is it dependent on transmission intensity or net usage?

    Directory of Open Access Journals (Sweden)

    Philippa A West

    Full Text Available Insecticide treated nets (ITNs and indoor residual spraying (IRS are effective vector control tools that protect against malaria. There is conflicting evidence regarding whether using ITNs and IRS in combination provides additional benefit over using either of these methods alone. This study investigated factors that may modify the effect of the combined use of IRS and ITNs compared to using ITNs alone on malaria infection prevalence.Secondary analysis was carried out on data from a cluster randomised trial in north-west Tanzania. 50 clusters received ITNs from a universal coverage campaign; of these 25 were randomly allocated to additionally receive two rounds of IRS in 2012. In cross-sectional household surveys children 0.5-14 years old were tested for Plasmodium falciparum infections (PfPR two, six and ten months after the first IRS round.IRS protected those sleeping under nets (OR = 0.38, 95%CI 0.26-0.57 and those who did not (OR = 0.43, 95%CI 0.29-0.63. The protective effect of IRS was not modified by community level ITN use (ITN use = 50%, OR = 0.46, 95%CI 0.28-0.74. The additional protection from IRS was similar in low (<10% PfPR, OR = 0.38, 95%CI 0.19-0.75 and high transmission areas (≥10% PfPR, OR = 0.34, 95%CI 0.18-0.67. ITN use was protective at the individual-level regardless of whether the village had been sprayed (OR = 0.83, 95%CI 0.70-0.98. Living in a sprayed village was protective regardless of whether the individual slept under an ITN last night (OR = 0.41, 95%CI 0.29-0.58.Implementing IRS in addition to ITNs was beneficial for individuals from villages with a wide range of transmission intensities and net utilisation levels. Net users received additional protection from IRS. ITNs were providing some individual protection, even in this area with high levels of pyrethroid insecticide resistance. These results demonstrate that there is a supplementary benefit of IRS even when ITNs are effective.ClinicalTrials.gov NCT01697852.

  12. Increasing prevalence of wildtypes in the dihydrofolate reductase gene of Plasmodium falciparum in an area with high levels of sulfadoxine/pyrimethamine resistance after introduction of treated bed nets

    DEFF Research Database (Denmark)

    Alifrangis, Michael; Lemnge, Martha M; Rønn, Anita M

    2003-01-01

    years old living in the villages from 1998 to 2000. In 2000, after two years of bed net use, the prevalence of wild types in codon 51, 59, and 108 of dhfr increased significantly in Magoda compared with previous years. Furthermore, the prevalence of dhfr wild types was significantly higher in Magoda...

  13. Effective utilization period of long-lasting insecticide treated nets ...

    African Journals Online (AJOL)

    The study was conducted to evaluate the bioefficacy of long-lasting insecticide treated nets (LLITNs) (PermaNet®2.0) over time and the species composition of Anopheles mosquitoes around Bahir Dar. The space spray collection method was used to determine the species composition of indoor resting Anopheles ...

  14. Mutations in the voltage-gated sodium channel gene of anophelines and their association with resistance to pyrethroids - a review.

    Science.gov (United States)

    Silva, Ana Paula B; Santos, Joselita Maria M; Martins, Ademir J

    2014-10-07

    infection in kdr individuals. Considering the limitation of insecticides available for employment in public health campaigns and the absence of a vaccine able to brake the life cycle of the malaria parasites, the use of pyrethroids is likely to remain as the main strategy against mosquitoes by either indoor residual spraying (IR) and insecticide treated nets (ITN). Therefore, monitoring insecticide resistance programs is a crucial need in malaria endemic countries.

  15. Fate of Pyrethroids in Farmland Ponds

    DEFF Research Database (Denmark)

    Mogensen, B. B.; Sørensen, P. B.; Stuer-Lauridsen, F.

    Pyrethroids constitute a group of widely used insecticides, which are toxic to aquatic organisms. This report presents the results from a 2-year study of the fate of pyrethroids in ponds, i.e. their distribution in the water column, the sediment and the surface microlayer respectively. The measur......Pyrethroids constitute a group of widely used insecticides, which are toxic to aquatic organisms. This report presents the results from a 2-year study of the fate of pyrethroids in ponds, i.e. their distribution in the water column, the sediment and the surface microlayer respectively...

  16. Control of Malaria Vector Mosquitoes by Insecticide-Treated Combinations of Window Screens and Eave Baffles.

    Science.gov (United States)

    Killeen, Gerry F; Masalu, John P; Chinula, Dingani; Fotakis, Emmanouil A; Kavishe, Deogratius R; Malone, David; Okumu, Fredros

    2017-05-01

    We assessed window screens and eave baffles (WSEBs), which enable mosquitoes to enter but not exit houses, as an alternative to indoor residual spraying (IRS) for malaria vector control. WSEBs treated with water, the pyrethroid lambda-cyhalothrin, or the organophosphate pirimiphos-methyl, with and without a binding agent for increasing insecticide persistence on netting, were compared with IRS in experimental huts. Compared with IRS containing the same insecticide, WSEBs killed similar proportions of Anopheles funestus mosquitoes that were resistant to pyrethroids, carbamates and organochlorines and greater proportions of pyrethroid-resistant, early exiting An. arabiensis mosquitoes. WSEBs with pirimiphos-methyl killed greater proportions of both vectors than lambda-cyhalothrin or lambda-cyhalothrin plus pirimiphos-methyl and were equally efficacious when combined with binding agent. WSEBs required far less insecticide than IRS, and binding agents might enhance durability. WSEBs might enable affordable deployment of insecticide combinations to mitigate against physiologic insecticide resistance and improve control of behaviorally resistant, early exiting vectors.

  17. The effectiveness of non-pyrethroid insecticide-treated durable wall lining to control malaria in rural Tanzania: study protocol for a two-armed cluster randomized trial

    Directory of Open Access Journals (Sweden)

    George Mtove

    2016-07-01

    Full Text Available Abstract Background Despite considerable reductions in malaria achieved by scaling-up long-lasting insecticidal nets (LLINs and indoor residual spraying (IRS, maintaining sustained community protection remains operationally challenging. Increasing insecticide resistance also threatens to jeopardize the future of both strategies. Non-pyrethroid insecticide­treated wall lining (ITWL may represent an alternate or complementary control method and a potential tool to manage insecticide resistance. To date no study has demonstrated whether ITWL can reduce malaria transmission nor provide additional protection beyond the current best practice of universal coverage (UC of LLINs and prompt case management. Methods/design A two-arm cluster randomized controlled trial will be conducted in rural Tanzania to assess whether non-pyrethroid ITWL and UC of LLINs provide added protection against malaria infection in children, compared to UC of LLINs alone. Stratified randomization based on malaria prevalence will be used to select 22 village clusters per arm. All 44 clusters will receive LLINs and half will also have ITWL installed on interior house walls. Study children, aged 6 months to 11 years old, will be enrolled from each cluster and followed monthly to estimate cumulative incidence of malaria parasitaemia (primary endpoint, time to first malaria episode and prevalence of anaemia before and after intervention. Entomological inoculation rate will be estimated using indoor CDC light traps and outdoor tent traps followed by detection of Anopheles gambiae species, sporozoite infection, insecticide resistance and blood meal source. ITWL bioefficacy and durability will be monitored using WHO cone bioassays and household surveys, respectively. Social and cultural factors influencing community and household ITWL acceptability will be explored through focus-group discussions and in-depth interviews. Cost-effectiveness, compared between study arms, will be

  18. Do Size and Insecticide Treatment Matter? Evaluation of Different Nets against Phlebotomus argentipes, the Vector of Visceral Leishmaniasis in Nepal.

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    Murari Lal Das

    Full Text Available In the Indian subcontinent, Leishmania donovani, the parasite causing visceral leishmaniasis (VL is transmitted by the sand fly vector Phlebotomus argentipes. Long lasting insecticide treated nets (LN have been postulated as alternative or complement to Indoor Residual Spraying but there are few field studies evaluating the entomological efficacy of different nets against this vector. We conducted two crossover trials in a VL endemic area in Nepal to compare the barrier effect of (1 LN with different mesh sizes (156 holes/inch2 vs 625 holes/inch2 and (2 alpha-cypermethrin treated LN and untreated nets having the same mesh size (156 holes/inch2. Each crossover trial had two arms consisting of a sequence of two different nets for 8 nights. We used 10 cattle sheds per trial. A cow placed under the net was used as bait. CDC light traps placed inside the nets were used to evaluate the number of P. argentipes crossing the net barrier. Negative binomial generalized estimating equation (GEE population-averaged models adjusted by night and sequence were used to estimate the barrier effect of the different nets. The crossover trials conducted in a rural village in Morang district (South-eastern Nepal demonstrated that reducing the size of the holes in treated nets (625 holes/inch2 increased the barrier effect of LN by 77% (95% confidence interval (CI: 56%-88% compared with treated nets with larger holes (156 holes/inch2. Treating nets with alpha-cypermethrin reduced the number of P. argentipes captured inside the nets by 77% (95% CI: 27%-93% compared with untreated nets. The effectiveness and acceptability of finer mesh pyrethroid treated LN should be tested for VL prevention in a randomized controlled trial.

  19. Africa's largest long-lasting insecticide-treated net producer: lessons from A to Z Textiles.

    Science.gov (United States)

    Masum, Hassan; Shah, Ronak; Schroeder, Karl; Daar, Abdallah S; Singer, Peter A

    2010-12-13

    Field trials have demonstrated the efficacy of insecticide-treated nets, and the WHO has recently endorsed a shift toward Long-Lasting Insecticide Treated nets (LLINs) due to factors such as reduced distribution costs. However, the need for LLINs poses several challenges. Is it possible to manufacture LLINs in large quantities in the African continent, where malaria is most endemic? When production is located in low-income countries, what role is played by local funding and employment, scaling up manufacturing, and partnerships? What factors influence availability and pricing? A case study of A to Z Textiles was undertaken to answer the question of how large-scale production of LLINs can occur in a low income setting. One of the largest sources of bed nets for Africa, A to Z Textiles is Africa-based, and its Tanzanian operations have a production capacity of 30 million LLINs per year, along with full WHO recommendation for its nets. Our analysis is based on semi-structured interviews with key informants familiar with A to Z, site visits in Tanzania, and literature reviews.This paper discusses the history and current status of A to Z Textiles, identifies the factors that led to its success, and suggests policy considerations that could support similar initiatives in the future. Local funding, scaling up manufacturing, technology transfer, and partnerships all played important roles in A to Z's ascent, as did perceived benefits of local employment and capacity-building. Regulatory issues and procurement rules acted as barriers. A to Z cost-effectively manufactures high-quality LLINs where malaria is most endemic. With a production capacity of 30 million LLINs per year, and full WHOPES (WHO Pesticide Evaluation Scheme) certification, A to Z Textiles demonstrates how key health goods can be successfully produced in the low-income countries that use them. Its example may be instructive and of high interest to readers in the malaria community, especially in developing

  20. Developmental neurotoxicity of pyrethroid insecticides in zebrafish embryos.

    Science.gov (United States)

    DeMicco, Amy; Cooper, Keith R; Richardson, Jason R; White, Lori A

    2010-01-01

    Pyrethroid insecticides are one of the most commonly used residential and agricultural insecticides. Based on the increased use of pyrethroids and recent studies showing that pregnant women and children are exposed to pyrethroids, there are concerns over the potential for developmental neurotoxicity. However, there have been relatively few studies on the developmental neurotoxicity of pyrethroids. In this study, we sought to investigate the developmental toxicity of six common pyrethroids, three type I compounds (permethrin, resmethrin, and bifenthrin) and three type II compounds (deltamethrin, cypermethrin, and lambda-cyhalothrin), and to determine whether zebrafish embryos may be an appropriate model for studying the developmental neurotoxicity of pyrethroids. Exposure of zebrafish embryos to pyrethroids caused a dose-dependent increase in mortality and pericardial edema, with type II compounds being the most potent. At doses approaching the LC(50), permethrin and deltamethrin caused craniofacial abnormalities. These findings are consistent with mammalian studies demonstrating that pyrethroids are mildly teratogenic at very high doses. However, at lower doses, body axis curvature and spasms were observed, which were reminiscent of the classic syndromes observed with pyrethroid toxicity. Treatment with diazepam ameliorated the spasms, while treatment with the sodium channel antagonist MS-222 ameliorated both spasms and body curvature, suggesting that pyrethroid-induced neurotoxicity is similar in zebrafish and mammals. Taken in concert, these data suggest that zebrafish may be an appropriate alternative model to study the mechanism(s) responsible for the developmental neurotoxicity of pyrethroid insecticides and aid in identification of compounds that should be further tested in mammalian systems.

  1. Scepticism towards insecticide treated mosquito nets for malaria ...

    African Journals Online (AJOL)

    Scepticism towards insecticide treated mosquito nets for malaria control in rural ... especially among under-five year children and pregnant women in poor rural ... through social marketing strategy for malaria control prior to the introduction of ...

  2. Towards an identification of the pyrethroid pharmacophore. A molecular modelling study of some pyrethroid esters

    DEFF Research Database (Denmark)

    Byberg, J R; Jørgensen, Flemming Steen; Klemmensen, P D

    1987-01-01

    A molecular modelling and computer graphics study of a series of pyrethroid insecticides has been carried out. The three-dimensional arrangement of the groups essential for the biological activity (pharmacophore) has been identified for the acid and the alcohol moieties, respectively....... These pharmacophores are based on the relationship between molecular structure and biological activity for a number of pyrethroid esters. The pharmacophores, which describe the relative location in space of the unsaturated systems, the dimethyl groups and the ester moiety, may be useful in the design of novel...... compounds with pyrethroid activity....

  3. "We are supposed to take care of it": a qualitative examination of care and repair behaviour of long-lasting, insecticide-treated nets in Nasarawa State, Nigeria.

    Science.gov (United States)

    Hunter, Gabrielle C; Scandurra, Leah; Acosta, Angela; Koenker, Hannah; Obi, Emmanuel; Weber, Rachel

    2014-08-14

    The longevity of long-lasting insecticidal nets (LLIN) under field conditions has important implications for malaria vector control. The behaviour of bed net users, including net care and repair, may protect or damage bed nets and impact the physical integrity of nets. However, this behaviour, and the motivating and inhibiting factors, is not well understood. Qualitative research methods were used to examine behaviour, attitudes and norms around damage, care and repair of LLINs. Eighteen in-depth interviews (IDI) and six focus group discussions (FGD) were conducted with LLIN users in two local government areas of Nasarawa State, Nigeria. A brief background questionnaire with the 73 participants prior to IDIs or FGDs collected additional data on demographics, net use, and care and repair behaviour. Respondents cited that the major causes of damage to bed nets are primarily children, followed by rodents, everyday handling that is not gentle, and characteristics of sleeping spaces. Caring for nets was perceived as both preventing damage by careful handling and keeping the net clean, which may lead to over-washing of LLINs. Repairing a damaged net was considered something that net users should do and the responsibility of adults in the household. Despite this, reported frequency of net repair was low (18%). Motivations for taking care of and repairing nets centred around caring for one's family, avoiding mosquito bites, saving money, and maintaining the positive opinion of others by keeping a clean and intact net. Barriers to net care and repair related to time availability and low perceived value of bed nets or of one's health. This study provides novel and valuable insights on the perceptions and attitudes of LLIN users in Nasarawa, Nigeria on the durability of bed nets, how to care for and repair nets, and for what reasons. Communication around net care should stress proper daily storage of nets, regular net inspections, prompt repairs, and clarify misconceptions

  4. Efficacy of bifenthrin-impregnated bednets against Anopheles funestus and pyrethroid-resistant Anopheles gambiae in North Cameroon

    Directory of Open Access Journals (Sweden)

    Chouaibou Mouhamadou

    2006-09-01

    Full Text Available Abstract Background Recent field studies indicated that insecticide-treated bednets (ITNs maintain their efficacy despite a high frequency of the knock-down resistance (kdr gene in Anopheles gambiae populations. It was essential to evaluate ITNs efficacy in areas with metabolic-based resistance. Methods Bifenthrin was used in this experiment because it is considered a promising candidate for bednets impregnation. Nets were treated at 50 mg/m2, a dose that has high insecticidal activity on kdr mosquitoes and at 5 mg/m2, a dose that kills 95% of susceptible mosquitoes under laboratory conditions with 3 minutes exposure. Bednets were holed to mimic physical damage. The trial was conducted in three experimental huts from Pitoa, North-Cameroon where Anopheles gambiae displays metabolic resistance and cohabits with An. funestus. Results Bifenthrin at 50 mg/m2 significantly reduced anophelines' entry rate (>80%. This was not observed at 5 mg/m2. Both treatments increased exophily in An. gambiae, and to a lesser extent in An. funestus. With bifenthrin at high dosage, over 60% reduction in blood feeding and 75–90% mortality rates were observed in both vectors. Despite presence of holes, only a single An. gambiae and two An. funestus females were collected inside the treated net, and all were found dead. The same trends were observed with low dosage bifenthrin though in most cases, no significant difference was found with the untreated control net. Conclusion Bifenthrin-impregnated bednets at 50 mg/m2 were efficient in the reduction of human-vector contact in Pitoa. Considerable personal protection was gained against An. funestus and metabolic pyrethroid resistant An. gambiae populations.

  5. Efficacy of bifenthrin-impregnated bednets against Anopheles funestus and pyrethroid-resistant Anopheles gambiae in North Cameroon

    Science.gov (United States)

    Chouaibou, Mouhamadou; Simard, Frédéric; Chandre, Fabrice; Etang, Josiane; Darriet, Frédéric; Hougard, Jean-Marc

    2006-01-01

    Background Recent field studies indicated that insecticide-treated bednets (ITNs) maintain their efficacy despite a high frequency of the knock-down resistance (kdr) gene in Anopheles gambiae populations. It was essential to evaluate ITNs efficacy in areas with metabolic-based resistance. Methods Bifenthrin was used in this experiment because it is considered a promising candidate for bednets impregnation. Nets were treated at 50 mg/m2, a dose that has high insecticidal activity on kdr mosquitoes and at 5 mg/m2, a dose that kills 95% of susceptible mosquitoes under laboratory conditions with 3 minutes exposure. Bednets were holed to mimic physical damage. The trial was conducted in three experimental huts from Pitoa, North-Cameroon where Anopheles gambiae displays metabolic resistance and cohabits with An. funestus. Results Bifenthrin at 50 mg/m2 significantly reduced anophelines' entry rate (>80%). This was not observed at 5 mg/m2. Both treatments increased exophily in An. gambiae, and to a lesser extent in An. funestus. With bifenthrin at high dosage, over 60% reduction in blood feeding and 75–90% mortality rates were observed in both vectors. Despite presence of holes, only a single An. gambiae and two An. funestus females were collected inside the treated net, and all were found dead. The same trends were observed with low dosage bifenthrin though in most cases, no significant difference was found with the untreated control net. Conclusion Bifenthrin-impregnated bednets at 50 mg/m2 were efficient in the reduction of human-vector contact in Pitoa. Considerable personal protection was gained against An. funestus and metabolic pyrethroid resistant An. gambiae populations. PMID:16961938

  6. Free distribution of insecticidal bed nets improves possession and preferential use by households and is equitable: findings from two cross-sectional surveys in thirteen malaria endemic districts of Bangladesh

    Directory of Open Access Journals (Sweden)

    Ahmed Syed M

    2011-12-01

    Full Text Available Abstract Background BRAC, an indigenous non-governmental development organization (NGO, has been implementing a programme to prevent and control malaria in the 13 malaria-endemic districts of Bangladesh since 2007. One of the critical preventive interventions is the distribution of insecticidal bed nets (long-lasting insecticide-treated nets, LLINs and insecticide-treated ordinary nets, ITNs to the community free of cost. This study aimed to assess progress in the possession, preferential use, and knowledge on use of the LLIN/ITNs including the programme's avowed pro-poor inclination one and three and half years after intervention began. Methods A convenient sampling strategy based on malaria endemicity in the districts was adopted. First, thirty upazila (sub-district, with a population around 250,000s were selected at random, with high prevalent districts contributing more upazilas; second, from each upazila, one (2008 to two (2011 villages (covered by insecticidal bed net distribution programme were selected. From each village, households that had either one under-five child and/or a pregnant woman were included in the survey, one household being included only once. Data were collected using a pre-tested structured questionnaire. Results In all, 3,760 households in 2008 and 7,895 households in 2011 were surveyed for collecting relevant information. Proportion of households with at least one LLIN, and at least one LLIN/ITN increased (22-59 to 62-67% and 22-64% to 74-76% respectively over time, including increase in the mean number of LLIN/ITNs per household (≤ 1 to 1 +. The programme achieved > 80% coverage in sleeping under an LLIN/ITN in the case of under-five children and pregnant women, especially in the high-endemic districts. Knowledge regarding critical time of hanging the net also increased over time (7-22 to 44-54%, but remained low. The pro-poor inclination of the programme is reflected in the status of relevant indicators according

  7. Willingness to pay for insecticide-treated nets in Berehet District, Amhara Region, Northern Ethiopia: implication of social marketing.

    Science.gov (United States)

    Aleme, Adisu; Girma, Eshetu; Fentahun, Netsanet

    2014-01-01

    Understanding the feasibility of achieving widespread coverage with Insecticide-Treated Nets has to be preceded by learning how people value the Insecticide-Treated Nets and estimating the potential demand and willingness to pay so that sustainability of the intervention can be assured. The objective of this study was to determine willingness to pay for Insecticide-Treated Nets among households in Berehet District, Northern Ethiopia. A community-based cross-sectional study was conducted using both quantitative and qualitative methods in five randomly selected Kebeles from January-February 2012. Open ended contingent valuation technique with follow-up method was used. Qualitative data were collected through focus group discussions and observation methods. Binary logistic regression was used to determine the association between dependent and independent variables. The average number of individuals per Insecticide-Treated Nets was 3.83. Nearly 68.5% persons had willingness to buy Insecticide-Treated Nets if they have access to these Nets. The median maximum price a person is willingness to pay for blue rectangular Insecticide-Treated Net was 20 ETB. People had willingness to pay 30 ETB for blue and white conical insecticide-treated nets. Working on knowledge of malaria (OR=0.68, CI (0.47, 0.98; ppay Insecticide-Treated Nets. Respondents who prefer Kebele/place/ to buy Insecticide-Treated Net for rectangular shape had a significant association with a willingness to pay for Insecticide-Treated Nets (OR=1.92, CI= 1.07-3.92). Promotions, products, price and place had significant association with willingness to pay for Insecticide-Treated Nets. Designing a social marketing strategy helps ensure sustainable supply of Insecticide-Treated Nets and proper use of Insecticide-Treated Nets.

  8. Efficacy of Olyset® Plus, a new long-lasting insecticidal net incorporating permethrin and piperonyl-butoxide against multi-resistant malaria vectors [corrected].

    Directory of Open Access Journals (Sweden)

    Cédric Pennetier

    Full Text Available Due to the rapid extension of pyrethroid resistance in malaria vectors worldwide, manufacturers are developing new vector control tools including insecticide mixtures containing at least two active ingredients with different mode of action as part of insecticide resistance management. Olyset® Plus is a new long-lasting insecticidal net (LLIN incorporating permethrin and a synergist, piperonyl butoxide (PBO, into its fibres in order to counteract metabolic-based pyrethroid resistance of mosquitoes. In this study, we evaluated the efficacy of Olyset® Plus both in laboratory and field against susceptible and multi-resistant malaria vectors and compared with Olyset Net, which is a permethrin incorporated into polyethylene net. In laboratory, Olyset® Plus performed better than Olyset® Net against susceptible Anopheles gambiae strain with a 2-day regeneration time owing to an improved permethrin bleeding rate with the new incorporation technology. It also performed better than Olyset® Net against multiple resistant populations of An. gambiae in experimental hut trials in West Africa. Moreover, the present study showed evidence for a benefit of incorporating a synergist, PBO, with a pyrethroid insecticide into mosquito netting. These results need to be further validated in a large-scale field trial to assess the durability and acceptability of this new tool for malaria vector control.

  9. Impact of promoting longer-lasting insecticide treatment of bed nets upon malaria transmission in a rural Tanzanian setting with pre-existing high coverage of untreated nets

    NARCIS (Netherlands)

    Russell, T.L.; Lwetoijera, D.W.; Maliti, D.; Chipwaza, B.; Kihonda, J.; Charlwood, J.D.; Smith, T.A.; Lengeler, C.; Mwanyangala, M.A.; Nathan, R.; Knols, B.G.J.; Takken, W.; Killeen, G.F.

    2010-01-01

    Background The communities of Namawala and Idete villages in southern Tanzania experienced extremely high malaria transmission in the 1990s. By 2001-03, following high usage rates (75% of all age groups) of untreated bed nets, a 4.2-fold reduction in malaria transmission intensity was achieved.

  10. Africa's largest long-lasting insecticide-treated net producer: lessons from A to Z Textiles

    Directory of Open Access Journals (Sweden)

    Daar Abdallah S

    2010-12-01

    Full Text Available Abstract Background Field trials have demonstrated the efficacy of insecticide-treated nets, and the WHO has recently endorsed a shift toward Long-Lasting Insecticide Treated nets (LLINs due to factors such as reduced distribution costs. However, the need for LLINs poses several challenges. Is it possible to manufacture LLINs in large quantities in the African continent, where malaria is most endemic? When production is located in low-income countries, what role is played by local funding and employment, scaling up manufacturing, and partnerships? What factors influence availability and pricing? Discussion A case study of A to Z Textiles was undertaken to answer the question of how large-scale production of LLINs can occur in a low income setting. One of the largest sources of bed nets for Africa, A to Z Textiles is Africa-based, and its Tanzanian operations have a production capacity of 30 million LLINs per year, along with full WHO recommendation for its nets. Our analysis is based on semi-structured interviews with key informants familiar with A to Z, site visits in Tanzania, and literature reviews. This paper discusses the history and current status of A to Z Textiles, identifies the factors that led to its success, and suggests policy considerations that could support similar initiatives in the future. Local funding, scaling up manufacturing, technology transfer, and partnerships all played important roles in A to Z’s ascent, as did perceived benefits of local employment and capacity-building. Regulatory issues and procurement rules acted as barriers. A to Z cost-effectively manufactures high-quality LLINs where malaria is most endemic. Summary With a production capacity of 30 million LLINs per year, and full WHOPES (WHO Pesticide Evaluation Scheme certification, A to Z Textiles demonstrates how key health goods can be successfully produced in the low-income countries that use them. Its example may be instructive and of high interest to

  11. Physical and chemical properties of pyrethroids.

    Science.gov (United States)

    Laskowski, Dennis A

    2002-01-01

    The physical and chemical properties of the pyrethroids bifenthrin, cyfluthrin, cypermethrin (also zetacypermethrin), deltamethrin, esfenvalerate (also fenvalerate), fenpropathrin, lambda-cyhalothrin (also cyhalothrin), permethrin, and tralomethrin have been reviewed and summarized in this paper. Physical properties included molecular weight, octanol-water partition coefficient, vapor pressure, water solubility, Henry's law constant, fish biocencentration factor, and soil sorption, desorption, and Freundlich coefficients. Chemical properties included rates of degradation in water as a result of hydrolysis, photodecomposition, aerobic or anaerobic degradation by microorganisms in the absence of light, and also rates of degradation in soil incubated under aerobic or anaerobic conditions. Collectively, the pyrethroids display a highly nonpolar nature of low water solubility, low volatility, high octanol-water partition coefficients, and have high affinity for soil and sediment particulate matter. Pyrethroids have low mobility in soil and are sorbed strongly to the sediments of natural water systems. Although attracted to living organisms because of their nonpolar nature, their capability to bioconcentrate is mitigated by their metabolism and subsequent elimination by the organisms. In fish, bioconcentration factors (BCF) ranged from 360 and 6000. Pyrethroids in water solution tend to be stable at acid and neutral pH but [table: see text] become increasingly susceptible to hydrolysis at pH values beyond neutral. Exceptions at higher pH are bifenthrin (stable), esfenvalerate (stable), and permethrin (half-life, 240 d). Pyrethroids vary in susceptibility to sunlight. Cyfluthrin and tralomethrin in water had half-lives of 0.67 and 2.5 d; lambda-cyhalothrin, esfenvalerate, deltamethrin, permethrin, and cypermethrin were intermediate with a range of 17-110 d; and bifenthrin and fenpropathrin showed the least susceptibility with half-lives of 400 and 600 d, respectively

  12. Insecticide-treated net ownership and utilization and factors that influence their use in Itang, Gambella region, Ethiopia: cross-sectional study

    Directory of Open Access Journals (Sweden)

    Watiro AH

    2016-05-01

    Full Text Available Aklilu Habte Watiro,1 Worku Awoke,2 1Médecins Sans Frontières OCA (MSF Holland Ethiopia Mission, Addis Ababa, 2Department of Epidemiology, School of Public Health, College of Medicine and Health Sciences, Bahir Dar University, Bahir Dar, Ethiopia Background: Malaria remains a major public health problem in Ethiopia. Consequently, Ethiopia designed the 2011–2015, Malaria Prevention and Control Strategic Plan to fight the vector. It was discovered that most of the studies conducted on the use of insecticide-treated nets (ITNs were not in line with the strategic plan of the country. This study aimed to assess ITN ownership and utilization, and includes barriers related to its use among the target-area population at household (HH level. Materials and methods: A cross-sectional design was employed in Itang for this study. Data were collected by trained nurses through face-to-face interview and observation. A total of 845 participants were selected through multistage sampling, and the size was determined by using a single-population proportion formula. EPI Info and SPSS was used for analysis, and all necessary statistical association was computed in order to explain the outcome variable through explanatory variables of this study. Results: Among 845 HHs interviewed, 81.7% (690 had at least one ITN, while 52.3% (361 had used the ITN the night preceding the data-collection day. HH awareness of malaria prevention, number of ITNs, family size, number of family members sharing sleeping area/beds, sleeping patterns of adolescents, HH-head age, and inconvenience of using ITNs were found to be barriers to the use of ITNs in this study. Conclusion and recommendation: The study concluded that very few HHs owned ITNs and there was very low usage of ITNs. In recommendation, the regional health bureau and district health office should consider bigger nets that can accommodate family members who share the same sleeping area/bed in the area. Keywords: consistent

  13. Insecticide-treated nets ownership and utilization among under-five children following the 2010 mass distribution in Burkina Faso.

    Science.gov (United States)

    Diabaté, Souleymane; Druetz, Thomas; Bonnet, Emmanuel; Kouanda, Seni; Ridde, Valéry; Haddad, Slim

    2014-09-04

    Periodic mass distributions contribute significantly to universal access to insecticide-treated nets (ITNs). However, due to the limited number of nets distributed, needs remain unsatisfied, particularly in large households. This study was conducted in Kaya health district following the 2010 mass distribution of ITNs in Burkina Faso. Data were collected on the socio-economic and geo-spatial characteristics and ITN possession and utilization levels of 2,004 households. The study explored: 1) ITN access, in terms of intra-household saturation with ITNs (households with at least one ITN for every two members) correctly installed and in very good physical condition; and 2) factors influencing the decision to place under-five children under a net. Particular attention was given to vector control activities undertaken by mothers. Of the 2,004 households, 90% possessed at least one ITN. However, intra-household saturation with ITNs was below 60% in small households and below 20% in large ones (>6 members). Crude proportion ratios comparing possession and levels of intra-household saturation with ITNs varied between 1.5 (small households) and 7.8 (large households). The proportions of households with ITNs for every two members that were correctly hung or in very good physical condition ranged from 0% to 6.5% in large households and 27.8% to 40.7% in small ones. ITN use to protect under-five children was lower in large households; it was significantly higher when there was at least one ITN for every two members. In large households, it was significantly higher when a child had experienced an episode of any illness in the previous two weeks and when the mother had taken actions to control vector proliferation. In small households, ITN use was significantly higher in families with agricultural land and children aged 12-23 months. Ownership rates were high, but real access to bed nets remained limited. The allocation process disadvantages large families. Real access to bed

  14. Increased proportions of outdoor feeding among residual malaria vector populations following increased use of insecticide-treated nets in rural Tanzania

    Directory of Open Access Journals (Sweden)

    Azizi Salum

    2011-04-01

    Full Text Available Abstract Background Insecticide-treated nets (ITNs and indoor residual spraying (IRS represent the front-line tools for malaria vector control globally, but are optimally effective where the majority of baseline transmission occurs indoors. In the surveyed area of rural southern Tanzania, bed net use steadily increased over the last decade, reducing malaria transmission intensity by 94%. Methods Starting before bed nets were introduced (1997, and then after two milestones of net use had been reached-75% community-wide use of untreated nets (2004 and then 47% use of ITNs (2009-hourly biting rates of malaria vectors from the Anopheles gambiae complex and Anopheles funestus group were surveyed. Results In 1997, An. gambiae s.l. and An. funestus mosquitoes exhibited a tendency to bite humans inside houses late at night. For An. gambiae s.l., by 2009, nocturnal activity was less (p = 0.0018. At this time, the sibling species composition of the complex had shifted from predominantly An. gambiae s.s. to predominantly An. arabiensis. For An. funestus, by 2009, nocturnal activity was less (p = 0.0054 as well as the proportion biting indoors (p An. funestus s.s. remained the predominant species within this group. As a consequence of these altered feeding patterns, the proportion (mean ± standard error of human contact with mosquitoes (bites per person per night occurring indoors dropped from 0.99 ± 0.002 in 1997 to 0.82 ± 0.008 in 2009 for the An. gambiae complex (p = 0.0143 and from 1.00 ± An. funestus complex (p = 0.0004 over the same time period. Conclusions High usage of ITNs can dramatically alter African vector populations so that intense, predominantly indoor transmission is replaced by greatly lowered residual transmission, a greater proportion of which occurs outdoors. Regardless of the underlying mechanism, the residual, self-sustaining transmission will respond poorly to further insecticidal measures within houses. Additional vector control

  15. Toxicological effects of pyrethroids on non-target aquatic insects.

    Science.gov (United States)

    Antwi, Frank B; Reddy, Gadi V P

    2015-11-01

    The toxicological effects of pyrethroids on non-target aquatic insects are mediated by several modes of entry of pyrethroids into aquatic ecosystems, as well as the toxicological characteristics of particular pyrethroids under field conditions. Toxicokinetics, movement across the integument of aquatic insects, and the toxicodynamics of pyrethroids are discussed, and their physiological, symptomatic and ecological effects evaluated. The relationship between pyrethroid toxicity and insecticide uptake is not fully defined. Based on laboratory and field data, it is likely that the susceptibility of aquatic insects (vector and non-vector) is related to biochemical and physiological constraints associated with life in aquatic ecosystems. Understanding factors that influence aquatic insects susceptibility to pyrethroids is critical for the effective and safe use of these compounds in areas adjacent to aquatic environments. Copyright © 2015 The Authors. Published by Elsevier B.V. All rights reserved.

  16. Efficacy of an Essential Oil-Based Pesticide for Controlling Bed Bug (Cimex lectularius Infestations in Apartment Buildings

    Directory of Open Access Journals (Sweden)

    Changlu Wang

    2014-11-01

    Full Text Available Bed bugs (Cimex lectularius L. and Cimex hemipterus F. are among the most difficult urban pests to manage. Many essential oil-based bed bug control products that are considered reduced risk to mammals compared to synthetic insect neurotoxins have become commercially available, but their effectiveness as a stand-alone control method is unknown. This study assessed the field efficacy of an essential oil-based bed bug control product (EcoRaider; a.i. 1% geraniol + 1% cedar oil + 2% sodium lauryl sulfate compared to a pyrethroid and neonicotinoid mixture spray (0.075% Temprid SC; a.i. beta-cyfluthrin + imidacloprid. After 12 weeks, the three treatments—EcoRaider, Temprid SC, and EcoRaider + Temprid SC caused 92.5 ± 2.7, 92.9 ± 3.0, and 91.7% ± 2.7% bed bug count reduction, respectively. No significant differences existed in the bed bug reduction among the treatments. Bed bugs were eliminated from only 22% of the treated apartments. Among those still with bed bugs, 76% of the residents did not know bed bugs were present. We documented the residents’ self-control practices and discussed the potential of using essential oil-based insecticides in bed bug management programs to minimize the health risks to building occupants and pets and to slow down the development of insecticide resistance.

  17. Larval application of sodium channel homologous dsRNA restores pyrethroid insecticide susceptibility in a resistant adult mosquito population.

    Science.gov (United States)

    Bona, Ana Caroline Dalla; Chitolina, Rodrigo Faitta; Fermino, Marise Lopes; de Castro Poncio, Lisiane; Weiss, Avital; Lima, José Bento Pereira; Paldi, Nitzan; Bernardes, Emerson Soares; Henen, Jonathan; Maori, Eyal

    2016-07-14

    Mosquitoes host and pass on to humans a variety of disease-causing pathogens such as infectious viruses and other parasitic microorganisms. The emergence and spread of insecticide resistance is threatening the effectiveness of current control measures for common mosquito vector borne diseases, such as malaria, dengue and Zika. Therefore, the emerging resistance to the widely used pyrethroid insecticides is an alarming problem for public health. Herein we demonstrated the use of RNA interference (RNAi) to increase susceptibility of adult mosquitoes to a widely used pyrethroid insecticide. Experiments were performed on a field-collected pyrethroid resistant strain of Ae. aegypti (Rio de Janeiro; RJ). Larvae from the resistant Ae. aegypti population were soaked with double-stranded RNAs (dsRNAs) that correspond either to voltage-gate sodium channel (VGSC), P-glycoprotein, or P450 detoxification genes and reared to adulthood. Adult mortality rates in the presence of various Deltamethrin pyrethroid concentrations were used to assess mosquito insecticide susceptibility. We characterized the RJ Ae. aegypti strain with regard to its level of resistance to a pyrethroid insecticide and found that it was approximately 6 times more resistant to Deltamethrin compared to the laboratory Rockefeller strain. The RJ strain displayed a higher frequency of Val1016Ile and Phe1534Cys substitutions of the VGSC gene. The resistant strain also displayed a higher basal expression level of VGSC compared to the Rockefeller strain. When dsRNA-treated mosquitoes were subjected to a standard pyrethroid contact bioassay, only dsRNA targeting VGSC increased the adult mortality of the pyrethroid resistant strain. The dsRNA treatment proved effective in increasing adult mosquito susceptibility over a range of pyrethroid concentrations and these results were associated with dsRNA-specific small interfering RNAs in treated adults, and the corresponding specific down regulation of VGSC gene expression

  18. Sodium Channel Mutations and Pyrethroid Resistance in Aedes aegypti

    Directory of Open Access Journals (Sweden)

    Yuzhe Du

    2016-10-01

    Full Text Available Pyrethroid insecticides are widely used to control insect pests and human disease vectors. Voltage-gated sodium channels are the primary targets of pyrethroid insecticides. Mutations in the sodium channel have been shown to be responsible for pyrethroid resistance, known as knockdown resistance (kdr, in various insects including mosquitoes. In Aedes aegypti mosquitoes, the principal urban vectors of dengue, zika, and yellow fever viruses, multiple single nucleotide polymorphisms in the sodium channel gene have been found in pyrethroid-resistant populations and some of them have been functionally confirmed to be responsible for kdr in an in vitro expression system, Xenopus oocytes. This mini-review aims to provide an update on the identification and functional characterization of pyrethroid resistance-associated sodium channel mutations from Aedes aegypti. The collection of kdr mutations not only helped us develop molecular markers for resistance monitoring, but also provided valuable information for computational molecular modeling of pyrethroid receptor sites on the sodium channel.

  19. Factors Influencing the Usage of Insecticide Treated Mosquito Nets ...

    African Journals Online (AJOL)

    Purpose: Malaria in Sudan is a leading cause of morbidity and mortality. ... treated mosquito nets (ITNs) for prevention of malaria among pregnant women. ... on malaria causes, 103 (99%) had good knowledge on malaria complications and ... and accessibility to ITNs were significantly associated with current usage of ITNs.

  20. [Efficacy of permethrin-impregnated Olyset Net mosquito nets in a zone with pyrethroid resistant vectors. I--Entomologic evaluation].

    Science.gov (United States)

    Doannio, J M; Dossou-Yovo, J; Diarrassouba, S; Chauvancy, G; Darriet, F; Chandre, F; Henry, M C; Nzeyimana, I; Guillet, P; Carnevale, P

    1999-01-01

    The efficacy of permethrin-treated Olyset Net mosquito nets on malaria transmission and morbidity was studied in Kafine, a village located in the savanna region of the Cote d'Ivoire in Africa. After collecting sociodemographic, entomological, and parasitological data, bednets were distributed first in the southern half of the village and then in the whole village. Throughout the study period, mosquito specimens were captured on the skin of inhabitants at four points in the village between 6 PM and 6 AM both inside (but outside bednets) and outside houses. Prior to distribution of bednets, the mean biting rate (MBR) by Anopheles gambiae was 77.4 bites per man per night (b/m/n). The mean parturity rate (MPR) was 40.6 p. 100, the sporozootic index (SI) was 0.99 p. 100, and the mean entomological inoculation rate (MEIR) was 0.7 infectious bites per man per night (b+/m/n). Six months after distribution of bednets in the southern half of the village, MBR was 80.2 b/m/n, MPR was 32 p. 100, SI was 1.8 p. 100, and MEIR was 0.83 b+/m/n. After extending distribution to the whole village, data from November 1996 to July 1997 were as follows: MBR, 67.8 b/m/n; MPR, 20.1 p. 100; SI, 0.65 p. 100; and MEIR, 0.66 p. 100. From August 1977 to July 1998, data were as follows: MBR, 102.6 b/m/n; MPR, 26.2 p. 100; SI, 1.15 p. 100; and MEIR, 0.74 b+/m/n. Comparative analysis of these data showed that use of bednets had no effect on the bite or entomological inoculation rate. This is in agreement with the documented resistance of vectors in the study zone to permethrin. Despite the known stimulation/repulsion effect of permethrin, use of treated bednets had no real impact on transmission. This inefficacy could be related to the high prevalence (80 p. 100) of the Kdr gene (responsible for resistance) in the savanna form of Anopheles gambiae.

  1. Lambda-Cyhalothrin Resistance in the Lady Beetle Eriopis connexa (Coleoptera: Coccinellidae) Confers Tolerance to Other Pyrethroids.

    Science.gov (United States)

    Torres, J B; Rodrigues, A R S; Barros, E M; Santos, D S

    2015-02-01

    Pyrethroid insecticides are widely recommended to control insect defoliators but lack efficacy against most aphid species. Thus, conserving aphid predators such as the lady beetle Eriopis connexa (Germar) is important to pest management in crop ecosystems that require pyrethroid sprays. In a greenhouse, early fourth-instar larvae and 5-day-old adults from susceptible (S) and resistant (R) E. connexa populations were caged on lambda-cyhalothrin-treated cotton plants, after which survival and egg production (for those caged at adult stage) were assessed. In the laboratory, similar groups were subjected to dried residues and topical treatment with one of eight pyrethroids (alpha-cypermethrin, bifenthrin, deltamethrin, esfenvalerate, fenpropathrin, permethrin, zeta-cypermethrin, and lambda-cyhalothrin), the organophosphate methidathion, or water and wetting agent. After caging on treated cotton terminals, 66% of the R-population larvae survived to adulthood, compared with 2% of those from the S-population. At 12 d after caging at adult stage under the same conditions, 64% of the females from the R-population survived and laid eggs, compared with 100% mortality and no oviposition for the S-females. In trials involving dried insecticide residues, gain in survival based on the survival difference (percentage for R-population minus percentage for S-population) across all tested pyrethroids varied from 3 to 63% for larvae and from 3 to 70% for adults. In trials involving topical sprays of the tested pyrethroids, survival differences ranged from 36 to 96% for larvae and from 21 to 82% for adults. Fenpropathrin and bifenthrin were the least and most toxic, respectively. © The Authors 2015. Published by Oxford University Press on behalf of Entomological Society of America. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

  2. Neurological Deficits After Long-term Pyrethroid Exposure

    DEFF Research Database (Denmark)

    Hansen, Martin Rune Hassan; Jørs, Erik; Lander, Flemming

    2017-01-01

    Pyrethroid pesticides have been suggested to be a cause of Parkinson disease and other neurodegenerative diseases. To investigate this, a cross-sectional study was conducted among 120 Bolivian public health vector program spray men, primarily exposed to pyrethroids. Pesticide exposure and central...

  3. A good night's sleep and the habit of net use: perceptions of risk and reasons for bed net use in Bukoba and Zanzibar.

    Science.gov (United States)

    Koenker, Hannah M; Loll, Dana; Rweyemamu, Datius; Ali, Abdullah S

    2013-06-13

    Intensive malaria control interventions in the United Republic of Tanzania have contributed to reductions in malaria prevalence. Given that malaria control remains reliant upon continued use of long-lasting insecticidal bed nets (LLINs) even when the threat of malaria has been reduced, this qualitative study sought to understand how changes in perceived risk influence LLIN usage, and to explore in more detail the benefits of net use that are unrelated to malaria. Eleven focus group discussions were conducted in Bukoba Rural district and in Zanzibar Urban West district in late 2011. Participants were males aged 18 and over, females between the ages of 18 and 49, and females at least 50 years old. The perceived risk of malaria had decreased among the respondents, and malaria control interventions were credited for the decline. Participants cited reductions in both the severity of malaria and in their perceived susceptibility to malaria. However, malaria was still considered a significant threat. Participants' conceptualization of risk appeared to be an important consideration for net use. At the same time, comfort and aspects of comfort (getting a good night's sleep, avoiding biting pests) appeared to play a large role in personal decisions to use nets consistently or not. Barriers to comfort (feeling uncomfortable or trapped; perceived difficulty breathing, or itching/rashes) were frequently cited as reasons not to use a net consistently. While it was apparent that participants acknowledged the malaria-prevention benefits of net use, the exploration of the risk and comfort determinants of net use provides a richer understanding of net use behaviours, particularly in a setting where transmission has fallen and yet consistent net use is still crucial to maintaining those gains. Future behaviour change communication campaigns should capitalize on the non-malaria benefits of net use that provide a long-term rationale for consistent use even when the immediate threat of

  4. Impact of environment on mosquito response to pyrethroid insecticides: facts, evidences and prospects.

    Science.gov (United States)

    Nkya, Theresia Estomih; Akhouayri, Idir; Kisinza, William; David, Jean-Philippe

    2013-04-01

    By transmitting major human diseases such as malaria, dengue fever and filariasis, mosquito species represent a serious threat worldwide in terms of public health, and pose a significant economic burden for the African continent and developing tropical regions. Most vector control programmes aiming at controlling life-threatening mosquitoes rely on the use of chemical insecticides, mainly belonging to the pyrethroid class. However, resistance of mosquito populations to pyrethroids is increasing at a dramatic rate, threatening the efficacy of control programmes throughout insecticide-treated areas, where mosquito-borne diseases are still prevalent. In the absence of new insecticides and efficient alternative vector control methods, resistance management strategies are therefore critical, but these require a deep understanding of adaptive mechanisms underlying resistance. Although insecticide resistance mechanisms are intensively studied in mosquitoes, such adaptation is often considered as the unique result of the selection pressure caused by insecticides used for vector control. Indeed, additional environmental parameters, such as insecticides/pesticides usage in agriculture, the presence of anthropogenic or natural xenobiotics, and biotic interactions between vectors and other organisms, may affect both the overall mosquito responses to pyrethroids and the selection of resistance mechanisms. In this context, the present work aims at updating current knowledge on pyrethroid resistance mechanisms in mosquitoes and compiling available data, often from different research fields, on the impact of the environment on mosquito response to pyrethroids. Key environmental factors, such as the presence of urban or agricultural pollutants and biotic interactions between mosquitoes and their microbiome are discussed, and research perspectives to fill in knowledge gaps are suggested. Copyright © 2012 Elsevier Ltd. All rights reserved.

  5. "People will say that I am proud": a qualitative study of barriers to bed net use away from home in four Ugandan districts.

    Science.gov (United States)

    Monroe, April; Harvey, Steven A; Lam, Yukyan; Muhangi, Denis; Loll, Dana; Kabali, Asaph Turinde; Weber, Rachel

    2014-03-06

    Despite increased access and ownership, barriers to insecticide-treated bed net (ITN) use persist. While barriers within the home have been well documented, the challenges to net use when sleeping away from home remain relatively unexplored. This study examines common situations in which people sleep away from home and the barriers to ITN use in those situations. To explore these issues, a group of researchers conducted 28 in-depth interviews and four focus groups amongst adults from net-owning households in four Ugandan districts. In addition to sleeping outside during hot season, participants identified social events, livelihood activities, and times of difficulty as circumstances in which large numbers of people sleep away from home. Associated challenges to ITN use included social barriers such as fear of appearing proud, logistical barriers such as not having a place to hang a net, and resource limitations such as not having an extra net with which to travel. Social disapproval emerged as an important barrier to ITN use in public settings. Unique barriers to ITN use exist when people spend the night away from home. It is essential to identify and address these barriers in order to reduce malaria exposure in such situations. For events like funerals or religious "crusades" where large numbers of people sleep away from home, alternative approaches, such as spatial repellents may be more appropriate than ITNs. Additional research is required to identify the acceptability and feasibility of alternative prevention strategies in situations where ITNs are unlikely to be effective.

  6. Simultaneous presence of DDT and pyrethroid residues in human breast milk from a malaria endemic area in South Africa

    Energy Technology Data Exchange (ETDEWEB)

    Bouwman, H. [School for Environmental Sciences and Development, North-West University (Potchefstroom Campus), Private Bag X6001, Potchefstroom 2520 (South Africa)]. E-mail: drkhb@puk.ac.za; Sereda, B. [Agricultural Research Council, Plant Protection Research Institute, Private Bag X134 Queenswood, Pretoria 0121 (South Africa); Meinhardt, H.M. [South African Bureau of Standards, Testing and Conformity Services (Pty) Ltd, Private Bag X191, Pretoria 0001 (South Africa)

    2006-12-15

    DDT and pyrethroids were determined in 152 breast-milk samples from three towns in KwaZulu-Natal, South Africa, one of which had no need for DDT for malaria control. All compounds were found present in breast milk. Primiparae from one town had the highest mean {sigma}DDT whole milk levels (238.23 {mu}g/l), and multiparae from the same town had the highest means for permethrin (14.51 {mu}g/l), cyfluthrin (41.74 {mu}g/l), cypermethrin (4.24 {mu}g/l), deltamethrin (8.39 {mu}g/l), and {sigma}pyrethroid (31.5 {mu}g/l), most likely derived from agriculture. The ADI for DDT was only exceeded by infants from one town, but the ADI for pyrethroids was not exceeded. Since the ADI for DDT was recently reduced from 20 to 10 {mu}g/kg/bw, we suggest that this aspect be treated with concern. We therefore raise a concern based on toxicant interactions, due to the presence of four different pyrethroids and DDT. Breastfeeding however, remains safe under prevailing conditions. - The simultaneous presence of DDT and pyrethroid residues in breast milk raises the question of infant exposure and safety.

  7. Experiments and simulation of a net closing mechanism for tether-net capture of space debris

    Science.gov (United States)

    Sharf, Inna; Thomsen, Benjamin; Botta, Eleonora M.; Misra, Arun K.

    2017-10-01

    This research addresses the design and testing of a debris containment system for use in a tether-net approach to space debris removal. The tether-net active debris removal involves the ejection of a net from a spacecraft by applying impulses to masses on the net, subsequent expansion of the net, the envelopment and capture of the debris target, and the de-orbiting of the debris via a tether to the chaser spacecraft. To ensure a debris removal mission's success, it is important that the debris be successfully captured and then, secured within the net. To this end, we present a concept for a net closing mechanism, which we believe will permit consistently successful debris capture via a simple and unobtrusive design. This net closing system functions by extending the main tether connecting the chaser spacecraft and the net vertex to the perimeter and around the perimeter of the net, allowing the tether to actuate closure of the net in a manner similar to a cinch cord. A particular embodiment of the design in a laboratory test-bed is described: the test-bed itself is comprised of a scaled-down tether-net, a supporting frame and a mock-up debris. Experiments conducted with the facility demonstrate the practicality of the net closing system. A model of the net closure concept has been integrated into the previously developed dynamics simulator of the chaser/tether-net/debris system. Simulations under tether tensioning conditions demonstrate the effectiveness of the closure concept for debris containment, in the gravity-free environment of space, for a realistic debris target. The on-ground experimental test-bed is also used to showcase its utility for validating the dynamics simulation of the net deployment, and a full-scale automated setup would make possible a range of validation studies of other aspects of a tether-net debris capture mission.

  8. Syntetiske pyrethroider i private hjem

    DEFF Research Database (Denmark)

    Jensen, Karl-Martin Vagn; Fomsgaard, Inge S.; Kilpinen, Ole Østerlund

    2015-01-01

    A number of different methods are tested to elucidate the accumulation of synthetic pyrethroids in private homes. When the target pest is resistant, there is a potential risk that persistent synthetic pyrethroids accumulate because of repeated treatments. The highest residue found was 8260 µg lam...... lambda-cyhalothrin in a vacuum-cleaner sample (vacuumed for 10 minutes) and 1252 µg lambda-cyhalothrin in a “cotton sock dosimeter” sample. Similar data for deltamethrin was 805 µg in a vacuum-cleaner sample and 806 µg in a “cotton sock dosimeter” sample....

  9. An amino acid substitution (L925V associated with resistance to pyrethroids in Varroa destructor.

    Directory of Open Access Journals (Sweden)

    Joel González-Cabrera

    Full Text Available The Varroa mite, Varroa destructor, is an important pest of honeybees and has played a prominent role in the decline in bee colony numbers over recent years. Although pyrethroids such as tau-fluvalinate and flumethrin can be highly effective in removing the mites from hives, their intensive use has led to many reports of resistance. To investigate the mechanism of resistance in UK Varroa samples, the transmembrane domain regions of the V. destructor voltage-gated sodium channel (the main target site for pyrethroids were PCR amplified and sequenced from pyrethroid treated/untreated mites collected at several locations in Central/Southern England. A novel amino acid substitution, L925V, was identified that maps to a known hot spot for resistance within the domain IIS5 helix of the channel protein; a region that has also been proposed to form part of the pyrethroid binding site. Using a high throughput diagnostic assay capable of detecting the mutation in individual mites, the L925V substitution was found to correlate well with resistance, being present in all mites that had survived tau-fluvalinate treatment but in only 8 % of control, untreated samples. The potential for using this assay to detect and manage resistance in Varroa-infected hives is discussed.

  10. KINET: a social marketing programme of treated nets and net treatment for malaria control in Tanzania, with evaluation of child health and long-term survival.

    Science.gov (United States)

    Schellenberg, J R; Abdulla, S; Minja, H; Nathan, R; Mukasa, O; Marchant, T; Mponda, H; Kikumbih, N; Lyimo, E; Manchester, T; Tanner, M; Lengeler, C

    1999-01-01

    We present a large-scale social marketing programme of insecticide-treated nets in 2 rural districts in southwestern Tanzania (population 350,000) and describe how the long-term child health and survival impact will be assessed. Formative and market research were conducted in order to understand community perceptions, knowledge, attitudes and practice with respect to the products to be socially marketed. We identified Zuia Mbu (Kiswahili for 'prevent mosquitoes') as a suitable brand name for both treated nets and single-dose insecticide treatment sachets. A mix of public and private sales outlets is used for distribution. In the first stage of a stepped introduction 31 net agents were appointed and trained in 18 villages: 15 were shop owners, 14 were village leaders, 1 was a parish priest and 1 a health worker. For net treatment 37 young people were appointed in the same villages and trained as agents. Further institutions in both districts such as hospitals, development projects and employers were also involved in distribution. Promotion for both products was intense and used a variety of channels. A total of 22,410 nets and 8072 treatments were sold during the first year: 18 months after launching, 46% of 312 families with children aged under 5 years reported that their children were sleeping under treated nets. A strong evaluation component in over 50,000 people allows assessment of the long-term effects of insecticide-treated nets on child health and survival, anaemia in pregnancy, and the costs of the intervention. This evaluation is based on cross-sectional surveys, and case-control and cohort studies.

  11. Interactions of pyrethroid insecticides with GABAA and peripheral-type benzodiazepine receptors

    International Nuclear Information System (INIS)

    Devaud, L.L.

    1988-01-01

    Pyrethroid insecticides are potent proconvulsants in the rat. All pyrethroids evincing proconvulsant activity elicited a similar 25-30% maximal reduction of seizure threshold. The Type II pyrethroids were the most potent proconvulsants with 1RαS, cis cypermethrin having an ED 50 value of 6.3 nmol/kg. The proconvulsant activity of both Type I and Type II pyrenthroids was blocked by pretreatment with PK 11195, the peripheral-type benzodiazepine receptor (PTBR) antagonist. In contrast, phenytoin did not antagonize the proconvulsant activity of either deltamethrin or permethrin. Pyrethroids displaced the specific binding of [ 3 H]Ro5-4864 to rat brain membranes with a significant correlation between the log EC 50 values for their activities as proconvulsants and the log IC 50 values for their inhibition of [ 3 H]Ro5-4864 binding. Both Ro5-4864 and pyrethroid insecticides were found to influence specific [ 35 S]TBPS binding in a GABA-dependent manner. PK 11195 and the Type II pyrethroid, deltamethrin antagonized the Ro5-4864-induced modulation of [ 35 S]TBPS binding. Pyrethroid insecticides, Ro5-4864 and veratridine influenced GABA-gated 36 Chloride influx. Moreover, the Type II pyrethroids elicited an increase in 36 chloride influx in the absence of GABA-stimulation. Both of these actions were antagonized by PK 11195 and tetrodotoxin

  12. Development of the fluidized bed thermal treatment process for treating mixed waste

    International Nuclear Information System (INIS)

    Semones, G.B.; Williams, P.M.; Stiefvater, S.P.; Mitchell, D.L.; Roecker, B.D.

    1993-01-01

    A fluidized bed system is being developed at Rocky Flats for the treatment of mixed waste (a mixture of radioactive and chemically hazardous waste). The current program builds on experience gained in the 1970's and 1980's in tests with bench-scale, pilot-scale, and demonstration-scale fluidized bed systems. The system operates at low temperatures (∼ 525--600 degree C) which eliminates many of the disadvantages associated with high temperature thermal treatment processes. The process has shown the ability to destroy polychlorinated biphenyls (PCB's) with 99.9999% (''six-nines'') destruction efficiency in tests monitored by the Environmental Protection Agency (EPA). The bed makes use of in situ neutralization of acidic off-gases by incorporating sodium carbonate (Na 2 CO 3 ) in the bed media. This eliminates using wet scrubbers to treat the off-gas; these produce a high volume of secondary waste. Once in operation, it is expected that the fluidized bed process will yield up to a 40:1 reduction in the volume of the waste

  13. Effects of bed net use, female size, and plant abundance on the first meal choice (blood vs sugar of the malaria mosquito Anopheles gambiae

    Directory of Open Access Journals (Sweden)

    Stone Chris M

    2012-01-01

    Full Text Available Abstract Background The purpose of this study was to determine whether the sugar-or-blood meal choice of Anopheles gambiae females one day after emergence is influenced by blood-host presence and accessibility, nectariferous plant abundance, and female size. This tested the hypothesis that the initial meal of female An. gambiae is sugar, even when a blood host is available throughout the night, and, if not, whether the use of a bed net diverts mosquitoes to sugar sources. Methods Females and males Senna didymobotrya plants. Simultaneously they had access to a human blood host, either for 8 h or for only 30 min at dusk and dawn (the remainder of the night being excluded by an untreated bed net. In a third situation, the blood host was not present. All mosquitoes were collected in the morning. Their wing lengths, an indicator of pre-meal energetic state, were measured, and their meal choice was determined by the presence of midgut blood and of fructose. Results Female sugar feeding after emergence was facultative. When a blood host was accessible for 8 h per night, 92% contained blood, and only 3.7% contained sugar. Even with the use of a bed net, 78% managed to obtain a blood meal during the 30 min of accessibility at dusk or dawn, but 14% of females were now fructose-positive. In the absence of a blood host, and when either one or six plants were available, a total of 21.7% and 23.6% of females and 30.8% and 43.5% of males contained fructose, respectively. Feeding on both sugar and blood was more likely with bed net use and with greater plant abundance. Further, mosquitoes that fed on both resources were more often small and had taken a sugar meal earlier than the blood meal. The abundance of sugar hosts also affected the probability of sugar feeding by males and the amount of fructose obtained by both males and females. Conclusion Even in an abundance of potential sugar sources, female An. gambiae appear to prefer a nearby human source of blood

  14. Perceived Threat of Malaria and the Use of Insecticide Treated Bed ...

    African Journals Online (AJOL)

    2013-12-17

    Dec 17, 2013 ... Keywords: malaria; children; insecticide treated nets; health belief model; .... including malaria, were usually handled by the only designated nurse. .... The familiar saying that “prevention is better and cheaper than cure” may ...

  15. Pyrethroid insecticides in urban salmon streams of the Pacific Northwest

    Energy Technology Data Exchange (ETDEWEB)

    Weston, D.P., E-mail: dweston@berkeley.edu [Department of Integrative Biology, University of California, 3060 Valley Life Sciences Bldg., Berkeley, CA 94720-3140 (United States); Asbell, A.M., E-mail: aasbell@berkeley.edu [Department of Integrative Biology, University of California, 3060 Valley Life Sciences Bldg., Berkeley, CA 94720-3140 (United States); Hecht, S.A., E-mail: scott.hecht@noaa.gov [NOAA Fisheries, Office of Protected Resources, 510 Desmond Drive S.E., Lacey, WA 98503 (United States); Scholz, N.L., E-mail: nathaniel.scholz@noaa.gov [NOAA Fisheries, Northwest Fisheries Science Center, 2725 Montlake Blvd. E., Seattle, WA 98112 (United States); Lydy, M.J., E-mail: mlydy@siu.edu [Fisheries and Illinois Aquaculture Center and Department of Zoology, Southern Illinois University, 171 Life Sciences II, Carbondale, IL 62901 (United States)

    2011-10-15

    Urban streams of the Pacific Northwest provide spawning and rearing habitat for a variety of salmon species, and food availability for developing salmon could be adversely affected by pesticide residues in these waterbodies. Sediments from Oregon and Washington streams were sampled to determine if current-use pyrethroid insecticides from residential neighborhoods were reaching aquatic habitats, and if they were at concentrations acutely toxic to sensitive invertebrates. Approximately one-third of the 35 sediment samples contained measurable pyrethroids. Bifenthrin was the pyrethroid of greatest concern with regards to aquatic life toxicity, consistent with prior studies elsewhere. Toxicity to Hyalella azteca and/or Chironomus dilutus was found in two sediment samples at standard testing temperature (23 deg. C), and in one additional sample at a more environmentally realistic temperature (13 deg. C). Given the temperature dependency of pyrethroid toxicity, low temperatures typical of northwest streams can increase the potential for toxicity above that indicated by standard testing protocols. - Highlights: > Salmon-bearing creeks can be adversely impacted by insecticides from urban runoff. > Pyrethroid insecticides were found in one-third of the creeks in Washington and Oregon. > Two creeks contained concentrations acutely lethal to sensitive invertebrates. > Bifenthrin was of greatest concern, though less than in prior studies. > Standard toxicity testing underestimates the ecological risk of pyrethroids. - Pyrethroid insecticides are present in sediments of urban creeks of Oregon and Washington, though less commonly than in studies elsewhere in the U.S.

  16. Pyrethroid insecticides in urban salmon streams of the Pacific Northwest

    International Nuclear Information System (INIS)

    Weston, D.P.; Asbell, A.M.; Hecht, S.A.; Scholz, N.L.; Lydy, M.J.

    2011-01-01

    Urban streams of the Pacific Northwest provide spawning and rearing habitat for a variety of salmon species, and food availability for developing salmon could be adversely affected by pesticide residues in these waterbodies. Sediments from Oregon and Washington streams were sampled to determine if current-use pyrethroid insecticides from residential neighborhoods were reaching aquatic habitats, and if they were at concentrations acutely toxic to sensitive invertebrates. Approximately one-third of the 35 sediment samples contained measurable pyrethroids. Bifenthrin was the pyrethroid of greatest concern with regards to aquatic life toxicity, consistent with prior studies elsewhere. Toxicity to Hyalella azteca and/or Chironomus dilutus was found in two sediment samples at standard testing temperature (23 deg. C), and in one additional sample at a more environmentally realistic temperature (13 deg. C). Given the temperature dependency of pyrethroid toxicity, low temperatures typical of northwest streams can increase the potential for toxicity above that indicated by standard testing protocols. - Highlights: → Salmon-bearing creeks can be adversely impacted by insecticides from urban runoff. → Pyrethroid insecticides were found in one-third of the creeks in Washington and Oregon. → Two creeks contained concentrations acutely lethal to sensitive invertebrates. → Bifenthrin was of greatest concern, though less than in prior studies. → Standard toxicity testing underestimates the ecological risk of pyrethroids. - Pyrethroid insecticides are present in sediments of urban creeks of Oregon and Washington, though less commonly than in studies elsewhere in the U.S.

  17. Pyrethroid as a Substance of Abuse

    Directory of Open Access Journals (Sweden)

    Pravesh Sharma

    2014-01-01

    Full Text Available This is a case of a 22-year-old Hispanic male with a history of bipolar disorder and methamphetamine dependence who was admitted after presenting with suicidal ideations by slashing his throat with a machete. The patient had been smoking and inhaling “processed” pyrethroid for about eight weeks as an inexpensive methamphetamine substitute. He reported experiencing a “rush” similar to methamphetamine after using pyrethroid from liquid insecticide that had been heated (electrocuted or sprayed on hot metal sheets until it crystallized. The patient presented with no significant physical markings or findings but claimed to have his suicidal ideations precipitated by concerns of ill effects of pyrethroid on his health. He also had positive urine drug screen for methamphetamine, which he admitted to using on the day of admission. We conclude that it is important for physicians to maintain a high level of suspicion for alternate and uncommon substances of abuse as well as risks for suicidal tendencies in these patients.

  18. GC X GCTOFMS OF SYNTHETIC PYRETHROIDS IN FOODS SAMPLES

    Science.gov (United States)

    Pyrethrins are natural insecticides in the extract of chrysanthemum flowers1. Pyrethroids are synthetic forms of pyrethrins, and many are halogenated (F, Cl, Br). Synthetic pyrethroids have become popular replacements for organophosphorus pesticides, which have become increasin...

  19. Identification and characterisation of Aedes aegypti aldehyde dehydrogenases involved in pyrethroid metabolism.

    Directory of Open Access Journals (Sweden)

    Nongkran Lumjuan

    Full Text Available Pyrethroid insecticides, especially permethrin and deltamethrin, have been used extensively worldwide for mosquito control. However, insecticide resistance can spread through a population very rapidly under strong selection pressure from insecticide use. The upregulation of aldehyde dehydrogenase (ALDH has been reported upon pyrethroid treatment. In Aedes aegypti, the increase in ALDH activity against the hydrolytic product of pyrethroid has been observed in DDT/permethrin-resistant strains. The objective of this study was to identify the role of individual ALDHs involved in pyrethroid metabolism.Three ALDHs were identified; two of these, ALDH9948 and ALDH14080, were upregulated in terms of both mRNA and protein levels in a DDT/pyrethroid-resistant strain of Ae. aegypti. Recombinant ALDH9948 and ALDH14080 exhibited oxidase activities to catalyse the oxidation of a permethrin intermediate, phenoxybenzyl aldehyde (PBald, to phenoxybenzoic acid (PBacid.ALDHs have been identified in association with permethrin resistance in Ae. aegypti. Characterisation of recombinant ALDHs confirmed the role of this protein in pyrethroid metabolism. Understanding the biochemical and molecular mechanisms of pyrethroid resistance provides information for improving vector control strategies.

  20. Demand and willingness-to-pay for bed nets in Tanzania: results from a choice experiment.

    Science.gov (United States)

    Gingrich, Chris D; Ricotta, Emily; Kahwa, Amos; Kahabuka, Catherine; Koenker, Hannah

    2017-07-14

    Universal coverage campaigns for long-lasting insecticide-treated nets do not always reach the goal of one net for every two household members, and even when ownership of at least one net per household is high, many households may not own enough nets. The retail market provides these households options for replacing or increasing the number of nets they own with products that best fit their needs since a variety of net shapes, sizes, and colours are available. Hence, it is important to understand the factors affecting private net demand. This study explores private demand for nets in Tanzania using a discrete choice experiment. The experiment provides participants the option to buy nets with their own money, and thus should prove more accurate than a hypothetical survey of net preferences. Nearly 800 participants sampled in two regions showed an overall strong demand for nets, with 40% choosing to buy a net across all seven combinations of net prices and characteristics such as size, shape, and insecticide treatment. Only 8% of all participants chose not to buy a single net. A key factor influencing demand was whether a participant's household currently owned sufficient nets for all members, with rural participants showing lower net coverage and greater demand than urban participants. Both poor and less poor households showed strong evidence of making purchase decisions based on more than price alone. Mean willingness-to-pay values for a net started at US$1.10 and grew by US$0.50-1.40 for various attributes such as rectangular shape, large size, and insecticide treatment. The impact of price on demand was negative but small, with elasticity values between -0.25 and -0.45. The results suggest that private demand for nets in Tanzania could potentially supplement future coverage campaigns. Net manufacturers and retailers should advertise and promote consumers' preferred net attributes to improve sales and further expand net access and coverage. To overcome household

  1. Pyrethroid insecticides and radioligand displacement from the GABA receptor chloride ionophore complex

    International Nuclear Information System (INIS)

    Crofton, K.M.; Reiter, L.W.; Mailman, R.B.

    1987-01-01

    Radioligand binding displacement studies were conducted to determine the effects of Type I and II pyrethroids on 3 H-flunitrazepam (FLU), 3 H-muscimol (MUS), and ( 35 S-t-butylbicyclophosphorothionate (TBPS) binding. Competition experiments with 3 H-FLU and 3 H-MUS indicate a lack of competition for binding by the pyrethroids. Type I pyrethroids failed to compete for the binding of ( 35 S-TBPS at concentrations as high as 50 pM. Type II pyrethroids inhibited ( 35 S-TBPS binding to rat brain synaptosomes with Ki values ranging from 5-10 pM. The data presented suggest that the interaction of Type II pyrethroids with the GABA receptor-ionophore complex is restricted to a site near the TBPS/picrotoxinin binding site

  2. Optimizing nitrate removal in woodchip beds treating aquaculture effluents

    DEFF Research Database (Denmark)

    von Ahnen, Mathis; Pedersen, Per Bovbjerg; Hoffmann, Carl Christian

    2016-01-01

    Nitrate is typically removed from aquaculture effluents using heterotrophic denitrification reactors. Heterotrophic denitrification reactors, however, require a constant input of readily available organic carbon (C) sources which limits their application in many aquaculture systems for practical...... and/or economic reasons.A potential alternative technology for removing nitrate currently applied for treating surface and drainage water is based on using wood by-products as a carbon source for denitrification. Using lab-scale horizontal-flow woodchip filters, the current study investigated...... the potential of optimizing woodchip reactors for treating aquaculture effluent. A central composite design (CCD) was applied to assess the effects of simultaneously changing the empty bed contact time (EBCTs of 5.0-15.0 h; corresponding to theoretical hydraulic retention times of 3.3-9.9 h) and bicarbonate...

  3. Correlation of tissue concentrations of the pyrethroid bifenthrin with neurotoxicity in the rat

    Science.gov (United States)

    Pyrethroids are neurotoxic insecticides used in a variety of agricultural and household products. Due to the phase-out oforganophosphate pesticides, the use of pyrethroids has increased. The potential for human exposure to pyrethroids has prompted pharmacodynamic and pharmacokine...

  4. Utilization, retention and bio-efficacy studies of PermaNet® in selected villages in Buie and Fentalie districts of Ethiopia

    Directory of Open Access Journals (Sweden)

    Balkew Meshesha

    2009-05-01

    Full Text Available Abstract Background Malaria remains a major public health problem in Ethiopia. Pyrethroid-treated mosquito nets are one of the major tools available for the prevention and control of malaria transmission. PermaNet® is a long-lasting insecticide-treated net (LLIN recommended by WHO for malaria control. Objective The objective of the study was to assess utilization and retention of PermaNet® nets distributed for malaria control in Buie and Fentalie districts and monitor the bio-efficacy of the nets using the WHO cone bioassay test procedures. Methods A cross sectional study was carried out by interviewing household heads or their representative in Buie and Fentalie districts. The two districts were selected based on a priori knowledge of variations on ethnic background and housing construction. Clusters of houses were chosen within each of the study villages for selection of households. 20 households that had received one or more PermaNet® nets were chosen randomly from the clusters in each village. A total of eight used PermaNet® nets were collected for the bio-efficacy test. The bio-efficacy of PermaNet® nets was monitored according to the standard WHO procedures using a susceptible colony of Anopheles arabiensis to deltamethrin. Results A total of 119 household heads were interviewed during the study. The retention rate of nets that were distributed in 2005 and 2006 season was 72%. A total of 62.2% of the interviewees claimed children under five years of age slept under LLIN, while only 50.7% of the nets were observed to be hanged inside houses when used as a proxy indicator of usage of LLIN. For the bio-efficacy test the mean knock-down was 94% and 100%, while the mean mortality rate observed after 24 hr holding period was 72.2% and 67% for Buie and Fentalie districts respectively. Conclusion The study revealed a moderately high retention of PermaNet® in the study villages and effectiveness of the nets when tested according to the

  5. Residential runoff as a source of pyrethroid pesticides to urban creeks

    Energy Technology Data Exchange (ETDEWEB)

    Weston, D.P. [Department of Integrative Biology, University of California, 3060 Valley Life Sciences Building, Berkeley, CA 94720-3140 (United States)], E-mail: dweston@berkeley.edu; Holmes, R.W. [Water Branch, California Department of Fish and Game, 830 S Street, Sacramento, CA 95811 (United States)], E-mail: rholmes@dfg.ca.gov; Lydy, M.J. [Fisheries and Illinois Aquaculture Center, Department of Zoology, Southern Illinois University, 171 Life Sciences II, Carbondale, IL 62901 (United States)], E-mail: mlydy@siu.edu

    2009-01-15

    Pyrethroid pesticides occur in urban creek sediments at concentrations acutely toxic to sensitive aquatic life. To better understand the source of these residues, runoff from residential neighborhoods around Sacramento, California was monitored over the course of a year. Pyrethroids were present in every sample. Bifenthrin, found at up to 73 ng/L in the water and 1211 ng/g on suspended sediment, was the pyrethroid of greatest toxicological concern, with cypermethrin and cyfluthrin of secondary concern. The bifenthrin could have originated either from use by consumers or professional pest controllers, though the seasonal pattern of discharge from the drain was more consistent with professional use as the dominant source. Stormwater runoff was more important than dry season irrigation runoff in transporting pyrethroids to urban creeks. A single intense storm was capable of discharging as much bifenthrin to an urban creek in 3 h as that discharged over 6 months of irrigation runoff. - Pyrethroid insecticides regularly detected in residential runoff at toxicologically significant concentrations.

  6. Residential runoff as a source of pyrethroid pesticides to urban creeks

    International Nuclear Information System (INIS)

    Weston, D.P.; Holmes, R.W.; Lydy, M.J.

    2009-01-01

    Pyrethroid pesticides occur in urban creek sediments at concentrations acutely toxic to sensitive aquatic life. To better understand the source of these residues, runoff from residential neighborhoods around Sacramento, California was monitored over the course of a year. Pyrethroids were present in every sample. Bifenthrin, found at up to 73 ng/L in the water and 1211 ng/g on suspended sediment, was the pyrethroid of greatest toxicological concern, with cypermethrin and cyfluthrin of secondary concern. The bifenthrin could have originated either from use by consumers or professional pest controllers, though the seasonal pattern of discharge from the drain was more consistent with professional use as the dominant source. Stormwater runoff was more important than dry season irrigation runoff in transporting pyrethroids to urban creeks. A single intense storm was capable of discharging as much bifenthrin to an urban creek in 3 h as that discharged over 6 months of irrigation runoff. - Pyrethroid insecticides regularly detected in residential runoff at toxicologically significant concentrations

  7. Toxicokinetics of the pyrethroid insecticide bifenthrin in blood and brain of the rat

    Science.gov (United States)

    Bifenthrin is a pyrethroid insecticide and human exposure to it can occur by oral, pulmonary and dermal routes. Pyrethroids are neurotoxic agents and it is generally believed that the parent pyrethroid is the toxic entity. The objective of this study was to assess the toxicokinet...

  8. Inequalities in purchase of mosquito nets and willingness to pay for insecticide-treated nets in Nigeria: Challenges for malaria control interventions

    Directory of Open Access Journals (Sweden)

    Hanson Kara

    2004-03-01

    Full Text Available Abstract Objective To explore the equity implications of insecticide-treated nets (ITN distribution programmes that are based on user charges. Methods A questionnaire was used to collect information on previous purchase of untreated nets and hypothetical willingness to pay (WTP for ITNs from a random sample of householders. A second survey was conducted one month later to collect information on actual purchases of ITNs. An economic status index was used for characterizing inequity. Major findings The lower economic status quintiles were less likely to have previously purchased untreated nets and also had a lower hypothetical and actual WTP for ITNs. Conclusion ITN distribution programmes need to take account of the diversity in WTP for ITNs if they are to ensure equity in access to the nets. This could form part of the overall poverty reduction strategy.

  9. Pyrethroid-Degrading Microorganisms and Their Potential for the Bioremediation of Contaminated Soils: A Review

    Science.gov (United States)

    Cycoń, Mariusz; Piotrowska-Seget, Zofia

    2016-01-01

    Pyrethroid insecticides have been used to control pests in agriculture, forestry, horticulture, public health and for indoor home use for more than 20 years. Because pyrethroids were considered to be a safer alternative to organophosphate pesticides (OPs), their applications significantly increased when the use of OPs was banned or limited. Although, pyrethroids have agricultural benefits, their widespread and continuous use is a major problem as they pollute the terrestrial and aquatic environments and affect non-target organisms. Since pyrethroids are not degraded immediately after application and because their residues are detected in soils, there is an urgent need to remediate pyrethroid-polluted environments. Various remediation technologies have been developed for this purpose; however, bioremediation, which involves bioaugmentation and/or biostimulation and is a cost-effective and eco-friendly approach, has emerged as the most advantageous method for cleaning-up pesticide-contaminated soils. This review presents an overview of the microorganisms that have been isolated from pyrethroid-polluted sites, characterized and applied for the degradation of pyrethroids in liquid and soil media. The paper is focused on the microbial degradation of the pyrethroids that have been most commonly used for many years such as allethrin, bifenthrin, cyfluthrin, cyhalothrin, cypermethrin, deltamethrin, fenpropathrin, fenvalerate, and permethrin. Special attention is given to the bacterial strains from the genera Achromobacter, Acidomonas, Bacillus, Brevibacterium, Catellibacterium, Clostridium, Lysinibacillus, Micrococcus, Ochrobactrum, Pseudomonas, Serratia, Sphingobium, Streptomyces, and the fungal strains from the genera Aspergillus, Candida, Cladosporium, and Trichoderma, which are characterized by their ability to degrade various pyrethroids. Moreover, the current knowledge on the degradation pathways of pyrethroids, the enzymes that are involved in the cleavage of

  10. Pyrethroid-Degrading Microorganisms and Their Potential for the Bioremediation of Contaminated Soils: A Review

    Directory of Open Access Journals (Sweden)

    Mariusz Sebastian Cycoń

    2016-09-01

    Full Text Available Pyrethroid insecticides have been used to control pests in agriculture, forestry, horticulture, public health and for indoor home use for more than 20 years. Because pyrethroids were considered to be a safer alternative to organophosphate pesticides (OPs, their applications significantly increased when the use of OPs was banned or limited. Although pyrethroids have agricultural benefits, their widespread and continuous use is a major problem as they pollute the terrestrial and aquatic environments and affect non-target organisms. Since pyrethroids are not degraded immediately after application and because their residues are detected in soils, there is an urgent need to remediate pyrethroid-polluted environments. Various remediation technologies have been developed for this purpose; however, bioremediation, which involves bioaugmentation and/or biostimulation and is a cost-effective and eco-friendly approach, has emerged as the most advantageous method for cleaning-up pesticide-contaminated soils. This review presents an overview of the microorganisms that have been isolated from pyrethroid-polluted sites, characterized and applied for the degradation of pyrethroids in liquid and soil media. The paper is focused on the microbial degradation of the pyrethroids that have been most commonly used for many years such as allethrin, bifenthrin, cyfluthrin, cyhalothrin, cypermethrin, deltamethrin, fenpropathrin, fenvalerate and permethrin. Special attention is given to the bacterial strains from the genera Achromobacter, Acidomonas, Bacillus, Brevibacterium, Catellibacterium, Clostridium, Lysinibacillus, Micrococcus, Ochrobactrum, Pseudomonas, Serratia, Sphingobium, Streptomyces and the fungal strains from the genera Aspergillus, Candida, Cladosporium and Trichoderma, which are characterized by their ability to degrade various pyrethroids. Moreover, the current knowledge on the degradation pathways of pyrethroids, the enzymes that are involved in the

  11. Is cumulated pyrethroid exposure associated with prediabetes?

    DEFF Research Database (Denmark)

    Hansen, Martin Rune; Jørs, Erik; Lander, Flemming

    2014-01-01

    was to investigate an association between exposure to pyrethroids and abnormal glucose regulation (prediabetes or diabetes). A cross-sectional study was performed among 116 pesticide sprayers from public vector control programs in Bolivia and 92 nonexposed controls. Pesticide exposure (duration, intensity...... pyrethroids, a significant positive trend was observed between cumulative pesticide exposure (total number of hours sprayed) and adjusted OR of abnormal glucose regulation, with OR 14.7 [0.9-235] in the third exposure quintile. The study found a severely increased prevalence of prediabetes among Bolivian...

  12. Use of insecticide-treated mosquito nets for children under five years ...

    African Journals Online (AJOL)

    2011-06-13

    Jun 13, 2011 ... Background: Insecticide-treated nets (ITNs) have proven to be one of the most effective means of reducing malaria morbidity and mortality in children and pregnant women. This study is carried out to determine the practice and determinants of ITN use for children under five years among care givers in an ...

  13. Mobility of adult Tribolium castaneum (Coleoptera: Tenebrionidae) and Rhyzopertha dominica (Coleoptera: Bostrichidae) after exposure to long-lasting insecticide netting

    Science.gov (United States)

    Stored products represent an enormous economic output, but insects regularly immigrate into stored products from the surrounding landscape throughout the post-harvest supply chain. Long-lasting insecticide netting (LLIN), which usually contains an impregnated pyrethroid, has been used as part of a s...

  14. Transcription profiling of a recently colonised pyrethroid resistant Anopheles gambiae strain from Ghana

    Directory of Open Access Journals (Sweden)

    Donnelly Martin J

    2007-01-01

    Full Text Available Abstract Background Mosquito resistance to the pyrethroid insecticides used to treat bednets threatens the sustainability of malaria control in sub-Saharan Africa. While the impact of target site insensitivity alleles is being widely discussed the implications of insecticide detoxification – though equally important – remains elusive. The successful development of new tools for malaria intervention and management requires a comprehensive understanding of insecticide resistance, including metabolic resistance mechanisms. Although three enzyme families (cytochrome P450s, glutathione S-transferases and carboxylesterases have been widely associated with insecticide detoxification the role of individual enzymes is largely unknown. Results Here, constitutive expression patterns of genes putatively involved in conferring pyrethroid resistance was investigated in a recently colonised pyrethroid resistant Anopheles gambiae strain from Odumasy, Southern Ghana. RNA from the resistant strain and a standard laboratory susceptible strain, of both sexes was extracted, reverse transcribed and labelled with either Cy3- or Cy5-dye. Labelled cDNA was co-hybridised to the detox chip, a custom-made microarray containing over 230 A. gambiae gene fragments predominantly from enzyme families associated with insecticide resistance. After hybridisation, Cy3- and Cy5-signal intensities were measured and compared gene by gene. In both females and males of the resistant strain the cytochrome P450s CYP6Z2 and CYP6M2 are highly over-expressed along with a member of the superoxide dismutase (SOD gene family. Conclusion These genes differ from those found up-regulated in East African strains of pyrethroid resistant A. gambiae and constitute a novel set of candidate genes implicated in insecticide detoxification. These data suggest that metabolic resistance may have multiple origins in A. gambiae, which has strong implications for the management of resistance.

  15. Bed Bugs

    Science.gov (United States)

    Prevent, identify, and treat bed bug infestations using EPA’s step-by-step guides, based on IPM principles. Find pesticides approved for bed bug control, check out the information clearinghouse, and dispel bed bug myths.

  16. Long-lasting insecticidal net source, ownership and use in the context of universal coverage: a household survey in eastern Rwanda.

    Science.gov (United States)

    Kateera, Fredrick; Ingabire, Chantal M; Hakizimana, Emmanuel; Rulisa, Alexis; Karinda, Parfait; Grobusch, Martin P; Mutesa, Leon; van Vugt, Michèle; Mens, Petra F

    2015-10-06

    Universal long-lasting insecticidal net (LLIN) coverage (ULC) has reduced malaria morbidity and mortality across Africa. Although information is available on bed net use in specific groups, such as pregnant women and children under 5 years, there is paucity of data on their use among the general population. Bed net source, ownership and determinants of use among individuals from households in an eastern Rwanda community 8 months after a ULC were characterized. Using household-based, interviewer-administered questionnaires and interviewer-direct observations, data on bed net source, ownership and key determinants of net use, including demographics, socio-economic status indicators, house structure characteristics, as well as of bed net quantity, type and integrity, were collected from 1400 randomly selected households. Univariate and mixed effects logistic regression modelling was done to assess for determinants of bed net use. A total of 1410 households and 6598 individuals were included in the study. Overall, the proportion of households with at least one net was 92 % while bed net usage was reported among 72 % of household members. Of the households surveyed, a total ownership of 2768 nets was reported, of which about 96 % were reportedly LLINs received from the ULC. By interviewer-physical observation, 88 % of the nets owned were of the LLIN type with the remaining 12 % did not carry any mark to enable type recognition. The odds of bed net use were significantly lower among males and individuals: from households of low socio-economic status, from households with economic status, number of bed nets and type and number of sleeping spaces were key determinants of bed net use. To maximize impact of ULC, strategies that target males as well as those that ensure ITN coverage for all, address barriers to feasible and convenient bed net use including covering over all sleeping space types, and provide net hanging supports, are needed.

  17. A survey of pyrethroid-resistant populations of Meligethes aeneus F. in Poland indicates the incidence of numerous substitutions in the pyrethroid target site of voltage-sensitive sodium channels in individual beetles.

    Science.gov (United States)

    Wrzesińska, B; Czerwoniec, A; Wieczorek, P; Węgorek, P; Zamojska, J; Obrępalska-Stęplowska, A

    2014-10-01

    The pollen beetle (Meligethes aeneus F.) is the most devastating pest of oilseed rape (Brassica napus) and is controlled by pyrethroid insecticides. However, resistance to pyrethroids in Europe is becoming widespread and predominant. Pyrethroids target the voltage-sensitive sodium channel (VSSC), and mutations in VSSC may be responsible for pyrethroid insensitivity. Here, we analysed individual beetles that were resistant to esfenvalerate, a pyrethroid, from 14 populations that were collected from oilseed rape fields in Poland. We screened the VSSC domains that were presumed to directly interact with pyrethroids. We identified 18 heterozygous nucleic acid substitutions, amongst which six caused an amino acid change: N912S, G926S, I936V, R957G, F1538L and E1553G. Our analysis of the three-dimensional structure of these domains in VSSC revealed that some of these changes may slightly influence the protein structure and hence the docking efficiency of esfenvalerate. Therefore, these mutations may impact the susceptibility of the sodium channel to the action of this insecticide. © 2014 The Royal Entomological Society.

  18. Novel Mutations in the Voltage-Gated Sodium Channel of Pyrethroid-Resistant Varroa destructor Populations from the Southeastern USA

    Science.gov (United States)

    González-Cabrera, Joel; Rodríguez-Vargas, Sonia; Davies, T. G. Emyr; Field, Linda M.; Schmehl, Daniel; Ellis, James D.; Krieger, Klemens; Williamson, Martin S.

    2016-01-01

    The parasitic mite Varroa destructor has a significant worldwide impact on bee colony health. In the absence of control measures, parasitized colonies invariably collapse within 3 years. The synthetic pyrethroids tau-fluvalinate and flumethrin have proven very effective at managing this mite within apiaries, but intensive control programs based mainly on one active ingredient have led to many reports of pyrethroid resistance. In Europe, a modification of leucine to valine at position 925 (L925V) of the V. destructor voltage-gated sodium channel was correlated with resistance, the mutation being found at high frequency exclusively in hives with a recent history of pyrethroid treatment. Here, we identify two novel mutations, L925M and L925I, in tau-fluvalinate resistant V. destructor collected at seven sites across Florida and Georgia in the Southeastern region of the USA. Using a multiplexed TaqMan® allelic discrimination assay, these mutations were found to be present in 98% of the mites surviving tau-fluvalinate treatment. The mutations were also found in 45% of the non-treated mites, suggesting a high potential for resistance evolution if selection pressure is applied. The results from a more extensive monitoring programme, using the Taqman® assay described here, would clearly help beekeepers with their decision making as to when to include or exclude pyrethroid control products and thereby facilitate more effective mite management programmes. PMID:27191597

  19. Novel Mutations in the Voltage-Gated Sodium Channel of Pyrethroid-Resistant Varroa destructor Populations from the Southeastern USA.

    Science.gov (United States)

    González-Cabrera, Joel; Rodríguez-Vargas, Sonia; Davies, T G Emyr; Field, Linda M; Schmehl, Daniel; Ellis, James D; Krieger, Klemens; Williamson, Martin S

    2016-01-01

    The parasitic mite Varroa destructor has a significant worldwide impact on bee colony health. In the absence of control measures, parasitized colonies invariably collapse within 3 years. The synthetic pyrethroids tau-fluvalinate and flumethrin have proven very effective at managing this mite within apiaries, but intensive control programs based mainly on one active ingredient have led to many reports of pyrethroid resistance. In Europe, a modification of leucine to valine at position 925 (L925V) of the V. destructor voltage-gated sodium channel was correlated with resistance, the mutation being found at high frequency exclusively in hives with a recent history of pyrethroid treatment. Here, we identify two novel mutations, L925M and L925I, in tau-fluvalinate resistant V. destructor collected at seven sites across Florida and Georgia in the Southeastern region of the USA. Using a multiplexed TaqMan® allelic discrimination assay, these mutations were found to be present in 98% of the mites surviving tau-fluvalinate treatment. The mutations were also found in 45% of the non-treated mites, suggesting a high potential for resistance evolution if selection pressure is applied. The results from a more extensive monitoring programme, using the Taqman® assay described here, would clearly help beekeepers with their decision making as to when to include or exclude pyrethroid control products and thereby facilitate more effective mite management programmes.

  20. Evolution of resistance to pyrethroid insecticides in Musca domestica.

    Science.gov (United States)

    Scott, Jeffrey G

    2017-04-01

    Houseflies, Musca domestica L., are a significant pest because of the numerous diseases they transmit. Control of housefly populations, particularly at animal production facilities, is frequently done using pyrethroid insecticides which kill insects by prolonging the open time of the voltage-sensitive sodium channel (VSSC). Houseflies have evolved resistance to pyrethroids owing to mutations in Vssc and by cytochrome-P450-mediated detoxification. Three Vssc mutations are known: kdr (L1014F), kdr-his (L1014H) and super-kdr (M918T + L1014F). Generally, the levels of resistance conferred by these mutations are kdr-his resistance than kdr. P450-mediated resistance can result from overexpression of CYP6D1 or another P450 (unidentified) whose overexpression is linked to autosomes II or V. The initial use of field-stable pyrethroids resulted in different patterns of evolution across the globe, but with time these mutations have become more widespread in their distribution. What is known about the fitness costs of the resistance alleles in the absence of insecticide is discussed, particularly with respect to the current and future utility of pyrethroid insecticides. © 2016 Society of Chemical Industry. © 2016 Society of Chemical Industry.

  1. A cluster randomized controlled cross-over bed net acceptability and preference trial in Solomon Islands: community participation in shaping policy for malaria elimination

    Directory of Open Access Journals (Sweden)

    Appleyard Bridget

    2009-12-01

    Full Text Available Abstract Background A key component of the malaria elimination strategy in Solomon Islands (SI is widespread coverage of long-lasting insecticidal nets (LLINs. The success of this strategy is dependent on LLIN acceptability and compliance. There has been unresolved debate among policy makers and donors as to which type of LLIN would be most appropriate for large-scale distribution in SI, and anecdotal reports of a lack of acceptability of certain brands of LLINs. A cluster randomized controlled crossover bed net acceptability and preference trial was therefore carried out from July to September, 2008 to inform policy and to facilitate community engagement and participation in the selection of the most appropriate LLIN for use in SI. Method A three-stage sampling method was used to randomly select the study population from Malaita Province, SI. Three brands of LLINs were assessed in this study: Olyset®, PermaNet® and DuraNet®. Bed net acceptability and preference were evaluated through surveys at three defined time points after short and longer-term trial of each LLIN. Results The acceptability of PermaNet® after short-term use (96.5% was significantly greater than Olyset® (67.3%, p and DuraNet® (69.8%, p . The acceptability of DuraNet® and Olyset® after short-term use was not significantly different at the 5% level. LLINs that were perceived not to prevent mosquito bites were significantly less acceptable than LLINs that were perceived to prevent mosquito bites (OR 0.15; 95%CI 0.03 to 0.6. LLINs that allow a pleasant night's sleep (OR 6.3; 95%CI:3.3-12.3 and have a soft texture (OR 5.7; 95%CI:1.9-20.5 were considered more acceptable than those that did not. Olyset®'s acceptability decreased over time and this was due to net wrinkling/shrinkage after washing resulting in reduced efficiency in preventing mosquito bites. The increase in DuraNet® acceptability was a result of a reduction in minor adverse events following longer-term use

  2. Recent advances of pyrethroids for household use.

    Science.gov (United States)

    Ujihara, Kazuya; Mori, Tatsuya; Matsuo, Noritada

    2012-01-01

    Development of pyrethroids for household use and recent advances in the syntheses of (1R)-trans-chrysanthemic acid, the acid moiety of most of the household pyrethroids, are reviewed. As another important acid moiety, we discovered norchrysanthemic acid to have a significant vapor action at room temperature when esterified with fluorobenzyl alcohols. In particular, 2,3,5,6-tetrafluoro-4-methoxymethylbenzyl (1R)-trans-norchrysanthemate (metofluthrin) exhibits the highest potency in mosquito coil formulations as well as the vapor action at room temperature against various mosquitoes. Structure-activity relationships of norchrysanthemic acid esters and synthetic studies of norchrysanthemic acid are discussed.

  3. Benefit of insecticide-treated nets, curtains and screening on vector borne diseases, excluding malaria: a systematic review and meta-analysis

    NARCIS (Netherlands)

    Wilson, A.L.; Dhiman, R.C.; Kitron, U.; Scott, T.W.; Berg, van den H.; Lindsay, S.W.

    2014-01-01

    Introduction Insecticide-treated nets (ITNs) are one of the main interventions used for malaria control. However, these nets may also be effective against other vector borne diseases (VBDs). We conducted a systematic review and meta-analysis to estimate the efficacy of ITNs, insecticide-treated

  4. Knowledge, access and utilization of bed-nets among stable and seasonal migrants in an artemisinin resistance containment area of Myanmar

    OpenAIRE

    Phyo Than, Wint; Oo, Tin; Wai, Khin Thet; Thi, Aung; Owiti, Philip; Kumar, Binay; Deepak Shewade, Hemant; Zachariah, Rony

    2017-01-01

    Background Myanmar lies in the Greater Mekong sub-region of South-East Asia faced with the challenge of emerging resistance to artemisinin combination therapies (ACT). Migrant populations are more likely than others to spread ACT resistance. A vital intervention to reduce malaria transmission, resistance spread and eliminate malaria is the use of bed nets. Among seasonal and stable migrants in an artemisinin resistance containment region of Myanmar, we compared a) their household characterist...

  5. Computational tool for immunotoxic assessment of pyrethroids toward adaptive immune cell receptors.

    Science.gov (United States)

    Kumar, Anoop; Behera, Padma Charan; Rangra, Naresh Kumar; Dey, Suddhasattya; Kant, Kamal

    2018-01-01

    Pyrethroids have prominently known for their insecticidal actions worldwide, but recent reports as anticancer and antiviral applications gained a lot of interest to further understand their safety and immunotoxicity. This encouraged us to carry out our present study to evaluate the interactions of pyrethroids toward adaptive immune cell receptors. Type 1 and Type 2 pyrethroids were tested on T (CD4 and CD8) and B (CD28 and CD45) immune cell receptors using Maestro 9.3 (Schrödinger, LLC, Cambridge, USA). In addition, top-ranked tested ligands were too explored for toxicity prediction in rodents using ProTOX tool. Pyrethroids (specifically type 2) such as fenvalerate (-5.534 kcal/mol: CD8), fluvalinate (-4.644 and - 4.431 kcal/mol: CD4 and CD45), and cypermethrin (-3.535 kcal/mol: CD28) have outcome in less energy or more affinity for B-cell and T-cell immune receptors which may later result in the immunosuppressive and hypersensitivity reactions. The current findings have uncovered that there is a further need to assess the Type 2 pyrethroids with wet laboratory experiments to understand the chemical nature of pyrethroid-induced immunotoxicity. Fenvalerate showed apex glide score toward CD8 immune receptor, while fluvalinate confirmed top-ranked binding with CD4 and CD45 immune proteinsIn addition, cypermethrin outcame in top glide score against CD28 immune receptorTop dock hits (Type 2) pyrethroids have shown probable toxicity targets toward AOFA: Amine oxidase (flavin-containing) A and PGH1: Prostaglandin G/H synthase 1, respectively. Abbreviations used: PDB: Protein Data Bank; AOFA: Amine oxidase (flavin-containing) A; PGH 1: Prostaglandin G/H synthase 1.

  6. In vitro and in vivo experimental data for pyrethroid pharmacokinetic models: the case of bifenthrin

    Science.gov (United States)

    Pyrethroids are a class of neurotoxic synthetic pesticides. Exposure to pyrethroids has increased due to declining use of other classes of pesticides. Our studies are focused on generating in vitro and in vivo data for the development of pharmacokinetic models for pyrethroids. Us...

  7. Tissue time course and bioavailability of the pyrethroid insecticide bifenthrin in the Long-Evans rat

    Science.gov (United States)

    Bifenthrin is a pyrethroid insecticide and human exposure to it can occur by oral, pulmonary and dermal routes. Pyrethroids are neurotoxic agents and it is generally believed that the parent pyrethroid is the toxic entity. This study evaluated the oral disposition and bioavaila...

  8. Decreased proportions of indoor feeding and endophily in Anopheles gambiae s.l. populations following the indoor residual spraying and insecticide-treated net interventions in Benin (West Africa).

    Science.gov (United States)

    Padonou, Gil Germain; Gbedjissi, Ghelus; Yadouleton, Anges; Azondekon, Roseric; Razack, Ossé; Oussou, Olivier; Gnanguenon, Virgile; Rock, Aikpon; Sezonlin, Michel; Akogbeto, Martin

    2012-11-14

    In many parts of Africa as in Benin, the main strategies of vector control are based on the scaling-up of Long Lasting Insecticide Treated Nets (LLITNs) and indoor residual spraying (IRS). The need to understand the biological implications of IRS in large scale and full coverage of LLITNs is paramount. It is in this context that the present study was conducted. It aims to evaluate the effect of a large scale IRS using a non-pyrethroid insecticide and full coverage of deltamethrin treated nets on the behavior of An. gambiae s.l. in the intervention areas compared to untreated areas used as controls. Mosquitoes were collected using human landing catches, pyrethrum spray catches and window exit traps to assess reduction of entry rate, endophily rate, endophagy rate and overall mortality rate in natural populations of An. gambiae s.l. before IRS and LLITNs intervention (2007) and after in 2008 and 2010. In the IRS arm, endophily rate was 67.13% before intervention and 4.5% after intervention, whereas in the control arm it was stable at 51.67% (P > 0 .05). In the LLITN arm endophily rates also decreased after intervention. After the IRS, no gravid mosquitoes were collected from all treated localities, but LLITN performance was not that spectacular. The proportion of mosquitoes biting indoors in the IRS arm decreased from 67.09% before intervention to 42.85% after intervention, compared to a low but significant decrease (71.31% to 57. 46%) in the LLITN arm.The use of vector control tools and behavior of the host would be the main factors that modify the behavior of taking a human blood meal observed on An. gambiae s.l. inside human dwellings. The impact on the behavior of An. gambiae s.l. observed with the bendiocarb used in IRS was highly effective compared with the free distribution of LLITNs in terms of mortality and the decrease of proportions of indoor feeding. Despite this efficacy, there is a need for complementary tools and research of alternative strategy

  9. Decreased proportions of indoor feeding and endophily in Anopheles gambiae s.l. populations following the indoor residual spraying and insecticide-treated net interventions in Benin (West Africa

    Directory of Open Access Journals (Sweden)

    Padonou Gil

    2012-11-01

    Full Text Available Abstract Background In many parts of Africa as in Benin, the main strategies of vector control are based on the scaling-up of Long Lasting Insecticide Treated Nets (LLITNs and indoor residual spraying (IRS. The need to understand the biological implications of IRS in large scale and full coverage of LLITNs is paramount. It is in this context that the present study was conducted. It aims to evaluate the effect of a large scale IRS using a non-pyrethroid insecticide and full coverage of deltamethrin treated nets on the behavior of An. gambiae s.l. in the intervention areas compared to untreated areas used as controls. Methods Mosquitoes were collected using human landing catches, pyrethrum spray catches and window exit traps to assess reduction of entry rate, endophily rate, endophagy rate and overall mortality rate in natural populations of An. gambiae s.l. before IRS and LLITNs intervention (2007 and after in 2008 and 2010. Results In the IRS arm, endophily rate was 67.13% before intervention and 4.5% after intervention, whereas in the control arm it was stable at 51.67% (P > 0 .05. In the LLITN arm endophily rates also decreased after intervention. After the IRS, no gravid mosquitoes were collected from all treated localities, but LLITN performance was not that spectacular. The proportion of mosquitoes biting indoors in the IRS arm decreased from 67.09% before intervention to 42.85% after intervention, compared to a low but significant decrease (71.31% to 57. 46% in the LLITN arm. The use of vector control tools and behavior of the host would be the main factors that modify the behavior of taking a human blood meal observed on An. gambiae s.l. inside human dwellings. Conclusion The impact on the behavior of An. gambiae s.l. observed with the bendiocarb used in IRS was highly effective compared with the free distribution of LLITNs in terms of mortality and the decrease of proportions of indoor feeding. Despite this efficacy, there is a need

  10. Household possession, use and non-use of treated or untreated mosquito nets in two ecologically diverse regions of Nigeria – Niger Delta and Sahel Savannah

    Directory of Open Access Journals (Sweden)

    Otsemobor Peju

    2009-02-01

    Full Text Available Abstract Background Current use of treated mosquito nets for the prevention of malaria falls short of what is expected in sub-Saharan Africa (SSA, though research within the continent has indicated that the use of these commodities can reduce malaria morbidity by 50% and malaria mortality by 20%. Governments in sub-Sahara Africa are investing substantially in scaling-up treated mosquito net coverage for impact. However, certain significant factors still prevent the use of the treated mosquito nets, even among those who possess them. This survey examines household ownership as well as use and non-use of treated mosquito nets in Sahel Savannah and Niger Delta regions of Nigeria. Methodology This survey employed cross-sectional survey to collect data from households on coverage and use of mosquito nets, whether treated or not. Fever episodes in previous two weeks among children under the age of five were also recorded. The study took place in August 1 – 14 2007, just five months after the March distribution of treated mosquito nets, coinciding with the second raining period of the year and a time of high malaria transmission during the wet season. EPI INFO version 2003 was used in data analysis. Results The survey covered 439 households with 2,521 persons including 739 under-fives, 585 women in reproductive age and 78 pregnant women in Niger Delta Region and Sahel Savannah Region. Of the 439 HHs, 232 had any mosquito nets. Significantly higher proportion of households in the Niger Delta Region had any treated or untreated mosquito nets than those in the Sahel Savannah Region. In the Niger Delta Region, the proportion of under-fives that had slept under treated nets the night before the survey exceeded those that slept under treated nets in the Sahel Savannah Region. Children under the age of five years in the Niger Delta Region were four times more likely to sleep under treated nets than those in the Sahel Savannah Region. Conclusion This study

  11. Novel Mutations in the Voltage-Gated Sodium Channel of Pyrethroid-Resistant Varroa destructor Populations from the Southeastern USA.

    Directory of Open Access Journals (Sweden)

    Joel González-Cabrera

    Full Text Available The parasitic mite Varroa destructor has a significant worldwide impact on bee colony health. In the absence of control measures, parasitized colonies invariably collapse within 3 years. The synthetic pyrethroids tau-fluvalinate and flumethrin have proven very effective at managing this mite within apiaries, but intensive control programs based mainly on one active ingredient have led to many reports of pyrethroid resistance. In Europe, a modification of leucine to valine at position 925 (L925V of the V. destructor voltage-gated sodium channel was correlated with resistance, the mutation being found at high frequency exclusively in hives with a recent history of pyrethroid treatment. Here, we identify two novel mutations, L925M and L925I, in tau-fluvalinate resistant V. destructor collected at seven sites across Florida and Georgia in the Southeastern region of the USA. Using a multiplexed TaqMan® allelic discrimination assay, these mutations were found to be present in 98% of the mites surviving tau-fluvalinate treatment. The mutations were also found in 45% of the non-treated mites, suggesting a high potential for resistance evolution if selection pressure is applied. The results from a more extensive monitoring programme, using the Taqman® assay described here, would clearly help beekeepers with their decision making as to when to include or exclude pyrethroid control products and thereby facilitate more effective mite management programmes.

  12. Medications to Treat Bed-Wetting

    Science.gov (United States)

    ... suggest that depression plays a role in the cause of bed-wetting. This type of drug is thought to work one of several ways: by changing the child's sleep and wakening pattern by affecting the time ...

  13. Pyrethroid Activity-Based Probes for Profiling Cytochrome P450 Activities Associated with Insecticide Interactions

    Energy Technology Data Exchange (ETDEWEB)

    Ismail, Hanafy M.; O' Neill, Paul M.; Hong, David; Finn, Robert; Henderson, Colin; Wright, Aaron T.; Cravatt, Benjamin; Hemingway, Janet; Paine, Mark J.

    2014-01-18

    Pyrethroid insecticides are used to control a diverse spectrum of diseases spread by arthropods. We have developed a suite of pyrethroid mimetic activity based probes (PyABPs) to selectively label and identify P450s associated with pyrethroid metabolism. The probes were screened against pyrethroid metabolizing and non-metabolizing mosquito P450s, as well as rodent microsomes to measure labeling specificity, plus CPR and b5 knockout mouse livers to validate P450 activation and establish the role for b5 in probe activation. Using a deltamethrin mimetic PyABP we were able to profile active enzymes in rat liver microsomes and identify pyrethroid metabolizing enzymes in the target tissue. The most reactive enzyme was a P450, CYP2C11, which is known to metabolize deltamethrin. Furthermore, several other pyrethroid metabolizers were identified (CYPs 2C6, 3A4, 2C13 and 2D1) along with related detoxification enzymes, notably UDP-g’s 2B1 - 5, suggesting a network of associated pyrethroid metabolizing enzymes, or ‘pyrethrome’. Considering the central role that P450s play in metabolizing insecticides, we anticipate that PyABPs will aid the identification and profiling of P450s associated with insecticide pharmacology in a wide range of species, improving understanding of P450-insecticide interactions and aiding the development of new tools for disease control.

  14. Influence of Pyrethroid Insecticides on Sodium and Calcium Influx in Neocortical Neurons

    Science.gov (United States)

    Pyrethroid insecticides bind to voltage-gated sodium channels and modify their gating kinetics, thereby disrupting neuronal function. Using murine neocortical neurons in primary culture, we have compared the ability of 11 structurally diverse pyrethroid insecticides to evoke Na+ ...

  15. N-player mosquito net game: individual and social rationality in the misuse of insecticide-treated nets.

    Science.gov (United States)

    Honjo, Keita; Satake, Akiko

    2014-02-07

    Many governmental and non-governmental organizations have distributed insecticide-treated nets (ITNs) to malaria endemic areas, which contributed to the reduction of malaria deaths. However, some people in malaria endemic areas used ITNs for alternative purposes such as fishery and agriculture. It is unclear why people threatened by malaria misuse ITNs. Here we develop a N-player mosquito net game, and theoretically show that the misuse of ITNs might be underpinned by individual and social rationality. In the mosquito net game, each player uses ITNs for malaria prevention or alternative purposes. The proper ITN use decreases the probability of malaria infection, while the improper ITN use increases the player's labor productivity. Each player's expected payoff is influenced by other players' strategies. We found that the misuse of ITNs can be a Pareto efficient Nash equilibrium. The maximum number of players using ITNs for malaria prevention is limited by insecticidal effectiveness of ITNs and extra income from ITN misuse. Furthermore, we found that players in a low-income community are attracted to the misuse of ITNs even if the probability of malaria infection is high. Introduction of a tax on ITN misuse was shown to be effective to motivate the players to use ITNs for malaria prevention. Our results demonstrate that understanding decision making of people in malaria endemic areas is essential to design more effective malaria control programs. © 2013 Published by Elsevier Ltd. All rights reserved.

  16. Voltage-gated sodium channels as targets for pyrethroid insecticides.

    Science.gov (United States)

    Field, Linda M; Emyr Davies, T G; O'Reilly, Andrias O; Williamson, Martin S; Wallace, B A

    2017-10-01

    The pyrethroid insecticides are a very successful group of compounds that have been used extensively for the control of arthropod pests of agricultural crops and vectors of animal and human disease. Unfortunately, this has led to the development of resistance to the compounds in many species. The mode of action of pyrethroids is known to be via interactions with the voltage-gated sodium channel. Understanding how binding to the channel is affected by amino acid substitutions that give rise to resistance has helped to elucidate the mode of action of the compounds and the molecular basis of their selectivity for insects vs mammals and between insects and other arthropods. Modelling of the channel/pyrethroid interactions, coupled with the ability to express mutant channels in oocytes and study function, has led to knowledge of both how the channels function and potentially how to design novel insecticides with greater species selectivity.

  17. Mechanisms of pyrethroid insecticide-induced stimulation of calcium influx in neocortical neurons

    Science.gov (United States)

    Pyrethroid insecticides bind to voltage-gated sodium channels (VGSCs) and modify their gating kinetics, thereby disrupting neuronal function. Pyrethroids have also been reported to alter the function of other channel types, including activation of voltage-gated Ca2+ calcium chann...

  18. Pyrethroid activity-based probes for profiling cytochrome P450 activities associated with insecticide interactions.

    Science.gov (United States)

    Ismail, Hanafy M; O'Neill, Paul M; Hong, David W; Finn, Robert D; Henderson, Colin J; Wright, Aaron T; Cravatt, Benjamin F; Hemingway, Janet; Paine, Mark J I

    2013-12-03

    Pyrethroid insecticides are used to control diseases spread by arthropods. We have developed a suite of pyrethroid mimetic activity-based probes (PyABPs) to selectively label and identify P450s associated with pyrethroid metabolism. The probes were screened against pyrethroid-metabolizing and nonmetabolizing mosquito P450s, as well as rodent microsomes, to measure labeling specificity, plus cytochrome P450 oxidoreductase and b5 knockout mouse livers to validate P450 activation and establish the role for b5 in probe activation. Using PyABPs, we were able to profile active enzymes in rat liver microsomes and identify pyrethroid-metabolizing enzymes in the target tissue. These included P450s as well as related detoxification enzymes, notably UDP-glucuronosyltransferases, suggesting a network of associated pyrethroid-metabolizing enzymes, or "pyrethrome." Considering the central role P450s play in metabolizing insecticides, we anticipate that PyABPs will aid in the identification and profiling of P450s associated with insecticide pharmacology in a wide range of species, improving understanding of P450-insecticide interactions and aiding the development of unique tools for disease control.

  19. Is imidacloprid an effective alternative for controlling pyrethroid-resistant populations of Triatoma infestans (Hemiptera: Reduviidae in the Gran Chaco ecoregion?

    Directory of Open Access Journals (Sweden)

    Guillermo Carvajal

    2014-09-01

    Full Text Available The prevention of Chagas disease is based primarily on the chemical control of Triatoma infestans (Klug using pyrethroid insecticides. However, high resistance levels, correlated with control failures, have been detected in Argentina and Bolivia. A previous study at our laboratory found that imidacloprid could serve as an alternative to pyrethroid insecticides. We studied the delayed toxicity of imidacloprid and the influence of the blood feeding condition of the insect on the toxicity of this insecticide; we also studied the effectiveness of various commercial imidacloprid formulations against a pyrethroid-resistant T. infestans population from the Gran Chaco ecoregion. Variations in the toxic effects of imidacloprid were not observed up to 72 h after exposure and were not found to depend on the blood feeding condition of susceptible and resistant individuals. Of the three different studied formulations of imidacloprid on glass and filter paper, only the spot-on formulation was effective. This formulation was applied to pigeons at doses of 1, 5, 20 and 40 mg/bird. The nymphs that fed on pigeons treated with 20 mg or 40 mg of the formulation showed a higher mortality rate than the control group one day and seven days post-treatment (p < 0.01. A spot-on formulation of imidacloprid was effective against pyrethroid-resistant T. infestans populations at the laboratory level.

  20. Modeling the effects of integrating larval habitat source reduction and insecticide treated nets for malaria control.

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    Laith Yakob

    Full Text Available Integrated vector management for malaria control has received a lot of recent interest. Attacking multiple points in the transmission cycle is hoped to act synergistically and improve upon current single-tool interventions based on the use of insecticide-treated bed nets (ITNs. In the present study, we theoretically examined the application of larval habitat source reduction with ITNs in reducing malaria transmission. We selected this type of environmental management to complement ITNs because of a potential secondary mode of action that both control strategies share. In addition to increasing vector mortality, ITNs reduce the rate at which female mosquitoes locate human hosts for blood feeding, thereby extending their gonotrophic cycle. Similarly, while reducing adult vector emergence and abundance, source reduction of larval habitats may prolong the cycle duration by extending delays in locating oviposition sites. We found, however, that source reduction of larval habitats only operates through this secondary mode of action when habitat density is below a critical threshold. Hence, we illustrate how this strategy becomes increasingly effective when larval habitats are limited. We also demonstrate that habitat source reduction is better suited to human populations of higher density and in the presence of insecticide resistance or when the insecticidal properties of ITNs are depleted.

  1. System effectiveness of a targeted free mass distribution of long lasting insecticidal nets in Zanzibar, Tanzania

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    Abass Ali K

    2010-06-01

    Full Text Available Abstract Background Insecticide-treated nets (ITN and long-lasting insecticidal treated nets (LLIN are important means of malaria prevention. Although there is consensus regarding their importance, there is uncertainty as to which delivery strategies are optimal for dispensing these life saving interventions. A targeted mass distribution of free LLINs to children under five and pregnant women was implemented in Zanzibar between August 2005 and January 2006. The outcomes of this distribution among children under five were evaluated, four to nine months after implementation. Methods Two cross-sectional surveys were conducted in May 2006 in two districts of Zanzibar: Micheweni (MI on Pemba Island and North A (NA on Unguja Island. Household interviews were conducted with 509 caretakers of under-five children, who were surveyed for socio-economic status, the net distribution process, perceptions and use of bed nets. Each step in the distribution process was assessed in all children one to five years of age for unconditional and conditional proportion of success. System effectiveness (the accumulated proportion of success and equity effectiveness were calculated, and predictors for LLIN use were identified. Results The overall proportion of children under five sleeping under any type of treated net was 83.7% (318/380 in MI and 91.8% (357/389 in NA. The LLIN usage was 56.8% (216/380 in MI and 86.9% (338/389 in NA. Overall system effectiveness was 49% in MI and 87% in NA, and equity was found in the distribution scale-up in NA. In both districts, the predicting factor of a child sleeping under an LLIN was caretakers thinking that LLINs are better than conventional nets (OR = 2.8, p = 0.005 in MI and 2.5, p = 0.041 in NA, in addition to receiving an LLIN (OR = 4.9, p Conclusions Targeted free mass distribution of LLINs can result in high and equitable bed net coverage among children under five. However, in order to sustain high effective coverage, there

  2. Metabolic Resistance in Bed Bugs

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    Omprakash Mittapalli

    2011-03-01

    Full Text Available Blood-feeding insects have evolved resistance to various insecticides (organochlorines, pyrethroids, carbamates, etc. through gene mutations and increased metabolism. Bed bugs (Cimex lectularius are hematophagous ectoparasites that are poised to become one of the major pests in households throughout the United States. Currently, C. lectularius has attained a high global impact status due to its sudden and rampant resurgence. Resistance to pesticides is one factor implicated in this phenomenon. Although much emphasis has been placed on target sensitivity, little to no knowledge is available on the role of key metabolic players (e.g., cytochrome P450s and glutathione S-transferases towards pesticide resistance in C. lectularius. In this review, we discuss different modes of resistance (target sensitivity, penetration resistance, behavioral resistance, and metabolic resistance with more emphasis on metabolic resistance.

  3. Baixa aderência e alto custo como fatores de insucesso do uso de mosquiteiros impregnados com inseticida no controle da malária na Amazônia Brasileira Low adherence and high cost as failure factors of impregnated bed nets with insecticide for malaria control in the Brazilian Amazon

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    João Barberino Santos

    1999-08-01

    Full Text Available Em 1992, durante um ensaio com mosquiteiros impregnados com deltametrina, conduzido em Porto Murtinho, município de Costa Marques, Rondônia, na Amazônia Brasileira, analisou-se a aderência e os fatores econômicos capazes de reduzir o impacto do uso de mosquiteiros impregnados sobre a morbidade da malária. Os mosquiteiros impregnados tiveram excelente receptividade pela população local. No entanto, a aderência foi muito baixa, principalmente pelos adultos maiores de 15 anos de idade e, durante a estiagem. O preço do mosquiteiro impregnado foi calculado em US$18,83 para casal e, em US$13,82, para solteiro. Apesar das vantagens econômicas do emprego dos mosquiteiros impregnados em larga escala, desde que subsidiados pelas agências governamentais, a baixa aderência verificada, aliada aos fatores epidemiológicos locais, não permitem indicar o uso de mosquiteiros impregnados como medida de proteção em massa na Amazônia.In 1992 during a trial with deltamethrin-impregnated bed nets conducted in Porto Murtinho, municipality of Costa Marques, Rondonia, in the Brazilian Amazon, we investigated community compliance and the economic aspects capable of reducing the impact of this intervention on malaria morbidity. Impregnated bed nets were well accepted by the local population. However, compliance was found to be very low among adults over 15 years of age and mainly during the dry season. The cost of impregnated bed nets was US$18.83 for double-bed nets and US$13.82 for single bed nets. Despite the economic advantages of using impregnated bed nets subsidized by the government, the low compliance and local epidemiological factors do not allow to indicate the use of impregnated bed nets for mass malaria control in the Amazon region.

  4. Determinants of use of insecticide-treated nets among pregnant women in Nigeria

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    Ezire O

    2015-06-01

    Full Text Available Onoriode Ezire,1 Samson B Adebayo,2 Omokhudu Idogho,3 Elijah A Bamgboye,4 Ernest Nwokolo5 1Research and Evaluation Division, Society for Family Health, Abuja, 2National Agency for Food and Drug Administration and Control, Abuja, 3Enhancing Nigeria’s Response to HIV & AIDS, Abuja, 4Medical Statistics, University of Ibadan, Ibadan, 5Society for Family Health, Abuja, Nigeria Background: Malaria in pregnancy is still a major health issue in Nigeria, accounting for about 33% of cause of maternal death. Despite massive efforts to make insecticide-treated net (ITN available to pregnant women in Nigeria, the use is still low. This study was conducted to identify facilitators and inhibitors for the use of ITN/long-lasting insecticidal net (LLIN among pregnant women in Nigeria.Methods: Data were obtained from the 2011 State-Specific HIV & AIDS, Reproductive and Child Health Survey conducted in 18 states of Nigeria. The survey was a population-based study among men and women of reproductive age living in households in rural and urban areas of Nigeria. Multistage cluster sampling technique was used to select eligible respondents. The sample size per state was 960 respondents. Data were collected between October and November 2011. The analysis was done using Statistical Package for Social Sciences (SPSS version 20.Results: A total of 11.5% of the respondents were pregnant at the time of the survey of which 73.2% lived in rural location and approximately 70% were either not educated or attained at most a primary school education. A total of 93.2% of respondents have heard of net, 82.6% were confident that they can hang or use a net, and 64.6% owned an ITN/LLIN in their household while the actual use was just 19.2%. We found education, location (urban–rural, confidence to use a net, and knowledge that the use of a net can protect a pregnant woman from malaria to be significant at 5% level. The number of nets owned per household, the length of time the net

  5. Detection of Reduced Susceptibility to Chlorfenapyr- and Bifenthrin-Containing Products in Field Populations of the Bed Bug (Hemiptera: Cimicidae).

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    Ashbrook, Aaron R; Scharf, Michael E; Bennett, Gary W; Gondhalekar, Ameya D

    2017-06-01

    Insecticide resistance is a major impediment for effective control of Cimex lectularius L. Previous resistance detection studies with bed bugs have focused on certain pyrethroid, neonicotinoid, organochlorine, organophosphate, and carbamate insecticides. Within the pyrethroid class, resistance studies have mostly been limited to deltamethrin, lambda-cyhalothrin, and alpha- and beta-cyfluthrin. The goal of this study was to develop diagnostic concentration bioassays for assessing bed bug susceptibility levels to chlorfenapyr- and bifenthrin-containing products. First, glass vial and filter paper bioassay methods were compared for their utility in susceptibility monitoring. Statistical comparison of toxicity data between bioassays indicated that the vial assay was less confounded by assay susbtrate effects, required less insecticide, and was faster, especially for chlorfenapyr. Next, using vial diagnostic concentrations (LC99) for each insecticide, 10 laboratory-adapted field strains and the Harlan lab-susceptible strain were screened for susceptibility to chlorfenapyr and bifenthrin. The results of this study reveal recent bed bug susceptibility levels to certain chlorfenapyr- and bifenthrin-containing products. Reduced susceptibility was detected in three and five field strains to chlorfenapyr and bifenthrin, respectively. Detection of reduced susceptibility suggests that certain strains may be segregating toward greater chlorfenapyr and bifenthrin resistance. These results merit continuous resistance monitoring efforts to detect chlorfenapyr and bifenthrin susceptibility shifts. Additionally, to reduce insecticide selection pressures and delay resistance development, adoption of integrated bed bug control strategies that combine chemical and nonchemical methods is recommended. © The Authors 2017. Published by Oxford University Press on behalf of Entomological Society of America. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

  6. An integrative approach to understanding pyrethroid resistance in Rhipicephalus microplus and R. decoloratus ticks.

    Science.gov (United States)

    Wyk, Roelof Dj van; Baron, Samantha; Maritz-Olivier, Christine

    2016-06-01

    Rhipicephalus microplus and Rhipicephalus decoloratus species occur in regions with savannah and temperate climates, typically in grassland and wooded areas used as cattle pasture. Both species are associated with the transmission of Anaplasma and Babesia spp., impacting livestock health and quality of livestock-associated products. In Africa, tick control is predominantly mediated with the use of acaricides, such as synthetic pyrethroids. After several years on the market, reports of resistance to synthetic pyrethroids escalated but limited field data and validation studies have been conducted to determine the extent of acaricide resistance in Africa. Without this data, knowledge-based tick control will remain problematic and selection pressure will remain high increasing the rate of resistance acquisition. To date, several pyrethroid resistance associated single nucleotide polymorphisms (SNPs) have been reported for arthropods within the voltage-gated sodium channel. Three SNPs have been identified within this channel in pyrethroid resistant R. microplus ticks, but none has been reported for R. decoloratus. This study is the first to report the presence of a shared SNP within the voltage-gated sodium channel in both R. microplus and R. decoloratus, which is directly linked to pyrethroid resistance in R. microplus. As the mode of action by which these SNPs mediate pyrethroid resistance remains unknown, this study aims to set hypotheses by means of predictive structural modelling. This not only paves the way forward to elucidating the underlying biological mechanisms involved in pyrethroid resistance, but also improvement of existing acaricides and ultimately sustainable tick control management. Copyright © 2016 Elsevier GmbH. All rights reserved.

  7. PYRETHROID MODULATION OF SPONTANEOUS NEURONAL EXCITABILITY AND NEUROTRANSMISSION IN HIPPOCAMPAL NEURONS IN CULTURE

    Science.gov (United States)

    Pyrethroid insecticides have potent actions on voltage-gated sodium channels, inhibiting inactivation and increasing channel open times. These are thought to underlie, at least in part, the clinical symptoms of pyrethroid intoxication. However, disruption of neuronal activity at ...

  8. Traditional nets interfere with the uptake of long-lasting insecticidal nets in the Peruvian Amazon: the relevance of net preference for achieving high coverage and use.

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    Koen Peeters Grietens

    Full Text Available While coverage of long-lasting insecticide-treated nets (LLIN has steadily increased, a growing number of studies report gaps between net ownership and use. We conducted a mixed-methods social science study assessing the importance of net preference and use after Olyset® LLINs were distributed through a mass campaign in rural communities surrounding Iquitos, the capital city of the Amazonian region of Peru.The study was conducted in the catchment area of the Paujil and Cahuide Health Centres (San Juan district between July 2007 and November 2008. During a first qualitative phase, participant observation and in-depth interviews collected information on key determinants for net preference and use. In a second quantitative phase, a survey among recently confirmed malaria patients evaluated the acceptability and use of both LLINs and traditional nets, and a case control study assessed the association between net preference/use and housing structure (open vs. closed houses.A total of 10 communities were selected for the anthropological fieldwork and 228 households participated in the quantitative studies. In the study area, bed nets are considered part of the housing structure and are therefore required to fulfil specific architectural and social functions, such as providing privacy and shelter, which the newly distributed Olyset® LLINs ultimately did not. The LLINs' failure to meet these criteria could mainly be attributed to their large mesh size, transparency and perceived ineffectiveness to protect against mosquitoes and other insects, resulting in 63.3% of households not using any of the distributed LLINs. Notably, LLIN usage was significantly lower in houses with no interior or exterior walls (35.2% than in those with walls (73.8% (OR = 5.2, 95CI [2.2; 12.3], p<0.001.Net preference can interfere with optimal LLIN use. In order to improve the number of effective days of LLIN protection per dollar spent, appropriate quantitative and qualitative

  9. Evaluation of a clay-based acidic bedding conditioner for dairy cattle bedding.

    Science.gov (United States)

    Proietto, R L; Hinckley, L S; Fox, L K; Andrew, S M

    2013-02-01

    This study investigated the effects of a clay-based acidic bedding conditioner on sawdust bedding pH, dry matter (DM), environmental pathogen counts, and environmental bacterial counts on teat ends of lactating dairy cows. Sixteen lactating Holstein cows were paired based on parity, days in milk, milk yield, and milk somatic cell count, and were negative for the presence of an intramammary pathogen. Within each pair, cows were randomly assigned to 1 of 2 treatments with 3-wk periods in a crossover design. Treatment groups consisted of 9 freestalls per group bedded with either untreated sawdust or sawdust with a clay-based acidic bedding conditioner, added at 3- to 4-d intervals over each 21-d period. Bedding and teat ends were aseptically sampled on d 0, 1, 2, 7, 14, and 21 for determination of environmental bacterial counts. At the same time points, bedding was sampled for DM and pH determination. The bacteria identified in the bedding material were total gram-negative bacteria, Streptococcus spp., and coliform bacteria. The bacteria identified on the teat ends were Streptococcus spp., coliform bacteria, and Klebsiella spp. Teat end score, milk somatic cell count, and intramammary pathogen presence were measured weekly. Bedding and teat cleanliness, environmental high and low temperatures, and dew point data were collected daily. The bedding conditioner reduced the pH, but not the DM, of the sawdust bedding compared with untreated sawdust. Overall environmental bacterial counts in bedding were lower for treated sawdust. Total bacterial counts in bedding and on teat ends increased with time over both periods. Compared with untreated sawdust, the treated bedding had lower counts of total gram-negative bacteria and streptococci, but not coliform counts. Teat end bacterial counts were lower for cows bedded on treated sawdust for streptococci, coliforms, and Klebsiella spp. compared with cows bedded on untreated sawdust. The clay-based acidic bedding conditioner

  10. Genome-Wide Transcription and Functional Analyses Reveal Heterogeneous Molecular Mechanisms Driving Pyrethroids Resistance in the Major Malaria Vector Anopheles funestus Across Africa.

    Science.gov (United States)

    Riveron, Jacob M; Ibrahim, Sulaiman S; Mulamba, Charles; Djouaka, Rousseau; Irving, Helen; Wondji, Murielle J; Ishak, Intan H; Wondji, Charles S

    2017-06-07

    Pyrethroid resistance in malaria vector, An. funestus is increasingly reported across Africa, threatening the sustainability of pyrethroid-based control interventions, including long lasting insecticidal nets (LLINs). Managing this problem requires understanding of the molecular basis of the resistance from different regions of the continent, to establish whether it is being driven by a single or independent selective events. Here, using a genome-wide transcription profiling of pyrethroid resistant populations from southern (Malawi), East (Uganda), and West Africa (Benin), we investigated the molecular basis of resistance, revealing strong differences between the different African regions. The duplicated cytochrome P450 genes ( CYP6P9a and CYP6P9b ) which were highly overexpressed in southern Africa are not the most upregulated in other regions, where other genes are more overexpressed, including GSTe2 in West (Benin) and CYP9K1 in East (Uganda). The lack of directional selection on both CYP6P9a and CYP6P9b in Uganda in contrast to southern Africa further supports the limited role of these genes outside southern Africa. However, other genes such as the P450 CYP9J11 are commonly overexpressed in all countries across Africa. Here, CYP9J11 is functionally characterized and shown to confer resistance to pyrethroids and moderate cross-resistance to carbamates (bendiocarb). The consistent overexpression of GSTe2 in Benin is coupled with a role of allelic variation at this gene as GAL4-UAS transgenic expression in Drosophila flies showed that the resistant 119F allele is highly efficient in conferring both DDT and permethrin resistance than the L119. The heterogeneity in the molecular basis of resistance and cross-resistance to insecticides in An. funestus populations throughout sub-Saharan African should be taken into account in designing resistance management strategies. Copyright © 2017 Riveron et al.

  11. Genome-Wide Transcription and Functional Analyses Reveal Heterogeneous Molecular Mechanisms Driving Pyrethroids Resistance in the Major Malaria Vector Anopheles funestus Across Africa

    Science.gov (United States)

    Riveron, Jacob M.; Ibrahim, Sulaiman S.; Mulamba, Charles; Djouaka, Rousseau; Irving, Helen; Wondji, Murielle J.; Ishak, Intan H.; Wondji, Charles S.

    2017-01-01

    Pyrethroid resistance in malaria vector, An. funestus is increasingly reported across Africa, threatening the sustainability of pyrethroid-based control interventions, including long lasting insecticidal nets (LLINs). Managing this problem requires understanding of the molecular basis of the resistance from different regions of the continent, to establish whether it is being driven by a single or independent selective events. Here, using a genome-wide transcription profiling of pyrethroid resistant populations from southern (Malawi), East (Uganda), and West Africa (Benin), we investigated the molecular basis of resistance, revealing strong differences between the different African regions. The duplicated cytochrome P450 genes (CYP6P9a and CYP6P9b) which were highly overexpressed in southern Africa are not the most upregulated in other regions, where other genes are more overexpressed, including GSTe2 in West (Benin) and CYP9K1 in East (Uganda). The lack of directional selection on both CYP6P9a and CYP6P9b in Uganda in contrast to southern Africa further supports the limited role of these genes outside southern Africa. However, other genes such as the P450 CYP9J11 are commonly overexpressed in all countries across Africa. Here, CYP9J11 is functionally characterized and shown to confer resistance to pyrethroids and moderate cross-resistance to carbamates (bendiocarb). The consistent overexpression of GSTe2 in Benin is coupled with a role of allelic variation at this gene as GAL4-UAS transgenic expression in Drosophila flies showed that the resistant 119F allele is highly efficient in conferring both DDT and permethrin resistance than the L119. The heterogeneity in the molecular basis of resistance and cross-resistance to insecticides in An. funestus populations throughout sub-Saharan African should be taken into account in designing resistance management strategies. PMID:28428243

  12. The costs and effects of a nationwide insecticide-treated net programme: the case of Malawi

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    Ortiz Juan

    2005-05-01

    Full Text Available Abstract Background Insecticide-treated nets (ITNs are a proven intervention to reduce the burden of malaria, yet there remains a debate as to the best method of ensuring they are universally utilized. This study is a cost-effectiveness analysis of an intervention in Malawi that started in 1998, in Blantyre district, before expanding nationwide. Over the 5-year period, 1.5 million ITNs were sold. Methods The costs were calculated retrospectively through analysis of expenditure data. Costs and effects were measured as cost per treated-net year (cost/TNY and cost per net distributed. Results The mean cost/TNY was calculated at $4.41, and the mean cost/ITN distributed at $2.63. It also shows evidence of economies of scale, with the cost/TNY falling from $7.69 in year one (72,196 ITN to $3.44 in year five (720,577 ITN. Cost/ITN distributed dropped from $5.04 to $1.92. Conclusion Combining targeting and social marketing has the potential of being both cost-effective and capable of achieving high levels of coverage, and it is possible that increasing returns to scale can be achieved.

  13. Hydrolysis of pyrethroids by human and rat tissues: Examination of intestinal, liver and serum carboxylesterases

    International Nuclear Information System (INIS)

    Crow, J. Allen; Borazjani, Abdolsamad; Potter, Philip M.; Ross, Matthew K.

    2007-01-01

    Hydrolytic metabolism of pyrethroid insecticides in humans is one of the major catabolic pathways that clear these compounds from the body. Rodent models are often used to determine the disposition and clearance rates of these esterified compounds. In this study the distribution and activities of esterases that catalyze pyrethroid metabolism have been investigated in vitro using several human and rat tissues, including small intestine, liver and serum. The major esterase in human intestine is carboxylesterase 2 (hCE2). We found that the pyrethroid trans-permethrin is effectively hydrolyzed by a sample of pooled human intestinal microsomes (5 individuals), while deltamethrin and bioresmethrin are not. This result correlates well with the substrate specificity of recombinant hCE2 enzyme. In contrast, a sample of pooled rat intestinal microsomes (5 animals) hydrolyze trans-permethrin 4.5-fold slower than the sample of human intestinal microsomes. Furthermore, it is demonstrated that pooled samples of cytosol from human or rat liver are ∼ 2-fold less hydrolytically active (normalized per mg protein) than the corresponding microsomal fraction toward pyrethroid substrates; however, the cytosolic fractions do have significant amounts (∼ 40%) of the total esteratic activity. Moreover, a 6-fold interindividual variation in carboxylesterase 1 protein expression in human hepatic cytosols was observed. Human serum was shown to lack pyrethroid hydrolytic activity, but rat serum has hydrolytic activity that is attributed to a single CE isozyme. We purified the serum CE enzyme to homogeneity to determine its contribution to pyrethroid metabolism in the rat. Both trans-permethrin and bioresmethrin were effectively cleaved by this serum CE, but deltamethrin, esfenvalerate, alpha-cypermethrin and cis-permethrin were slowly hydrolyzed. Lastly, two model lipase enzymes were examined for their ability to hydrolyze pyrethroids. However, no hydrolysis products could be detected

  14. Distinct roles of the DmNav and DSC1 channels in the action of DDT and pyrethroids.

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    Rinkevich, Frank D; Du, Yuzhe; Tolinski, Josh; Ueda, Atsushi; Wu, Chun-Fang; Zhorov, Boris S; Dong, Ke

    2015-03-01

    Voltage-gated sodium channels (Nav channels) are critical for electrical signaling in the nervous system and are the primary targets of the insecticides DDT and pyrethroids. In Drosophila melanogaster, besides the canonical Nav channel, Para (also called DmNav), there is a sodium channel-like cation channel called DSC1 (Drosophila sodium channel 1). Temperature-sensitive paralytic mutations in DmNav (para(ts)) confer resistance to DDT and pyrethroids, whereas DSC1 knockout flies exhibit enhanced sensitivity to pyrethroids. To further define the roles and interaction of DmNav and DSC1 channels in DDT and pyrethroid neurotoxicology, we generated a DmNav/DSC1 double mutant line by introducing a para(ts1) allele (carrying the I265N mutation) into a DSC1 knockout line. We confirmed that the I265N mutation reduced the sensitivity to two pyrethroids, permethrin and deltamethrin of a DmNav variant expressed in Xenopus oocytes. Computer modeling predicts that the I265N mutation confers pyrethroid resistance by allosterically altering the second pyrethroid receptor site on the DmNav channel. Furthermore, we found that I265N-mediated pyrethroid resistance in para(ts1) mutant flies was almost completely abolished in para(ts1);DSC1(-/-) double mutant flies. Unexpectedly, however, the DSC1 knockout flies were less sensitive to DDT, compared to the control flies (w(1118A)), and the para(ts1);DSC1(-/-) double mutant flies were even more resistant to DDT compared to the DSC1 knockout or para(ts1) mutant. Our findings revealed distinct roles of the DmNav and DSC1 channels in the neurotoxicology of DDT vs. pyrethroids and implicate the exciting possibility of using DSC1 channel blockers or modifiers in the management of pyrethroid resistance. Copyright © 2015 Elsevier Inc. All rights reserved.

  15. Pyrethrum flowers and pyrethroid insecticides.

    OpenAIRE

    Casida, J E

    1980-01-01

    The natural pyrethrins from the daisy-like flower, Tanacetum or Chrysanthemum cinerariifolium, are nonpersistent insecticides of low toxicity to mammals. Synthetic analogs or pyrethroids, evolved from the natural compounds by successive isosteric modifications, are more potent and stable and are the newest important class of crop protection chemicals. They retain many of the favorable properties of the pyrethrins.

  16. Assessing Dietary Exposure to Pyrethroid Insecticides by LC/MS/MS of Food Composites

    Science.gov (United States)

    Introduction Pyrethroid insecticides are widely used to control household pests such as cockroaches, for public works control of mosquitoes, and on crops and livestock. Though more toxic to insects than to mammals, some pyrethroids are highly toxic to fish, bees, and cats. Perme...

  17. Predictive 3D modelling of the interactions of pyrethroids with the voltage-gated sodium channels of ticks and mites.

    Science.gov (United States)

    O'Reilly, Andrias O; Williamson, Martin S; González-Cabrera, Joel; Turberg, Andreas; Field, Linda M; Wallace, B A; Davies, T G Emyr

    2014-03-01

    The pyrethroid insecticides are a very successful group of compounds that target invertebrate voltage-gated sodium channels and are widely used in the control of insects, ticks and mites. It is well established that some pyrethroids are good insecticides whereas others are more effective as acaricides. This species specificity is advantageous for controlling particular pest(s) in the presence of another non-target invertebrate, for example controlling the Varroa mite in honeybee colonies. We applied in silico techniques to compare the voltage-gated sodium channels of insects versus ticks and mites and their interactions with a range of pyrethroids and DDT analogues. We identified a single amino acid difference within the pyrethroid binding pocket of ticks/mites that may have significant impact on the effectiveness of pyrethroids as acaricides. Other individual amino acid differences within the binding pocket in distinct tick and mite species may provide a basis for future acaricidal selectivity. Three-dimensional modelling of the pyrethroid/DDT receptor site has led to a new hypothesis to explain the preferential binding of acaricidal pyrethroids to the sodium channels of ticks/mites. This is important for understanding pyrethroid selectivity and the potential effects of mutations that can give rise to resistance to pyrethroids in commercially-important pest species. © 2013 Society of Chemical Industry.

  18. Molecular cloning and characterization of a novel pyrethroid-hydrolyzing esterase originating from the Metagenome

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    Liu Yu

    2008-12-01

    Full Text Available Abstract Background Pyrethroids and pyrethrins are widely used insecticides. Extensive applications not only result in pest resistance to these insecticides, but also may lead to environmental issues and human exposure. Numerous studies have shown that very high exposure to pyrethroids might cause potential problems to man and aquatic organisms. Therefore, it is important to develop a rapid and efficient disposal process to eliminate or minimize contamination of surface water, groundwater and agricultural products by pyrethroid insecticides. Bioremediation is considered to be a reliable and cost-effective technique for pesticides abatement and a major factor determining the fate of pyrethroid pesticides in the environment, and suitable esterase is expected to be useful for potential application for detoxification of pyrethroid residues. Soil is a complex environment considered as one of the main reservoirs of microbial diversity on the planet. However, most of the microorganisms in nature are inaccessible as they are uncultivable in the laboratory. Metagenomic approaches provide a powerful tool for accessing novel valuable genetic resources (novel enzymes and developing various biotechnological applications. Results The pyrethroid pesticides residues on foods and the environmental contamination are a public safety concern. Pretreatment with pyrethroid-hydrolyzing esterase has the potential to alleviate the conditions. To this end, a pyrethroid-hydrolyzing esterase gene was successfully cloned using metagenomic DNA combined with activity-based functional screening from soil, sequence analysis of the DNA responsible for the pye3 gene revealed an open reading frame of 819 bp encoding for a protein of 272 amino acid residues. Extensive multiple sequence alignments of the deduced amino acid of Pye3 with the most homologous carboxylesterases revealed moderate identity (45–49%. The recombinant Pye3 was heterologously expressed in E. coli BL21(DE3

  19. Simultaneous determination of 18 pyrethroids in indoor air by gas chromatography/mass spectrometry.

    Science.gov (United States)

    Yoshida, Toshiaki

    2009-06-26

    An analytical method was developed for the simultaneous measurement of 18 pyrethroids (allethrin, bifenthrin, cyfluthrin, cypermethrin, cyphenothrin, deltamethrin, empenthrin, fenpropathrin, furamethrin, imiprothrin, metofluthrin, permethrin, phenothrin, prallethrin, profluthrin, resmethrin, tetramethrin and transfluthrin) in indoor air. The pyrethroids were collected for 24 h using a combination of adsorbents (quartz fiber filter disk and Empore C18 disk), with protection from light, and then extracted with acetone, concentrated, and analyzed by GC/MS. They could be determined accurately and precisely (detection limits: ca. 1 ng/m(3)). The collected pyrethroid samples could be stored for up to one month at 4 degrees C in a refrigerator.

  20. Residual pyrethroids in fresh horticultural products in Sonora, Mexico.

    Science.gov (United States)

    Aldana-Madrid, Maria L; Valenzuela-Quintanar, Ana I; Silveira-Gramont, Maria I; Rodríguez-Olibarría, Guillermo; Grajeda-Cota, Patricia; Zuno-Floriano, Fabiola G; Miller, Marion G

    2011-10-01

    This study was conducted to evaluate the presence of cyhialothrin, cyfluthrin, cypermethrin, fenvalerate, and deltamethrin in vegetables produced and consumed in Sonora, Mexico. A total of 345 samples were collected from cluster sampling of markets and fields. Approximately 9% of the samples tested positive for pyrethroids (residue range 0.004-0.573 mg kg(-1)). Based on the results, the potential toxicological risk of human exposure to the pyrethroid insecticides measured in vegetables appears to be minimal, with the estimated exposure being 1,000 times lower than admissible levels. © Springer Science+Business Media, LLC 2011

  1. Cuticle thickening associated with pyrethroid resistance in the major malaria vector Anopheles funestus

    Directory of Open Access Journals (Sweden)

    Coetzee M

    2010-08-01

    Full Text Available Abstract Background Malaria in South Africa is primarily transmitted by Anopheles funestus Giles. Resistance to pyrethroid insecticides in An. funestus in northern Kwazulu/Natal, South Africa, and in neighbouring areas of southern Mozambique enabled populations of this species to increase their ranges into areas where pyrethroids were being exclusively used for malaria control. Pyrethroid resistance in southern African An. funestus is primarily conferred by monooxygenase enzyme metabolism. However, selection for this resistance mechanism is likely to have occurred in conjunction with other factors that improve production of the resistance phenotype. A strong candidate is cuticle thickening. This is because thicker cuticles lead to slower rates of insecticide absorption, which is likely to increase the efficiency of metabolic detoxification. Results Measures of mean cuticle thickness in laboratory samples of female An. funestus were obtained using scanning electron microscopy (SEM. These females were drawn from a laboratory colony carrying the pyrethroid resistance phenotype at a stable rate, but not fixed. Prior to cuticle thickness measurements, these samples were characterised as either more or less tolerant to permethrin exposure in one experiment, and either permethrin resistant or susceptible in another experiment. There was a significant and positive correlation between mean cuticle thickness and time to knock down during exposure to permethrin. Mean cuticle thickness was significantly greater in those samples characterised either as more tolerant or resistant to permethrin exposure compared to those characterised as either less tolerant or permethrin susceptible. Further, insecticide susceptible female An. funestus have thicker cuticles than their male counterparts. Conclusion Pyrethroid tolerant or resistant An. funestus females are likely to have thicker cuticles than less tolerant or susceptible females, and females generally have

  2. Suspended particles only marginally reduce pyrethroid toxicity to the freshwater invertebrate Gammarus pulex (L.) during pulse exposure.

    Science.gov (United States)

    Rasmussen, Jes Jessen; Cedergreen, Nina; Kronvang, Brian; Andersen, Maj-Britt Bjergager; Nørum, Ulrik; Kretschmann, Andreas; Strobel, Bjarne Westergaard; Hansen, Hans Christian Bruun

    2016-04-01

    Current ecotoxicological research on particle-associated pyrethroids in freshwater systems focuses almost exclusively on sediment-exposure scenarios and sediment-dwelling macroinvertebrates. We studied how suspended particles influence acute effects of lambda-cyhalothrin and bifenthrin on the epibenthic freshwater amphipod Gammarus pulex (L.) using brief pulse exposures followed by a 144 h post exposure recovery phase. Humic acid (HA) and the clay mineral montmorillonite (MM) were used as model sorbents in environmentally realistic concentrations (5, 25 and 125 mg L(-1)). Mortality of G. pulex was recorded during the post exposure recovery phase and locomotor behavior was measured during exposure to lambda-cyhalothrin. We found that HA in concentrations ≥25 mg L(-1) adsorbed the majority of pyrethroids but only reduced mortality of G. pulex up to a factor of four compared to pyrethroid-only treatments. MM suspensions adsorbed a variable fraction of pyrethroids (10% for bifenthrin and 70% for lambda-cyhalothrin) but did not significantly change the concentration-response relationship compared to pure pyrethroid treatments. Behavioral responses and immobilisation rate of G. pulex were reduced in the presence of HA, whereas behavioral responses and immobilisation rate were increased in the presence of MM. This indicates that G. pulex was capable of sensing the bioavailable fraction of lambda-cyhalothrin. Our results imply that suspended particles reduce to only a limited extent the toxicity of pyrethroids to G. pulex and that passive uptake of pyrethroids can be significant even when pyrethroids are adsorbed to suspended particles.

  3. The effect of household heads training about the use of treated bed nets on the burden of malaria and anaemia in under-five children: a cluster randomized trial in Ethiopia

    Directory of Open Access Journals (Sweden)

    Deribew Amare

    2012-01-01

    Full Text Available Abstract Background Long-lasting insecticide-treated bed nets (LLITN have demonstrated a significant effect in reducing malaria-related morbidity and mortality. However, barriers on the utilization of LLITN have hampered the desired outcomes. The aim of this study was to assess the effect of community empowerment on the burden of malaria and anaemia in under-five children in Ethiopia. Methods A cluster randomized trial was done in 22 (11 intervention and 11 control villages in south-west Ethiopia. The intervention consisted of tailored training of household heads about the proper use of LLITN and community network system. The burden of malaria and anaemia in under-five children was determined through mass blood investigation at baseline, six and 12 months of the project period. Cases of malaria and anaemia were treated based on the national protocol. The burden of malaria and anaemia between the intervention and control villages was compared using the complex logistic regression model by taking into account the clustering effect. Eight Focus group discussions were conducted to complement the quantitative findings. Results A total of 2,105 household heads received the intervention and the prevalence of malaria and anaemia was assessed among 2410, 2037 and 2612 under-five children at baseline, six and 12 months of the project period respectively. During the high transmission/epidemic season, children in the intervention arm were less likely to have malaria as compared to children in the control arm (OR = 0.42; 95%CI: 0.32, 0.57. Symptomatic malaria also steadily declined in the intervention villages compared to the control villages in the follow up periods. Children in the intervention arm were less likely to be anaemic compared to those in the control arm both at the high (OR = 0.84; 95%CI: 0.71, 0.99 and low (OR = 0.73; 95%CI: 0.60, 0.89 transmission seasons. Conclusion Training of household heads on the utilization of LLITN significantly

  4. Pyrethroid effects on freshwater invertebrates: A meta-analysis of pulse exposures

    DEFF Research Database (Denmark)

    Rasmussen, Jes Jessen; Wiberg-Larsen, Peter; Kristensen, Esben Astrup

    2013-01-01

    Pyrethroids are widely used insecticides that may seriously harm aquatic organisms. Being strongly hydrophobic, pyrethroids in solution occur only in short pulses but may be retained in sediments for longer periods. Consequently, most studies consider the chronic exposure of sediment dwelling org......-exposure observation periods in future studies. The current risk assessment procedures and the higher tier approach are discussed in the light of our results. (C) 2013 Elsevier Ltd. All rights reserved....

  5. Stability and Wash Resistance of Local Made Mosquito Bednets and Detergents Treated with Pyrethroids against Anopheles stephensi

    Directory of Open Access Journals (Sweden)

    H Vatandoost

    2009-06-01

    Full Text Available Background: We aimed to evaluate different fibres of bednets impregnated with various pyrethroids. The stability of insecticide on the bednet was measured using different methods of washings as well as local made detergents.Methods: The entire test was carried out according to the WHO-recommended methods. In addition, the impact of the numbers of washes on the stability of the insecticides was determined. Permethrin 10% (EC, deltamethrin 10% (SC, lambdacyhalothrin 2.5% (CS and cyfluthrin 5% (EW were used at the recommended dosages. Three different lo­cal detergents were used. Two kinds of washing methods (shaking, no shaking were used and in each method four kinds of washings, i.e. no wash, one wash, two washes and three washes was done. The main malaria vectors, Anophe­les stephensi, which is susceptible to all insecticides (BEECH strain, was tested with impregnated bednets in 3 minutes exposure time and the mortality was measured after 24 hours recovery period. Knock-down was measured as well using appropriate statistical methods.Results: Lambdacyhalothrin has saved its insecticidal impact after being washed, whereas, deltamethrin has lost its activ­ity faster than other insecticides. Tow other insecticides had moderate effect. Golnar soap detergent has least ef­fect on the durability of insecticides, but the Shoma had the most. Whit increasing  the times of washing, insecticidal ef­fects was decreased , but shaking had no influence on the decreasing  of the quality of insecticidal impact.Conclusion: Results will be useful for local people who wish to use pyrethroid-impregnated bednets with their own lo­cal made detergent and bednets. 

  6. Bed Bug Infestations and Control Practices in China: Implications for Fighting the Global Bed Bug Resurgence

    Directory of Open Access Journals (Sweden)

    Changlu Wang

    2011-04-01

    Full Text Available The bed bug resurgence in North America, Europe, and Australia has elicited interest in investigating the causes of the widespread and increasing infestations and in developing more effective control strategies. In order to extend global perspectives on bed bug management, we reviewed bed bug literature in China by searching five Chinese language electronic databases. We also conducted telephone interviews of 68 pest control firms in two cities during March 2011. In addition, we conducted telephone interviews to 68 pest control companies within two cities in March 2011. Two species of bed bugs (Cimex lectularius L. and Cimex hemipterus (F. are known to occur in China. These were common urban pests before the early1980s. Nationwide “Four-Pest Elimination” campaigns (bed bugs being one of the targeted pests were implemented in China from 1960 to the early 1980s. These campaigns succeeded in the elimination of bed bug infestations in most communities. Commonly used bed bug control methods included applications of hot water, sealing of bed bug harborages, physical removal, and applications of residual insecticides (mainly organophosphate sprays or dusts. Although international and domestic travel has increased rapidly in China over the past decade (2000–2010, there have only been sporadic new infestations reported in recent years. During 1999–2009, all documented bed bug infestations were found in group living facilities (military dormitories, worker dormitories, and prisons, hotels, or trains. One city (Shenzhen city near Hong Kong experienced significantly higher number of bed bug infestations. This city is characterized by a high concentration of migratory factory workers. Current bed bug control practices include educating residents, washing, reducing clutter, putting items under the hot sun in summer, and applying insecticides (pyrethroids or organophosphates. There have not been any studies or reports on bed bug insecticide

  7. A qualitative study of community perception and acceptance of biological larviciding for malaria mosquito control in rural Burkina Faso.

    Science.gov (United States)

    Dambach, Peter; Jorge, Margarida Mendes; Traoré, Issouf; Phalkey, Revati; Sawadogo, Hélène; Zabré, Pascal; Kagoné, Moubassira; Sié, Ali; Sauerborn, Rainer; Becker, Norbert; Beiersmann, Claudia

    2018-03-23

    Vector and malaria parasite's rising resistance against pyrethroid-impregnated bed nets and antimalarial drugs highlight the need for additional control measures. Larviciding against malaria vectors is experiencing a renaissance with the availability of environmentally friendly and target species-specific larvicides. In this study, we analyse the perception and acceptability of spraying surface water collections with the biological larvicide Bacillus thuringiensis israelensis in a single health district in Burkina Faso. A total of 12 focus group discussions and 12 key informant interviews were performed in 10 rural villages provided with coverage of various larvicide treatments (all breeding sites treated, the most productive breeding sites treated, and untreated control). Respondents' knowledge about the major risk factors for malaria transmission was generally good. Most interviewees stated they performed personal protective measures against vector mosquitoes including the use of bed nets and sometimes mosquito coils and traditional repellents. The acceptance of larviciding in and around the villages was high and the majority of respondents reported a relief in mosquito nuisance and malarial episodes. There was high interest in the project and demand for future continuation. This study showed that larviciding interventions received positive resonance from the population. People showed a willingness to be involved and financially support the program. The positive environment with high acceptance for larviciding programs would facilitate routine implementation. An essential factor for the future success of such programs would be inclusion in regional or national malaria control guidelines.

  8. Electrodialysis reversal: Process and cost approximations for treating coal-bed methane waters

    Energy Technology Data Exchange (ETDEWEB)

    Sajtar, E.T.; Bagley, D.M. [University of Wyoming, Laramie, WY (United States)

    2009-02-15

    Brackish waters with total dissolved solids (TDS) concentrations less than 10,000 mg/L are extracted from coal-beds in the Wyoming Powder River basin to facilitate the production of coal-bed methane. These waters frequently require treatment before disposal or use. Electrodialysis reversal (EDR) has not yet been used to treat these waters but this technology should be suitable. The question is whether EDR would be cost-effective. The purpose of this work, then, was to develop models for predicting the cost of EDR for brackish waters. These models, developed from data available in the literature, were found to predict actual EDR costs as a function of TDS removal, influent flow rate, chemical rejection efficiency, water recovery, electricity use, and labor cost within 10% of reported values. The total amortized cost for removing 1,000 mg/L of TDS from 10,000 m{sup 3}/day of influent assuming no concentrate disposal costs was predicted to range from $0.23/m{sup 3} to $0.85/m{sup 3} and was highly dependent on capital cost and facility life. Concentrate disposal costs significantly affected total treatment cost, providing a total treatment cost range from $0.38/m{sup 3} to $6.38/m{sup 3}, depending on concentrate disposal cost and water recovery. Pilot demonstrations of EDR in the Powder River basin should be conducted to determine the achievable water recovery when treating these waters.

  9. Concentrations of the urinary pyrethroid metabolite 3-phenoxybenzoic acid in farm worker families in the MICASA study

    Energy Technology Data Exchange (ETDEWEB)

    Trunnelle, Kelly J., E-mail: kjtrunnelle@ucdavis.edu [Department of Environmental Toxicology, University of California, Davis 1 Shields Avenue, Davis, CA 95616 (United States); Bennett, Deborah H. [Department of Public Health Sciences, University of California, Davis, CA 95616 (United States); Ahn, Ki Chang [Department of Entomology and Cancer Center, University of California, Davis 1 Shields Avenue, Davis, CA 95616 (United States); Schenker, Marc B. [Department of Public Health Sciences, University of California, Davis, CA 95616 (United States); Tancredi, Daniel J. [Department of Pediatrics, University of California, Davis School of Medicine, 4610 X Street Sacramento, CA 95817 (United States); Gee, Shirley J. [Department of Entomology and Cancer Center, University of California, Davis 1 Shields Avenue, Davis, CA 95616 (United States); Stoecklin-Marois, Maria T. [Department of Public Health Sciences, University of California, Davis, CA 95616 (United States); Hammock, Bruce D. [Department of Entomology and Cancer Center, University of California, Davis 1 Shields Avenue, Davis, CA 95616 (United States)

    2014-05-01

    Indoor pesticide exposure is a growing concern, particularly from pyrethroids, a commonly used class of pesticides. Pyrethroid concentrations may be especially high in homes of immigrant farm worker families who often live in close proximity to agricultural fields, and are faced with poor housing conditions, causing higher pest infestation and more pesticide use. We investigate exposure of farm worker families to pyrethroids in a study of mothers and children living in Mendota, CA within the population-based Mexican Immigration to California: Agricultural Safety and Acculturation (MICASA) Study. We present pyrethroid exposure based on an ELISA analysis of urinary metabolite 3-phenoxybenzoic acid (3PBA) levels among 105 women and 103 children. The median urinary 3PBA levels (children=2.56 ug/g creatinine, mothers=1.46 ug/g creatinine) were higher than those reported in population based studies for the United States general population, but similar to or lower than studies with known high levels of pyrethroid exposure. A positive association was evident between poor housing conditions and the urinary metabolite levels, showing that poor housing conditions are a contributing factor to the higher levels of 3PBA seen in the urine of these farm worker families. Further research is warranted to fully investigate sources of exposure. - Highlights: • We investigate exposure of farm worker families to pyrethroids. • We present pyrethroid exposure based on an ELISA analysis of urinary 3PBA levels. • 3PBA levels were higher than those reported for the U.S. general population. • Poor housing conditions may be associated with pyrethroid exposure.

  10. Concentrations of the urinary pyrethroid metabolite 3-phenoxybenzoic acid in farm worker families in the MICASA study

    International Nuclear Information System (INIS)

    Trunnelle, Kelly J.; Bennett, Deborah H.; Ahn, Ki Chang; Schenker, Marc B.; Tancredi, Daniel J.; Gee, Shirley J.; Stoecklin-Marois, Maria T.; Hammock, Bruce D.

    2014-01-01

    Indoor pesticide exposure is a growing concern, particularly from pyrethroids, a commonly used class of pesticides. Pyrethroid concentrations may be especially high in homes of immigrant farm worker families who often live in close proximity to agricultural fields, and are faced with poor housing conditions, causing higher pest infestation and more pesticide use. We investigate exposure of farm worker families to pyrethroids in a study of mothers and children living in Mendota, CA within the population-based Mexican Immigration to California: Agricultural Safety and Acculturation (MICASA) Study. We present pyrethroid exposure based on an ELISA analysis of urinary metabolite 3-phenoxybenzoic acid (3PBA) levels among 105 women and 103 children. The median urinary 3PBA levels (children=2.56 ug/g creatinine, mothers=1.46 ug/g creatinine) were higher than those reported in population based studies for the United States general population, but similar to or lower than studies with known high levels of pyrethroid exposure. A positive association was evident between poor housing conditions and the urinary metabolite levels, showing that poor housing conditions are a contributing factor to the higher levels of 3PBA seen in the urine of these farm worker families. Further research is warranted to fully investigate sources of exposure. - Highlights: • We investigate exposure of farm worker families to pyrethroids. • We present pyrethroid exposure based on an ELISA analysis of urinary 3PBA levels. • 3PBA levels were higher than those reported for the U.S. general population. • Poor housing conditions may be associated with pyrethroid exposure

  11. Phytoremediation of organochlorine and pyrethroid pesticides by aquatic macrophytes and algae in freshwater systems.

    Science.gov (United States)

    Riaz, Ghazala; Tabinda, Amtul Bari; Iqbal, Shakir; Yasar, Abdullah; Abbas, Mateen; Khan, Abdul Muqeet; Mahfooz, Yusra; Baqar, Mujtaba

    2017-10-03

    Extensive use of Pesticides in agriculture and its surface runoff in river water is a major environmental concern. The present study evaluated the phytoremediation potential of Eichornia crassipes, Pistia strateotes and algae (Chaetomorpha sutoria, Sirogonium sticticum and Zygnema sp.) for organochlorine and pyrethroid pesticides. Water and plant samples were extracted by liquid phase and solid phase extraction respectively and analyzed by high-performance liquid chromatography. Eleven treatments (T1-T11) with and without plants were used for phytoremediation of organochlorine and pyrethroid pesticides. During the experiment, P. strateotes, E. crassipes and algae (C. sutoria, S. sticticum and Zygnema sp.) showed the highest removal efficiency with 62 (71% root, 29% shoot), 60 (67% root, 33% shoot), and 58% respectively for organochlorine and 76 (76% root, 24% shoot), 68 (69% root, 31% shoot), and 70% respectively for pyrethroids for the respective aquatic plants. Dissipation rate constant of treatments with plants (T2, T3, T5, T6, T8, and T9) was significantly higher (p < 0.05) as compared to that of treatments without plants (T10 and T11, control) for both organochlorine and pyrethroid. The bioconcentration factor of pyrethroid treatments (T3, T6, and T9) was significantly higher (p < 0.05) as compared to that of organochlorine treatments (T2, T5 and T8). The removal efficiency of E. crassipes, P. strateotes and algae (C. sutoria, S. sticticum and Zygnema sp.) for pyrethroids was significantly higher (p < 0.01) as compared to that of organochlorine.

  12. Insecticide Resistance in Eggs and First Instars of the Bed Bug, Cimex lectularius (Hemiptera: Cimicidae

    Directory of Open Access Journals (Sweden)

    Brittany E. Campbell

    2015-01-01

    Full Text Available Two strains of the common bed bug, Cimex lectularius L., eggs and first instars collected from pyrethroid-resistant adults were evaluated for insecticide resistance and compared to a susceptible strain. Dose-response bioassays were conducted using two insecticide formulations (Temprid: imidacloprid/β-cyfluthrin, and Transport: acetamiprid/ bifenthrin. The lethal concentration (LC50 for the two resistant egg strains exposed to imidacloprid/β-cyfluthrin ranged from 3 to 5-fold higher than susceptible strain eggs. Resistant strain eggs dipped into formulations of acetamiprid/bifenthrin had LC50 values which were significantly greater (39 to 1,080-fold than susceptible strain eggs. Similar to eggs, resistant strain first instars exposed to residual applications of imidacloprid/β-cyfluthrin had LC50 values ranging from 121 to 493-fold greater than susceptible strain first instars. When resistant strain first instars were treated with acetamiprid/bifenthrin, they had LC50 values that were 99 to >1,900-fold greater than susceptible strain first instars. To determine differences between egg and first instar resistance, stage resistance ratios (SRR were compared between the two stages. There was little difference between the egg and first instar stages, indicated by small SRR values ranging from 1.1 to 10.0. This study suggests that insecticide resistance is expressed early during bed bug development.

  13. Assessment of the inhibitory effects of pyrethroids against human carboxylesterases

    Energy Technology Data Exchange (ETDEWEB)

    Lei, Wei [The Second Affiliated Hospital of Dalian Medical University, Dalian 110623 (China); Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023 (China); Wang, Dan-Dan; Dou, Tong-Yi [Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023 (China); Hou, Jie [Dalian Medical University, Dalian 116044 (China); Feng, Liang; Yin, Heng [Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023 (China); Luo, Qun [Beijing National Laboratory for Molecular Science, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100080 (China); Sun, Jie [The Second Affiliated Hospital of Dalian Medical University, Dalian 110623 (China); Ge, Guang-Bo, E-mail: geguangbo@dicp.ac.cn [Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023 (China); Yang, Ling [Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023 (China)

    2017-04-15

    Pyrethroids are broad-spectrum insecticides that widely used in many countries, while humans may be exposed to these toxins by drinking or eating pesticide-contaminated foods. This study aimed to investigate the inhibitory effects of six commonly used pyrethroids against two major human carboxylesterases (CES) including CES1 and CES2. Three optical probe substrates for CES1 (DME, BMBT and DMCB) and a fluorescent probe substrate for CES2 (DDAB) were used to characterize the inhibitory effects of these pyrethroids. The results demonstrated that most of the tested pyrethroids showed moderate to weak inhibitory effects against both CES1 and CES2, but deltamethrin displayed strong inhibition towards CES1. The IC{sub 50} values of deltamethrin against CES1-mediated BMBT, DME, and DMCB hydrolysis were determined as 1.58 μM, 2.39 μM, and 3.3 μM, respectively. Moreover, deltamethrin was cell membrane permeable and capable of inhibition endogenous CES1 in living cells. Further investigation revealed that deltamethrin inhibited CES1-mediated BMBT hydrolysis via competitive manner but noncompetitively inhibited DME or DMCB hydrolysis. The inhibition behaviors of deltamethrin against CES1 were also studied by molecular docking simulation. The results demonstrated that CES1 had at least two different ligand-binding sites, one was the DME site and another was the BMBT site which was identical to the binding site of deltamethrin. In summary, deltamethrin was a strong reversible inhibitor against CES1 and it could tightly bind on CES1 at the same ligand-binding site as BMBT. These findings are helpful for the deep understanding of the interactions between xenobiotics and CES1. - Highlights: • The inhibitory effects of six commonly used pyrethroids on human carboxylesterases were investigated. • Deltamethrin displayed strong inhibitory effects against human carboxylesterase 1 (CES1). • Deltamethrin was cell membrane permeable and could inhibit intracellular CES1 in living

  14. Assessment of the inhibitory effects of pyrethroids against human carboxylesterases

    International Nuclear Information System (INIS)

    Lei, Wei; Wang, Dan-Dan; Dou, Tong-Yi; Hou, Jie; Feng, Liang; Yin, Heng; Luo, Qun; Sun, Jie; Ge, Guang-Bo; Yang, Ling

    2017-01-01

    Pyrethroids are broad-spectrum insecticides that widely used in many countries, while humans may be exposed to these toxins by drinking or eating pesticide-contaminated foods. This study aimed to investigate the inhibitory effects of six commonly used pyrethroids against two major human carboxylesterases (CES) including CES1 and CES2. Three optical probe substrates for CES1 (DME, BMBT and DMCB) and a fluorescent probe substrate for CES2 (DDAB) were used to characterize the inhibitory effects of these pyrethroids. The results demonstrated that most of the tested pyrethroids showed moderate to weak inhibitory effects against both CES1 and CES2, but deltamethrin displayed strong inhibition towards CES1. The IC 50 values of deltamethrin against CES1-mediated BMBT, DME, and DMCB hydrolysis were determined as 1.58 μM, 2.39 μM, and 3.3 μM, respectively. Moreover, deltamethrin was cell membrane permeable and capable of inhibition endogenous CES1 in living cells. Further investigation revealed that deltamethrin inhibited CES1-mediated BMBT hydrolysis via competitive manner but noncompetitively inhibited DME or DMCB hydrolysis. The inhibition behaviors of deltamethrin against CES1 were also studied by molecular docking simulation. The results demonstrated that CES1 had at least two different ligand-binding sites, one was the DME site and another was the BMBT site which was identical to the binding site of deltamethrin. In summary, deltamethrin was a strong reversible inhibitor against CES1 and it could tightly bind on CES1 at the same ligand-binding site as BMBT. These findings are helpful for the deep understanding of the interactions between xenobiotics and CES1. - Highlights: • The inhibitory effects of six commonly used pyrethroids on human carboxylesterases were investigated. • Deltamethrin displayed strong inhibitory effects against human carboxylesterase 1 (CES1). • Deltamethrin was cell membrane permeable and could inhibit intracellular CES1 in living cells

  15. Global occurrence of pyrethroid insecticides in sediment and the associated toxicological effects on benthic invertebrates: An overview.

    Science.gov (United States)

    Li, Huizhen; Cheng, Fei; Wei, Yanli; Lydy, Michael J; You, Jing

    2017-02-15

    Pyrethroids are the third most applied group of insecticides worldwide and are extensively used in agricultural and non-agricultural applications. Pyrethroids exhibit low toxicity to mammals, but have extremely high toxicity to fish and non-target invertebrates. Their high hydrophobicity, along with pseudo-persistence due to continuous input, indicates that pyrethroids will accumulate in sediment, pose long-term exposure concerns to benthic invertebrates and ultimately cause significant risk to benthic communities and aquatic ecosystems. The current review synthesizes the reported sediment concentrations of pyrethroids and associated toxicity to benthic invertebrates on a global scale. Geographically, the most studied area was North America, followed by Asia, Europe, Australia and Africa. Pyrethroids were frequently detected in both agricultural and urban sediments, and bifenthrin and cypermethrin were identified as the main contributors to toxicity in benthic invertebrates. Simulated hazard quotients (HQ) for sediment-associated pyrethroids to benthic organisms ranged from 10.5±31.1 (bifenthrin) to 41.7±204 (cypermethrin), suggesting significant risk. The current study has provided evidence that pyrethroids are not only commonly detected in the aquatic environment, but also can cause toxic effects to benthic invertebrates, and calls for better development of accurate sediment quality criteria and effective ecological risk assessment methods for this emerging class of insecticides. Copyright © 2016 Elsevier B.V. All rights reserved.

  16. Comparative Bio-Efficacy and Synergism of New Generation Polyfluorobenzyl and Conventional Pyrethroids Against Culex quinquefasciatus (Diptera: Culicidae).

    Science.gov (United States)

    Sarkar, Manas; Akulwad, Ambadas; Kshirsagar, Rajendra; Muthukrishnan, Siva

    2018-05-28

    Intensive exposure to insecticides has resulted in the evolution of insecticide resistance in the mosquitoes. We tested the bio-efficacy of two Culex quinquefasciatus Say (Diptera: Culicidae) laboratory strains differentially bio-responsive to pyrethroids to understand the comparative efficacy of different polyfluorobenzyle and conventional pyrethroid molecules and the role of piperonyl butoxide (PBO) in synergizing these molecules in increased tolerance of mosquitoes to these molecules. We have taken deltamethrin (α-cyano pyrethroid with phenoxybenzyl moiety); permethrin (phenoxybenzyl pyrethroid without an α-cyano group); transfluthrin, dimefluthrin, metofluthrin, and meperfluthrin (polyfluorinated benzyl compounds); and prallethrin (modified cyclopentadienone compound) for this study. We found higher bio-efficacy in dimefluthrin, metofluthrin, and meperfluthrin compared with transfluthrin against tested mosquito strains. We found that transfluthrin exhibited synergism with PBO, which supports the hypothesis that P450 enzymes could play a role in the detoxification process of transfluthrin, which was earlier not believed. However, other polyfluorobenzyl pyrethroids with a 4-(methoxymethyl) phenyl capping in the tetrafluorobenzyl ring (dimefluthrin, metofluthrin, and meperfluthrin) exhibit greater synergism with PBO compared with transfluthrin. Further study is required to understand the mechanism for higher synergistic ratios in polyfluorobenzyl pyrethroids with 4-(methoxymethyl) phenyl moiety and ascertain the possible involvement of novel mechanisms that may involve in developing resistance. This is the first report of comparative bio-efficacy of multiple polyfluorobenzyl pyrethroids and PBO synergism against mosquitoes.

  17. Physical conditions affecting pyrethroid toxicity in arthropods

    NARCIS (Netherlands)

    Jagers op Akkerhuis, G.

    1993-01-01

    The aim of this thesis was to obtain mechanistic information about how the toxicity of pesticides in the field is affected by physical factors, pesticide bioavailability and arthropod behaviour. The pyrethroid insecticide deltamethrin and linyphiid spiders were selected as pesticide-effect

  18. Which family members use the best nets? An analysis of the condition of mosquito nets and their distribution within households in Tanzania

    Directory of Open Access Journals (Sweden)

    Lines Jo

    2010-07-01

    Full Text Available Abstract Background Household ownership of insecticide-treated mosquito nets (ITNs is increasing, and coverage targets have been revised to address universal coverage with ITNs. However, many households do not have enough nets to cover everyone, and the nets available vary in physical condition and insecticide treatment status. Since 2004, the Government of Tanzania has been implementing the Tanzania National Voucher Scheme (TNVS, which distributes vouchers for ITNs through antenatal clinics to target pregnant women and their infants. This analysis aimed to determine the following: (1 coverage patterns of bed nets within households according to physical condition and treatment status; (2 who might be at risk if mosquitoes were diverted from occupants of untreated nets to those not using nets? (3 the degree to which those at highest risk of malaria use the most protective nets. Methods Data from the 2006 TNVS household survey were analysed to assess within-household distribution of net use. The associations between net characteristics and net user were also evaluated. Multivariate analysis was applied to the relationship between the number of holes per net and user characteristics while adjusting for confounders. Results In households with a net:person ratio better than 1:4 (one net for every four household members, more than 80% of the people in such households reported using a net the previous night. ITNs were most likely to be used by infants, young children (1-4 y, and women of childbearing age; they were least likely to be used by older women (≥50 y, older children (5-14 y, and adult men. The nets used by infants and women of childbearing age were in better-than-average physical condition; the nets used by older women and older children were in worse-than-average condition; while young children and adult men used nets in intermediate (average condition. When adjusted for confounders, the nets used by young and older children had more holes

  19. Passive dosing of pyrethroid insecticides to Daphnia magna: Expressing excess toxicity by chemical activity

    DEFF Research Database (Denmark)

    Nørgaard Schmidt, Stine; Gan, Jay; Kretschmann, A. C.

    2015-01-01

    ) Effective chemical activities resulting in 50% immobilisation (Ea50) will be estimated from pyrethroid EC50 values via the correlation of sub-cooled liquid solubility (S L, [mmol/L], representing a=1) and octanol to water partitioning ratios (Kow), (3) The excess toxicity observed for pyrethroids...

  20. Dissipation and Migration of Pyrethroids in Auricularia polytricha Mont. from Cultivation to Postharvest Processing and Dietary Risk

    Directory of Open Access Journals (Sweden)

    Jin-Jing Xiao

    2018-03-01

    Full Text Available In order to ensure raw consumption safety the dissipation behavior, migration, postharvest processing, and dietary risk assessment of five pyrethroids in mushroom (Auricularia polytricha Mont. cultivated under Chinese greenhouse-field conditions. Half-lives (t1/2 of pyrethroids in fruiting body and substrate samples were 3.10–5.26 and 17.46–40.06 d, respectively. Fenpropathrin dissipated rapidly in fruiting bodies (t1/2 3.10 d; bifenthrin had the longest t1/2. At harvest, pyrethroid residues in A. polytricha (except fenpropathrin were above the respective maximum residue limits (MRLs. Some migration of lambda-cyhalothrin was observed in the substrate-fruit body system. In postharvest-processing, sun-drying and soaking reduced pyrethroid residues by 25–83%. We therefore recommend that consumers soak these mushrooms in 0.5% NaHCO3 at 50 °C for 90 min. Pyrethroids exhibit a particularly low PF value of 0.08–0.13%, resulting in a negligible exposure risk upon mushroom consumption. This study provides guidance for the safe application of pyrethroids to edible fungi, and for the establishment of MRLs in mushrooms to reduce pesticide exposure in humans.

  1. Ownership and Use of Insecticide-Treated Nets among People Living in Malaria Endemic Areas of Eastern Myanmar.

    Science.gov (United States)

    Aung, Tin; Wei, Chongyi; McFarland, Willi; Aung, Ye Kyaw; Khin, Hnin Su Su

    2016-01-01

    Myanmar has the highest burden of malaria in the Greater Mekong. However, there is limited information on ownership and use of insecticide-treated nets (ITNs) in areas of Myanmar most severely affected by malaria. We describe ownership and use of ITNs among people in the malaria-endemic eastern parts of Myanmar and factors associated with ITN use. A cross-sectional household survey using a multi-stage cluster design was conducted in malaria-endemic townships in eastern Myanmar during the high malaria season of August to September, 2014. An effective ITN was defined as 1) a long-lasting insecticide-treated net obtained within the past three years, or 2) any net treated with insecticide within the past year. In 4,679 households, the average number of ITNs per household was higher in rural compared to urban areas (0.6 vs. 0.4, p Myanmar in comparison to the goal of one for every two household members. Use of ITNs was low even when present. Findings are of concern given the study areas were part of enhanced efforts to reduce artemisinin-resistant malaria. Nonetheless, groups vulnerable to malaria such as individuals in rural settings, lower socio-economic households, and workers in high mosquito exposure jobs, had higher rates of ITN ownership. Malaria knowledge was linked to effective ITN use suggesting that distribution campaigns should be complemented by behavior change communications.

  2. Large-scale implementation of disease control programmes: a cost-effectiveness analysis of long-lasting insecticide-treated bed net distribution channels in a malaria-endemic area of western Kenya-a study protocol.

    Science.gov (United States)

    Gama, Elvis; Were, Vincent; Ouma, Peter; Desai, Meghna; Niessen, Louis; Buff, Ann M; Kariuki, Simon

    2016-11-21

    Historically, Kenya has used various distribution models for long-lasting insecticide-treated bed nets (LLINs) with variable results in population coverage. The models presently vary widely in scale, target population and strategy. There is limited information to determine the best combination of distribution models, which will lead to sustained high coverage and are operationally efficient and cost-effective. Standardised cost information is needed in combination with programme effectiveness estimates to judge the efficiency of LLIN distribution models and options for improvement in implementing malaria control programmes. The study aims to address the information gap, estimating distribution cost and the effectiveness of different LLIN distribution models, and comparing them in an economic evaluation. Evaluation of cost and coverage will be determined for 5 different distribution models in Busia County, an area of perennial malaria transmission in western Kenya. Cost data will be collected retrospectively from health facilities, the Ministry of Health, donors and distributors. Programme-effectiveness data, defined as the number of people with access to an LLIN per 1000 population, will be collected through triangulation of data from a nationally representative, cross-sectional malaria survey, a cross-sectional survey administered to a subsample of beneficiaries in Busia County and LLIN distributors' records. Descriptive statistics and regression analysis will be used for the evaluation. A cost-effectiveness analysis will be performed from a health-systems perspective, and cost-effectiveness ratios will be calculated using bootstrapping techniques. The study has been evaluated and approved by Kenya Medical Research Institute, Scientific and Ethical Review Unit (SERU number 2997). All participants will provide written informed consent. The findings of this economic evaluation will be disseminated through peer-reviewed publications. Published by the BMJ Publishing

  3. Providing insecticide treated bed nets in antiretroviral treatment ...

    African Journals Online (AJOL)

    HIV-replication.5-13 Mathematical models show that repeated ... antiretroviral treatment clinics in Malawi: a pilot ... related disease or AIDS.3 In addition, there are between 300 - ... and growing evidence of interactive pathology.1,2. HIV ..... by the HIV Unit and its partners. ... procurement and supply chain systems developed.

  4. Efficacy of Selected Insecticide Sprays and Aerosols against the Common Bed Bug, Cimex lectularius (Hemiptera: Cimicidae

    Directory of Open Access Journals (Sweden)

    Changlu Wang

    2016-01-01

    Full Text Available We evaluated the residual efficacy of four liquid sprays and four ready-to-use aerosols that are commonly used in the U.S. against a field-collected bed bug, Cimex lectularius L., strain with moderate resistance level to pyrethroids. The four liquid sprays were: Tandem (0.1% thiamethoxam, 0.03% lambda-cyhalothrin, Temprid SC (0.05% imidacloprid, 0.025% cyfluthrin, Transport GHP (0.05% acetamiprid, 0.06% bifenthrin, and Demand CS (0.03% lambda-cyhalothrin. The four aerosols were: Alpine (0.5% dinotefuran, Bedlam (0.4% sumithrin, 1.6% MGK 264, Bedlam Plus (0.4% sumithrin, 1% MGK 264, 0.05% imidacloprid, and Phantom (0.5% chlorfenapyr. Bed bugs were confined for 4 h to treated substrates (aged 24 h. Four substrates were tested: fabric, unpainted wood, painted wood, and vinyl. Bedlam, Demand CS, and Temprid SC resulted in ≤70% mortality on all tested substrates. Among the other five products, substrate type significantly affected their residual efficacy, except for Transport GHP, which caused ≥89.7% mortality regardless of the substrate. The effect of exposure time (5 min, 4 h, and 24 h on the efficacy of Transport GHP and Phantom aerosol also was evaluated. A 4 h continuous exposure to Phantom aerosol or Transport GHP residue caused similar mortality to 24 h exposure and higher mortality than 5 min exposure.

  5. Effect of malaria transmission reduction by insecticide-treated bed nets (ITNs) on the genetic diversity of Plasmodium falciparum merozoite surface protein (MSP-1) and circumsporozoite (CSP) in western Kenya.

    Science.gov (United States)

    Kariuki, Simon K; Njunge, James; Muia, Ann; Muluvi, Geofrey; Gatei, Wangeci; Ter Kuile, Feiko; Terlouw, Dianne J; Hawley, William A; Phillips-Howard, Penelope A; Nahlen, Bernard L; Lindblade, Kim A; Hamel, Mary J; Slutsker, Laurence; Shi, Ya Ping

    2013-08-27

    Although several studies have investigated the impact of reduced malaria transmission due to insecticide-treated bed nets (ITNs) on the patterns of morbidity and mortality, there is limited information on their effect on parasite diversity. Sequencing was used to investigate the effect of ITNs on polymorphisms in two genes encoding leading Plasmodium falciparum vaccine candidate antigens, the 19 kilodalton blood stage merozoite surface protein-1 (MSP-1(19kDa)) and the Th2R and Th3R T-cell epitopes of the pre-erythrocytic stage circumsporozoite protein (CSP) in a large community-based ITN trial site in western Kenya. The number and frequency of haplotypes as well as nucleotide and haplotype diversity were compared among parasites obtained from children diversity of > 0.7. No MSP-1(19kDa) 3D7 sequence-types were detected in 1996 and the frequency was less than 4% in 2001. The CSP Th2R and Th3R domains were highly polymorphic with a total of 26 and 14 haplotypes, respectively detected in 1996 and 34 and 13 haplotypes in 2001, with an overall haplotype diversity of > 0.9 and 0.75 respectively. The frequency of the most predominant Th2R and Th3R haplotypes was 14 and 36%, respectively. The frequency of Th2R and Th3R haplotypes corresponding to the 3D7 parasite strain was less than 4% at both time points. There was no significant difference in nucleotide and haplotype diversity in parasite isolates collected at both time points. High diversity in these two genes has been maintained overtime despite marked reductions in malaria transmission due to ITNs use. The frequency of 3D7 sequence-types was very low in this area. These findings provide information that could be useful in the design of future malaria vaccines for deployment in endemic areas with high ITN coverage and in interpretation of efficacy data for malaria vaccines based on 3D7 parasite strains.

  6. Engineering Pseudomonas putida KT2440 for simultaneous degradation of organophosphates and pyrethroids and its application in bioremediation of soil.

    Science.gov (United States)

    Zuo, Zhenqiang; Gong, Ting; Che, You; Liu, Ruihua; Xu, Ping; Jiang, Hong; Qiao, Chuanling; Song, Cunjiang; Yang, Chao

    2015-06-01

    Agricultural soils are usually co-contaminated with organophosphate (OP) and pyrethroid pesticides. To develop a stable and marker-free Pseudomonas putida for co-expression of two pesticide-degrading enzymes, we constructed a suicide plasmid with expression cassettes containing a constitutive promoter J23119, an OP-degrading gene (mpd), a pyrethroid-hydrolyzing carboxylesterase gene (pytH) that utilizes the upp gene as a counter-selectable marker for upp-deficient P. putida. By introduction of suicide plasmid and two-step homologous recombination, both mpd and pytH genes were integrated into the chromosome of a robust soil bacterium P. putida KT2440 and no selection marker was left on chromosome. Functional expression of mpd and pytH in P. putida KT2440 was demonstrated by Western blot analysis and enzyme activity assays. Degradation experiments with liquid cultures showed that the mixed pesticides including methyl parathion, fenitrothion, chlorpyrifos, permethrin, fenpropathrin, and cypermethrin (0.2 mM each) were degraded completely within 48 h. The inoculation of engineered strain (10(6) cells/g) to soils treated with the above mixed pesticides resulted in a higher degradation rate than in noninoculated soils. All six pesticides could be degraded completely within 15 days in fumigated and nonfumigated soils with inoculation. Theses results highlight the potential of the engineered strain to be used for in situ bioremediation of soils co-contaminated with OP and pyrethroid pesticides.

  7. Costs and effects of the Tanzanian national voucher scheme for insecticide-treated nets

    Directory of Open Access Journals (Sweden)

    Hanson Kara

    2008-02-01

    Full Text Available Abstract Background The cost-effectiveness of insecticide-treated nets (ITNs in reducing morbidity and mortality is well established. International focus has now moved on to how best to scale up coverage and what financing mechanisms might be used to achieve this. The approach in Tanzania has been to deliver a targeted subsidy for those most vulnerable to the effects of malaria while at the same time providing support to the development of the commercial ITN distribution system. In October 2004, with funds from the Global Fund to Fight AIDS Tuberculosis and Malaria, the government launched the Tanzania National Voucher Scheme (TNVS, a nationwide discounted voucher scheme for ITNs for pregnant women and their infants. This paper analyses the costs and effects of the scheme and compares it with other approaches to distribution. Methods Economic costs were estimated using the ingredients approach whereby all resources required in the delivery of the intervention (including the user contribution are quantified and valued. Effects were measured in terms of number of vouchers used (and therefore nets delivered and treated nets years. Estimates were also made for the cost per malaria case and death averted. Results and Conclusion The total financial cost of the programme represents around 5% of the Ministry of Health's total budget. The average economic cost of delivering an ITN using the voucher scheme, including the user contribution, was $7.57. The cost-effectiveness results are within the benchmarks set by other malaria prevention studies. The Government of Tanzania's approach to scaling up ITNs uses both the public and private sectors in order to achieve and sustain the level of coverage required to meet the Abuja targets. The results presented here suggest that the TNVS is a cost-effective strategy for delivering subsidized ITNs to targeted vulnerable groups.

  8. Scepticism towards insecticide treated mosquito nets for malaria control in a rural community in northwestern Tanzania

    DEFF Research Database (Denmark)

    Nnko, Soori; Whyte, Susan Reynolds; Geissler, Wenzel

    2012-01-01

    in Mwanza region, North-Western Tanzania. The study explores reasons for scepticism and low uptake of insecticide treated mosquito nets (ITNs) that were promoted through social marketing strategy for malaria control prior to the introduction of long lasting nets (LLN). The paper breaks from traditional...... attendances. In terms of mortality, malaria is known to be responsible for more than one third of deaths among children of age below 5 years and also contributes for up to one fifth of deaths among pregnant women. This paper is based on a study conducted in a rural community along the shores of Lake Victoria...

  9. Factors Affecting Transfer of Pyrethroid Residues from Herbal Teas to Infusion and Influence of Physicochemical Properties of Pesticides

    Directory of Open Access Journals (Sweden)

    Jin-Jing Xiao

    2017-09-01

    Full Text Available The transfer of pesticide residues from herbal teas to their infusion is a subject of particular interest. In this study, a multi-residue analytical method for the determination of pyrethroids (fenpropathrin, beta-cypermethrin, lambda-cyhalothrin, and fenvalerate in honeysuckle, chrysanthemum, wolfberry, and licorice and their infusion samples was validated. The transfer of pyrethroid residues from tea to infusion was investigated at different water temperatures, tea/water ratios, and infusion intervals/times. The results show that low amounts (0–6.70% of pyrethroids were transferred under the different tea brewing conditions examined, indicating that the infusion process reduced the pyrethroid content in the extracted liquid by over 90%. Similar results were obtained for the different tea varieties, and pesticides with high water solubility and low octanol–water partition coefficients (log Kow exhibited high transfer rates. Moreover, the estimated values of the exposure risk to the pyrethroids were in the range of 0.0022–0.33, indicating that the daily intake of the four pyrethroid residues from herbal tea can be regarded as safe. The present results can support the identification of suitable tea brewing conditions for significantly reducing the pesticide residue levels in the infusion.

  10. Malaria infection and disease in an area with pyrethroid-resistant vectors in southern Benin

    Directory of Open Access Journals (Sweden)

    Akogbéto Martin

    2010-12-01

    Full Text Available Abstract Background This study aimed to investigate baseline data on malaria before the evaluation of new vector control strategies in an area of pyrethroid-resistance of vectors. The burden of malaria was estimated in terms of infection (prevalence and parasite density and of clinical episodes. Methods Between December 2007 and December 2008 in the health district of Ouidah - Kpomassè - Tori Bossito (southern Benin, a descriptive epidemiological survey of malaria was conducted. From 28 selected villages, seven were randomized from which a total of 440 children aged 0 to 5 years were randomly selected. Clinical and parasitological information was obtained by active case detection of malaria episodes carried out during eight periods of six consecutive days scheduled at six weekly intervals and by cross-sectional surveys of asymptomatic infection. Entomological information was also collected. The ownership, the use and the correct use of long-lasting insecticide-treated nets (LLINs were checked over weekly-survey by unannounced visits at home in the late evening. Results Mean parasite density in asymptomatic children was 586 P. falciparum asexual forms per μL of blood (95%CI 504-680. Pyrogenic parasite cut-off was estimated 2,000 P. falciparum asexual blood forms per μL. The clinical incidence of malaria was 1.5 episodes per child per year (95%CI 1.2-1.9. Parasitological and clinical variables did not vary with season. Anopheles gambiae s.l. was the principal vector closely followed by Anopheles funestus. Entomological inoculation rate was 5.3 (95%CI 1.1-25.9 infective bites per human per year. Frequency of the L1014F kdr (West allele was around 50%. Annual prevalence rate of Plasmodium falciparum asymptomatic infection was 21.8% (95%CI 19.1-24.4 and increased according to age. Mean rates of ownership and use of LLINs were 92% and 70% respectively. The only correct use of LLINs (63% conferred 26% individual protection against only infection (OR

  11. Voltage-gated sodium channel polymorphism and metabolic resistance in pyrethroid-resistant Aedes aegypti from Brazil.

    Science.gov (United States)

    Martins, Ademir Jesus; Lins, Rachel Mazzei Moura de Andrade; Linss, Jutta Gerlinde Birgitt; Peixoto, Alexandre Afranio; Valle, Denise

    2009-07-01

    The nature of pyrethroid resistance in Aedes aegypti Brazilian populations was investigated. Quantification of enzymes related to metabolic resistance in two distinct populations, located in the Northeast and Southeast regions, revealed increases in Glutathione-S-transferase (GST) and Esterase levels. Additionally, polymorphism was found in the IIS6 region of Ae. aegypti voltage-gated sodium channel (AaNa(V)), the pyrethroid target site. Sequences were classified in two haplotype groups, A and B, according to the size of the intron in that region. Rockefeller, a susceptible control lineage, contains only B sequences. In field populations, some A sequences present a substitution in the 1011 site (Ile/Met). When resistant and susceptible individuals were compared, the frequency of both A (with the Met mutation) and B sequences were slightly increased in resistant specimens. The involvement of the AaNa(V) polymorphism in pyrethroid resistance and the metabolic mechanisms that lead to potential cross-resistance between organophosphate and pyrethroids are discussed.

  12. Evaluation of an integrated sponge--granular activated carbon fluidized bed bioreactor for treating primary treated sewage effluent.

    Science.gov (United States)

    Xing, W; Ngo, H H; Guo, W S; Listowski, A; Cullum, P

    2011-05-01

    An integrated fluidized bed bioreactor (iFBBR) was designed to incorporate an aerobic sponge FBBR (ASB-FBBR) into an anoxic granular activated carbon FBBR (GAC-FBBR). This iFBBR was operated with and without adding a new starch based flocculant (NSBF) to treat synthetic primary treated sewage effluent (PTSE). The NSBF contains starch based cationic flocculants and trace nutrients. The results indicate that the iFBBR with NSBF addition could remove more than 93% dissolved organic carbon (DOC), 61% total nitrogen (T-N) and 60% total phosphorus (T-P) at just a very short hydraulic retention time of 50 min. The optimum frequency of adding NSBF to the iFFBR is four times per day. As a pretreatment to microfiltration, the iFFBR could increase 5L/m(2)h of critical flux thus reducing the membrane fouling. In addition, better microbial activity was also observed with high DO consumption (>66%) and specific oxygen uptake rate (>35 mg O(2)/g VSS h). Copyright © 2010 Elsevier Ltd. All rights reserved.

  13. Exposure to pyrethroids insecticides and serum levels of thyroid-related measures in pregnant women

    International Nuclear Information System (INIS)

    Zhang, Jie; Hisada, Aya; Yoshinaga, Jun; Shiraishi, Hiroaki; Shimodaira, Kazuhisa; Okai, Takashi; Noda, Yumiko; Shirakawa, Miyako; Kato, Nobumasa

    2013-01-01

    Possible association between environmental exposure to pyrethroid insecticides and serum thyroid-related measures was explored in 231 pregnant women of 10–12 gestational weeks recruited at a university hospital in Tokyo during 2009–2011. Serum levels of free thyroxine (fT4), thyroid stimulating hormone (TSH) and thyroid biding globulin (TBG) and urinary pyrethroid insecticide metabolite (3-phenoxybenzoic acid, 3-PBA) were measured. Obstetrical information was obtained from medical records and dietary and lifestyle information was collected by self-administered questionnaire. Geometric mean concentration of creatinine-adjusted urinary 3-PBA was 0.363 (geometric standard deviation: 3.06) μg/g cre, which was consistent with the previously reported levels for non-exposed Japanese adult females. The range of serum fT4, TSH and TBG level was 0.83–3.41 ng/dL, 0.01–27.4 μIU/mL and 16.4–54.4 μg/mL, respectively. Multiple regression analysis was carried out by using either one of serum levels of thyroid-related measures as a dependent variable and urinary 3-PBA as well as other potential covariates (age, pre-pregnancy BMI, parity, urinary iodine, smoking and drinking status) as independent variables: 3-PBA was not found as a significant predictor of serum level of thyroid-related measures. Lack of association may be due to lower pyrethroid insecticide exposure level of the present subjects. Taking the ability of pyrethroid insecticides and their metabolite to bind to nuclear thyroid hormone (TH) receptor, as well as their ability of placental transfer, into consideration, it is warranted to investigate if pyrethroid pesticides do not have any effect on TH actions in fetus brain even though maternal circulating TH level is not affected. -- Highlights: • Pyrethroid exposure and thyroid hormone status was examined in pregnant women. • Urinary 3-phenoxybenzoic acid was used as a biomarker of exposure. • Iodine nutrition, age and other covariates were included

  14. Exposure to pyrethroids insecticides and serum levels of thyroid-related measures in pregnant women

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Jie; Hisada, Aya [Department of Environmental Studies, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8563 (Japan); Yoshinaga, Jun, E-mail: junyosh@k.u-tokyo.ac.jp [Department of Environmental Studies, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8563 (Japan); Shiraishi, Hiroaki [National Institute for Environmental Studies, Onogawa 16-2, Tsukuba, Ibaraki 305-8563 (Japan); Shimodaira, Kazuhisa; Okai, Takashi [Department of Obstetrics and Gynecology, Showa University School of Medicine, 1-5-8 Hatanodai, Shinagawa, Tokyo 142-8555 (Japan); Noda, Yumiko; Shirakawa, Miyako; Kato, Nobumasa [Department of Psychiatry and Neurology, Showa University School of Medicine, 1-5-8 Hatanodai, Shinagawa, Tokyo 142-8555 (Japan)

    2013-11-15

    Possible association between environmental exposure to pyrethroid insecticides and serum thyroid-related measures was explored in 231 pregnant women of 10–12 gestational weeks recruited at a university hospital in Tokyo during 2009–2011. Serum levels of free thyroxine (fT4), thyroid stimulating hormone (TSH) and thyroid biding globulin (TBG) and urinary pyrethroid insecticide metabolite (3-phenoxybenzoic acid, 3-PBA) were measured. Obstetrical information was obtained from medical records and dietary and lifestyle information was collected by self-administered questionnaire. Geometric mean concentration of creatinine-adjusted urinary 3-PBA was 0.363 (geometric standard deviation: 3.06) μg/g cre, which was consistent with the previously reported levels for non-exposed Japanese adult females. The range of serum fT4, TSH and TBG level was 0.83–3.41 ng/dL, 0.01–27.4 μIU/mL and 16.4–54.4 μg/mL, respectively. Multiple regression analysis was carried out by using either one of serum levels of thyroid-related measures as a dependent variable and urinary 3-PBA as well as other potential covariates (age, pre-pregnancy BMI, parity, urinary iodine, smoking and drinking status) as independent variables: 3-PBA was not found as a significant predictor of serum level of thyroid-related measures. Lack of association may be due to lower pyrethroid insecticide exposure level of the present subjects. Taking the ability of pyrethroid insecticides and their metabolite to bind to nuclear thyroid hormone (TH) receptor, as well as their ability of placental transfer, into consideration, it is warranted to investigate if pyrethroid pesticides do not have any effect on TH actions in fetus brain even though maternal circulating TH level is not affected. -- Highlights: • Pyrethroid exposure and thyroid hormone status was examined in pregnant women. • Urinary 3-phenoxybenzoic acid was used as a biomarker of exposure. • Iodine nutrition, age and other covariates were included

  15. Identification and characterization of a novel thermostable pyrethroid-hydrolyzing enzyme isolated through metagenomic approach

    Directory of Open Access Journals (Sweden)

    Fan Xinjiong

    2012-03-01

    Full Text Available Abstract Background Pyrethroid pesticides are broad-spectrum pest control agents in agricultural production. Both agricultural and residential usage is continuing to grow, leading to the development of insecticide resistance in the pest and toxic effects on a number of nontarget organisms. Thus, it is necessary to hunt suitable enzymes including hydrolases for degrading pesticide residues, which is an efficient "green" solution to biodegrade polluting chemicals. Although many pyrethroid esterases have consistently been purified and characterized from various resources including metagenomes and organisms, the thermostable pyrethroid esterases have not been reported up to the present. Results In this study, we identified a novel pyrethroid-hydrolyzing enzyme Sys410 belonging to familyV esterases/lipases with activity-based functional screening from Turban Basin metagenomic library. Sys410 contained 280 amino acids with a predicted molecular mass (Mr of 30.8 kDa and was overexpressed in Escherichia coli BL21 (DE3 in soluble form. The optimum pH and temperature of the recombinant Sys410 were 6.5 and 55°C, respectively. The enzyme was stable in the pH range of 4.5-8.5 and at temperatures below 50°C. The activity of Sys410 decreased a little when stored at 4°C for 10 weeks, and the residual activity reached 94.1%. Even after incubation at 25°C for 10 weeks, it kept 68.3% of its activity. The recombinant Sys410 could hydrolyze a wide range of ρ-nitrophenyl esters, but its best substrate is ρ-nitrophenyl acetate with the highest activity (772.9 U/mg. The enzyme efficiently degraded cyhalothrin, cypermethrin, sumicidin, and deltamethrin under assay conditions of 37°C for 15 min, with exceeding 95% hydrolysis rate. Conclusion This is the first report to construct metagenomic libraries from Turban Basin to obtain the thermostable pyrethroid-hydrolyzing enzyme. The recombinant Sys410 with broad substrate specificities and high activity was the most

  16. Additivity of Pyrethroid Actions on Sodium Influx in Cortical Neurons in Cerebrocortical Neurons in Primary Culture

    Science.gov (United States)

    BACKGROUND: Pyrethroid insecticides bind to voltage-gated sodium channels and modify their gating kinetics, thereby disrupting neuronal function. Although previous work has tested the additivity of pyrethroids in vivo, this has not been assessed directly at the primary molecular ...

  17. Toxic heritage: Maternal transfer of pyrethroid insecticides and sunscreen agents in dolphins from Brazil

    International Nuclear Information System (INIS)

    Alonso, Mariana B.; Feo, Maria Luisa; Corcellas, Cayo; Gago-Ferrero, Pablo; Bertozzi, Carolina P.; Marigo, Juliana; Flach, Leonardo; Meirelles, Ana Carolina O.; Carvalho, Vitor L.; Azevedo, Alexandre F.; Torres, João Paulo M.

    2015-01-01

    Pyrethroids (PYR) and UV filters (UVF) were investigated in tissues of paired mother-fetus dolphins from Brazilian coast in order to investigate the possibility of maternal transfer of these emerging contaminants. Comparison of PYR and UVF concentrations in maternal and fetal blubber revealed Franciscana transferred efficiently both contaminants to fetuses (F/M > 1) and Guiana dolphin transferred efficiently PYR to fetuses (F/M > 1) different than UVF (F/M < 1). PYR and UVF concentrations in fetuses were the highest-ever reported in biota (up to 6640 and 11,530 ng/g lw, respectively). Muscle was the organ with the highest PYR and UVF concentrations (p < 0.001), suggesting that these two classes of emerging contaminants may have more affinity for proteins than for lipids. The high PYR and UVF concentrations found in fetuses demonstrate these compounds are efficiently transferred through placenta. This study is the first to report maternal transfer of pyrethroids and UV filters in marine mammals. - Highlights: • First time maternal transfer of pyrethroids and UV filters in mammals was reported. • Pollutants in fetus tissues characterize their transplacental transfer. • Fetuses had pyrethroid and UV filter levels 10 times higher than their mothers. • Muscle was the organ presented with the highest concentrations of PYR and UVF. - Pyrethroids and UV filter concentrations in fetus and mother dolphin tissues demonstrated placenta and milk transfer in marine mammals.

  18. Pest Prevalence and Evaluation of Community-Wide Integrated Pest Management for Reducing Cockroach Infestations and Indoor Insecticide Residues.

    Science.gov (United States)

    Zha, Chen; Wang, Changlu; Buckley, Brian; Yang, Ill; Wang, Desen; Eiden, Amanda L; Cooper, Richard

    2018-04-02

    Pest infestations in residential buildings are common, but community-wide pest survey data are lacking. Frequent insecticide applications for controlling indoor pests leave insecticide residues and pose potential health risks to residents. In this study, a community-wide pest survey was carried out in a housing complex consisting of 258 units in 40 buildings in New Brunswick, New Jersey. It was immediately followed by implementation of an integrated pest management (IPM) program in all the cockroach-infested apartments and two bed bug apartments with the goal of eliminating pest infestations, reducing pyrethroid residues, and increasing resident satisfaction with pest control services. The IPM-treated apartments were revisited and treated biweekly or monthly for 7 mo. Initial inspection found the top three pests and their infestation rates to be as follows: German cockroaches (Blattella germanica L. [Blattodea: Blattellidae]), 28%; rodents, 11%; and bed bugs (Cimex lectularius L. [Hemiptera: Cimicidae]), 8%. Floor wipe samples were collected in the kitchens and bedrooms of 20 apartments for pyrethroid residue analysis before the IPM implementation; 17 of the 20 apartments were resampled again at 7 mo. The IPM program reduced cockroach counts per apartment by 88% at 7 wk after initial treatment. At 7 mo, 85% of the cockroach infestations found in the initial survey were eliminated. The average number of pyrethroids detected decreased significantly from 6 ± 1 (mean ± SEM) and 5 ± 1 to 2 ± 1 and 3 ± 1 in the kitchens and bedrooms, respectively. The average concentrations of targeted pyrethroids residue also decreased significantly in the kitchens and bedrooms.

  19. Mitigation of two pyrethroid insecticides in a Mississippi Delta constructed wetland

    Energy Technology Data Exchange (ETDEWEB)

    Moore, M.T. [USDA Agricultural Research Service National Sedimentation Laboratory, Water Quality and Ecology Research Unit, PO Box 1157, 598 McElroy Drive, Oxford, MS 38655 (United States)], E-mail: matt.moore@ars.usda.gov; Cooper, C.M.; Smith, S.; Cullum, R.F.; Knight, S.S.; Locke, M.A.; Bennett, E.R. [USDA Agricultural Research Service National Sedimentation Laboratory, Water Quality and Ecology Research Unit, PO Box 1157, 598 McElroy Drive, Oxford, MS 38655 (United States)

    2009-01-15

    Constructed wetlands are a suggested best management practice to help mitigate agricultural runoff before entering receiving aquatic ecosystems. A constructed wetland system (180 m x 30 m), comprising a sediment retention basin and two treatment cells, was used to determine the fate and transport of simulated runoff containing the pyrethroid insecticides lambda-cyhalothrin and cyfluthrin, as well as suspended sediment. Wetland water, sediment, and plant samples were collected spatially and temporally over 55 d. Results showed 49 and 76% of the study's measured lambda-cyhalothrin and cyfluthrin masses were associated with vegetation, respectively. Based on conservative effects concentrations for invertebrates and regression analyses of maximum observed wetland aqueous concentrations, a wetland length of 215 m x 30 m width would be required to adequately mitigate 1% pesticide runoff from a 14 ha contributing area. Results of this experiment can be used to model future design specifications for constructed wetland mitigation of pyrethroid insecticides. - A wetland length of 215 m x 30 m mitigated pyrethroid runoff from a 14 ha field.

  20. Mitigation of two pyrethroid insecticides in a Mississippi Delta constructed wetland

    International Nuclear Information System (INIS)

    Moore, M.T.; Cooper, C.M.; Smith, S.; Cullum, R.F.; Knight, S.S.; Locke, M.A.; Bennett, E.R.

    2009-01-01

    Constructed wetlands are a suggested best management practice to help mitigate agricultural runoff before entering receiving aquatic ecosystems. A constructed wetland system (180 m x 30 m), comprising a sediment retention basin and two treatment cells, was used to determine the fate and transport of simulated runoff containing the pyrethroid insecticides lambda-cyhalothrin and cyfluthrin, as well as suspended sediment. Wetland water, sediment, and plant samples were collected spatially and temporally over 55 d. Results showed 49 and 76% of the study's measured lambda-cyhalothrin and cyfluthrin masses were associated with vegetation, respectively. Based on conservative effects concentrations for invertebrates and regression analyses of maximum observed wetland aqueous concentrations, a wetland length of 215 m x 30 m width would be required to adequately mitigate 1% pesticide runoff from a 14 ha contributing area. Results of this experiment can be used to model future design specifications for constructed wetland mitigation of pyrethroid insecticides. - A wetland length of 215 m x 30 m mitigated pyrethroid runoff from a 14 ha field

  1. Effectiveness and Cost of Insecticide-Treated Bed Nets and Indoor Residual Spraying for the Control of Cutaneous Leishmaniasis: A Cluster-Randomized Control Trial in Morocco

    Science.gov (United States)

    Faraj, Chafika; Yukich, Joshua; Adlaoui, El Bachir; Wahabi, Rachid; Mnzava, Abraham Peter; Kaddaf, Mustapha; El Idrissi, Abderrahmane Laamrani; Ameur, Btissam; Kleinschmidt, Immo

    2016-01-01

    Cutaneous leishmaniasis (CL) remains an important public health problem in Morocco. A cluster-randomized trial was conducted with the following three study arms: 1) long-lasting insecticide-treated nets (LLINs) plus standard of care environmental management (SoC-EM), 2) indoor residual spraying (IRS) with α-cypermethrin plus SoC-EM, and 3) SoC-EM alone. Incidence of new CL cases by passive and active case detection, sandfly abundance, and cost and cost-effectiveness was compared between study arms over 5 years. Incidence of CL and sandfly abundance were significantly lower in the IRS arm compared with SoC-EM (CL incidence rate ratio = 0.32, 95% confidence interval [CI] = 0.15–0.69, P = 0.005 and sandfly abundance ratio = 0.39, 95% CI = 0.18–0.85, P = 0.022). Reductions in the LLIN arm of the study were not significant, possibly due to poor compliance. IRS was effective and more cost-effective for the prevention of CL in Morocco. PMID:26811431

  2. Comparative acute toxicity of neonicotinoid and pyrethroid insecticides to non-target crayfish (Procambarus clarkii) associated with rice-crayfish crop rotations.

    Science.gov (United States)

    Barbee, Gary C; Stout, Michael J

    2009-11-01

    Most insecticides used to control rice water weevil (Lissorhoptrus oryzophilus Kuscel) infestations are pyrethroids. However, pyrethroids are highly toxic to non-target crayfish associated with rice-crayfish crop rotations. One solution to the near-exclusive reliance on pyrethroids in a rice-crayfish pest management program is to incorporate neonicotinoid insecticides, which are insect specific and effective against weevils but not extremely toxic to crayfish. This study aimed to take the first step to assess neonicotinoids as alternatives to pyrethroids in rice-crayfish crop rotations by measuring the acute toxicities of three candidate neonicotinoid insecticides, clothianidin, dinotefuran and thiamethoxam, to juvenile Procambarus clarkii (Girard) crayfish and comparing them with the acute toxicities of two currently used pyrethroid insecticides, lambda-cyhalothrin and etofenprox. Neonicotinoid insecticides are at least 2-3 orders of magnitude less acutely toxic (96 h LC(50)) than pyrethroids to juvenile Procambarid crayfish: lambda-cyhalothrin (0.16 microg AI L(-1)) = etofenprox (0.29 microg AI L(-1)) > clothianidin (59 microg AI L(-1)) > thiamethoxam (967 microg AI L(-1)) > dinotefuran (2032 microg AI L(-1)). Neonicotinoid insecticides appear to be much less hazardous alternatives to pyrethroids in rice-crayfish crop rotations. Further field-level neonicotinoid acute and chronic toxicity testing with crayfish is needed. (c) 2009 Society of Chemical Industry.

  3. Occurrence and potential toxicity of pyrethroids and other insecticides in bed sediments of urban streams in central Texas

    Energy Technology Data Exchange (ETDEWEB)

    Hintzen, Emily P. [Department of Environmental Studies, Baylor University, Waco, TX 76798 (United States); Lydy, Michael J. [Fisheries and Illinois Aquaculture Center, and Department of Zoology, Southern Illinois University, Carbondale, IL 62091 (United States); Belden, Jason B. [Department of Zoology, Oklahoma State University, 430 Life Science West, Stillwater, OK 74078 (United States)], E-mail: jbelden@okstate.edu

    2009-01-15

    Despite heavy insecticide usage in urban areas, only a few studies have investigated the impact of current-use insecticides on benthic invertebrates in urban streams. The objective of this study was to measure the presence and concentration of current-use pesticides in sediments of residential streams in central Texas. Additionally, toxicity of these sediments to Hyalella azteca was evaluated. Sediment samples were collected from several sites in urban streams over the course of a year, of which, 66% had greater than one toxic unit (TU) of insecticide. Bifenthrin was the greatest contributor accounting for 65% of the TUs, and sediment toxicity to H. azteca correlated with the magnitude of total insecticides and bifenthrin TUs. The results of this study further raise concerns over the environmental consequences posed by many current-use insecticides, especially pyrethroids, in urban settings. - This study examined the presence of insecticides in Texas stream sediments as a model for evaluating the potential impact of urban insecticide use in the Southern United States.

  4. Occurrence and potential toxicity of pyrethroids and other insecticides in bed sediments of urban streams in central Texas

    International Nuclear Information System (INIS)

    Hintzen, Emily P.; Lydy, Michael J.; Belden, Jason B.

    2009-01-01

    Despite heavy insecticide usage in urban areas, only a few studies have investigated the impact of current-use insecticides on benthic invertebrates in urban streams. The objective of this study was to measure the presence and concentration of current-use pesticides in sediments of residential streams in central Texas. Additionally, toxicity of these sediments to Hyalella azteca was evaluated. Sediment samples were collected from several sites in urban streams over the course of a year, of which, 66% had greater than one toxic unit (TU) of insecticide. Bifenthrin was the greatest contributor accounting for 65% of the TUs, and sediment toxicity to H. azteca correlated with the magnitude of total insecticides and bifenthrin TUs. The results of this study further raise concerns over the environmental consequences posed by many current-use insecticides, especially pyrethroids, in urban settings. - This study examined the presence of insecticides in Texas stream sediments as a model for evaluating the potential impact of urban insecticide use in the Southern United States

  5. Incoordination, Paralysis and Recovery after Pyrethroid Treatment on Nymphs III of Triatoma infestans (Hemiptera: Reduviidae

    Directory of Open Access Journals (Sweden)

    Raúl A Alzogaray

    1997-05-01

    Full Text Available Symptoms of poisoning for deltamethrin and cis-permethrin on nymphs III of Triatoma infestans were described. The time required for incoordination and paralysis were determined. Deltamethrin was equal or more rapid in the onset of the first effect (accordingly to dose, and cis-permethrin in the onset of the second one. There were no significant differences between incoordination doses 50% (IncD50s at different times for the two pyrethroids. They showed equivalent incoordination power, but the nymphs treated with deltamethrin recovered slightly more rapid and in greater amount than the nymphs treated with cis-permethrin. The recovery was inhibited by the simultaneus application of piperonyl butoxide. This result suggests that biotransformation by mixed-function microsomal oxidases are involved in the process of recovery

  6. Suspended particles only marginally reduce pyrethroid toxicity to the freshwater invertebrate Gammarus pulex (L.) during pulse exposure

    DEFF Research Database (Denmark)

    Rasmussen, Jes; Cedergreen, Nina; Kronvang, Brian

    2016-01-01

    Current ecotoxicological research on particle associated pyrethroids in freshwater systems focuses almost exclusively on sediment-exposure scenarios and sediment-dwelling macroinvertebrates. We studied how suspended particles influence acute effects of lambda-cyhalothrin and bifenthrin on the epi......Current ecotoxicological research on particle associated pyrethroids in freshwater systems focuses almost exclusively on sediment-exposure scenarios and sediment-dwelling macroinvertebrates. We studied how suspended particles influence acute effects of lambda-cyhalothrin and bifenthrin....... MM suspensions adsorbed a variable fraction of pyrethroids (10% for bifenthrin and 70% for lambda-cyhalothrin) but did not significantly change the concentration–response relationship compared to pure pyrethroid treatments. Behavioral responses and immobilisation rate of G. pulex were reduced...

  7. Media arrangement impacts cell growth in anaerobic fixed-bed reactors treating sugarcane vinasse: Structured vs. randomic biomass immobilization.

    Science.gov (United States)

    de Aquino, Samuel; Fuess, Lucas Tadeu; Pires, Eduardo Cleto

    2017-07-01

    This study reports on the application of an innovative structured-bed reactor (FVR) as an alternative to conventional packed-bed reactors (PBRs) to treat high-strength solid-rich wastewaters. Using the FVR prevents solids from accumulating within the fixed-bed, while maintaining the advantages of the biomass immobilization. The long-term operation (330days) of a FVR and a PBR applied to sugarcane vinasse under increasing organic loads (2.4-18.0kgCODm -3 day -1 ) was assessed, focusing on the impacts of the different media arrangements over the production and retention of biomass. Much higher organic matter degradation rates, as well as long-term operational stability and high conversion efficiencies (>80%) confirmed that the FVR performed better than the PBR. Despite the equivalent operating conditions, the biomass growth yield was different in both reactors, i.e., 0.095gVSSg -1 COD (FVR) and 0.066gVSSg -1 COD (PBR), indicating a clear control of the media arrangement over the biomass production in fixed-bed reactors. Copyright © 2017 Elsevier Ltd. All rights reserved.

  8. Molecular analysis of the biomass of a fluidized bed reactor treating synthetic vinasse at anaerobic and micro-aerobic conditions

    NARCIS (Netherlands)

    Rodriguez, E.; Lopes, A.; Fdz-Polanco, M.; Stams, A.J.M.; Garcia Encina, P.A.

    2012-01-01

    The microbial communities (Bacteria and Archaea) established in an anaerobic fluidized bed reactor used to treat synthetic vinasse (betaine, glucose, acetate, propionate, and butyrate) were characterized by denaturing gradient gel electrophoresis (DGGE) and phylogenetic analysis. This study was

  9. Conflict of interest: use of pyrethroids and amidines against tsetse and ticks in zoonotic sleeping sickness endemic areas of Uganda.

    Science.gov (United States)

    Bardosh, Kevin; Waiswa, Charles; Welburn, Susan C

    2013-07-10

    effective way to increase pyrethroid use. Conflicts of interest between veterinary business and vector control were found to constrain sleeping sickness control. While a variety of strategies could increase pyrethroid use, regulation of the insecticide market could effectively double the number of treated cattle with little cost to government, donors or farmers. Such regulation is entirely consistent with the role of the state in a privatised veterinary system and should include a mitigation strategy against the potential development of tick resistance.

  10. Pyrethroid insecticides in wild bird eggs from a World Heritage Listed Park: A case study in Doñana National Park (Spain).

    Science.gov (United States)

    Corcellas, Cayo; Andreu, Ana; Máñez, Manuel; Sergio, Fabrizio; Hiraldo, Fernando; Eljarrat, Ethel; Barceló, Damià

    2017-09-01

    Recent studies demonstrated that the common pyrethroid insecticides are present in aquatic biota tissues. In this study, 123 samples of unhatched eggs of 16 wild bird species collected from 2010 to 2012 in Doñana National and Natural Park were analysed to determine 13 pyrethroids. This study represents the first time that pyrethroids are detected in tissues of terrestrial biota, 93% of these samples being positive to those pollutants. Levels of total pyrethroids ranged from not detected to 324 ng g -1 lw. The samples were characterized by stable isotope analysis. Species with diets based on anthropogenic food showed higher levels of pyrethroids and lower values of δ 15 N. Finally, we characterized the isomers of pyrethroids and discerned some isomeric- and enantiomeric-specific accumulations. In particular, tetramethrin and cyhalothrin showed an enantiomeric-selective accumulation of one enantiomer, highlighting the need to assess toxicological effects of each enantiomer separately to be able to make a correct risk assessment of pyrethroids in birds. Copyright © 2017 Elsevier Ltd. All rights reserved.

  11. Vegetated agricultural drainage ditches for the mitigation of pyrethroid-associated runoff.

    Science.gov (United States)

    Bennett, Erin R; Moore, Matthew T; Cooper, Charles M; Smith, Sammie; Shields, F Douglas; Drouillard, Ken G; Schulz, Ralf

    2005-09-01

    Drainage ditches are indispensable components of the agricultural production landscape. A benefit of these ditches is contaminant mitigation of agricultural storm runoff. This study determined bifenthrin and lambda-cyhalothrin (two pyrethroid insecticides) partitioning and retention in ditch water, sediment, and plant material as well as estimated necessary ditch length required for effective mitigation. A controlled-release runoff simulation was conducted on a 650-m vegetated drainage ditch in the Mississippi Delta, USA. Bifenthrin and lambda-cyhalothrin were released into the ditch in a water-sediment slurry. Samples of water, sediment, and plants were collected and analyzed for pyrethroid concentrations. Three hours following runoff initiation, inlet bifenthrin and lambda-cyhalothrin water concentrations ranged from 666 and 374 microg/L, respectively, to 7.24 and 5.23 microg/L at 200 m downstream. No chemical residues were detected at the 400-m sampling site. A similar trend was observed throughout the first 7 d of the study where water concentrations were elevated at the front end of the ditch (0-25 m) and greatly reduced by the 400-m sampling site. Regression formulas predicted that bifenthrin and lambda-cyhalothrin concentrations in ditch water were reduced to 0.1% of the initial value within 280 m. Mass balance calculations determined that ditch plants were the major sink and/or sorption site responsible for the rapid aqueous pyrethroid dissipation. By incorporating vegetated drainage ditches into a watershed management program, agriculture can continue to decrease potential non-point source threats to downstream aquatic receiving systems. Overall results of this study illustrate that aquatic macrophytes play an important role in the retention and distribution of pyrethroids in vegetated agricultural drainage ditches.

  12. Pyrethroid resistance and cross-resistance in the German cockroach, Blattella germanica (L).

    Science.gov (United States)

    Wei, Y; Appel, A G; Moar, W J; Liu, N

    2001-11-01

    A German cockroach (Blatella germanica (L)) strain, Apyr-R, was collected from Opelika, Alabama after control failures with pyrethroid insecticides. Levels of resistance to permethrin and deltamethrin in Apyr-R (97- and 480-fold, respectively, compared with a susceptible strain, ACY) were partially or mostly suppressed by piperonyl butoxide (PBO) and S,S,S,-tributylphosphorotrithioate (DEF), suggesting that P450 monooxygenases and hydrolases are involved in resistance to these two pyrethroids in Apyr-R. However, incomplete suppression of pyrethroid resistance with PBO and DEF implies that one or more additional mechanisms are involved in resistance. Injection, compared with topical application, resulted in 43- and 48-fold increases in toxicity of permethrin in ACY and Apyr-R, respectively. Similarly, injection increased the toxicity of deltamethrin 27-fold in ACY and 28-fold in Apyr-R. These data indicate that cuticular penetration is one of the obstacles for the effectiveness of pyrethroids against German cockroaches. However, injection did not change the levels of resistance to either permethrin or deltamethrin, suggesting that a decrease in the rate of cuticular penetration may not play an important role in pyrethroid resistance in Apyr-R. Apyr-R showed cross-resistance to imidacloprid, with a resistance ratio of 10. PBO treatment resulted in no significant change in the toxicity of imidacloprid, implying that P450 monooxygenase-mediated detoxication is not the mechanism responsible for cross-resistance. Apyr-R showed no cross-resistance to spinosad, although spinosad had relatively low toxicity to German cockroaches compared with other insecticides tested in this study. This result further confirmed that the mode of action of spinosad to insects is unique. Fipronil, a relatively new insecticide, was highly toxic to German cockroaches, and the multi-resistance mechanisms in Apyr-R did not confer significant cross-resistance to this compound. Thus, we propose

  13. Predicting runoff induced mass loads in urban watersheds: Linking land use and pyrethroid contamination.

    Science.gov (United States)

    Chinen, Kazue; Lau, Sim-Lin; Nonezyan, Michael; McElroy, Elizabeth; Wolfe, Becky; Suffet, Irwin H; Stenstrom, Michael K

    2016-10-01

    Pyrethroid pesticide mass loadings in the Ballona Creek Watershed were calculated using the volume-concentration method with a Geographic Information Systems (GIS) to explore potential relationships between urban land use, impervious surfaces, and pyrethroid runoff flowing into an urban stream. A calibration of the GIS volume-concentration model was performed using 2013 and 2014 wet-weather sampling data. Permethrin and lambda-cyhalothrin were detected as the highest concentrations; deltamethrin, lambda-cyhalothrin, permethrin and cyfluthrin were the most frequently detected synthetic pyrethroids. Eight neighborhoods within the watershed were highlighted as target areas based on a Weighted Overlay Analysis (WOA) in GIS. Water phase concentration of synthetic pyrethroids (SPs) were calculated from the reported usage. The need for stricter BMP and consumer product controls was identified as a possible way of reducing the detections of pyrethroids in Ballona Creek. This model has significant implications for determining mass loadings due to land use influence, and offers a flexible method to extrapolate data for a limited amount of samplings for a larger watershed, particularly for chemicals that are not subject to environmental monitoring. Offered as a simple approach to watershed management, the GIS-volume concentration model has the potential to be applied to other target pesticides and is useful for simulating different watershed scenarios. Further research is needed to compare results against other similar urban watersheds situated in mediterranean climates. Copyright © 2016 Elsevier Ltd. All rights reserved.

  14. EPA-Registered Bed Bug Products

    Science.gov (United States)

    ... rest or hide in hampers, bed frames, even furniture); Failing to treat adjacent areas where bed bugs ... to work (some pesticides, such as desiccators or growth regulators, may be very effective but take some ...

  15. Correlation of tissue concentrations of the pyrethroid bifenthrin with neurotoxicity in the rat

    OpenAIRE

    Scollon, Edward J.; Starr, James M.; Crofton, Kevin M.; Wolansky, Marcelo J.; DeVito, Michael J.; Hughes, Michael F.

    2011-01-01

    The potential for human exposure to pyrethroid pesticides has prompted pharmacodynamic and pharmacokinetic research to better characterize risk. This work tested the hypothesis that blood and brain concentrations of the pyrethroid bifenthrin are predictive of neurotoxic effects. Adult male Long Evans rats received a single oral dose of bifenthrin dissolved in corn oil. Using figure-eight mazes, motor activity was measured for 1 h at 4- and 7-h following exposure to bifenthrin (0–16 mg/kg or 0...

  16. Comparative sensitivity of field and laboratory populations of Hyalella azteca to the pyrethroid insecticides bifenthrin and cypermethrin.

    Science.gov (United States)

    Clark, Stephen L; Ogle, R Scott; Gantner, Andrew; Hall, Lenwood W; Mitchell, Gary; Giddings, Jeffrey; McCoole, Matthew; Dobbs, Michael; Henry, Kevin; Valenti, Ted

    2015-10-01

    Hyalella azteca are epibenthic invertebrates that are widely used for toxicity studies. They are reported to be more sensitive to pyrethroid insecticides than most other test species, which has prompted considerable use of this species in toxicity testing of ambient surface waters where the presence of pyrethroids is suspected. However, resident H. azteca have been found in some ambient water bodies reported to contain surface water and/or sediment pyrethroid concentrations that are toxic to laboratory reared H. azteca. This observation suggests differences in the sensitivities of laboratory reared and field populations of H. azteca to pyrethroids. The goal of the present study was to determine the sensitivities of laboratory reared and field populations of H. azteca to the pyrethroids bifenthrin and cypermethrin. Specimens of H. azteca were collected from resident populations at field sites that are subject to varied land-use activities as well as from laboratory populations. These organisms were exposed to bifenthrin- or cypermethrin-spiked water in 96-h water-only toxicity tests. The resulting data demonstrated that: 1) field-collected populations in urban and agricultural settings can be >2 orders of magnitude less sensitive to the pyrethroids than laboratory reared organisms; 2) field-collected organisms varied in their sensitivity (possibly based on land-use activities), with organisms collected from undeveloped sites exhibiting sensitivities similar to laboratory reared organisms; and 3) the sensitivity of field-collected "tolerant" organisms increased in subsequent generations reared under laboratory conditions. Potential mechanisms for these differences are discussed. © 2015 SETAC.

  17. Microwave-assisted extraction of pyrethroid insecticides from semi permeable membrane devices (SPMDs) used to indoor air monitoring

    Energy Technology Data Exchange (ETDEWEB)

    Esteve-Turrillas, Francesc A. [Analytical Chemistry Department, University of Valencia, Edifici Jeroni Munoz, 50th Dr. Moliner, 46100 Burjassot, Valencia (Spain); Pastor, Agustin [Analytical Chemistry Department, University of Valencia, Edifici Jeroni Munoz, 50th Dr. Moliner, 46100 Burjassot, Valencia (Spain)]. E-mail: agustin.pastor@uv.es; Guardia, Miguel de la [Analytical Chemistry Department, University of Valencia, Edifici Jeroni Munoz, 50th Dr. Moliner, 46100 Burjassot, Valencia (Spain)

    2006-02-23

    A rapid and environmentally friendly methodology was developed for the extraction of pyrethroid insecticides from semi permeable membrane devices (SPMDs), in which they were preconcentrated in gas phase. The method was based on gas chromatography mass-mass spectrometry determination after a microwave-assisted extraction, in front of the widely employed dialysis method. SPMDs were extracted twice with 30 mL hexane:acetone, irradiated with 250 W power output, until 90 deg. C in 10 min, this temperature being held for another 10 min. Clean-up of the extracts was performed by acetonitrile-hexane partitioning and solid-phase extraction (SPE) with a combined cartridge of 2 g basic-alumina, deactivated with 5% water, and 500 mg C{sub 18}. Pyrethroids investigated were Allethrin, Prallethrin, Tetramethrin, Bifenthrin, Phenothrin, {lambda}-Cyhalothrin, Permethrin, Cyfluthrin, Cypermethrin, Flucythrinate, Esfenvalerate, Fluvalinate and Deltamethrin. The main pyrethroid synergist compound, Pyperonyl Butoxide, was also studied. Limit of detection values ranging from 0.3 to 0.9 ng/SPMD and repeatability data, as relative standard deviation, from 2.9 to 9.4%, were achieved. Pyrethroid recoveries, for spiked SPMDs, with 100 ng of each one of the pyrethroids evaluated, were from 61 {+-} 8 to 103 {+-} 7% for microwave-assisted extraction, versus 54 {+-} 4 to 104 {+-} 3% for dialysis reference method. Substantial reduction of solvent consumed (from 400 to 60 mL) and analysis time (from 48 to 1 h) was achieved by using the developed procedure. High concentration levels of pyrethroid compounds, from 0.14 to 7.3 {mu}g/SPMD, were found in indoor air after 2 h of a standard application.

  18. Efficacy of a long-lasting bifenthrin-treated net against horticultural pests and its compatibility with the predatory mite Amblyseius swirskii and the parasitic wasp Eretmocerus mundus.

    Science.gov (United States)

    Fernández, Maria Del Mar; Colomer, Ignacio; Medina, Pilar; Fereres, Alberto; Del Estal, Pedro; Viñuela, Elisa

    2017-08-01

    Insecticide-treated nets (ITNs) have been investigated recently for their use in agriculture. Depending on the insecticide, the hole size and the way they are produced, these nets can target different pests and therefore they could be interesting options for use in integrated pest management (IPM). As the information on their compatibility with beneficial fauna is practically negligible, in this work we have tested the compatibility of an experimental bifenthrin long-lasting insecticide-treated net (LLITN) with Amblyseius swirskii and Eretmocerus mundus, important natural enemies of whiteflies and thrips, under laboratory, semi-field and commercial greenhouse conditions. In the laboratory, the treated net was very deleterious to adults of both natural enemies, after 72 h exposure. However, in choice tests with Y-tubes, both natural enemies were neither attracted nor repelled by the treated net and no short-term mortality was detected in individuals that had crossed it. No deleterious effects on the E. mundus beneficial capacity were detected in semi-field trials. In field trials, the LLITN proved to be compatible with A. swirskii while decreasing pest densities. Bifenthrin LLITN studied could be a valuable method for reducing pest population infestations in IPM programmes while being compatible with biocontrol agents. © 2017 Society of Chemical Industry. © 2017 Society of Chemical Industry.

  19. Assessing bed net damage: comparisons of three measurement methods for estimating the size, shape, and distribution of holes on bed nets.

    Science.gov (United States)

    Vanden Eng, Jodi L; Mathanga, Don P; Landman, Keren; Mwandama, Dyson; Minta, Anna A; Shah, Monica; Sutcliffe, James; Chisaka, Joseph; Lindblade, Kim A; Steinhardt, Laura

    2017-10-10

    Measuring the physical condition of long-lasting insecticidal nets (LLINs) under field conditions is of great importance for malaria control programmes to guide decisions on how frequently to replace LLINs. Current guidelines by the World Health Organization Pesticide Evaluation Scheme (WHOPES) propose a proportionate hole index (pHI) for assessing LLIN condition by counting the number of holes the size of a thumb, fist, head, and larger than a head. However, this method does not account for irregular hole shapes or exact hole sizes which could result in inaccurate decisions about when to replace LLINs. LLINs were collected during a 2013 health facility-based malaria case control study in Machinga District, Malawi. To evaluate the accuracy of the pHI, the physical condition of 277 LLINs was estimated by the WHOPES method and then compared with two more thorough measurement methods: image analysis of digital photographs of each LLIN side; and for 10 nets, ruler measurements of the length, width, and location of each hole. Total hole counts and areas per net were estimated by each method, and detailed results of hole shapes and composite pictures of hole locations were generated using image analysis. The WHOPES method and image analysis resulted in similar estimates of total hole counts, each with a median of 10 (inter-quartile range (IQR) 4-24 and 4-23, respectively; p = 0.004); however, estimated hole areas were significantly larger using the WHOPES method (median 162 cm 2 , IQR 28-793) than image analysis (median 13 cm 2 , IQR 3-101; p holes than image analysis did (p = 0.002) in 10 LLINs; however, total hole area was not significantly different (p = 0.16). Most holes were not circular but roughly 2-5 times longer in one direction. The lower quarter of LLIN sides was found to have the most holes. The WHOPES method overestimated total hole area, likely because holes are elongated rather than circular, suggesting further adjustments to the pHI formula may be

  20. A rapid and sensitive analytical method for the determination of 14 pyrethroids in water samples.

    Science.gov (United States)

    Feo, M L; Eljarrat, E; Barceló, D

    2010-04-09

    A simple, efficient and environmentally friendly analytical methodology is proposed for extracting and preconcentrating pyrethroids from water samples prior to gas chromatography-negative ion chemical ionization mass spectrometry (GC-NCI-MS) analysis. Fourteen pyrethroids were selected for this work: bifenthrin, cyfluthrin, lambda-cyhalothrin, cypermethrin, deltamethrin, esfenvalerate, fenvalerate, fenpropathrin, tau-fluvalinate, permethrin, phenothrin, resmethrin, tetramethrin and tralomethrin. The method is based on ultrasound-assisted emulsification-extraction (UAEE) of a water-immiscible solvent in an aqueous medium. Chloroform was used as extraction solvent in the UAEE technique. Target analytes were quantitatively extracted achieving an enrichment factor of 200 when 20 mL aliquot of pure water spiked with pyrethroid standards was extracted. The method was also evaluated with tap water and river water samples. Method detection limits (MDLs) ranged from 0.03 to 35.8 ng L(-1) with RSDs values or =0.998. Recovery values were in the range of 45-106%, showing satisfactory robustness of the method for analyzing pyrethroids in water samples. The proposed methodology was applied for the analysis of river water samples. Cypermethrin was detected at concentration levels ranging from 4.94 to 30.5 ng L(-1). Copyright 2010 Elsevier B.V. All rights reserved.

  1. Pyrethroid insecticides: Isoform-dependent hydrolysis, induction of cytochrome P450 3A4 and evidence on the involvement of the pregnane X receptor

    International Nuclear Information System (INIS)

    Yang Dongfang; Wang Xiliang; Chen Yitzai; Deng Ruitang; Yan Bingfang

    2009-01-01

    Pyrethroids account for more than one-third of the insecticides currently marketed in the world. In mammals, these insecticides undergo extensive metabolism by carboxylesterases and cytochrome P450s (CYPs). In addition, some pyrethroids are found to induce the expression of CYPs. The aim of this study was to determine whether pyrethroids induce carboxylesterases and CYP3A4, and whether the induction is correlated inversely with their hydrolysis. Human liver microsomes were pooled and tested for the hydrolysis of 11 pyrethroids. All pyrethroids were hydrolyzed by the pooled microsomes, but the hydrolytic rates varied by as many as 14 fold. Some pyrethroids such as bioresmethrin were preferably hydrolyzed by carboxylesterase HCE1, whereas others such as bifenthrin preferably by HCE2. In primary human hepatocytes, all pyrethroids except tetramethrin significantly induced CYP3A4. In contrast, insignificant changes were detected on the expression of carboxylesterases. The induction of CYP3A4 was confirmed in multiple cell lines including HepG2, Hop92 and LS180. Overall, the magnitude of the induction was correlated inversely with the rates of hydrolysis, but positively with the activation of the pregnane X receptor (PXR). Transfection of a carboxylesterase markedly decreased the activation of PXR, and the decrease was in agreement with carboxylesterase-based preference for hydrolysis. In addition, human PXR variants as well as rat PXR differed from human PXR (wild-type) in responding to certain pyrethroids (e.g., lambda-cyhalothrin), suggesting that induction of PXR target genes by these pyrethroids varies depending on polymorphic variants and the PXR species identity.

  2. Effects of an environmentally-relevant mixture of pyrethroid insecticides on spontaneous activity in primary cortical networks on microelectrode arrays.

    Science.gov (United States)

    Johnstone, Andrew F M; Strickland, Jenna D; Crofton, Kevin M; Gennings, Chris; Shafer, Timothy J

    2017-05-01

    Pyrethroid insecticides exert their insecticidal and toxicological effects primarily by disrupting voltage-gated sodium channel (VGSC) function, resulting in altered neuronal excitability. Numerous studies of individual pyrethroids have characterized effects on mammalian VGSC function and neuronal excitability, yet studies examining effects of complex pyrethroid mixtures in mammalian neurons, especially in environmentally relevant mixture ratios, are limited. In the present study, concentration-response functions were characterized for five pyrethroids (permethrin, deltamethrin, cypermethrin, β-cyfluthrin and esfenvalerate) in an in vitro preparation containing cortical neurons and glia. As a metric of neuronal network activity, spontaneous mean network firing rates (MFR) were measured using microelectorde arrays (MEAs). In addition, the effect of a complex and exposure relevant mixture of the five pyrethroids (containing 52% permethrin, 28.8% cypermethrin, 12.9% β-cyfluthrin, 3.4% deltamethrin and 2.7% esfenvalerate) was also measured. Data were modeled to determine whether effects of the pyrethroid mixture were predicted by dose-addition. At concentrations up to 10μM, all compounds except permethrin reduced MFR. Deltamethrin and β-cyfluthrin were the most potent and reduced MFR by as much as 60 and 50%, respectively, while cypermethrin and esfenvalerate were of approximately equal potency and reduced MFR by only ∼20% at the highest concentration. Permethrin caused small (∼24% maximum), concentration-dependent increases in MFR. Effects of the environmentally relevant mixture did not depart from the prediction of dose-addition. These data demonstrate that an environmentally relevant mixture caused dose-additive effects on spontaneous neuronal network activity in vitro, and is consistent with other in vitro and in vivo assessments of pyrethroid mixtures. Published by Elsevier B.V.

  3. Microwave-assisted extraction of pyrethroid insecticides from semi permeable membrane devices (SPMDs) used to indoor air monitoring

    International Nuclear Information System (INIS)

    Esteve-Turrillas, Francesc A.; Pastor, Agustin; Guardia, Miguel de la

    2006-01-01

    A rapid and environmentally friendly methodology was developed for the extraction of pyrethroid insecticides from semi permeable membrane devices (SPMDs), in which they were preconcentrated in gas phase. The method was based on gas chromatography mass-mass spectrometry determination after a microwave-assisted extraction, in front of the widely employed dialysis method. SPMDs were extracted twice with 30 mL hexane:acetone, irradiated with 250 W power output, until 90 deg. C in 10 min, this temperature being held for another 10 min. Clean-up of the extracts was performed by acetonitrile-hexane partitioning and solid-phase extraction (SPE) with a combined cartridge of 2 g basic-alumina, deactivated with 5% water, and 500 mg C 18 . Pyrethroids investigated were Allethrin, Prallethrin, Tetramethrin, Bifenthrin, Phenothrin, λ-Cyhalothrin, Permethrin, Cyfluthrin, Cypermethrin, Flucythrinate, Esfenvalerate, Fluvalinate and Deltamethrin. The main pyrethroid synergist compound, Pyperonyl Butoxide, was also studied. Limit of detection values ranging from 0.3 to 0.9 ng/SPMD and repeatability data, as relative standard deviation, from 2.9 to 9.4%, were achieved. Pyrethroid recoveries, for spiked SPMDs, with 100 ng of each one of the pyrethroids evaluated, were from 61 ± 8 to 103 ± 7% for microwave-assisted extraction, versus 54 ± 4 to 104 ± 3% for dialysis reference method. Substantial reduction of solvent consumed (from 400 to 60 mL) and analysis time (from 48 to 1 h) was achieved by using the developed procedure. High concentration levels of pyrethroid compounds, from 0.14 to 7.3 μg/SPMD, were found in indoor air after 2 h of a standard application

  4. Comparative metabolism of the pyrethroids bifenthrin and deltamethrin in the bulb mite Rhizoglyphus robini

    International Nuclear Information System (INIS)

    Ruzo, L.O.; Cohen, E.; Capua, S.

    1988-01-01

    The fate of 14 C-radiolabeled bifenthrin and deltamethrin was studied in the mite, Rhizoglyphus robini. Administered either by ingestion or by contact, both pyrethroids were efficiently metabolized, but deltamethrin was degraded to a much greater extent. The identified metabolites arise from a combination of ester cleavage, oxidation, and conjugation reactions. With 14 C-acid- and 14 C-alcohol-labeled bifenthrin, the free metabolites detected were the 4'-hydroxy derivative of the ester, the primary ester cleavage products, the acid, and its 4'-hydroxy derivative from the alcohol moiety, as well as several unidentified metabolites. Using 14 C-alcohol-labeled deltamethrin, 3-phenoxybenzoic acid and its 4'-hydroxylated product and several unknown metabolites were detected. Conjugates comprised the bulk of total pyrethroid metabolites. In addition to ester cleavage products, the 4'-hydroxylated bifenthrin was also identified. For the first time in invertebrates, a conjugated pyrethroid ester was observed

  5. Mapping a Quantitative Trait Locus (QTL conferring pyrethroid resistance in the African malaria vector Anopheles funestus

    Directory of Open Access Journals (Sweden)

    Hunt Richard H

    2007-01-01

    Full Text Available Abstract Background Pyrethroid resistance in Anopheles funestus populations has led to an increase in malaria transmission in southern Africa. Resistance has been attributed to elevated activities of cytochrome P450s but the molecular basis underlying this metabolic resistance is unknown. Microsatellite and SNP markers were used to construct a linkage map and to detect a quantitative trait locus (QTL associated with pyrethroid resistance in the FUMOZ-R strain of An. funestus from Mozambique. Results By genotyping 349 F2 individuals from 11 independent families, a single major QTL, rp1, at the telomeric end of chromosome 2R was identified. The rp1 QTL appears to present a major effect since it accounts for more than 60% of the variance in susceptibility to permethrin. This QTL has a strong additive genetic effect with respect to susceptibility. Candidate genes associated with pyrethroid resistance in other species were physically mapped to An. funestus polytene chromosomes. This showed that rp1 is genetically linked to a cluster of CYP6 cytochrome P450 genes located on division 9 of chromosome 2R and confirmed earlier reports that pyrethroid resistance in this strain is not associated with target site mutations (knockdown resistance. Conclusion We hypothesize that one or more of these CYP6 P450s clustered on chromosome 2R confers pyrethroid resistance in the FUMOZ-R strain of An. funestus.

  6. A negative charge in transmembrane segment 1 of domain II of the cockroach sodium channel is critical for channel gating and action of pyrethroid insecticides

    International Nuclear Information System (INIS)

    Du Yuzhe; Song Weizhong; Groome, James R.; Nomura, Yoshiko; Luo Ningguang; Dong Ke

    2010-01-01

    Voltage-gated sodium channels are the primary target of pyrethroids, an important class of synthetic insecticides. Pyrethroids bind to a distinct receptor site on sodium channels and prolong the open state by inhibiting channel deactivation and inactivation. Recent studies have begun to reveal sodium channel residues important for pyrethroid binding. However, how pyrethroid binding leads to inhibition of sodium channel deactivation and inactivation remains elusive. In this study, we show that a negatively charged aspartic acid residue at position 802 (D802) located in the extracellular end of transmembrane segment 1 of domain II (IIS1) is critical for both the action of pyrethroids and the voltage dependence of channel activation. Charge-reversing or -neutralizing substitutions (K, G, or A) of D802 shifted the voltage dependence of activation in the depolarizing direction and reduced channel sensitivity to deltamethrin, a pyrethroid insecticide. The charge-reversing mutation D802K also accelerated open-state deactivation, which may have counteracted the inhibition of sodium channel deactivation by deltamethrin. In contrast, the D802G substitution slowed open-state deactivation, suggesting an additional mechanism for neutralizing the action of deltamethrin. Importantly, Schild analysis showed that D802 is not involved in pyrethroid binding. Thus, we have identified a sodium channel residue that is critical for regulating the action of pyrethroids on the sodium channel without affecting the receptor site of pyrethroids.

  7. In vitro dermal absorption of pyrethroid pesticides in human and rat skin

    International Nuclear Information System (INIS)

    Hughes, Michael F.; Edwards, Brenda C.

    2010-01-01

    Dermal exposure to pyrethroid pesticides can occur during manufacture and application. This study examined the in vitro dermal absorption of pyrethroids using rat and human skin. Dermatomed skin from adult male Long Evans rats or human cadavers was mounted in flow-through diffusion cells, and radiolabeled bifenthrin, deltamethrin or cis-permethrin was applied in acetone to the skin. Fractions of receptor fluid were collected every 4 h. At 24 h, the skins were washed with soap and water to remove unabsorbed chemical. The skin was then solubilized. Two additional experiments were performed after washing the skin; the first was tape-stripping the skin and the second was the collection of receptor fluid for an additional 24 h. Receptor fluid, skin washes, tape strips and skin were analyzed for radioactivity. For rat skin, the wash removed 53-71% of the dose and 26-43% remained in the skin. The cumulative percentage of the dose at 24 h in the receptor fluid ranged from 1 to 5%. For human skin, the wash removed 71-83% of the dose and 14-25% remained in the skin. The cumulative percentage of the dose at 24 h in the receptor fluid was 1-2%. Tape-stripping removed 50-56% and 79-95% of the dose in rat and human skin, respectively, after the wash. From 24-48 h, 1-3% and about 1% of the dose diffused into the receptor fluid of rat and human skin, respectively. The pyrethroids bifenthrin, deltamethrin and cis-permethrin penetrated rat and human skin following dermal application in vitro. However, a skin wash removed 50% or more of the dose from rat and human skin. Rat skin was more permeable to the pyrethroids than human skin. Of the dose in skin, 50% or more was removed by tape-stripping, suggesting that permeation of pyrethroids into viable tissue could be impeded. The percentage of the dose absorbed into the receptor fluid was considerably less than the dose in rat and human skin. Therefore, consideration of the skin type used and fractions analyzed are important when using

  8. Pyrethroid insecticides evoke neurotransmitter release from rabbit striatal slices

    International Nuclear Information System (INIS)

    Eells, J.T.; Dubocovich, M.L.

    1988-01-01

    The effects of the synthetic pyrethroid insecticide fenvalerate ([R,S]-alpha-cyano-3-phenoxybenzyl[R,S]-2-(4-chlorophenyl)-3- methylbutyrate) on neurotransmitter release in rabbit brain slices were investigated. Fenvalerate evoked a calcium-dependent release of [ 3 H]dopamine and [ 3 H]acetylcholine from rabbit striatal slices that was concentration-dependent and specific for the toxic stereoisomer of the insecticide. The release of [ 3 H]dopamine and [ 3 H]acetylcholine by fenvalerate was modulated by D2 dopamine receptor activation and antagonized completely by the sodium channel blocker, tetrodotoxin. These findings are consistent with an action of fenvalerate on the voltage-dependent sodium channels of the presynaptic membrane resulting in membrane depolarization, and the release of dopamine and acetylcholine by a calcium-dependent exocytotic process. In contrast to results obtained in striatal slices, fenvalerate did not elicit the release of [ 3 H]norepinephrine or [ 3 H]acetylcholine from rabbit hippocampal slices indicative of regional differences in sensitivity to type II pyrethroid actions

  9. Synthesis and Insecticidal Activity of an Oxabicyclolactone and Novel Pyrethroids

    Directory of Open Access Journals (Sweden)

    Elson S. de Alvarenga

    2012-11-01

    Full Text Available Deltamethrin, a member of the pyrethroids, one of the safest classes of pesticides, is among some of the most popular and widely used insecticides in the World. Our objective was to synthesize an oxabicyclolactone 6 and five novel pyrethroids 8–12 from readily available furfural and D-mannitol, respectively, and evaluate their biological activity against four insect species of economic importance namely A. obtectus, S. zeamais, A. monuste orseis, and P. americana. A concise and novel synthesis of 6,6-dimethyl-3-oxabicyclo[3.1.0]hexan-2-one (6 from furfural is described. Photochemical addition of isopropyl alcohol to furan-2(5H-one afforded 4-(1'-hydroxy-1'-methylethyltetrahydro-furan-2-one (3. The alcohol 3 was directly converted into 4-(1'-bromo-1'-methylethyl-tetrahydrofuran-2-one (5 in 50% yield by reaction with PBr3 and SiO2. The final step was performed by cyclization of 5 with potassium tert-butoxide in 40% yield. The novel pyrethroids 8–12 were prepared from methyl (1S,3S-3-formyl-2,2-dimethylcyclopropane-1-carboxylate (7a by reaction with five different aromatic phosphorous ylides. Compounds 6–12 presented high insecticidal activity, with 6 and 11 being the most active. Compound 6 killed 90% of S. zeamais and 100% of all the other insects evaluated. Compound 11 killed 100% of all insects tested.

  10. Comparative metabolism of the pyrethroids bifenthrin and deltamethrin in the bulb mite Rhizoglyphus robini

    Energy Technology Data Exchange (ETDEWEB)

    Ruzo, L.O.; Cohen, E.; Capua, S. (The Hebrew Univ. of Jerusalem (Israel))

    The fate of {sup 14}C-radiolabeled bifenthrin and deltamethrin was studied in the mite, Rhizoglyphus robini. Administered either by ingestion or by contact, both pyrethroids were efficiently metabolized, but deltamethrin was degraded to a much greater extent. The identified metabolites arise from a combination of ester cleavage, oxidation, and conjugation reactions. With {sup 14}C-acid- and {sup 14}C-alcohol-labeled bifenthrin, the free metabolites detected were the 4{prime}-hydroxy derivative of the ester, the primary ester cleavage products, the acid, and its 4{prime}-hydroxy derivative from the alcohol moiety, as well as several unidentified metabolites. Using {sup 14}C-alcohol-labeled deltamethrin, 3-phenoxybenzoic acid and its 4{prime}-hydroxylated product and several unknown metabolites were detected. Conjugates comprised the bulk of total pyrethroid metabolites. In addition to ester cleavage products, the 4{prime}-hydroxylated bifenthrin was also identified. For the first time in invertebrates, a conjugated pyrethroid ester was observed.

  11. Using SPME fibers and Tenax to predict the bioavailability of pyrethroids and chlorpyrifos in field sediments

    International Nuclear Information System (INIS)

    Harwood, Amanda D.; Landrum, Peter F.; Weston, Donald P.; Lydy, Michael J.

    2013-01-01

    The presence of pyrethroids in both urban and agricultural sediments at levels lethal to invertebrates has been well documented. However, variations in bioavailability among sediments make accurate predictions of toxicity based on whole sediment concentrations difficult. A proposed solution to this problem is the use of bioavailability-based estimates, such as solid phase microextraction (SPME) fibers and Tenax beads. This study compared three methods to assess the bioavailability and ultimately toxicity of pyrethroid pesticides including field-deployed SPME fibers, laboratory-exposed SPME fibers, and a 24-h Tenax extraction. The objective of the current study was to compare the ability of these methods to quantify the bioavailable fraction of pyrethroids in contaminated field sediments that were toxic to benthic invertebrates. In general, Tenax proved a more sensitive method than SPME fibers and a correlation between Tenax extractable concentrations and mortality was observed. - Highlights: ► Can use bioavailability-based methods for pyrethroids in sediments. ► Tenax was a more sensitive technique. ► Tenax extractable concentrations relate to invertebrate mortality. - This research provides an important first step in using bioavailability-based techniques for estimating the bioavailability and toxicity of hydrophobic pesticides in field sediments.

  12. Local evolution of pyrethroid resistance offsets gene flow among Aedes aegypti collections in Yucatan State, Mexico.

    Science.gov (United States)

    Saavedra-Rodriguez, Karla; Beaty, Meaghan; Lozano-Fuentes, Saul; Denham, Steven; Garcia-Rejon, Julian; Reyes-Solis, Guadalupe; Machain-Williams, Carlos; Loroño-Pino, Maria Alba; Flores-Suarez, Adriana; Ponce-Garcia, Gustavo; Beaty, Barry; Eisen, Lars; Black, William C

    2015-01-01

    The mosquito Aedes aegypti is the major vector of the four serotypes of dengue virus (DENV1-4). Previous studies have shown that Ae. aegypti in Mexico have a high effective migration rate and that gene flow occurs among populations that are up to 150 km apart. Since 2000, pyrethroids have been widely used for suppression of Ae. aegypti in cities in Mexico. In Yucatan State in particular, pyrethroids have been applied in and around dengue case households creating an opportunity for local selection and evolution of resistance. Herein, we test for evidence of local adaptation by comparing patterns of variation among 27 Ae. aegypti collections at 13 single nucleotide polymorphisms (SNPs): two in the voltage-gated sodium channel gene para known to confer knockdown resistance, three in detoxification genes previously associated with pyrethroid resistance, and eight in putatively neutral loci. The SNPs in para varied greatly in frequency among collections, whereas SNPs at the remaining 11 loci showed little variation supporting previous evidence for extensive local gene flow. Among Ae. aegypti in Yucatan State, Mexico, local adaptation to pyrethroids appears to offset the homogenizing effects of gene flow. © The American Society of Tropical Medicine and Hygiene.

  13. PCR-based methods for the detection of L1014 kdr mutation in Anopheles culicifacies sensu lato

    Science.gov (United States)

    Singh, Om P; Bali, Prerna; Hemingway, Janet; Subbarao, Sarala K; Dash, Aditya P; Adak, Tridibes

    2009-01-01

    Background Anopheles culicifacies s.l., a major malaria vector in India, has developed widespread resistance to DDT and is becoming resistant to pyrethroids–the only insecticide class recommended for the impregnation of bed nets. Knock-down resistance due to a point mutation in the voltage gated sodium channel at L1014 residue (kdr) is a common mechanism of resistance to DDT and pyrethroids. The selection of this resistance may pose a serious threat to the success of the pyrethroid-impregnated bed net programme. This study reports the presence of kdr mutation (L1014F) in a field population of An. culicifacies s.l. and three new PCR-based methods for kdr genotyping. Methods The IIS4-IIS5 linker to IIS6 segments of the para type voltage gated sodium channel gene of DDT and pyrethroid resistant An. culicifacies s.l. population from the Surat district of India was sequenced. This revealed the presence of an A-to-T substitution at position 1014 leading to a leucine-phenylalanine mutation (L1014F) in a few individuals. Three molecular methods viz. Allele Specific PCR (AS-PCR), an Amplification Refractory Mutation System (ARMS) and Primer Introduced Restriction Analysis-PCR (PIRA-PCR) were developed and tested for kdr genotyping. The specificity of the three assays was validated following DNA sequencing of the samples genotyped. Results The genotyping of this An. culicifacies s.l. population by the three PCR based assays provided consistent result and were in agreement with DNA sequencing result. A low frequency of the kdr allele mostly in heterozygous condition was observed in the resistant population. Frequencies of the different genotypes were in Hardy-Weinberg equilibrium. Conclusion The Leu-Phe mutation, which generates the kdr phenotype in many insects, was detected in a pyrethroid and DDT resistant An. culicifacies s.l. population. Three PCR-based methods were developed for kdr genotyping. All the three assays were specific. The ARMS method was refractory to non

  14. PCR-based methods for the detection of L1014 kdr mutation in Anopheles culicifacies sensu lato

    Directory of Open Access Journals (Sweden)

    Dash Aditya P

    2009-07-01

    Full Text Available Abstract Background Anopheles culicifacies s.l., a major malaria vector in India, has developed widespread resistance to DDT and is becoming resistant to pyrethroids–the only insecticide class recommended for the impregnation of bed nets. Knock-down resistance due to a point mutation in the voltage gated sodium channel at L1014 residue (kdr is a common mechanism of resistance to DDT and pyrethroids. The selection of this resistance may pose a serious threat to the success of the pyrethroid-impregnated bed net programme. This study reports the presence of kdr mutation (L1014F in a field population of An. culicifacies s.l. and three new PCR-based methods for kdr genotyping. Methods The IIS4-IIS5 linker to IIS6 segments of the para type voltage gated sodium channel gene of DDT and pyrethroid resistant An. culicifacies s.l. population from the Surat district of India was sequenced. This revealed the presence of an A-to-T substitution at position 1014 leading to a leucine-phenylalanine mutation (L1014F in a few individuals. Three molecular methods viz. Allele Specific PCR (AS-PCR, an Amplification Refractory Mutation System (ARMS and Primer Introduced Restriction Analysis-PCR (PIRA-PCR were developed and tested for kdr genotyping. The specificity of the three assays was validated following DNA sequencing of the samples genotyped. Results The genotyping of this An. culicifacies s.l. population by the three PCR based assays provided consistent result and were in agreement with DNA sequencing result. A low frequency of the kdr allele mostly in heterozygous condition was observed in the resistant population. Frequencies of the different genotypes were in Hardy-Weinberg equilibrium. Conclusion The Leu-Phe mutation, which generates the kdr phenotype in many insects, was detected in a pyrethroid and DDT resistant An. culicifacies s.l. population. Three PCR-based methods were developed for kdr genotyping. All the three assays were specific. The ARMS method

  15. Development of an allele-specific, loop-mediated, isothermal amplification method (AS-LAMP to detect the L1014F kdr-w mutation in Anopheles gambiae s. l.

    Directory of Open Access Journals (Sweden)

    Badolo Athanase

    2012-07-01

    Full Text Available Abstract Background Malaria control relies heavily on treated bed nets and indoor residual spraying with pyrethroid insecticides. Unfortunately, the resistance to pyrethroid insecticides, mainly due to the kdr mutation, is spreading in the main malaria vector Anopheles gambiae s.l., decreasing the insecticides’ efficacy. To manage the insecticide resistance rapidly and flexibly, simple and effective tools for the early detection of resistant mosquitoes are needed. This study aimed to develop an allele-specific, loop-mediated, isothermal amplification (AS-LAMP method to detect the West African-type kdr mutation (kdr-w; L1014F in field-collected mosquitoes. Methods DNA fragments of the wild-type and the mutated kdr gene were used to select the primers and develop the method. The primers were designed with the mutation at the 5’ end of the backward inner primer (BIP. The AS-LAMP method was compared to the AS-PCR method using the genomic DNA of 120 field-collected mosquitoes. Results The AS-LAMP method could discriminate between the wild-type homozygote, the heterozygote, and the kdr-w homozygote within 75 min. The AS-LAMP method has the advantage of being faster and at least as sensitive and specific as the AS-PCR method. Conclusions The AS-LAMP method can be used to detect the kdr mutation for quick decision-making, even in less well-equipped laboratories.

  16. Decline in frequency of the 2La chromosomal inversion in Anopheles gambiae (s.s.) in Western Kenya: correlation with increase in ownership of insecticide-treated bed nets.

    Science.gov (United States)

    Matoke-Muhia, Damaris; Gimnig, John E; Kamau, Luna; Shililu, Josephat; Bayoh, M Nabie; Walker, Edward D

    2016-06-10

    The 2La chromosomal inversion, a genetic polymorphism in An. gambiae (sensu stricto) (s.s.), is associated with adaptation to microclimatic differences in humidity and desiccation resistance and mosquito behaviors. Ownership of insecticide-treated bed nets (ITNs) for malaria control has increased markedly in western Kenya in the last 20 years. An increase in the frequency of ITNs indoors could select against house entering or indoor resting of Anopheles mosquitoes. Thus, the frequency of the 2La inversion is postulated to change in An. gambiae (s.s.) with the increase of ITN ownership over time. Anopheles gambiae mosquitoes were sampled between 1994 and 2011 using pyrethrum knockdown, bednet traps and human landing catches (HLC) from Asembo and Seme, western Kenya. The 2La inversion was detected by a PCR assay with primers designed for proximal breakpoints of the 2La/a and 2L+(a)/+(a) chromosomal conformation. Mosquitoes were tested for malaria parasite infection by sporozoite ELISA. The frequency of the 2La chromosomal inversion declined from 100 % of all chromosomes in 1994 to 17 % in 2005 and remained low through 2011 (21 %). ITN ownership increased from 0 to > 90 % of houses in the study area during this interval. The decline in the frequency of the 2La chromosomal inversion was significantly, negatively correlated with year (r = -0.93) and with increase in ITN ownership (r = -0.96). The frequency of the homo- and heterokaryotypes departed significantly from Hardy-Weinberg equilibrium, suggesting that 2La/a karyotype was under selection, earlier in its favor and later, against it. Precipitation and maximum monthly temperature did not vary over time, therefore there was no trend in climate that could account for the decline. There was no significant difference in frequency of the 2La inversion in An. gambiae (s.s.) females sampled indoors or outdoors in HCL in 2011, nor was there an association between the 2La inversion and infection with Plasmodium

  17. Use of antenatal care, maternity services, intermittent presumptive treatment and insecticide treated bed nets by pregnant women in Luwero district, Uganda

    Directory of Open Access Journals (Sweden)

    Mufubenga Patrobas

    2008-03-01

    Full Text Available Abstract Background To reduce the intolerable burden of malaria in pregnancy, the Ministry of Health in Uganda improved the antenatal care package by including a strong commitment to increase distribution of insecticide-treated nets (ITNs and introduction of intermittent preventive treatment with sulphadoxine-pyrimethamine for pregnant women (IPTp-SP as a national policy in 2000. This study assessed uptake of both ITNs and IPTp-SP by pregnant women as well as antenatal and maternity care use with the aim of optimizing their delivery. Methods 769 post-partum women were recruited from a rural area of central Uganda with perennial malaria transmission through a cross-sectional, community-based household survey in May 2005. Results Of the 769 women interviewed, antenatal clinic (ANC attendance was high (94.4%; 417 (57.7% visiting initially during the 2nd trimester, 242 (33.5% during the 3rd trimester and 266 (37.1% reporting ≥ 4 ANC visits. About 537 (71% and 272 (35.8% received one or ≥ 2 IPTp-SP doses respectively. Only 85 (15.8% received the first dose of IPTp-SP in the 3rd trimester. ITNs were used by 239 (31.3% of women during pregnancy and 314 (40.8% delivered their most recent pregnancy outside a health facility. Post-partum women who lacked post-primary education were more likely not to have attended four or more ANC visits (odds ratio [OR] 3.3, 95% confidence interval [CI] 1.2–9.3. Conclusion These findings illustrate the need to strengthen capacity of the district to further improve antenatal care and maternity services utilization and IPTp-SP uptake. More specific and effective community health strategies to improve effective ANC, maternity services utilization and IPTp-SP uptake in rural communities should be undertaken.

  18. Neurotoxicological effects and the mode of action of pyrethroid insecticides

    NARCIS (Netherlands)

    Vijverberg, H.P.M.; Bercken, Joep van den

    1990-01-01

    Neuroexcitatory symptoms of acute poisoning of vertebrates by pyrethroids are related to the ability of these insecticides to modify electrical activity in various parts of the nervous system. Repetitive nerve activity, particularly in the sensory nervous system, membrane depolarization, and

  19. Inter-compartmental transport of organophosphate and pyrethroid pesticides in South China: Implications for a regional risk assessment

    International Nuclear Information System (INIS)

    Li, Huizhen; Wei, Yanli; Lydy, Michael J.; You, Jing

    2014-01-01

    The dynamic flux of an organophosphate and four pyrethroid pesticides was determined in an air-(soil)-water-sediment system based on monitoring data from Guangzhou, China. The total air–water flux, including air–water gaseous exchange and atmospheric deposition, showed deposition from air to water for chlorpyrifos, bifenthrin and cypermethrin, but volatilization for lambda-cyhalothrin and permethrin. The transport of the pesticides from overlying water to sediment suggested that sediment acted as a sink for the pesticides. Additionally, distinct annual atmospheric depositional fluxes between legacy and current-use pesticides suggested the role of consumer usage in their transport throughout the system. Finally, pesticide toxicity was estimated from annual air–water-sediment flux within an urban stream in Guangzhou. A dynamic flux-based risk assessment indicated that inter-compartmental transport of chlorpyrifos decreased its atmospheric exposure, but had little influence on its aquatic toxicity. Instead, water-to-sediment transport of pyrethroids increased their sediment toxicity, which was supported by previously reported toxicity data. - Highlights: • Transport fluxes of chlorpyrifos and pyrethroids were assessed in Guangzhou, China. • Sediment acted as a sink for chlorpyrifos and pyrethroids. • Air-to-water transport decreased the exposure risk of atmospheric chlorpyrifos. • Dynamic transport might increase the risk of pyrethroids in air and sediment. • Flux-based pesticide concentrations provide a way to estimate sediment toxicity. - Regional risk assessment could be improved by integrating dynamic flux information derived from inter-compartmental models

  20. Late Consequential Surgical Bed Soft Tissue Necrosis in Advanced Oropharyngeal Squamous Cell Carcinomas Treated With Transoral Robotic Surgery and Postoperative Radiation Therapy

    International Nuclear Information System (INIS)

    Lukens, J. Nicholas; Lin, Alexander; Gamerman, Victoria; Mitra, Nandita; Grover, Surbhi; McMenamin, Erin M.; Weinstein, Gregory S.; O'Malley, Bert W.; Cohen, Roger B.; Orisamolu, Abimbola; Ahn, Peter H.; Quon, Harry

    2014-01-01

    Purpose: A subset of patients with oropharyngeal squamous cell carcinoma (OP-SCC) managed with transoral robotic surgery (TORS) and postoperative radiation therapy (PORT) developed soft tissue necrosis (STN) in the surgical bed months after completion of PORT. We investigated the frequency and risk factors. Materials and Methods: This retrospective analysis included 170 consecutive OP-SCC patients treated with TORS and PORT between 2006 and 2012, with >6 months' of follow-up. STN was defined as ulceration of the surgical bed >6 weeks after completion of PORT, requiring opioids, biopsy, or hyperbaric oxygen therapy. Results: A total of 47 of 170 patients (28%) had a diagnosis of STN. Tonsillar patients were more susceptible than base-of-tongue (BOT) patients, 39% (41 of 104) versus 9% (6 of 66), respectively. For patients with STN, median tumor size was 3.0 cm (range 1.0-5.6 cm), and depth of resection was 2.2 cm (range 1.0-5.1 cm). Median radiation dose and dose of fraction to the surgical bed were 6600 cGy and 220 cGy, respectively. Thirty-one patients (66%) received concurrent chemotherapy. Median time to STN was 2.5 months after PORT. All patients had resolution of STN after a median of 3.7 months. Multivariate analysis identified tonsillar primary (odds ratio [OR] 4.73, P=.01), depth of resection (OR 3.12, P=.001), total radiation dose to the resection bed (OR 1.51 per Gy, P<.01), and grade 3 acute mucositis (OR 3.47, P=.02) as risk factors for STN. Beginning May 2011, after implementing aggressive avoidance of delivering >2 Gy/day to the resection bed mucosa, only 8% (2 of 26 patients) experienced STN (all grade 2). Conclusions: A subset of OP-SCC patients treated with TORS and PORT are at risk for developing late consequential surgical bed STN. Risk factors include tonsillar location, depth of resection, radiation dose to the surgical bed, and severe mucositis. STN risk is significantly decreased with carefully avoiding a radiation dosage of >2 Gy/day to

  1. Mutation in the Sodium Channel Gene Corresponds With Phenotypic Resistance of Rhipicephalus sanguineus sensu lato (Acari: Ixodidae) to Pyrethroids.

    Science.gov (United States)

    Klafke, G M; Miller, R J; Tidwell, J; Barreto, R; Guerrero, F D; Kaufman, P E; Pérez de León, A A

    2017-11-07

    The brown dog tick, Rhipicephalus sanguineus sensu lato (Latreille), is a cosmopolitan ectoparasite and vector of pathogens that kill humans and animals. Pyrethroids represent a class of synthetic acaricides that have been used intensely to try to control the brown dog tick and mitigate the risk of tick-borne disease transmission. However, acaricide resistance is an emerging problem in the management of the brown dog tick. Understanding the mechanism of resistance to acaricides, including pyrethroids, is important to adapt brown dog tick control strategies. The main objective of this study was to determine if target-site mutations associated with pyrethroid resistance in other pests could be associated with phenotypic resistance detected in a brown dog tick population from Florida. We amplified segment 6 of the domain III of the voltage-sensitive sodium channel protein, using cDNAs synthesized from pyrethroid-susceptible and pyrethroid-resistant tick strains. A single nucleotide point mutation (SNP) identified in a highly conserved region of domain III S6 in the resistant ticks resulted in an amino acid change from phenylalanine to leucine. This mutation is characteristic of resistance phenotypes in other tick species, and is the first report of this mutation in R. sanguineus. Molecular assays based on this knowledge could be developed to diagnose the risk for pyrethroid resistance, and to inform decisions on integrated brown dog tick management practices. © The Authors 2017. Published by Oxford University Press on behalf of Entomological Society of America. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

  2. Performance of novel sludge-bed anaerobic membrane bioreactor (SB-AnMBR) treating prehydrolysis liquor.

    Science.gov (United States)

    Kale, Mayur M; Singh, Kripa S

    2014-01-01

    The feasibility of a novel sludge-bed anaerobic membrane bioreactor (SB-AnMBR) configuration for treating a waste stream from a dissolving pulp production industry was evaluated. The waste stream, called prehydrolysis liquor (PHL), is generated after the wood chips are subjected to high temperature steam to remove unwanted hemicelluloses. The PHL with total chemical oxygen demand (COD) of approximately 100 g/L contained mainly sugars, furfural, lignin, and acetic acid. The SB-AnMBR was fed with the PHL at organic loading rates in a range of 0.8 to10 kg-COD/(m(3)·d). The COD removal efficiency of more than 85% and an average rate of methane production of 0.35 m(3)/(kg-COD·d) were observed at each loading rate. No detectable sugars or furfural were present in the treated effluent from SB-AnMBR. Lignin removal varied from 60 to 90%. Flat-sheet membranes performed well with one fouling event during first 400 days of operation.

  3. Fast pyrolysis of creosote treated wood ties in a fluidized bed reactor and analytical characterization of product fractions

    International Nuclear Information System (INIS)

    Jung, Su-Hwa; Koo, Won-Mo; Kim, Joo-Sik

    2013-01-01

    A fraction of creosote treated wood ties was pyrolyzed in a pyrolysis plant equipped with a fluidized bed reactor and char-separation system at different temperatures. Analyses of each pyrolysis product, especially the oil, were carried out using a variety of analytical tools. The maximum oil yield was obtained at 458 °C with a value of 69.3 wt%. Oils obtained were easily separated into two phases, a creosote-derived fraction (CDF) and a wood-derived fraction (WDF). Major compounds of the WDF were acetic acid, furfural and levoglucosan, while the CDF was mainly composed of polycyclic aromatic hydrocarbons (PAHs), such as 1-methylnaphthalene, biphenyl, acenaphthene, dibenzofuran, fluorene, phenanthrene, anthracene, fluoranthene and pyrene. HPLC analysis showed that the concentration of PAHs of the CDF obtained at 458 °C constituted about 22.5 wt% of the oil. - Highlights: • Creosote treated wood ties was stably pyrolyzed in a fluidized bed reactor. • Pyrolysis oil contained extremely low metal content due to the char removal system. • Bio-oil components was quantitatively analyzed by relative response factor. • Creosote-derived pyrolysis oil fraction was composed of PHAs and has a high caloric value (39 MJ/kg)

  4. Determination of seven pyrethroids and six pyrethrins in water by liquid chromatography/mass spectrometry

    Science.gov (United States)

    ccanccapa, alexander; Masia, Ana; Pico, Yolanda

    2016-04-01

    Pyrethroids are the synthetic analogues of pyrethrins which were developed as pesticides from the extracts of dried and powdered flower heads of Chrysanthemum cinerariaefolium. They are increasingly used in agriculture due to their broad biological activity and slow development of pest resistance. Contamination of fresh-water ecosystems appears either because of the direct discharge of industrial and agricultural effluents or as a result of effluents from sewage treatment works; residues can thus accumulate in the surrounding biosphere [1, 2]. These substances, mostly determined by gas chromatography mass spectrometry (GC-MS) can be difficult to analyse due to their volatility and degradability. The purpose of this study is, as an alternative, to develop a fast and sensitive multi-residue method for the target analysis of 7 pyrethroids and the 6 natural pyrethrins currently used in water samples by liquid chromatography tandem mass spectrometry (LC-MS/MS). The compounds included in the study were acrinathrin, etofenprox, cyfluthrin, esfenvalerate, cyhalothrin, cypermethrin and flumethrin as pyrethroids and a commercial mix of pyrethrins containing Cinerin I, Jasmolin I, pyrethrin I, cinerin II, jasmolin II, pyrethrins II in different percentages. As a preliminary step, the ionization and fragmentation of the compounds were optimized injecting individual solutions of each analyte at 10 ppm in the system, using a gradient elution profile of water-methanol both with 10 mM ammonium formate. The ESI conditions were: capillary voltage 4000 V, nebulizer15 psi, source temperature 300◦C and gas flow 10 L min-1. [M+H]+, [M+Na]+ ,[M+NH3]+ ,[M+NH4+]+ were tested as precursor ions. The most intense signal was for ammonium adduct for all compounds. The optimal fragmentor range for product ions were between 20 to 80 ev and the collision energy ranged between 5 to 86 ev. The efficiency of the method was tested in water samples from Turia River without any known exposure to

  5. Corrosion Behavior of Heat-Treated AlSi10Mg Manufactured by Laser Powder Bed Fusion

    Directory of Open Access Journals (Sweden)

    Marina Cabrini

    2018-06-01

    Full Text Available This experimental work is aimed at studying the effect of microstructural modifications induced by post-processing heat treatments on the corrosion behavior of silicon-aluminum alloys produced by means of laser powder bed fusion (LPBF. The manufacturing technique leads to microstructures characterized by the presence of melt pools, which are quite different compared to casting alloys. In this study, the behavior of an AlSi10Mg alloy was evaluated by means of intergranular corrosion tests according to ISO 11846 standard on heat-treated samples ranging from 200 to 500 °C as well as on untreated samples. We found that temperatures above 200 °C reduced microhardness of the alloy, and different corrosion morphologies occurred due to the modification of both size and distribution of silicon precipitates. Selective penetrating attacks occurred at melt pool borders. The intergranular corrosion phenomena were less intense for as-produced specimens without heat treatments compared to the heat-treated specimens at 200 and 300 °C. General corrosion morphologies were noticed for specimens heat treated at temperatures exceeding 400 °C.

  6. Comparison of ingestion and topical application of insecticides against the common bed bug, Cimex lectularius (Hemiptera: Cimicidae)

    Science.gov (United States)

    Sierras, Angela; Schal, Coby

    2016-01-01

    Background The global prevalence of Cimex lectularius infestations has challenged current intervention efforts, as pyrethroid resistance has become ubiquitous, availability of labeled insecticides for bed bugs is limited, and non-chemical treatment options, such as heat, are often unaffordable. We evaluated representative insecticides toward the goal of developing a novel, ingestible liquid bait for hematophagous arthropods. Results LC50 values were estimated for adult males and first instar nymphs of an insecticide-susceptible strain for abamectin, clothianidin, fipronil and indoxacarb, after ingestion from an in vitro feeder. LD50 values were calculated based on the ingested blood volume. Ingested abamectin, clothianidin and fipronil caused rapid mortality in both life stages. Fipronil was ∼43-fold more effective by ingestion than by topical application. Indoxacarb and its bioactive metabolite decarbomethoxyllated JW062 (DCJW) were ineffective at causing bed bug mortality even at concentrations as high as 1000 ng mL−1 blood. Conclusions Fipronil, clothianidin and abamectin have potential for being incorporated into a liquid bait for bed bug control; indoxacarb and DCJW were not effective. Bed bugs are a good candidate for an ingestible liquid bait because systemic formulations generally require less active ingredient than residual sprays, they remain contained and more effectively target hematophagous arthropods. PMID:27766740

  7. Home Use of a Pyrethroid-Containing Pesticide and Facial Paresthesia in a Toddler: A Case Report

    Directory of Open Access Journals (Sweden)

    Alexandra Perkins

    2016-08-01

    Full Text Available Paresthesias have previously been reported among adults in occupational and non-occupational settings after dermal contact with pyrethroid insecticides. In this report, we describe a preverbal 13-month-old who presented to his primary care pediatrician with approximately 1 week of odd facial movements consistent with facial paresthesias. The symptoms coincided with a period of repeat indoor spraying at his home with a commercially available insecticide containing two active ingredients in the pyrethroid class. Consultation by the Northwest Pediatric Environmental Health Specialty Unit and follow-up by the Washington State Department of Health included urinary pyrethroid metabolite measurements during and after the symptomatic period, counseling on home clean up and use of safer pest control methods. The child’s symptoms resolved soon after home cleanup. A diagnosis of pesticide-related illness due to pyrethroid exposure was made based on the opportunity for significant exposure (multiple applications in areas where the child spent time, supportive biomonitoring data, and the consistency and temporality of symptom findings (paresthesias. This case underscores the vulnerability of children to uptake pesticides, the role of the primary care provider in ascertaining an exposure history to recognize symptomatic illness, and the need for collaborative medical and public health efforts to reduce significant exposures in children.

  8. Evaluation of the effects of repeated hand washing, sunlight, smoke and dirt on the persistence of deltamethrin on insecticide-treated nets.

    Science.gov (United States)

    Kayedi, M H; Lines, J D; Haghdoost, A A; Vatandoost, M H; Rassi, Y; Khamisabady, K

    2008-08-01

    Field studies were carried out in Iran to evaluate the effect of various factors (washing, sun, smoke, dust and dirt) on the residual insecticidal activity of PermaNet (a brand of long-lasting insecticidal net), and on nets conventionally treated with deltamethrin (K-O Tab), using bioassay tests. Thirty-two nets were washed five or 15 times, and eight nets were not washed at all. Nets were washed vigorously in cold tap water (17 degrees C, pH 8.9) with a detergent. Hand rubbing continued for 3min. After washing, some nets were exposed to dense smoke from a dung-hay fire for 3min and were also left exposed to the dusty wind between washes. One group of nets was exposed to the sunlight for the full 3-d interval between washes; another was exposed to sunlight for just 3h after each wash; two other groups were kept in the shade. There was a significantly greater loss of activity in nets exposed to the sun throughout the 3-d interval between washes: that is, for a total of 15 to 45 d. However, short sunlight exposure (maximum 3h between washes) during drying did not have any effect. We did not find any significant effect of exposure to dirt, dust and smoke after washing. It is concluded that the effect of sun is much smaller than that of washing, and that drying nets for a few hours in the sun is not harmful.

  9. In vivo dermal absorption of pyrethroid pesticides in the rat.

    Science.gov (United States)

    The potential for exposure to pyrethroid pesticides has risen recently because of their increased use. The objective of this study was to examine the in vivo dermal absorption of bifenthrin, deltamethrin and permethrin in the rat. Hair on the dorsal side of anesthetized adult m...

  10. Pinpointing P450s Associated with Pyrethroid Metabolism in the Dengue Vector, Aedes aegypti: Developing New Tools to Combat Insecticide Resistance

    OpenAIRE

    Stevenson, Bradley J.; Pignatelli, Patricia; Nikou, Dimitra; Paine, Mark J. I.

    2012-01-01

    Background\\ud \\ud Pyrethroids are increasingly used to block the transmission of diseases spread by Aedes aegypti such as dengue and yellow fever. However, insecticide resistance poses a serious threat, thus there is an urgent need to identify the genes and proteins associated with pyrethroid resistance in order to produce effective counter measures. In Ae. aegypti, overexpression of P450s such as the CYP9J32 gene have been linked with pyrethroid resistance. Our aim was to confirm the role of...

  11. The pyrethroid metabolites 3-phenoxybenzoic acid and 3-phenoxybenzyl alcohol do not exhibit estrogenic activity in the MCF-7 human breast carcinoma cell line or Sprague-Dawley rats

    International Nuclear Information System (INIS)

    Laffin, Brian; Chavez, Marco; Pine, Michelle

    2010-01-01

    Synthetic pyrethroids are one of the most frequently and widely used class of insecticides, primarily because they have a higher insect to mammalian toxicity ratio than organochlorines or organophosphates. The basic structure of pyrethroids can be characterized as an acid joined to an alcohol by an ester bond. Pyrethroid degradation occurs through either oxidation at one or more sites located in the alcohol or acid moieties or hydrolysis at the central ester bond, the latter reaction being important for mammalian metabolism of most pyrethroids. The primary alcohol liberated from the ester cleavage is hydroxylated to 3-phenoxybenzyl alcohol, which for most pyrethroids is then oxidized to 3-phenoxybenzoic acid. These products may then be conjugated with amino acids, sulfates, sugars, or sugar acids. In vitro studies have suggested that some of the pyrethroids may have estrogenic activity. Interestingly, the chemical structure of specific pyrethroid metabolites indicates that they may be more likely to interact with the estrogen receptor than the parent compounds. Two of the pyrethroid metabolites, 3-phenoxybenzoic acid (3PBA) and 3-phenoxybenzyl alcohol (3PBalc) have been reported to have endocrine activity using a yeast based assay. 3PBAlc exhibited estrogenic activity with reported EC 50 s of 6.67 x 10 -6 and 2 x 10 -5 while 3PBAcid exhibited anti-estrogenic activity with a calculated IC 50 of 6.5 x 10 -5 . To determine if the metabolites were able to cause the same effects in a mammalian system, the estrogen-dependent cell line, MCF-7, was utilized. Cells were treated with 1.0, 10.0 or 100.0 μM concentrations of each metabolite and cytotoxicity was assessed. The two lowest concentrations of both metabolites did not induce cell death and even appeared to increase proliferation over that of the control cells. However, when cellular proliferation was measured using a Coulter counter neither metabolite stimulated proliferation (1.0 nM, 10.0 nM, or 10.0 μM) or

  12. Transcriptional response of rat frontal cortex following acute In Vivo exposure to the pyrethroid insecticides permethrin and deltamethrin

    Directory of Open Access Journals (Sweden)

    Tornero-Velez Rogelio

    2008-11-01

    Full Text Available Abstract Background Pyrethroids are neurotoxic pesticides that interact with membrane bound ion channels in neurons and disrupt nerve function. The purpose of this study was to characterize and explore changes in gene expression that occur in the rat frontal cortex, an area of CNS affected by pyrethroids, following an acute low-dose exposure. Results Rats were acutely exposed to either deltamethrin (0.3 – 3 mg/kg or permethrin (1 – 100 mg/kg followed by collection of cortical tissue at 6 hours. The doses used range from those that cause minimal signs of intoxication at the behavioral level to doses well below apparent no effect levels in the whole animal. A statistical framework based on parallel linear (SAM and isotonic regression (PIR methods identified 95 and 53 probe sets as dose-responsive. The PIR analysis was most sensitive for detecting transcripts with changes in expression at the NOAEL dose. A sub-set of genes (Camk1g, Ddc, Gpd3, c-fos and Egr1 was then confirmed by qRT-PCR and examined in a time course study. Changes in mRNA levels were typically less than 3-fold in magnitude across all components of the study. The responses observed are consistent with pyrethroids producing increased neuronal excitation in the cortex following a low-dose in vivo exposure. In addition, Significance Analysis of Function and Expression (SAFE identified significantly enriched gene categories common for both pyrethroids, including some relating to branching morphogenesis. Exposure of primary cortical cell cultures to both compounds resulted in an increase (~25% in the number of neurite branch points, supporting the results of the SAFE analysis. Conclusion In the present study, pyrethroids induced changes in gene expression in the frontal cortex near the threshold for decreases in ambulatory motor activity in vivo. The penalized regression methods performed similarly in detecting dose-dependent changes in gene transcription. Finally, SAFE analysis of

  13. Prenatal Exposure to DDT and Pyrethroids for Malaria Control and Child Neurodevelopment: The VHEMBE Cohort, South Africa.

    Science.gov (United States)

    Eskenazi, Brenda; An, Sookee; Rauch, Stephen A; Coker, Eric S; Maphula, Angelina; Obida, Muvhulawa; Crause, Madelein; Kogut, Katherine R; Bornman, Riana; Chevrier, Jonathan

    2018-04-06

    Although indoor residual spraying (IRS) with dichlorodiphenyltrichloroethane (DDT) and pyrethroids effectively controls malaria, it potentially increases human exposure to these insecticides. Previous studies suggest that prenatal exposure to these insecticides may impact human neurodevelopment. We aimed to estimate the effects of maternal insecticide exposure and neurodevelopment of toddlers living in a malaria-endemic region currently using IRS. The Venda Health Examination of Mothers, Babies and their Environment (VHEMBE) is a birth cohort of 752 mother-child pairs in Limpopo, South Africa. We measured maternal exposure to DDT and its breakdown product, dichlorodiphenyldichloroethylene (DDE), in maternal serum, and measured pyrethroid metabolites in maternal urine. We assessed children's neurodevelopment at 1 and 2 y of age using the Bayley Scales of Infant Development, third edition (BSID-III), and examined associations with maternal exposure. DDT and DDE were not associated with significantly lower scores for any BSID-III scale. In contrast, each 10-fold increase in cis -DCCA, trans -DCCA, and 3-phenoxybenzoic acid were associated, respectively, with a -0.63 (95% CI: -1.14, -0.12), -0.48 (95% CI: -0.92, -0.05), and -0.58 (-1.11, -0.06) decrement in Social-Emotional scores at 1 y of age. In addition, each 10-fold increase in maternal cis -DBCA levels was associated with significant decrements at 2 y of age in Language Composite scores and Expressive Communication scores [β=-1.74 (95% CI: -3.34, -0.13) and β=-0.40 (95% CI: -0.77, -0.04), respectively, for a 10-fold increase]. Significant differences by sex were estimated for pyrethroid metabolites and motor function scores at 2 y of age, with higher scores for boys and lower scores for girls. Prenatal exposure to pyrethroids may be associated at 1 y of age with poorer social-emotional development. At 2 y of age, poorer language development was observed with higher prenatal pyrethroid levels. Considering the

  14. Vertical sorting and the morphodynamics of bed form-dominated rivers : a sorting evolution model

    NARCIS (Netherlands)

    Blom, Astrid; Ribberink, Jan S.; Parker, Gary

    2008-01-01

    Existing sediment continuity models for nonuniform sediment suffer from a number of shortcomings, as they fail to describe vertical sorting fluxes other than through net aggradation or degradation of the bed and are based on a discrete representation of the bed material interacting with the flow. We

  15. Comparison of the laboratory standard washing using CIPAC washing agent and the domestic washing on three recommended types of long-lasting insecticidal mosquito nets.

    Science.gov (United States)

    Ouattara, Jean Pierre Nabléni; Louwagie, Johanna; Pigeon, Olivier; Spanoghe, Pieter

    2013-01-01

    One of the best ways to prevent malaria is the use of insecticide-treated bed nets. Manufacturers pursue easier, safer and more efficient nets. Hence, many studies on the efficacy and wash resistance using World Health Organization standards have been reported. The commonly used detergent is "Savon de Marseille", because it closely resembles actually used soaps. At the 54(th) Collaborative International Pesticides Analytical Council (CIPAC) Technical Meeting in 2010, it was suggested to replace it by a standardized "CIPAC washing agent". The aim of this study was to investigate the difference between a laboratory hand washing simulation using the CIPAC washing agent (method-1) and a domestic washing (method-2) on different bed nets, as well as the effect of the drying process on the release of active ingredient. Interceptor®, Permanet®2.0 and Netprotect® nets were used in three treatments, each repeated 20 times. The first treatment included method-1 washing and indoor drying. The second treatment included method-2 washing and indoor drying. The third treatment used method-2 washing and UV-drying. The residual insecticide contents were determined using gas chromatography. The washing procedure and the number of washes have a significant effect on the release of active ingredient. Statistically, the two washing methods have the same effect on removing the active ingredient from the Interceptor® and Permanet®2.0 net, but a significantly different influence on the Netprotect® nets. The drying process has no significant effect on the insecticide. Both washing procedures affected the amount of insecticide remaining on nets independently of the impregnation technology. The active ingredient decreases with the number of washing cycles following an exponential or logarithmic model for coated nets. The laboratory hand washing simulation had more impact on the decrease of active ingredient content of the Netprotect® nets. All net types seemed to be effectively

  16. Comparison of the laboratory standard washing using CIPAC washing agent and the domestic washing on three recommended types of long-lasting insecticidal mosquito nets.

    Directory of Open Access Journals (Sweden)

    Jean Pierre Nabléni Ouattara

    Full Text Available One of the best ways to prevent malaria is the use of insecticide-treated bed nets. Manufacturers pursue easier, safer and more efficient nets. Hence, many studies on the efficacy and wash resistance using World Health Organization standards have been reported. The commonly used detergent is "Savon de Marseille", because it closely resembles actually used soaps. At the 54(th Collaborative International Pesticides Analytical Council (CIPAC Technical Meeting in 2010, it was suggested to replace it by a standardized "CIPAC washing agent". The aim of this study was to investigate the difference between a laboratory hand washing simulation using the CIPAC washing agent (method-1 and a domestic washing (method-2 on different bed nets, as well as the effect of the drying process on the release of active ingredient.Interceptor®, Permanet®2.0 and Netprotect® nets were used in three treatments, each repeated 20 times. The first treatment included method-1 washing and indoor drying. The second treatment included method-2 washing and indoor drying. The third treatment used method-2 washing and UV-drying. The residual insecticide contents were determined using gas chromatography.The washing procedure and the number of washes have a significant effect on the release of active ingredient. Statistically, the two washing methods have the same effect on removing the active ingredient from the Interceptor® and Permanet®2.0 net, but a significantly different influence on the Netprotect® nets. The drying process has no significant effect on the insecticide.Both washing procedures affected the amount of insecticide remaining on nets independently of the impregnation technology. The active ingredient decreases with the number of washing cycles following an exponential or logarithmic model for coated nets. The laboratory hand washing simulation had more impact on the decrease of active ingredient content of the Netprotect® nets. All net types seemed to be

  17. The Helicoverpa zea (Boddie) (Lepidoptera: Noctuidae) voltage-gated sodium channel and mutations associated with pyrethroid resistance in field-collected adult males.

    Science.gov (United States)

    Hopkins, B W; Pietrantonio, P V

    2010-05-01

    Helicoverpa zea is one of the most costly insect pests of food and fiber crops throughout the Americas. Pyrethroid insecticides are widely applied for its control as they are effective and relatively inexpensive; however, resistance to pyrethroids threatens agricultural systems sustainability because alternative insecticides are often more expensive or less effective. Although pyrethroid resistance has been identified in this pest since 1990, the mechanisms of resistance have not yet been elucidated at the molecular level. Pyrethroids exert their toxicity by prolonging the open state of the voltage-gated sodium channel. Here we report the cDNA sequence of the H. zea sodium channel alpha-subunit homologous to the para gene from Drosophila melanogaster. In field-collected males which were resistant to cypermethrin as determined by the adult vial test, we identify known resistance-conferring mutations L1029H and V421M, along with two novel mutations at the V421 residue, V421A and V421G. An additional mutation, I951V, may be the first example of a pyrethroid resistance mutation caused by RNA editing. Identification of the sodium channel cDNA sequence will allow for testing hypotheses on target-site resistance for insecticides acting on this channel through modeling and expression studies. Understanding the mechanisms responsible for resistance will greatly improve our ability to identify and predict resistance, as well as preserve susceptibility to pyrethroid insecticides. Copyright 2010 Elsevier Ltd. All rights reserved.

  18. Hypersensitivity Reaction and Acute Respiratory Distress Syndrome in Pyrethroid Poisoning and Role of Steroid Therapy

    Directory of Open Access Journals (Sweden)

    Jisa George

    2015-06-01

    Full Text Available Background: Pyrethroids are generally of low toxicity to humans, but in suicidal poisonings which are usually associated with ingestion of high doses, they lead to severe systemic effects. Case Report: A 30-year old woman presented to emergency department with a history of intentional ingestion of about 15 mL of prallethrin around 3 days earlier. She complained of shortness of breath along with chest pain for the last 2 days. She reported no vomiting or stomach pain prior to presentation to hospital. On chest auscultation, breath sounds were mildly decreased in bilateral infrascapular areas with generalized crepitation. Arterial blood gas analysis revealed respiratory alkalosis. Chest X ray and computed tomography of thorax revealed widespread confluent areas of consolidation with interlobular septal thickening involving bilateral parahilar regions suggestive of acute respiratory distress syndrome (ARDS. The patient did not respond to broad spectrum antibiotic coverage, diuretics and oxygen inhalation. Intravenous methylprednisolone (2 mg/kg/day divided 6 hourly was started and slowly tapered off during the next days. The patient discharged after 3 weeks in good health. Discussion: As pyrethroids can affect sodium channels, the osmotic gradient of alveolar epithelium probably disrupts and therefore, alveolar infiltrations gradually spread over lungs. In addition, there is a possibility of hypersensitivity reactions to pyrethroids, which can cause progressive inflammation and involve respiratory tract in severe cases. Conclusion: Pyrethroid poisoning can lead to ARDS. Steroid therapy may help such patients tide over the pulmonary crisis.

  19. Molecular Cloning and Characterization of a Newly Isolated Pyrethroid-Degrading Esterase Gene from a Genomic Library of Ochrobactrum anthropi YZ-1

    Science.gov (United States)

    Song, Jinlong; Shi, Yanhua; Li, Kang; Zhao, Bin; Yan, Yanchun

    2013-01-01

    A novel pyrethroid-degrading esterase gene pytY was isolated from the genomic library of Ochrobactrum anthropi YZ-1. It possesses an open reading frame (ORF) of 897 bp. Blast search showed that its deduced amino acid sequence shares moderate identities (30% to 46%) with most homologous esterases. Phylogenetic analysis revealed that PytY is a member of the esterase VI family. pytY showed very low sequence similarity compared with reported pyrethroid-degrading genes. PytY was expressed, purified, and characterized. Enzyme assay revealed that PytY is a broad-spectrum degrading enzyme that can degrade various pyrethroids. It is a new pyrethroid-degrading gene and enriches genetic resource. Kinetic constants of Km and Vmax were 2.34 mmol·L−1 and 56.33 nmol min−1, respectively, with lambda-cyhalothrin as substrate. PytY displayed good degrading ability and stability over a broad range of temperature and pH. The optimal temperature and pH were of 35°C and 7.5. No cofactors were required for enzyme activity. The results highlighted the potential use of PytY in the elimination of pyrethroid residuals from contaminated environments. PMID:24155944

  20. Pyrethroid insecticide accumulation in primary cultures of cortical neurons in vitro

    Science.gov (United States)

    Primary cultures of neurons have been widely utilized to study the actions of pyrethroids and other neurotoxicants, with the presumption that the media concentration accurately reflects the dose received by the cells. However, recent studies have demonstrated that lipophilic comp...

  1. The Effect of Indoor Residual Spraying on the Prevalence of Malaria Parasite Infection, Clinical Malaria and Anemia in an Area of Perennial Transmission and Moderate Coverage of Insecticide Treated Nets in Western Kenya.

    Directory of Open Access Journals (Sweden)

    John E Gimnig

    Full Text Available Insecticide treated nets (ITNs and indoor residual spraying (IRS have been scaled up for malaria prevention in sub-Saharan Africa. However, there are few studies on the benefit of implementing IRS in areas with moderate to high coverage of ITNs. We evaluated the impact of an IRS program on malaria related outcomes in western Kenya, an area of intense perennial malaria transmission and moderate ITN coverage (55-65% use of any net the previous night.The Kenya Division of Malaria Control, with support from the US President's Malaria Initiative, conducted IRS in one lowland endemic district with moderate coverage of ITNs. Surveys were conducted in the IRS district and a neighboring district before IRS, after one round of IRS in July-Sept 2008 and after a second round of IRS in April-May 2009. IRS was conducted with pyrethroid insecticides. At each survey, 30 clusters were selected for sampling and within each cluster, 12 compounds were randomly selected. The primary outcomes measured in all residents of selected compounds included malaria parasitemia, clinical malaria (P. falciparum infection plus history of fever and anemia (Hb<8 of all residents in randomly selected compounds. At each survey round, individuals from the IRS district were matched to those from the non-IRS district using propensity scores and multivariate logistic regression models were constructed based on the matched dataset.At baseline and after one round of IRS, there were no differences between the two districts in the prevalence of malaria parasitemia, clinical malaria or anemia. After two rounds of IRS, the prevalence of malaria parasitemia was 6.4% in the IRS district compared to 16.7% in the comparison district (OR = 0.36, 95% CI = 0.22-0.59, p<0.001. The prevalence of clinical malaria was also lower in the IRS district (1.8% vs. 4.9%, OR = 0.37, 95% CI = 0.20-0.68, p = 0.001. The prevalence of anemia was lower in the IRS district but only in children under 5 years of age (2

  2. Pyrethroid Susceptibility Has Been Maintained in the Dengue Vector, Aedes aegypti (Diptera: Culicidae), in Queensland, Australia.

    Science.gov (United States)

    Endersby-Harshman, Nancy M; Wuliandari, Juli Rochmijati; Harshman, Lawrence G; Frohn, Verena; Johnson, Brian J; Ritchie, Scott A; Hoffmann, Ary A

    2017-11-07

    Although pesticide resistance is common in insect vectors of human diseases, the evolution of resistance might be delayed if management practices are adopted that limit selection of resistance alleles. Outbreaks of dengue fever have occurred in Queensland, Australia, since the late 1800s, leading to ongoing attempts to control the mosquito vector, Aedes aegypti (L.). Since the 1990s, pyrethroid insecticides have been used for this purpose, but have been applied in a strategic manner with a variety of delivery methods including indoor residual spraying, lethal ovitraps, and use of insect growth regulators as larvicides. Separate selection experiments on mosquitoes from Queensland using Type I and Type II pyrethroids did not produce resistant lines of Ae. aegypti, and bioassays of field material from Queensland showed only weak tolerance in comparison with a susceptible line. There was no evidence of knockdown resistance (kdr) mutations in Ae. aegypti from Queensland, in stark contrast to the situation in nearby southeast Asia. We suspect that careful management of pyrethroid insecticide use combined with surveillance and interception of exotic incursions has helped to maintain pyrethroid (and particularly kdr-based) susceptibility in Ae. aegypti in Australia. © The Authors 2017. Published by Oxford University Press on behalf of Entomological Society of America. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

  3. Urinary concentrations of pyrethroid metabolites in the convenience sample of an urban population of Northern Poland.

    Science.gov (United States)

    Wielgomas, Bartosz; Nahorski, Wacław; Czarnowski, Wojciech

    2013-06-01

    Urinary concentrations of pyrethroid metabolites were measured in the first void urine samples collected from 132 healthy people living in the Gdańsk region of Northern Poland in 2010 and 2011. Four metabolites of synthetic pyrethroids: cis- and trans-3-(2,2-dichlorovinyl)-2,2-dimethylcyclopropane-1-carboxylic acids (cis-, trans-Cl2CA), cis-3-(2,2-dibromovinyl)-2,2-dimethylcyclopropane-1-carboxylic acid (Br2CA) and 3-phenoxybenzoic acid (3-PBA) were simultaneously liquid-liquid extracted, derivatized with hexafluoroisopropanol and analyzed by a gas chromatography ion-trap mass spectrometry. All the analytes were detected and quantified in the samples with various frequency, 3-phenoxybenzoic being the most often (80%) and the others less frequently (7-11%). Distribution of 3-PBA concentrations followed log-normal model, the mean concentration of 3-phenoxybenzoic acid: 0.393 μg/L (0.327 μg/g creatinine) is similar to those of the other general populations in various regions of the world. Neither sex nor age were predictors of urinary 3-PBA. Our findings suggest wide exposure to pyrethroid insecticides in the Polish general population. There is a continuous need to further study the exposure to synthetic pyrethroids among the general population since there is a strong, increasing trend in their usage. Copyright © 2012 Elsevier GmbH. All rights reserved.

  4. Nitrification in moving bed and fixed bed biofilters treating effluent water from a large commercial outdoor rainbow trout RAS

    DEFF Research Database (Denmark)

    Suhr, Karin; Pedersen, Per Bovbjerg

    2010-01-01

    The nitrification performance of two fixed bed (FB) biofilters and two moving bed (MB) biofilters was evaluated. They received the same cold (8 degrees C) influent water from a commercial outdoor RAS facility producing rainbow trout (average density 32 kg m(-3)). The filters were constructed as f...

  5. Resistance to pyrethroid insecticides in house flies, Musca domestica L., (Diptera: Muscidae) collected from urban areas in Punjab, Pakistan.

    Science.gov (United States)

    Khan, Hafiz Azhar Ali; Akram, Waseem; Fatima, Ammara

    2017-12-01

    House flies are one of the major public health pests in urban settings. People usually use insecticides containing pyrethroids for the management of house flies; however, there is a lack of information on pyrethroid resistance in house flies from urban areas. In the present study, resistance to four pyrethroids (beta-cyfluthrin, deltamethrin, permethrin, transfluthrin) was assessed in house flies collected from urban areas of Punjab, Pakistan. Significant levels of resistance to all the pyrethroids were found in different strains of house flies. The resistance ratios (RRs) at the median lethal dose (LD 50 ) level were in the range of 5.25- to 11.02-fold for beta-cyfluthrin, 7.22- to 19.31-fold for deltamethrin, 5.36- to 16.04-fold for permethrin, and 9.05- to 35.50-fold for transfluthrin. Pairwise comparison of the log LD 50 s revealed a highly significant correlation (p house flies from urban areas of Punjab. Regular resistance monitoring surveys and integrated approaches for the management of house flies are needed to retain the efficacy of these insecticides for a longer period of time.

  6. Strategic control of ticks with synthetic pyrethroids in Theileria parva ...

    African Journals Online (AJOL)

    The effect of tick control by strategic dipping in synthetic pyrethroids on growth and survival rates of calves in Eastern Tanzania where Theileria parva and other tick borne infections (babesiosis, anaplasmosis and ehrlichiosis) are endemic was measured. One day to five months old Tanganyika short horn zebu (Bos indicus) ...

  7. Pyrethroids in chicken eggs from commercial farms and home production in Rio de Janeiro: Estimated daily intake and diastereomeric selectivity.

    Science.gov (United States)

    Parente, Cláudio E T; Lestayo, Julliana; Guida, Yago S; Azevedo-Silva, Claudio E; Torres, João Paulo M; Meire, Rodrigo O; Malm, Olaf

    2017-10-01

    In this study, pyrethroids were determined in chicken eggs from commercial farm (n = 60) and home egg production (n = 30). These pyrethroids were investigated: bifenthrin, phenothrin, permethrin, cyfluthrin, cypermethrin and fenvalerate, including most diastereomers. Quantification was done using GC-MS in a negative chemical ionization mode. Pyrethroids residues were found in 79% of the analyzed samples. Cypermethrin presented the highest occurrence, being quantified in 62 samples (69%) in concentrations (lipid weight - l w.) varying between 0.29 and 6408 ng g -1 , followed by phenothrin (24%), 21-3910 ng g -1 , permethrin (14%), 2.96-328 ng g -1 , and bifenthrin (11%), 3.77-16.7 ng g -1 . Cyfluthrin and fenvalerate were not detected. Home-produced eggs had a higher occurrence of pyrethroids (97%), with a greater predominance of phenothrin. In commercial production, 70% of the samples presented pyrethroid residues (predominantly cypermethrin). This is the first report about the presence of pyrethroids in home-produced eggs and the first description of a selectivity pattern with the predominance of cis diastereomers in chicken eggs. In general, estimated daily intake does not present a risk to human consumption, according to Brazilian and international standards (FAO/WHO). However, one third of the samples (30 eggs) had concentrations above the maximum residue limits (MRLs). The maximum cypermethrin concentration was 66 times the MRL, while the maximum phenothrin concentration was 11 times the limit. Further studies about transfer dynamics, bioaccumulation and metabolic degradation of stereoisomers are required, as well as determining if this selectivity pattern in food can increase consumer's health risk. Copyright © 2017 Elsevier Ltd. All rights reserved.

  8. ISOLATION AND CHARACTERIZATION OF BIFENTHRIN CATABOLIZING BACTERIAL STRAIN BACILLUS CIBI FROM SOIL FOR PYRETHROIDS BIODEGRADATION

    OpenAIRE

    Preeti Pandey; Geetika Pant; G. Sibi

    2014-01-01

    Pyrethroids are commonly used in most parts of the world and are reported to have potential health risks. Bifenthrin, a third generation pyrethroid used as insecticide has caused potential effect on aquatic life and human health. Bioremediation is a practical approach to reduce pesticide in the environment and reports of microbial degradation of bifenthrin are meagre. This study was aimed at isolating and characterizing bacterial isolates for the efficient removal of bifenthrin residues in th...

  9. Sulfadoxine-Pyrimethamine-Based Intermittent Preventive Treatment, Bed Net Use, and Antenatal Care during Pregnancy: Demographic Trends and Impact on the Health of Newborns in the Kassena Nankana District, Northeastern Ghana

    Science.gov (United States)

    2010-01-01

    all children less than five years of age and for pregnant and nursing women. Design. This study was a prospective cohort study in which pregnant...during 2003.7 Similarly, bed net use during pregnancy, which was reported by 29% of 102 nursing and pregnant women sur- veyed in 2000, increased...malarious area of Malawi. Ann Trap Paediatr 24: 311-321. 27. Uneke CJ, I yare FE, Sunday-Adeoye H. Ajayi JA, 2008. Evalua- tion of maternal malaria at

  10. Frequent blood feeding enables insecticide-treated nets to reduce transmission by mosquitoes that bite predominately outdoors.

    Science.gov (United States)

    Russell, Tanya L; Beebe, Nigel W; Bugoro, Hugo; Apairamo, Allan; Chow, Weng K; Cooper, Robert D; Collins, Frank H; Lobo, Neil F; Burkot, Thomas R

    2016-03-10

    The effectiveness of vector control on malaria transmission by long-lasting insecticidal nets (LLINs) and indoor residual spraying (IRS) depends on the vectors entering houses to blood feed and rest when people are inside houses. In the Solomon Islands, significant reductions in malaria have been achieved in the past 20 years with insecticide-treated bed nets, IRS, improved diagnosis and treatment with artemisinin combination therapies; despite the preference of the primary vector, Anopheles farauti, to feed outdoors and early in the evening and thereby avoid potential exposure to insecticides. Rational development of tools to complement LLINs and IRS by attacking vectors outdoor requires detailed knowledge of the biology and behaviours of the target species. Malaria transmission in Central Province, Solomon Islands was estimated by measuring the components comprising the entomological inoculation rate (EIR) as well as the vectorial capacity of An. farauti. In addition, the daily and seasonal biting behaviour of An. farauti, was examined and the duration of the feeding cycle was estimated with a mark-release-recapture experiment. Anopheles farauti was highly exophagic with 72% captured by human landing catches (HLC) outside of houses. Three-quarters (76%) of blood feeding on humans was estimated to occur before 21.00 h. When the hourly location of humans was considered, the proportion of exposure to mosquito bites on humans occurring indoors (πi) was only 0.130 ± 0.129. Peak densities of host seeking An. farauti occurred between October and January. The annual EIR was estimated to be 2.5 for 2012 and 33.2 for 2013. The length of the feeding cycle was 2.1 days. The short duration of the feeding cycle by this species offers an explanation for the substantial control of malaria that has been achieved in the Solomon Islands by LLINs and IRS. Anopheles farauti is primarily exophagic and early biting, with 13% of mosquitoes entering houses to feed late at night during

  11. Pyrethroid tolerance of navel orangeworm after dietary exposure to almond phytochemicals

    Science.gov (United States)

    Inexpensive pyrethroid insecticides (IRAC Group 3A) play an increasingly important role for control of navel orangeworm in almonds and other nut crops. In addition to the insecticides used for their control, navel orangeworm larvae encounter a broad diversity of phytochemicals in their host plants. ...

  12. Community-randomized trial of lambdacyhalothrin-treated hammock nets for malaria control in Yanomami communities in the Amazon region of Venezuela.

    Science.gov (United States)

    Magris, M; Rubio-Palis, Y; Alexander, N; Ruiz, B; Galván, N; Frias, D; Blanco, M; Lines, J

    2007-03-01

    We conducted a community-randomized controlled trial in an area of moderate malaria transmission in the Amazon region, southern Venezuela, home of the Yanomami indigenous ethnic group. The aim was to compare the malaria incidence rate in villages with lambdacyhalothrin-treated hammock nets (ITHN) or with placebo-treated hammock nets (PTHN). In both arms of the study, intensive surveillance for early case detection was maintained and prompt malaria treatment was administered. Baseline data were collected before the intervention and a population of around 924 Yanomami was followed for 2 years. Despite the recent introduction of nets in the Yanomami villages and the adverse natural conditions in the area, the nets were accepted enthusiastically by the study population, used conscientiously and looked after carefully. The malaria incidence rate per thousand person-years at risk was 114.6 in the IHTN group and 186.8 in the PTHN group. The adjusted rate ratios indicated that ITHN prevent 56% [IRR: 0.44, 95% confidence interval (CI): 52-59%] of new malaria cases. ITHN reduced the prevalence of parasitaemia by 83% [relative risks (RR): 0.17, 95% CI: 47-100%], according to a cross-sectional survey carried out during the high transmission season. The prevalence of splenomegaly and anaemia was too low to detect any possible reduction as a result of ITHN. The main conclusion of the present study is that ITHN can reduce malaria incidence in the area and it is the most feasible method for malaria control in a forested area where indigenous villages are scattered over a large territory. This is the first community-level epidemiological trial to show that ITHN are highly effective against malaria transmitted by Anopheles darlingi.

  13. Pyrethroid resistance in an Anopheles funestus population from Uganda.

    Directory of Open Access Journals (Sweden)

    John C Morgan

    2010-07-01

    Full Text Available The susceptibility status of Anopheles funestus to insecticides remains largely unknown in most parts of Africa because of the difficulty in rearing field-caught mosquitoes of this malaria vector. Here we report the susceptibility status of the An. funestus population from Tororo district in Uganda and a preliminary characterisation of the putative resistance mechanisms involved.A new forced egg laying technique used in this study significantly increased the numbers of field-caught females laying eggs and generated more than 4000 F1 adults. WHO bioassays indicated that An. funestus in Tororo is resistant to pyrethroids (62% mortality after 1 h exposure to 0.75% permethrin and 28% mortality to 0.05% deltamethrin. Suspected DDT resistance was also observed with 82% mortality. However this population is fully susceptible to bendiocarb (carbamate, malathion (organophosphate and dieldrin with 100% mortality observed after exposure to each of these insecticides. Sequencing of a fragment of the sodium channel gene containing the 1014 codon conferring pyrethroid/DDT resistance in An. gambiae did not detect the L1014F kdr mutation but a correlation between haplotypes and resistance phenotype was observed indicating that mutations in other exons may be conferring the knockdown resistance in this species. Biochemical assays suggest that resistance in this population is mediated by metabolic resistance with elevated level of GSTs, P450s and pNPA compared to a susceptible strain of Anopheles gambiae. RT-PCR further confirmed the involvement of P450s with a 12-fold over-expression of CYP6P9b in the Tororo population compared to the fully susceptible laboratory colony FANG.This study represents the first report of pyrethroid/DDT resistance in An. funestus from East Africa. With resistance already reported in southern and West Africa, this indicates that resistance in An. funestus may be more widespread than previously assumed and therefore this should be taken

  14. Mosquito abundance, bed net coverage and other factors associated with variations in sporozoite infectivity rates in four villages of rural Tanzania

    DEFF Research Database (Denmark)

    Kweka, Eliningaya J; Nkya, Watoky M M; Mahande, Aneth M

    2008-01-01

    . Sporozoite infectivity rates, mosquito host blood meal source, bed net coverage and mosquito abundance were assessed in this study. METHODOLOGY: A longitudinal survey was conducted in four villages in two regions of Tanzania. Malaria vectors were sampled using the CDC light trap and pyrethrum spray catch...... methods. In each village, ten paired houses were selected for mosquitoes sampling. Sampling was done in fortnight case and study was undertaken for six months in both Kilimanjaro (Northern Tanzania) and Dodoma (Central Tanzania) regions. RESULTS: A total of 6,883 mosquitoes were collected including: 5......,628 (81.8%) Anopheles arabiensis, 1,100 (15.9%) Culex quinquefasciatus, 89 (1.4%) Anopheles funestus, and 66 (0.9%) Anopheles gambiae s.s. Of the total mosquitoes collected 3,861 were captured by CDC light trap and 3,022 by the pyrethrum spray catch method. The overall light trap: spray catch ratio was 1...

  15. Mitigation of two pyrethroid insecticides in a Mississippi Delta constructed wetland.

    Science.gov (United States)

    Moore, M T; Cooper, C M; Smith, S; Cullum, R F; Knight, S S; Locke, M A; Bennett, E R

    2009-01-01

    Constructed wetlands are a suggested best management practice to help mitigate agricultural runoff before entering receiving aquatic ecosystems. A constructed wetland system (180 m x 30 m), comprising a sediment retention basin and two treatment cells, was used to determine the fate and transport of simulated runoff containing the pyrethroid insecticides lambda-cyhalothrin and cyfluthrin, as well as suspended sediment. Wetland water, sediment, and plant samples were collected spatially and temporally over 55 d. Results showed 49 and 76% of the study's measured lambda-cyhalothrin and cyfluthrin masses were associated with vegetation, respectively. Based on conservative effects concentrations for invertebrates and regression analyses of maximum observed wetland aqueous concentrations, a wetland length of 215 m x 30 m width would be required to adequately mitigate 1% pesticide runoff from a 14 ha contributing area. Results of this experiment can be used to model future design specifications for constructed wetland mitigation of pyrethroid insecticides.

  16. From intervention to impact: modelling the potential mortality impact achievable by different long-lasting, insecticide-treated net delivery strategies

    Directory of Open Access Journals (Sweden)

    Okell Lucy C

    2012-09-01

    Full Text Available Abstract Background The current target of universal access to long-lasting, insecticide-treated nets (LLIN is 80% coverage to reduce malaria deaths by 75% by 2015. So far, campaigns have been the main channel for large-scale delivery of LLINs, however the World Health Organization has recommended that equal priority should be given to delivery via routine antenatal care (ANC and immunization systems (EPI to target pregnant women and children from birth. These various channels of LLIN delivery are targeted to children of different ages. Since risk of mortality varies with child age and LLIN effectiveness declines with net age, it was hypothesized that the age at which a child receives a new LLIN, and therefore the delivery channel, is important in optimizing the health impact of a net. Methods A simple dynamic mathematical model was developed of delivery and impact of LLINs among children under five years of age and their household members, incorporating data on age-specific malaria death rates, net use by household structure, and net efficacy over time. Results The presented analysis finds that supplementing a universal mass campaign with extra ANC delivery would achieve a 1.4 times higher mortality reduction than campaign delivery alone, reflecting that children born in the years between campaigns would otherwise have access to old nets or no nets at an age of high risk. The relative advantage of supplementary ANC delivery is still present though smaller if malaria transmission levels are lower or if there is a strong mass effect achieved by mass campaigns. Conclusion These results indicate that LLIN delivery policies must take into account the age of greatest malaria risk. Emphasis should be placed on supporting routine delivery of LLINs to young children as well as campaigns.

  17. Structure-related effects of pyrethroid insecticides on the lateral-line sense organ and on peripheral nerves of the clawed frog, Xenopus laevis

    NARCIS (Netherlands)

    Vijverberg, H.P.M.; Ruigt, GeS. F.; Bercken, J. van den

    1982-01-01

    The effects of seven different pyrethroid insecticides on the lateral-line sense organ and on peripheral nerves of the clawed frog, Xenopus laevis, were investigated by means of electrophysiological methods. The results show that two classes of pyrethroid can be clearly distinguished. (i)

  18. Assessing Dietary Exposure to Pyrethroid Insecticides by LCIMS/MS of Food Composites

    Science.gov (United States)

    Method Commercially-obtained vegetables, chips, cereal, meat, and other solid food products were homogenized together to create composited control matrices at 1%, 5%, and 100/0 fat content. Lyophilized homogenates were spiked with 7 pyrethroids, 6 degradation products, bisphen...

  19. Posttreatment Feeding Affects Mortality of Bed Bugs (Hemiptera: Cimicidae) Exposed to Insecticides.

    Science.gov (United States)

    Singh, Narinderpal; Wang, Changlu; Cooper, Richard

    2016-02-01

    Insecticide sprays and dusts are used for controlling bed bugs, Cimex lectularius L. In natural environments, bed bugs have daily access to hosts after they are exposed to insecticides. The established laboratory insecticide bioassay protocols do not provide feeding after insecticide treatments, which can result in inflated mortality compared with what would be encountered in the field. We evaluated the effect of posttreatment feeding on mortality of bed bugs treated with different insecticides. None of the insecticides tested had a significant effect on the amount of blood consumed and percent feeding. The effect of posttreatment feeding on bed bug mortality varied among different insecticides. Feeding significantly reduced mortality in bed bugs exposed to deltamethrin spray, an essential oil mixture (Bed Bug Fix) spray, and diatomaceous earth dust. Feeding increased the mean survival time for bed bugs treated with chlorfenapyr spray and a spray containing an essential oil mixture (Ecoraider), but did not affect the final mortality. First instars hatched from eggs treated with chlorfenapyr liquid spray had reduced feeding compared with nymphs hatched from nontreated eggs. Those nymphs hatched from eggs treated with chlorfenapyr liquid spray and successfully fed had reduced mortality and a higher mean survival time than those without feeding. We conclude that the availability of a bloodmeal after insecticide exposure has a significant effect on bed bug mortality. Protocols for insecticide efficacy testing should consider offering a bloodmeal to the treated bed bugs within 1 to 3 d after treatment. © The Authors 2015. Published by Oxford University Press on behalf of Entomological Society of America. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

  20. Comparative insecticidal efficacy of a new pyrethroid, metofluthrin, against colonies of Asian Culex quinquefasciatus and Culex pipiens pallens

    OpenAIRE

    Argueta, Tamara Belzabel Obispo; Kawada, Hitoshi; Shimabukuro, Kozue; Kubota, Shunichi; Shono, Yoshinori; Tsushima, Kazunori; Takagi, Masahiro

    2004-01-01

    Comparative insecticidal efficacy of metofluthrin, a newly synthesized pyrethroid, and other pyrethroids against several colonies of Asian Culex quinquefas-ciatus (from Indonesia, Thailand, Vietnam and Malaysia) was evaluated by topical application. Metofluthrin was the most effective against the four colonies of Cx. quinquefasciatus. The LD50-based relative effective ratio of metofluthrin against d-allethrin was higher in Cx. quinquefasciatus (33.3 to 78.8) than in Cx. pipiens pallens (27.8)...

  1. The Cytochrome P450 gene CYP6P12 confers pyrethroid resistance in kdr-free Malaysian populations of the dengue vector Aedes albopictus.

    Science.gov (United States)

    Ishak, Intan H; Riveron, Jacob M; Ibrahim, Sulaiman S; Stott, Rob; Longbottom, Joshua; Irving, Helen; Wondji, Charles S

    2016-04-20

    Control of Aedes albopictus, major dengue and chikungunya vector, is threatened by growing cases of insecticide resistance. The mechanisms driving this resistance remain poorly characterised. This study investigated the molecular basis of insecticide resistance in Malaysian populations of Ae. albopictus. Microarray-based transcription profiling revealed that metabolic resistance (cytochrome P450 up-regulation) and possibly a reduced penetration mechanism (consistent over-expression of cuticular protein genes) were associated with pyrethroid resistance. CYP6P12 over-expression was strongly associated with pyrethroid resistance whereas CYP6N3 was rather consistently over-expressed across carbamate and DDT resistant populations. Other detoxification genes also up-regulated in permethrin resistant mosquitoes included a glucuronosyltransferase (AAEL014279-RA) and the glutathione-S transferases GSTS1 and GSTT3. Functional analyses further supported that CYP6P12 contributes to pyrethroid resistance in Ae. albopictus as transgenic expression of CYP6P12 in Drosophila was sufficient to confer pyrethroid resistance in these flies. Furthermore, molecular docking simulations predicted CYP6P12 possessing enzymatic activity towards pyrethroids. Patterns of polymorphism suggested early sign of selection acting on CYP6P12 but not on CYP6N3. The major role played by P450 in the absence of kdr mutations suggests that addition of the synergist PBO to pyrethroids could improve the efficacy of this insecticide class and overcome resistance in field populations of Ae. albopictus.

  2. In-syringe dispersive liquid-liquid microextraction with liquid chromatographic determination of synthetic pyrethroids in surface water

    Directory of Open Access Journals (Sweden)

    Saeed S. Albaseer

    2012-03-01

    Full Text Available An indigenously fabricated in laboratory glass syringe was used for in-syringe dispersive liquid-liquid microextraction (is-DLLME and preconcentration of synthetic pyrethroids (SPs from surface waters suitable for their determination by high performance liquid chromatography. In contrast to classical DLLME, is-DLLME allows the use of lighter-than-water organic solvents and the analysis of environmental contaminants’ samples without prior filtration, which is of great importance due to the high affinity of pyrethroids to adsorb to solid particulates present in environmental samples. The effects of various parameters on the extraction efficiency were evaluated and optimized systemically using one-factor-at-a-time method (OFAT and statistically using full factorial design (24. Three SPs (viz.; cypermethrin, resmethrin and permethrin were analyzed. The method showed good accuracy with RSD% in the range of of 4.8–6.9%. The method detection limits of the three pesticides ranged from 0.14 to 0.16 ng mL-1. The proposed method was applied for the determination of synthetic pyrethroids in lake water

  3. Small-scale field evaluation of push-pull system against early- and outdoor-biting malaria mosquitoes in an area of high pyrethroid resistance in Tanzania [version 1; referees: 2 approved

    Directory of Open Access Journals (Sweden)

    Arnold S. Mmbando

    2017-11-01

    Full Text Available Background: Despite high coverage of indoor interventions like insecticide-treated nets, mosquito-borne infections persist, partly because of outdoor-biting, early-biting and insecticide-resistant vectors. Push-pull systems, where mosquitoes are repelled from humans and attracted to nearby lethal targets, may constitute effective complementary interventions. Methods: A partially randomized cross-over design was used to test efficacy of push-pull in four experimental huts and four local houses, in an area with high pyrethroid resistance in Tanzania. The push-pull system consisted of 1.1% or 2.2% w/v transfluthrin repellent dispensers and an outdoor lure-and-kill device (odour-baited mosquito landing box. Matching controls were set up without push-pull. Adult male volunteers collected mosquitoes attempting to bite them outdoors, but collections were also done indoors using exit traps in experimental huts and by volunteers in the local houses. The collections were done hourly (1830hrs-0730hrs and mosquito catches compared between push-pull and controls. An. gambiae s.l. and An. funestus s.l. were assessed by PCR to identify sibling species, and ELISA to detect Plasmodium falciparum and blood meal sources. Results: Push-pull in experimental huts reduced outdoor-biting for An. arabiensis and Mansonia species by 30% and 41.5% respectively. However, the reductions were marginal and insignificant for An. funestus (12.2%; p>0.05 and Culex (5%; p>0.05. Highest protection against all species occurred before 2200hrs. There was no significant difference in number of mosquitoes inside exit traps in huts with or without push-pull. In local households, push-pull significantly reduced indoor and outdoor-biting of An. arabiensis by 48% and 25% respectively, but had no effect on other species. Conclusion: This push-pull system offered modest protection against outdoor-biting An. arabiensis, without increasing indoor mosquito densities. Additional experimentation

  4. 1 Scepticism towards insecticide treated mosquito nets for malaria ...

    African Journals Online (AJOL)

    Abstract: Despite existence of effective tools for malaria control, malaria ... breaks from traditional approach that tend to study low uptake of health ... Key words: scepticism, low uptake, mosquito nets, malaria, social marketing, Tanzania.

  5. Parameters for Pyrethroid Insecticide QSAR and PBPK/PD Models for Human Risk Assessment

    Science.gov (United States)

    This pyrethroid insecticide parameter review is an extension of our interest in developing quantitative structure–activity relationship–physiologically based pharmacokinetic/pharmacodynamic (QSAR-PBPK/PD) models for assessing health risks, which interest started with the organoph...

  6. Voltage-sensitive sodium channel mutations S989P + V1016G in Aedes aegypti confer variable resistance to pyrethroids, DDT and oxadiazines.

    Science.gov (United States)

    Smith, Letícia B; Kasai, Shinji; Scott, Jeffrey G

    2018-03-01

    Aedes aegypti is a vector of several important human pathogens. Control efforts rely primarily on pyrethroid insecticides for adult mosquito control, especially during disease outbreaks. A. aegypti has developed resistance nearly everywhere it occurs and insecticides are used. An important mechanism of resistance is due to mutations in the voltage-sensitive sodium channel (Vssc) gene. Two mutations, in particular, S989P + V1016G, commonly occur together in parts of Asia. We have created a strain (KDR:ROCK) that contains the Vssc mutations S989P + V1016G as the only mechanism of pyrethroid resistance within the genetic background of Rockefeller (ROCK), a susceptible lab strain. We created KDR:ROCK by crossing the pyrethroid-resistant strain Singapore with ROCK followed by four backcrosses with ROCK and Vssc S989P + V1016G genotype selections. We determined the levels of resistance conferred to 17 structurally diverse pyrethroids, the organochloride DDT, and oxadiazines (VSSC blockers) indoxacarb (proinsecticide) and DCJW (the active metabolite of indoxacarb). Levels of resistance to the pyrethroids were variable, ranging from 21- to 107-fold, but no clear pattern between resistance and chemical structure was observed. Resistance is inherited as an incompletely recessive trait. KDR:ROCK had a > 2000-fold resistance to DDT, 37.5-fold cross-resistance to indoxacarb and 13.4-fold cross-resistance to DCJW. Etofenprox (and DDT) should be avoided in areas where Vssc mutations S989P + V1016G exist at high frequencies. We found that pyrethroid structure cannot be used to predict the level of resistance conferred by kdr. These results provide useful information for resistance management and for better understanding pyrethroid interactions with VSSC. © 2017 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry. © 2017 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of

  7. Effectiveness of antenatal clinics to deliver intermittent preventive treatment and insecticide treated nets for the control of malaria in pregnancy in Kenya

    NARCIS (Netherlands)

    Hill, Jenny; Dellicour, Stephanie; Bruce, Jane; Ouma, Peter; Smedley, James; Otieno, Peter; Ombock, Maurice; Kariuki, Simon; Desai, Meghna; Hamel, Mary J.; ter Kuile, Feiko O.; Webster, Jayne

    2013-01-01

    Malaria in pregnancy can have devastating consequences for mother and baby. Coverage with the WHO prevention strategy for sub-Saharan Africa of intermittent-preventive-treatment (IPTp) with two doses of sulphadoxine-pyrimethamine (SP) and insecticide-treated-nets (ITNs) in pregnancy is low. We

  8. THE PRESENCE OF A B SUBUNIT INCREASES SENSITIVITY OF SODIUM CHANNEL NAV1.3, BUT NOT NAV1.2, TO TYPE II PYRETHROIDS.

    Science.gov (United States)

    Voltage-sensitive sodium channels (VSSCs) are a primary target of pyrethroid insecticides. VSSCs are comprised of a pore-forming ¿ and auxillary ß subunits, and multiple isoforms of both subunit types exist. The sensitivity of different isoform combinations to pyrethroids has not...

  9. EFFECTS OF PYRETHROIDS ON VOLTAGE-SENSITIVE CALCIUM CHANNELS: A CRITICAL EVALUATION OF STRENGTHS, WEAKNESSES, DATA NEEDS, AND RELATIONSHIP TO ASSESSMENT OF CUMULATIVE NEUROTOXICITY.

    Science.gov (United States)

    A recently published review (Soderlund et al., 2002, Toxicology 171, 3-59.) of the mechanisms of acute neurotoxicity of pyrethroid compounds postulated that voltage-sensitive calcium channels (VSCC) may be a target of some pyrethroid compounds and that effects on VSCC may contrib...

  10. Two-step microextraction combined with high performance liquid chromatographic analysis of pyrethroids in water and vegetable samples.

    Science.gov (United States)

    Mukdasai, Siriboon; Thomas, Chunpen; Srijaranai, Supalax

    2014-03-01

    Dispersive liquid microextraction (DLME) combined with dispersive µ-solid phase extraction (D-µ-SPE) has been developed as a new approach for the extraction of four pyrethroids (tetramethrin, fenpropathrin, deltamethrin and permethrin) prior to the analysis by high performance liquid chromatography (HPLC) with UV detection. 1-Octanol was used as the extraction solvent in DLME. Magnetic nanoparticles (Fe3O4) functionalized with 3-aminopropyl triethoxysilane (APTS) were used as the dispersive in DLME and as the adsorbent in D-µ-SPE. The extracted pyrethroids were separated within 30 min using isocratic elution with acetonitrile:water (72:28). The factors affecting the extraction efficiency were investigated. Under the optimum conditions, the enrichment factors were in the range of 51-108. Linearity was obtained in the range 0.5-400 ng mL(-1) (tetramethrin) and 5-400 ng mL(-1) (fenpropathrin, deltamethrin and permethrin) with the correlation coefficients (R(2)) greater than 0.995. Detection limits were 0.05-2 ng mL(-1) (water samples) and 0.02-2.0 ng g(-1) (vegetable samples). The relative standard deviations of peak area varied from 1.8 to 2.5% (n=10). The extraction recoveries of the four pyrethroids in field water and vegetable samples were 91.7-104.5%. The proposed method has high potential for use as a sensitive method for determination of pyrethroid residues in water and vegetable samples. Copyright © 2013 Elsevier B.V. All rights reserved.

  11. Effects of Educational Intervention on Long-Lasting Insecticidal Nets Use in a Malarious Area, Southeast Iran

    Directory of Open Access Journals (Sweden)

    Abdol Hossein Madani

    2012-04-01

    Full Text Available Long-lasting insecticidal nets (LLINs have been advocated as an effective tool against malaria transmission. However, success of this community based intervention largely depends on the knowledge and practice regarding malaria and its prevention. According to the national strategy plan on evaluation of LLINs (Olyset nets, this study was conducted to determine the perceptions and practices about malaria and to improve use of LLINs in Bashagard district, one of the important foci of malaria in southeast Iran. The study area comprised 14 villages that were randomized in two clusters and designated as LLINs and untreated nets. Each of households in both clusters received two bed nets by the free distribution and delivery. After one month quantitative data collection method was used to collect information regarding the objectives of the study. On the basis of this information, an educational program was carried out in both areas to increase motivation for use of bed nets. Community knowledge and practice regarding malaria and LLIN use assessed pre- and post-educational program. The data were analyzed using SPSS ver.16 software. At baseline, 77.5% of respondents in intervention and 69.4 % in control area mentioned mosquito bite as the cause of malaria, this awareness increased significantly in intervention (90.3% and control areas (87.9%, following the educational program. A significant increase also was seen in the proportion of households who used LLINs the previous night (92.5% compared with untreated nets (87.1%. Educational status was an important predictor of LLINs use. Regular use of LLIN was considerably higher than the targeted coverage (80% which recommended by World Heaths Organization. About 81.1% and 85.3% of respondents from LLIN and control areas reported that mosquito nuisance and subsequent malaria transmission were the main determinants of bed net use. These findings highlight a need for educational intervention in implementation of

  12. The antioxidative response system in Glycine max (L.) Merr. exposed to Deltamethrin, a synthetic pyrethroid insecticide

    International Nuclear Information System (INIS)

    Bashir, Fozia; Mahmooduzzafar; Siddiqi, T.O.; Iqbal, Muhammad

    2007-01-01

    Forty-five-day-old plants of Glycine max (soybean) were exposed to several Deltamethrin (synthetic pyrethroid insecticide) concentrations (0.00 %, 0.05 %, 0.10 %, 0.15 % and 0.20 %) through foliar spray in the field conditions. In the treated plants, as observed at the pre-flowering (10 DAT), flowering (45 DAT) and post-flowering (70 DAT) stages, lipid peroxidation, proline content and total glutathione content increased, whereas the total ascorbate content decreased, as compared with the control. Among the enzymatic antioxidants, activity of superoxide dismutase, ascorbate peroxidase and glutathione reductase increased significantly whereas that of catalase declined markedly in relation to increasing concentration of Deltamethrin applied. The changes observed were dose-dependent, showing a strong correlation with the degree of treatment. - The Deltamethrin-induced oxidative stress alters the ascorbate-glutathione cycle in Glycine max

  13. Implications of insecticide resistance for malaria vector control with long-lasting insecticidal nets: a WHO-coordinated, prospective, international, observational cohort study.

    Science.gov (United States)

    Kleinschmidt, Immo; Bradley, John; Knox, Tessa Bellamy; Mnzava, Abraham Peter; Kafy, Hmooda Toto; Mbogo, Charles; Ismail, Bashir Adam; Bigoga, Jude D; Adechoubou, Alioun; Raghavendra, Kamaraju; Cook, Jackie; Malik, Elfatih M; Nkuni, Zinga José; Macdonald, Michael; Bayoh, Nabie; Ochomo, Eric; Fondjo, Etienne; Awono-Ambene, Herman Parfait; Etang, Josiane; Akogbeto, Martin; Bhatt, Rajendra M; Chourasia, Mehul Kumar; Swain, Dipak K; Kinyari, Teresa; Subramaniam, Krishanthi; Massougbodji, Achille; Okê-Sopoh, Mariam; Ogouyemi-Hounto, Aurore; Kouambeng, Celestin; Abdin, Mujahid Sheikhedin; West, Philippa; Elmardi, Khalid; Cornelie, Sylvie; Corbel, Vincent; Valecha, Neena; Mathenge, Evan; Kamau, Luna; Lines, Jonathan; Donnelly, Martin James

    2018-04-09

    Scale-up of insecticide-based interventions has averted more than 500 million malaria cases since 2000. Increasing insecticide resistance could herald a rebound in disease and mortality. We aimed to investigate whether insecticide resistance was associated with loss of effectiveness of long-lasting insecticidal nets and increased malaria disease burden. This WHO-coordinated, prospective, observational cohort study was done at 279 clusters (villages or groups of villages in which phenotypic resistance was measurable) in Benin, Cameroon, India, Kenya, and Sudan. Pyrethroid long-lasting insecticidal nets were the principal form of malaria vector control in all study areas; in Sudan this approach was supplemented by indoor residual spraying. Cohorts of children from randomly selected households in each cluster were recruited and followed up by community health workers to measure incidence of clinical malaria and prevalence of infection. Mosquitoes were assessed for susceptibility to pyrethroids using the standard WHO bioassay test. Country-specific results were combined using meta-analysis. Between June 2, 2012, and Nov 4, 2016, 40 000 children were enrolled and assessed for clinical incidence during 1·4 million follow-up visits. 80 000 mosquitoes were assessed for insecticide resistance. Long-lasting insecticidal net users had lower infection prevalence (adjusted odds ratio [OR] 0·63, 95% CI 0·51-0·78) and disease incidence (adjusted rate ratio [RR] 0·62, 0·41-0·94) than did non-users across a range of resistance levels. We found no evidence of an association between insecticide resistance and infection prevalence (adjusted OR 0·86, 0·70-1·06) or incidence (adjusted RR 0·89, 0·72-1·10). Users of nets, although significantly better protected than non-users, were nevertheless subject to high malaria infection risk (ranging from an average incidence in net users of 0·023, [95% CI 0·016-0·033] per person-year in India, to 0·80 [0·65-0·97] per person

  14. Irradiation of the tumor bed alone after lumpectomy in selected patients with early stage breast cancer treated with breast conserving therapy

    International Nuclear Information System (INIS)

    Vicini, F.; Chen, P; Benitez, P.; Johnson, P.; Gustafson, G.; Horwitz, E.; McCarthy, K.; Lacerna, M.; Goldstein, Neil; Martinez, A.

    1997-01-01

    Purpose: We present the initial findings of our in-house protocol treating the tumor bed alone after lumpectomy with low dose rate (LDR) interstitial brachytherapy in selected patients with early stage breast cancer treated with breast conserving therapy (BCT). Materials and Methods: Since 1/1/93, 50 women with early stage breast cancer were entered into a protocol of tumor bed irradiation alone using an interstitial LDR implant. Patients were eligible if their tumor was an infiltrating ductal carcinoma ≤ 3 cm in maximum diameter, pathologic margins were clear by at least 2 mm, the tumor did not contain an extensive intraductal component, the axilla was surgically staged with ≤ 3 nodes involved with cancer, and a postoperative mammogram was performed. Implants were positioned using a template guide delivering 50 Gy over 96 hours to the lumpectomy bed plus a 1-2 cm margin. Local control, cosmetic outcome, and complications were assessed. Results: Patients ranged in age from 40 to 84 years (median 65). The median tumor size was 10 mm (range, 1-25). Seventeen patients (34%) had well differentiated tumors, 22 (4%) had moderately differentiated tumors, and in 11 (22%) the tumor was poorly differentiated. Forty-five patients (90%) were node negative while 5 (10%) had 1-3 positive nodes. A total of 23 (46%) patients were placed on tamoxifen and 3 (6%) received adjuvant systemic chemotherapy. No patient was lost to follow-up. The median follow-up is 40 months (range 29-50). No patient has experienced a local, regional, or distant failure. One patient died from colorectal carcinoma with no evidence of recurrent breast cancer. Good-to-excellent cosmetic results have been observed in all 50 patients (median cosmetic follow-up 36 months). No patient has experienced significant sequelae related to their implant. Conclusions: Early results with treatment of the tumor bed alone with a LDR interstitial implant appear promising. Long-term follow-up of these patients will be

  15. Leg loss in Lutzomyia longipalpis (Diptera: Psychodidae) due to pyrethroid exposure: Toxic effect or defense by autotomy?

    Science.gov (United States)

    Santamaría, E; Cabrera, O L; Avendaño, J; Pardo, R H

    2016-01-01

    Phlebotomine sandflies lose their legs after exposure to pyrethroids. In some insects leg loss helps to defend them from intoxication and predation, a phenomenon known as autotomy. A field observation has shown that sandflies that have lost some legs are still able to blood-feed. The aims of the study were to determine whether leg loss in sandflies, after exposure to deltamethrin, is due to autotomy and to establish the effect of the leg loss on blood-feeding. Two experiments were carried out with Lutzomyia longipalpis: (i) Females were individually exposed to a sublethal time of deltamethrin and mortality and the number of leg loss were recorded; and (ii) Groups of females with complete legs or with 1-3 legs lost due to pyrethroid exposure were offered a blood meal and percentages of blood-fed and fully-fed females were recorded. Most females lost a median of 1 leg within 1-48 h post-exposure to deltamethrin. Mortality (after 24 h) was significantly higher for exposed females with lost legs (31.1%), compared to exposed females with complete legs (7.3%), and there were no differences in mortality between females with complete legs and the control (unexposed females). There were no differences between the three treatments in the percentages of blood-fed and fully-fed females. Leg loss in sandflies is a toxic effect of pyrethroids and there was no evidence of autotomy. The loss of up to three legs after exposure to pyrethroids does not affect blood-feeding behaviour in laboratory and probably also in wild conditions.

  16. IN VITRO ESTIMATES OF METABOLIC PARAMETERS AND THEIR USE IN PREDICTIVE PHYSIOLOGICALLY BASED PHARMACOKINETIC MODELING (PBPK) OF THE TYPE I PYRETHROIDS PERMETHRIN AND BIFENTHRIN

    Science.gov (United States)

    Pyrethroids are a class of neurotoxic insecticides that are used in a variety of agricultural and household activities. Hepatic clearance of the Type I pyrethroids permethrin and bifenthrin may be a critical determinant of their toxic effect. Rat LD50s reported in the literatur...

  17. Sleeping arrangements and mosquito net use among under-fives: results from the Uganda Demographic and Health Survey

    Directory of Open Access Journals (Sweden)

    Arinaitwe Jacqueline

    2003-11-01

    Full Text Available Abstract Background The Roll Back Malaria Initiative has identified the under-fives as one of the high risk groups for malaria, and one of the strategies to fight malaria in this group is increasing mosquito net use. This implies that there must be selective targeting at the household level such that the children are protected. However, the Roll Back Malaria preferences must be reconciled with those at the household level to take into account household level preferences. Methods This paper is based on the 2000–2001 Uganda Demographic and Health Survey data in which information on mosquito net ownership and use was collected. The patterns of household mosquito net ownership and use for children under five years of age were examined using both bi-variate and multivariate analysis. Results The preferences at the household level seem to be different; children use mosquito nets primarily because they happen to share a bed with their parents. A child who shares a bed with the mother is 21 times more likely to use a mosquito net than his/her counterpart. Conclusion Increasing mosquito net coverage such that 60% (the target for the RBM of households have at least one mosquito net will not necessarily protect the under-fives. Either the coverage will have to be expanded or appropriate targeting strategies designed.

  18. Structure-activity relationships for the action of 11 pyrethroid insecticides on rat Nav1.8 sodium channels expressed in Xenopus oocytes

    International Nuclear Information System (INIS)

    Choi, J.-S.; Soderlund, David M.

    2006-01-01

    Pyrethroid insecticides bind to voltage-sensitive sodium channels and modify their gating kinetics, thereby disrupting nerve function. This paper describes the action of 11 structurally diverse commercial pyrethroid insecticides on the rat Na v 1.8 sodium channel isoform, the principal carrier of the tetrodotoxin-resistant, pyrethroid-sensitive sodium current of sensory neurons, expressed in Xenopus laevis oocytes. All 11 compounds produced characteristic sodium tail currents following a depolarizing pulse that ranged from rapidly-decaying monoexponential currents (allethrin, cismethrin and permethrin) to persistent biexponential currents (cyfluthrin, cyhalothrin, cypermethrin and deltamethrin). Tail currents for the remaining compounds (bifenthrin, fenpropathrin, fenvalerate and tefluthrin) were monoexponential and decayed with kinetics intermediate between these extremes. Reconstruction of currents carried solely by the pyrethroid-modified subpopulation of channels revealed two types of pyrethroid-modified currents. The first type, found with cismethrin, allethrin, permethrin and tefluthrin, activated relatively rapidly and inactivated partially during a 40-ms depolarization. The second type, found with cypermethrin, cyfluthrin, cyhalothrin, deltamethrin, fenpropathrin and fenvalerate, activated more slowly and did not detectably inactivate during a 40-ms depolarization. Only bifenthrin did not produce modified currents that fit clearly into either of these categories. In all cases, the rate of activation of modified channels was strongly correlated with the rate of tail current decay following repolarization. Modification of Na v 1.8 sodium channels by cyfluthrin, cyhalothrin, cypermethrin and deltamethrin was enhanced 2.3- to 3.4-fold by repetitive stimulation; this effect appeared to result from the accumulation of persistently open channels rather than preferential binding to open channel states. Fenpropathrin was the most effective compound against Na v 1

  19. Semi-dry flue gas desulfurization using Ca(OH)2 in a fluidized bed reactor with bed materials

    International Nuclear Information System (INIS)

    Park, Young Oak; Roh, Hak Jae; Oh, Chang Sup; Kim, Yong Ha

    2010-01-01

    The main objective of present work is to reduce sulfur dioxide emission from power plant for the environment protection. The fluidized bed (FB) was used as the reactor with bed materials in a new semi-dry flue gas desulfurization (FGD) process to achieve high desulfurization efficiency (>98%). Fine powder of Ca(OH) 2 as sorbent and water were continuously fed separately to the bed reactor where bed materials (2 mm glass beads) were fluidized vigorously with flue gas (flow 720 Nm 3 / hr) using bench scale plant of stainless steel column. We have investigated different effects of water injection flow rate, Ca/ S molar ratio and weight of bed materials on SO 2 removal. The increments in the Ca/ S molar ratio and water injection flow rate have been resulted higher desulfurization efficiency with certain disadvantages such as higher sorbent cost and lower temperature of the treated flue gas, respectively. (author)

  20. Use of soft hydrothermal processing to improve and recycle bedding for laboratory animals.

    Science.gov (United States)

    Miyamoto, T; Li, Z; Kibushi, T; Yamasaki, N; Kasai, N

    2008-10-01

    Cage bedding for laboratory rodents can influence animal wellbeing and thus the experimental data. In addition, a large amount of used bedding containing excrement is discharged as medical waste from life science institutes and breeding companies. We developed a ground-breaking system to improve fresh bedding and recycle used bedding by applying a soft hydrothermal process with high-temperature and high-pressure dry steam. The system removes both harmful organic components and aromatic hydrocarbons that can affect animals' metabolism. The purpose of the present study was to evaluate the chemical and physical properties of the improved fresh bedding and the recycled used bedding treated by the system. The results showed that 68-99% of the predominant aromatic hydrocarbons were removed from fresh bedding treated at 0.35 MPa and 140 degrees C for 120 min ('improved bedding'). In addition, 59.4-99.0% of predominant harmful organic compounds derived from excrement were removed from used bedding treated at 0.45 MPa and 150 degrees C for 60 min ('recycled bedding'). The soft hydrothermal treatment increased the number of acidic functional groups on the bedding surface and gave it the high adsorptive efficiency of ammonia gas. Harmful substances such as microorganisms, heavy metals and pesticides decreased below the detection limit. The results clearly showed that the improved and recycled bedding is safer for laboratory rodents and has the potential to ameliorate conditions in primary and secondary enclosures (e.g. cages and animal rooms) used for maintaining laboratory animals. This process may be one of the most advanced techniques in providing an alternative to softwood and other bedding, economizing through the recycling of used bedding and reducing bedding waste from animal facilities.

  1. Investigating knockdown resistance (kdr) mechanism against pyrethroids/DDT in the malaria vector Anopheles funestus across Africa.

    Science.gov (United States)

    Irving, Helen; Wondji, Charles S

    2017-08-09

    Understanding the molecular basis of insecticide resistance is key to improve the surveillance and monitoring of malaria vector populations under control. In the major malaria vector Anopheles funestus, little is currently known about the role of the knockdown resistance (kdr) mechanism. Here, we investigated the presence and contribution of knockdown resistance (kdr) to pyrethroids/DDT resistance observed in Anopheles funestus across Africa. Pyrosequencing genotyping and sequencing of the voltage gated sodium channel (VGSC) gene did not detect the common L1014F mutation in field collected An. funestus across Africa. Amplification and cloning of the full-length of the sodium channel gene in pyrethroid resistant mosquitoes revealed evidences of alternative splicing events with three transcripts of 2092, 2061 and 2117 amino acids (93% average similarity to An. gambiae). Several amino acid changes were detected close to the domain II of the protein such as L928R, F938 W, I939S, L802S and T1008 M. However, all these mutations are found at low frequency and their role in pyrethroid resistance could not be established. The presence of the exclusive alternative splicing at exon 19 was not associated with resistance phenotype. Analysis of patterns of genetic diversity of the VGSC gene revealed a high polymorphism level of this gene across Africa with no evidence of directional selection suggesting a limited role for knockdown resistance in pyrethroid resistance in An. funestus. Patterns of genetic differentiation correlate with previous observations of the existence of barriers to gene flow Africa-wide with southern population significantly differentiated from other regions. Despite an apparent limited role of knockdown resistance in An. funestus, it is necessary to continue to monitor the contribution of the mutations detected here as increasing selection from insecticide-based interventions may change the dynamic in field populations as previously observed in other

  2. Management of glioblastoma at safety-net hospitals.

    Science.gov (United States)

    Brandel, Michael G; Rennert, Robert C; Lopez Ramos, Christian; Santiago-Dieppa, David R; Steinberg, Jeffrey A; Sarkar, Reith R; Wali, Arvin R; Pannell, J Scott; Murphy, James D; Khalessi, Alexander A

    2018-04-24

    Safety-net hospitals (SNHs) provide disproportionate care for underserved patients. Prior studies have identified poor outcomes, increased costs, and reduced access to certain complex, elective surgeries at SNHs. However, it is unknown whether similar patterns exist for the management of glioblastoma (GBM). We sought to determine if patients treated at HBHs receive equitable care for GBM, and if safety-net burden status impacts post-treatment survival. The National Cancer Database was queried for GBM patients diagnosed between 2010 and 2015. Safety-net burden was defined as the proportion of Medicaid and uninsured patients treated at each hospital, and stratified as low (LBH), medium (MBH), and high-burden (HBH) hospitals. The impact of safety-net burden on the receipt of any treatment, trimodality therapy, gross total resection (GTR), radiation, or chemotherapy was investigated. Secondary outcomes included post-treatment 30-day mortality, 90-day mortality, and overall survival. Univariate and multivariate analyses were utilized. Overall, 40,082 GBM patients at 1202 hospitals (352 LBHs, 553 MBHs, and 297 HBHs) were identified. Patients treated at HBHs were significantly less likely to receive trimodality therapy (OR = 0.75, p < 0.001), GTR (OR = 0.84, p < 0.001), radiation (OR = 0.73, p < 0.001), and chemotherapy (OR = 0.78, p < 0.001) than those treated at LBHs. Patients treated at HBHs had significantly increased 30-day (OR = 1.25, p = 0.031) and 90-day mortality (OR = 1.24, p = 0.001), and reduced overall survival (HR = 1.05, p = 0.039). GBM patients treated at SNHs are less likely to receive standard-of-care therapies and have increased short- and long-term mortality. Additional research is needed to evaluate barriers to providing equitable care for GBM patients at SNHs.

  3. Genome-wide and expression-profiling analyses suggest the main cytochrome P450 genes related to pyrethroid resistance in the malaria vector, Anopheles sinensis (Diptera Culicidae).

    Science.gov (United States)

    Yan, Zheng-Wen; He, Zheng-Bo; Yan, Zhen-Tian; Si, Feng-Ling; Zhou, Yong; Chen, Bin

    2018-02-02

    Anopheles sinensis is one of the major malaria vectors. However, pyrethroid resistance in An. sinensis is threatening malaria control. Cytochrome P450-mediated detoxification is an important pyrethroid resistance mechanism that has been unexplored in An. sinensis. In this study, we performed a comprehensive analysis of the An. sinensis P450 gene superfamily with special attention to their role in pyrethroid resistance using bioinformatics and molecular approaches. Our data revealed the presence of 112 individual P450 genes in An. sinensis, which were classified into four major clans (mitochondrial, CYP2, CYP3 and CYP4), 18 families and 50 subfamilies. Sixty-seven genes formed nine gene clusters, and genes within the same cluster and the same gene family had a similar gene structure. Phylogenetic analysis showed that most of An. sinensis P450s (82/112) had very close 1: 1 orthology with Anopheles gambiae P450s. Five genes (AsCYP6Z2, AsCYP6P3v1, AsCYP6P3v2, AsCYP9J5 and AsCYP306A1) were significantly upregulated in three pyrethroid-resistant populations in both RNA-seq and RT-qPCR analyses, suggesting that they could be the most important P450 genes involved in pyrethroid resistance in An. sinensis. Our study provides insight on the diversity of An. sinensis P450 superfamily and basis for further elucidating pyrethroid resistance mechanism in this mosquito species. © 2018 Society of Chemical Industry. © 2018 Society of Chemical Industry.

  4. Pyrethroid pesticide-induced alterations in dopamine transporter function

    International Nuclear Information System (INIS)

    Elwan, Mohamed A.; Richardson, Jason R.; Guillot, Thomas S.; Caudle, W. Michael; Miller, Gary W.

    2006-01-01

    Parkinson's disease (PD) is a progressive neurodegenerative disease affecting the nigrostriatal dopaminergic pathway. Several epidemiological studies have demonstrated an association between pesticide exposure and the incidence of PD. Studies from our laboratory and others have demonstrated that certain pesticides increase levels of the dopamine transporter (DAT), an integral component of dopaminergic neurotransmission and a gateway for dopaminergic neurotoxins. Here, we report that repeated exposure (3 injections over 2 weeks) of mice to two commonly used pyrethroid pesticides, deltamethrin (3 mg/kg) and permethrin (0.8 mg/kg), increases DAT-mediated dopamine uptake by 31 and 28%, respectively. Using cells stably expressing DAT, we determined that exposure (10 min) to deltamethrin and permethrin (1 nM-100 μM) had no effect on DAT-mediated dopamine uptake. Extending exposures to both pesticides for 30 min (10 μM) or 24 h (1, 5, and 10 μM) resulted in significant decrease in dopamine uptake. This reduction was not the result of competitive inhibition, loss of DAT protein, or cytotoxicity. However, there was an increase in DNA fragmentation, an index of apoptosis, in cells exhibiting reduced uptake at 30 min and 24 h. These data suggest that up-regulation of DAT by in vivo pyrethroid exposure is an indirect effect and that longer-term exposure of cells results in apoptosis. Since DAT can greatly affect the vulnerability of dopamine neurons to neurotoxicants, up-regulation of DAT by deltamethrin and permethrin may increase the susceptibility of dopamine neurons to toxic insult, which may provide insight into the association between pesticide exposure and PD

  5. Target-site resistance to pyrethroids in European populations of pollen beetle, Meligethes aeneus F

    DEFF Research Database (Denmark)

    Nauen, Ralf; Zimmer, Christoph T; Andrews, Melanie

    2012-01-01

    by cytochrome P450 monooxygenases was implicated in the resistance of several pollen beetle populations from different European regions. Here, we have also investigated the possible occurrence of a target-site mechanism caused by modification of the pollen beetle para-type voltage-gated sodium channel gene. We...... resulted in high selection pressure and subsequent development of resistance. Resistance to pyrethroid insecticides in this pest is now widespread and the levels of resistance are often sufficient to result in field control failures at recommended application rates. Recently, metabolic resistance mediated...... detected a single nucleotide change that results in an amino acid substitution (L1014F) within the domain IIS6 region of the channel protein. The L1014F mutation, often termed kdr, has been found in several other insect pests and is known to confer moderate levels of resistance to pyrethroids. We developed...

  6. A mutation (L1014F) in the voltage-gated sodium channel of the grain aphid, Sitobion avenae, is associated with resistance to pyrethroid insecticides.

    Science.gov (United States)

    Foster, Stephen P; Paul, Verity L; Slater, Russell; Warren, Anne; Denholm, Ian; Field, Linda M; Williamson, Martin S

    2014-08-01

    The grain aphid, Sitobion avenae Fabricius (Hemiptera: Aphididae), is an important pest of cereal crops. Pesticides are the main method for control but carry the risk of selecting for resistance. In response to reports of reduced efficacy of pyrethroid sprays applied to S. avenae, field samples were collected and screened for mutations in the voltage-gated sodium channel, the primary target site for pyrethroids. Aphid mobility and mortality to lambda-cyhalothrin were measured in coated glass vial bioassays. A single amino acid substitution (L1014F) was identified in the domain IIS6 segment of the sodium channel from the S. avenae samples exhibiting reduced pyrethroid efficacy. Bioassays on aphids heterozygous for the kdr mutation (SR) or homozygous for the wild-type allele (SS) showed that those carrying the mutation had significantly lower susceptibility to lambda-cyhalothrin. The L1014F (kdr) mutation, known to confer pyrethroid resistance in many insect pests, has been identified for the first time in S. avenae. Clonal lines heterozygous for the mutation showed 35-40-fold resistance to lambda-cyhalothrin in laboratory bioassays, consistent with the reported effect of this mutation on pyrethroid sensitivity in other aphid species. © 2013 Society of Chemical Industry.

  7. Measurement of Pyrethroids and Their Environmental Degradates in Fruits and Vegetables using a Modification of the Quick Easy Cheap Effective Rugged Safe (QuEChERS) Method

    Science.gov (United States)

    Pyrethroid insecticides are used extensively in agriculture and they, as well as their environmental degradates, may remain as residues on food products such as fruits and vegetables. Since pyrethroid degradates can be identical to the urinary markers used in human biomonitoring ...

  8. The activity of the pyrrole insecticide chlorfenapyr in mosquito bioassay: towards a more rational testing and screening of non-neurotoxic insecticides for malaria vector control.

    Science.gov (United States)

    Oxborough, Richard M; N'Guessan, Raphael; Jones, Rebecca; Kitau, Jovin; Ngufor, Corine; Malone, David; Mosha, Franklin W; Rowland, Mark W

    2015-03-24

    The rapid selection of pyrethroid resistance throughout sub-Saharan Africa is a serious threat to malaria vector control. Chlorfenapyr is a pyrrole insecticide which shows no cross resistance to insecticide classes normally used for vector control and is effective on mosquito nets under experimental hut conditions. Unlike neurotoxic insecticides, chlorfenapyr owes its toxicity to disruption of metabolic pathways in mitochondria that enable cellular respiration. A series of experiments explored whether standard World Health Organization (WHO) guidelines for evaluation of long-lasting insecticidal nets, developed through testing of pyrethroid insecticides, are suitable for evaluation of non-neurotoxic insecticides. The efficacy of WHO recommended cone, cylinder and tunnel tests was compared for pyrethroids and chlorfenapyr. To establish bioassay exposure times predictive of insecticide-treated net (ITN) efficacy in experimental hut trials, standard three-minute bioassays of pyrethroid and chlorfenapyr ITNs were compared with longer exposures. Mosquito behaviour and response to chlorfenapyr ITN in bioassays conducted at night were compared to day and across a range of temperatures representative of highland and lowland transmission. Standard three-minute bioassay of chlorfenapyr produced extremely low levels of mortality compared to pyrethroids. Thirty-minute day-time bioassay produced mortality closer to hut efficacy of chlorfenapyr ITN but still fell short of the WHO threshold. Overnight tunnel test with chlorfenapyr produced 100% mortality and exceeded the WHO threshold of 80%. The endogenous circadian activity rhythm of anophelines results in inactivity by day and raised metabolism and flight activity by night. A model which explains improved toxicity of chlorfenapyr ITN when tested at night, and during the day at higher ambient temperature, is that activation of chlorfenapyr and disruption of respiratory pathways is enhanced when the insect is more metabolically

  9. Estimating the opportunity costs of bed-days.

    Science.gov (United States)

    Sandmann, Frank G; Robotham, Julie V; Deeny, Sarah R; Edmunds, W John; Jit, Mark

    2018-03-01

    Opportunity costs of bed-days are fundamental to understanding the value of healthcare systems. They greatly influence burden of disease estimations and economic evaluations involving stays in healthcare facilities. However, different estimation techniques employ assumptions that differ crucially in whether to consider the value of the second-best alternative use forgone, of any available alternative use, or the value of the actually chosen alternative. Informed by economic theory, this paper provides a taxonomic framework of methodologies for estimating the opportunity costs of resources. This taxonomy is then applied to bed-days by classifying existing approaches accordingly. We highlight differences in valuation between approaches and the perspective adopted, and we use our framework to appraise the assumptions and biases underlying the standard approaches that have been widely adopted mostly unquestioned in the past, such as the conventional use of reference costs and administrative accounting data. Drawing on these findings, we present a novel approach for estimating the opportunity costs of bed-days in terms of health forgone for the second-best patient, but expressed monetarily. This alternative approach effectively re-connects to the concept of choice and explicitly considers net benefits. It is broadly applicable across settings and for other resources besides bed-days. © 2017 The Authors Health Economics published by John Wiley & Sons Ltd.

  10. Net Gain: A New Method for Preventing Malaria Deaths | CRDI ...

    International Development Research Centre (IDRC) Digital Library (Canada)

    A finely spun net could prevent as many as one-third of all child deaths in Africa, reports IDRC's new publication, Net Gain. Studies conducted in Gambia, Ghana, and Kenya show that the insecticide-treated mosquito net reduced the mortality rate of children under 5 years of age by up to 63 percent. Net Gain reviews and ...

  11. Distribution of Pyrethroid Resistant Populations of Triatoma infestans in the Southern Cone of South America.

    Directory of Open Access Journals (Sweden)

    Marinely Bustamante Gomez

    2016-03-01

    Full Text Available A number of studies published during the last 15 years showed the occurrence of insecticide resistance in Triatoma infestans populations. The different toxicological profiles and mechanisms of resistance to insecticides is due to a genetic base and environmental factors, being the insecticide selective pressure the best studied among the last factors. The studies on insecticide resistance on T. infestans did not consider the effect of environmental factors that may influence the distribution of resistance to pyrethroid insecticides. To fill this knowledge gap, the present study aims at studying the association between the spatial distribution of pyrethroid resistant populations of T. infestans and environmental variables.A total of 24 articles reporting on studies that evaluated the susceptibility to pyrethroids of 222 field-collected T. infestans populations were compiled. The relationship between resistance occurrence (according to different criteria with environmental variables was studied using a generalized linear model. The lethal dose that kills 50% of the evaluated population (LD50 showed a strong linear relationship with the corresponding resistance ratio (RR50. The statistical descriptive analysis of showed that the frequency distribution of the Log (LD50 is bimodal, suggesting the existence of two statistical groups. A significant model including 5 environmental variables shows the geographic distribution of high and low LD50 groups with a particular concentration of the highest LD50 populations over the region identified as the putative center of dispersion of T. infestans.The occurrence of these two groups concentrated over a particular region that coincides with the area where populations of the intermediate cytogenetic group were found might reflect the spatial heterogeneity of the genetic variability of T. infestans, that seems to be the cause of the insecticide resistance in the area, even on sylvatic populations of T. infestans

  12. Insecticide-treated nets mass distribution campaign: benefits and lessons in Zambia.

    Science.gov (United States)

    Masaninga, Freddie; Mukumbuta, Nawa; Ndhlovu, Ketty; Hamainza, Busiku; Wamulume, Pauline; Chanda, Emmanuel; Banda, John; Mwanza-Ingwe, Mercy; Miller, John M; Ameneshewa, Birkinesh; Mnzava, Abraham; Kawesha-Chizema, Elizabeth

    2018-04-24

    Zambia was an early adopter of insecticide-treated nets strategy in 2001, and policy for mass distribution with long-lasting insecticidal nets (LLINs) in 2005. Since then, the country has implemented mass distribution supplemented with routine delivery through antenatal care and under five clinics in health facilities. The national targets of universal (100%) coverage and 80% utilization of LLINs have not been attained. Free mass LLIN distribution campaign in Zambia offers important lessons to inform future campaigns in the African region. This study reviewed LLIN free mass distribution campaign information derived from Zambia's national and World Health Organization Global Malaria Programme annual reports and strategic plans published between 2001 and 2016. In 2014, a nationwide mass distribution campaign in Zambia delivered all the 6.0 million LLINs in 6 out of 10 provinces in 4 months between June and September before the onset of the rainy season. Compared with 235,800 LLINs and 2.9 million LLINs distributed on a rolling basis in 2008 and 2013, respectively, the 2014 mass campaign, which distributed 6 million LLINs represented the largest one-time-nationwide LLIN distribution in Zambia. The province (Luapula) with highest malaria transmission, mostly with rural settings recorded 98-100% sleeping spaces in homes covered with LLINs. The percentage of households owning at least 1 LLIN increased from 50.9% in 2006 to 77.7% in 2015. The 2014 mass campaign involved a coordinated response with substantial investments into macro (central) and micro (district) level planning, capacity building, tracking and logistics management supported by a new non-health sector partnership landscape. Coordination of LLIN distribution and logistics benefited from the mobile phone technology to transmit "real time" data on commodity tracking that facilitated timely delivery to districts. Free mass distribution of LLINs policy was adopted in 2005 in Zambia. Consistently implemented

  13. Malaria-related knowledge and prevention practices in four neighbourhoods in and around Mumbai, India: a cross-sectional study.

    Science.gov (United States)

    Dhawan, Gaurav; Joseph, Nidhin; Pekow, Penelope S; Rogers, Christine A; Poudel, Krishna C; Bulzacchelli, Maria T

    2014-08-07

    India accounts for the highest number of malaria cases outside of Africa. Eighty per cent of India's population lives in malaria-risk areas, with cases increasing in urban areas. Mumbai, India, one of the most populous cities in the world, has experienced such an increase. To be successful, many malaria control efforts require community participation, which in turn depends on individuals' knowledge and awareness of the disease. This study assessed the knowledge and prevention practices regarding malaria in residents of four different areas of Mumbai, India, around the time of a malaria outbreak and the start of a widespread awareness campaign. A cross-sectional comparative study assessed malaria-related knowledge and prevention practices in four geographically and socio-demographically distinct areas of Mumbai, India. A structured interviewer-administered questionnaire was administered to a stratified random sample of 119 households between 16 December 2010 and 30 January 2011. Participant socio-demographic characteristics, malaria knowledge, malaria prevention practices, and household environmental factors were examined overall and compared across the four areas of Mumbai. Overall, respondents had excellent knowledge of the mosquito as the means of transmission of malaria, mosquito biting times and breeding sites, and fever as a symptom of malaria. However, many respondents also held misconceptions about malaria transmission and symptoms. Respondents generally knew that bed nets are an effective prevention strategy, but only 30% used them, and only 4% used insecticide-treated bed nets. Knowledge and prevention practices varied across the four areas of Mumbai. Although most residents know that bed nets are effective in preventing malaria, usage of bed nets is very low, and almost no residents use insecticide-treated bed nets. As the four areas of Mumbai differed in knowledge, prevention practices, and primary sources of information, malaria control campaigns should

  14. Parents' perception on use of insecticide-treated bed net in Port ...

    African Journals Online (AJOL)

    It involved the distribution of 15-itemed questionnaires to 212 parents (with at least one under five aged child), who brought their children to the Paediatrics outpatient clinic of University of Port Harcourt Teaching Hospital. Questions asked covered: the awareness of ITN, the number of ITN owned by each participant and the ...

  15. Insecticide resistance in the West African malaria vector Anopheles gambiae and investigation of alternative tools for its delay

    NARCIS (Netherlands)

    N'Guessan, R.

    2009-01-01

    There is a current policy to eliminate malaria in the African continent. Pyrethroid-incorporated Long Lasting Insecticidal Nets (LLINs) and/or Indoor Residual Spraying (IRS) are the chemical weapons being deployed to achieve that goal. Rather worryingly, resistance to pyrethroids is well documented

  16. Filter bed systems treating domestic wastewater in the Nordic countries - Performance and reuse of filter media

    DEFF Research Database (Denmark)

    Jenssen, Petter D.; Krogstad, T.; Paruch, A.M.

    2010-01-01

    Nine filter beds have been constructed in the Nordic countries, Denmark, Finland, Norway and Sweden. Filter beds consist of a septic tank followed by an aerobic pre-treatment biofilter and a subsequent saturated flow grass-covered filter. Thus, filter beds are similar to subsurface flow construct...

  17. Kinetic evaluation of an anaerobic fluidised-bed reactor treating slaughterhouse wastewater

    Energy Technology Data Exchange (ETDEWEB)

    Borja, R. [Consejo Superior de Investigaciones Cientificas, Seville (Spain). Inst. de la Grasa; Banks, C.J.; Zhengjian Wang [Manchester Univ. (United Kingdom). Inst. of Science and Technology

    1995-09-01

    An anaerobic fluidised-bed reactor for purification of slaughterhouse wastewater was modelled as a continuous-flow, completely-mixed homogeneous microbial system, with the feed COD as the limiting-substrate concentration. The average microbial residence time in the reactor was defined in terms of conventional sludge-retention-time. The experimental data obtained indicated that the Michaelis-Menten expression was applicable to a description of substrate utilisation (i.e. COD removal) in the anaerobic fluidised-bed system. The maximum substrate utilisation rate, k, and the Michaelis constant, K{sub s}, were determined to be 1.2/day and 0.039 g/l. The observed biomass yield in the reactor decreased with increasing sludge-retention-time. The specific methane production rate observed was a linear function of the specific substrate-utilisation rate. (Author)

  18. An amino-functionalized magnetic framework composite of type Fe3O4-NH2@MIL-101(Cr) for extraction of pyrethroids coupled with GC-ECD.

    Science.gov (United States)

    He, Xi; Yang, Wei; Li, Sijia; Liu, Yu; Hu, Baichun; Wang, Ting; Hou, Xiaohong

    2018-01-24

    An amino-functionalized magnetic framework composite of type Fe 3 O 4 -NH 2 @MIL-101(Cr) was synthesized using a solvothermal method. The material was characterized by scanning electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, nitrogen adsorption, and magnetometry. The composite combines the advantages of amino-modified Fe 3 O 4 and MIL-101(Cr). The presence of amino groups facilitates the fairly specific adsorption of pyrethroids. The composite was employed as a sorbent for magnetic solid phase extraction of five pyrethroids from environmental water samples. Following desorption with acidified acetone, the pyrethroids were quantified by gas chromatography with electron capture detection. The detection limits for bifenthrin, fenpropathrin, λ-cyhalothrin, permethrin, and deltamethrin range from 5 to 9 pg·mL -1 . The method is rapid, accurate, and highly sensitive. The molecular interactions and free binding energies between MIL-101(Cr) and the five pyrethroids were calculated by means of molecular docking. Graphical abstract A novel functionalized magnetic framework composite of type Fe 3 O 4 -NH 2 @MIL-101(Cr) was synthesized. It was applied as a sorbent for magnetic solid phase extraction of pyrethroids prior to their quantitation by gas chromatography with electron capture detection. The molecular interactions of analytes and MIL-101(Cr) were studied.

  19. Numerical Simulations of the Effects of a Tidal Turbine Array on Near-Bed Velocity and Local Bed Shear Stress

    Directory of Open Access Journals (Sweden)

    Philip A. Gillibrand

    2016-10-01

    Full Text Available We apply a three-dimensional hydrodynamic model to consider the potential effects of energy extraction by an array of tidal turbines on the ambient near-bed velocity field and local bed shear stress in a coastal channel with strong tidal currents. Local bed shear stress plays a key role in local sediment dynamics. The model solves the Reynold-averaged Navier-Stokes (RANS equations on an unstructured mesh using mixed finite element and finite volume techniques. Tidal turbines are represented through an additional form drag in the momentum balance equation, with the thrust imparted and power generated by the turbines being velocity dependent with appropriate cut-in and cut-out velocities. Arrays of 1, 4 and 57 tidal turbines, each of 1.5 MW capacity, were simulated. Effects due to a single turbine and an array of four turbines were negligible. The main effect of the array of 57 turbines was to cause a shift in position of the jet through the tidal channel, as the flow was diverted around the tidal array. The net effect of this shift was to increase near-bed velocities and bed shear stress along the northern perimeter of the array by up to 0.8 m·s−1 and 5 Pa respectively. Within the array and directly downstream, near-bed velocities and bed shear stress were reduced by similar amounts. Changes of this magnitude have the potential to modify the known sand and shell banks in the region. Continued monitoring of the sediment distributions in the region will provide a valuable dataset on the impacts of tidal energy extraction on local sediment dynamics. Finally, the mean power generated per turbine is shown to decrease as the turbine array increased in size.

  20. Neurotoxicity profile of supermethrin, a new pyrethroid insecticide.

    Science.gov (United States)

    Hornychova, M; Frantik, E; Kubat, J; Formanek, J

    1995-11-01

    The use of a standard two-tier neurotoxicity screening procedure in the context of risk assessment is exemplified. Testing of a new pyrethroid in rats addressed the following sequence of questions: Does the substance evoke neurotoxic symptoms in sublethal doses? Do these symptoms reflect a primary neurotropic action? What are the dynamic characteristics of injury, the clinical profile of effect, and the relative potency of the tested substance compared to similar compounds? - The testing protocol is an animal analogue of a systematic neurological and psychological examination in man. First tier tests (structured observation, motor activity measurement, simple neurological examination) were applied after the first dose, during repeated dosing phase and in the restitution phase. Facultative tests for the second-tier examination (motor activity pattern, learning/retention test, evoked potentials, dynamic motor performance) were selected on the basis of effects revealed by the first-tier testing. Supermethrin evoked acute neurotoxicity in sublethal doses, ranging from 1/30 to 1/15 of LD50. The clinical pattern was similar to other cyano-substituted pyrethroids. Behavioural inhibition was transient and complete tolerance to it developed after 4-week repeated dosing. No indications of long-lasting changes in neuronal excitability or in learning and memory processes were found. Ataxia and excitomotoric phenomena dominated both the acute and the subchronic picture. Marked and persistent motor disturbances, including symptoms of lower motoneuron injury, were limited to individual animals of the highest, near-lethal dose group (27 mg-kg-1). Compared to lambda-cyhalothrin, the effects of supermethrin were 2 to 3 times weaker, disappeared more rapidly, cumulated less, and had higher tendency to tolerance.

  1. Determinants of insecticide-treated net ownership and utilization among pregnant women in Nigeria

    Directory of Open Access Journals (Sweden)

    Ankomah Augustine

    2012-02-01

    Full Text Available Abstract Background Malaria during pregnancy is a major public health problem in Nigeria leading to increase in the risk of maternal mortality, low birth weight and infant mortality. This paper is aimed at highlighting key predictors of the ownership of insecticide treated nets (ITNs and its use among pregnant women in Nigeria. Methods A total of 2348 pregnant women were selected by a multi-stage probability sampling technique. Structured interview schedule was used to elicit information on socio-demographic characteristics, ITN ownership, use, knowledge, behaviour and practices. Logistic regression was used to detect predictors of two indicators: ITN ownership, and ITN use in pregnancy among those who owned ITNs. Results ITN ownership was low; only 28.8% owned ITNs. Key predictors of ITN ownership included women who knew that ITNs prevent malaria (OR = 3.85; p p = 0.003. The use of ITNs was equally low with only 7.5% of all pregnant women, and 25.7% of all pregnant women who owned ITNs sleeping under a net. The predictors of ITN use in pregnancy among women who owned ITNs (N = 677 identified by logistic regression were: urban residence (OR = 1.87; p = 0.001; knowledge that ITNs prevent malaria (OR = 2.93; p p = 0.036. Educational level was not significantly related to any of the two outcome variables. Although registration at ANC is significantly associated with ownership of a bednet (perhaps through free ITN distribution this does not translate to significant use of ITNs. Conclusions ITN use lagged well behind ITN ownership. This seems to suggest that the current mass distribution of ITNs at antenatal facilities and community levels may not necessarily lead to use unless it is accompanied by behaviour change interventions that address the community level perceptions, misconceptions and positively position ITN as an effective prevention device to prevent malaria

  2. Determining and addressing obstacles to the effective use of long-lasting insecticide-impregnated nets in rural Tanzania

    Directory of Open Access Journals (Sweden)

    Benziger Peter W

    2009-12-01

    Full Text Available Abstract Background The objective of this project was to achieve high, sustainable levels of net coverage in a village in rural Tanzania by combining free distribution of long-lasting insecticide-impregnated nets (LLINs with community-tailored education. In Tanzania, malaria is the leading cause of morbidity and mortality. Although malaria bed nets have a well-established role in reducing disease burden, few rural households have access to nets, and effective use depends on personal practices and attitudes. Methods Five practices and attitudes inconsistent with effective LLIN use were identified from household interviews (n = 10. A randomized survey of villagers (n = 132 verified local prevalence of these practices and attitudes. Community leaders held an educational session for two members of every household addressing these practice and attitudes, demonstrating proper LLIN use, and emphasizing behaviour modification. Attendees received one or two LLINs per household. Surveys distributed three weeks (n = 104 and 15 months (n = 104 post-intervention assessed corrected practices and attitudes. Project efficacy was defined by correction of baseline practices and attitudes as well as high rates of reported daily net use, with statistical significance determined by chi-square test. Results Baseline interviews and surveys revealed incorrect practices and attitudes regarding 1 use of nets in dry season, 2 need to retreat LLINs, 3 children napping under nets, 4 need to repair nets, and 5 net procurement as a priority, with 53- 88.6% incorrect responses (11.4-47% correct responses. A three-week follow-up demonstrated 83-95% correct responses. Fifteen-month follow-up showed statistically significant (p Conclusions Results suggest that addressing community-specific practices and attitudes prior to LLIN distribution promotes consistent and correct use, and helps change attitudes towards bed nets as a preventative health measure. Future LLIN distributions

  3. Determination of Pyrethroids in Tea Brew by GC-MS Combined with SPME with Multiwalled Carbon Nanotube Coated Fiber.

    Science.gov (United States)

    Ren, Dongxia; Sun, Chengjun; Ma, Guanqun; Yang, Danni; Zhou, Chen; Xie, Jiayu; Li, Yongxin

    2018-01-01

    A new method has been developed to simultaneously determine 7 pyrethroid residues in tea brew using gas chromatography-mass spectrometry (GC-MS) combined with solid phase microextraction (SPME) with multiwalled carbon nanotubes (MWCNTs) coated fiber. The MWCNTs coated fiber of SPME was homemade by using stainless steel wire as coating carrier and polyacrylonitrile (PAN) solution as adhesive glue. Under the optimized conditions, a good linearity was shown for bifenthrin, fenpropathrin, permethrin, and cyfluthrin in 1-50 ng mL -1 and for cypermethrin, fenvalerate, and deltamethrin in 5-50 ng mL -1 . The correlation coefficients were in the range of 0.9948-0.9999. The average recoveries of 7 pyrethroids were 94.2%-107.3% and the relative standard deviations (RSDs) were less than 15%. The detection limit of the method ranged from 0.12 to 1.65 ng mL -1 . The tea brew samples made from some commercial tea samples were analyzed. Among them, bifenthrin, fenpropathrin, and permethrin were found. The results show that the method is rapid and sensitive and requires low organic reagent consumption, which can be well used for the detection of the pyrethroids in tea brew.

  4. Inhibition and recovery of nitrification in treating real coal gasification wastewater with moving bed biofilm reactor

    Institute of Scientific and Technical Information of China (English)

    Huiqiang Li; Hongjun Han; Maoan Du; Wei Wang

    2011-01-01

    Moving bed biofilm reactor (MBBR) was used to treat real coal gasification wastewater.Nitrification of the MBBR was inhibited almost completely during start-up period.Sudden increase of influent total NH3 concentration was the main factor inducing nitrification inhibition.Increasing DO concentration in the bulk liquid (from 2 to 3 mg/L) had little effect on nitrification recovery.Nitrification of the MBBR recovered partially by the addition of nitrifying sludge into the reactor and almost ceased within 5 days.Nitrification ratio of the MBBR achieved 65% within 12 days by increasing dilute ratio of the influent wastewater with tap water.The ratio of nitrification decreased to 25% when infiuent COD concentration increased from 650 to 1000 mg/L after nitrification recovery and recovered 70%for another 4 days.

  5. The biological activity of a novel pyrethroid: metofluthrin.

    Science.gov (United States)

    Sugano, Masayo; Ishiwatari, Takao

    2012-01-01

    Metofluthrin (commercial name: SumiOne(®), Eminence(®)) is a novel pyrethroid insecticide developed by Sumitomo Chemical Co., Ltd. Metofluthrin has extremely high insecticidal activity to various pest insects, especially to mosquitoes. In addition, Metofluthrin has relatively high volatility and low mammalian toxicity. Metofluthrin is therefore suitable for use not only in conventional mosquito control formulations such as coils and liquid vaporizers, but also in a variety of novel devices that do not require heating, such as fan vaporizers and paper and resin emanators. Here we describe the insecticidal activity of Metofluthrin mainly against mosquitoes in various formulations in both laboratory and field trials.

  6. Biannual monitoring of pyrethroid and neonicotinoid susceptibility in Danish pollen beetle (Meligethes aeneus F.) populations

    DEFF Research Database (Denmark)

    Kaiser, Caroline; Kristensen, Michael; Jensen, Karl-Martin Vagn

    2015-01-01

    ) were used. Pollen beetle populations were collected from 47 locations of Denmark with the help of the consultants and the farmers of the various regions in 2014. Further six populations were tested from Sweden and one from Germany. In the following year 2015, the monitoring continued to find out......The pollen beetle (Meligethes aeneus F.) is a serious pest in the northern countries in oilseed rape. To determine the present level of pyrethroid and neonicotinoid susceptibility of Danish pollen beetle populations, standardized methods recommended by IRAC (Insecticide Resistance Action Committee......, if the resistance level which was determined in 2014 was stable in selected regions. Therefore pollen beetle populations from 14 locations in Denmark and five locations in Germany have been tested. For all tests the standardised methods for pyrethroids, the Adult-vial-test No. 11 and the Adult-vials-test No. 21...

  7. Level of CYP4G19 Expression Is Associated with Pyrethroid Resistance in Blattella germanica

    Directory of Open Access Journals (Sweden)

    Guang-zhou Guo

    2010-01-01

    Full Text Available German cockroaches have become a large problem in the Shenzhen area because of their pesticide resistance, especially to pyrethroid. A pyrethroid called “Jia Chong Qing” to prevent pests for a long time were found to be resistant to “Jia Chong Qing” with resistance index of 3.88 measured using RT-PCR and immunohistochemistry analysis showed that both CYP4G19 mRNA and CYP4G19 protein expression levels in the wild strain were substantially higher than that of a sensitive strain. dsRNA segments derived from the target gene CYP4G19 were prepared using in vitro transcription and were microinjected into abdomens of the wild strain. Two to eight days after injection, the result showed that CYP4G19 mRNA expressions were significantly reduced in the groups injected with dsRNAs.

  8. Cloning and characterization of a pyrethroid pesticide decomposing esterase gene, Est3385, from Rhodopseudomonas palustris PSB-S.

    Science.gov (United States)

    Luo, Xiangwen; Zhang, Deyong; Zhou, Xuguo; Du, Jiao; Zhang, Songbai; Liu, Yong

    2018-05-09

    Full length open reading frame of pyrethroid detoxification gene, Est3385, contains 963 nucleotides. This gene was identified and cloned based on the genome sequence of Rhodopseudomonas palustris PSB-S available at the GneBank. The predicted amino acid sequence of Est3385 shared moderate identities (30-46%) with the known homologous esterases. Phylogenetic analysis revealed that Est3385 was a member in the esterase family I. Recombinant Est3385 was heterologous expressed in E. coli, purified and characterized for its substrate specificity, kinetics and stability under various conditions. The optimal temperature and pH for Est3385 were 35 °C and 6.0, respectively. This enzyme could detoxify various pyrethroid pesticides and degrade the optimal substrate fenpropathrin with a Km and Vmax value of 0.734 ± 0.013 mmol·l -1 and 0.918 ± 0.025 U·µg -1 , respectively. No cofactor was found to affect Est3385 activity but substantial reduction of enzymatic activity was observed when metal ions were applied. Taken together, a new pyrethroid degradation esterase was identified and characterized. Modification of Est3385 with protein engineering toolsets should enhance its potential for field application to reduce the pesticide residue from agroecosystems.

  9. Avoiding Carbon Bed Hot Spots in Thermal Process Off-Gas Systems

    International Nuclear Information System (INIS)

    Soelberg, Nick; Enneking, Joe

    2011-01-01

    Mercury has had various uses in nuclear fuel reprocessing and other nuclear processes, and so is often present in radioactive and mixed (radioactive and hazardous) wastes. Test programs performed in recent years have shown that mercury in off-gas streams from processes that treat radioactive wastes can be controlled using fixed beds of activated sulfur-impregnated carbon, to levels low enough to comply with air emission regulations such as the Hazardous Waste Combustor (HWC) Maximum Achievable Control Technology (MACT) standards. Carbon bed hot spots or fires have occurred several times during these tests, and also during a remediation of tanks that contained mixed waste. Hot spots occur when localized areas in a carbon bed become heated to temperatures where oxidation occurs. This heating typically occurs due to heat of absorption of gas species onto the carbon, but it can also be caused through external means such as external heaters used to heat the carbon bed vessel. Hot spots, if not promptly mitigated, can grow into bed fires. Carbon bed hot spots and fires must be avoided in processes that treat radioactive and mixed waste. Hot spots are detected by (a) monitoring in-bed and bed outlet gas temperatures, and (b) more important, monitoring of bed outlet gas CO concentrations. Hot spots are mitigated by (a) designing for appropriate in-bed gas velocity, for avoiding gas flow maldistribution, and for sufficient but not excessive bed depth, (b) appropriate monitoring and control of gas and bed temperatures and compositions, and (c) prompt implementation of corrective actions if bed hot spots are detected. Corrective actions must be implemented quickly if bed hot spots are detected, using a graded approach and sequence starting with corrective actions that are simple, quick, cause the least impact to the process, and are easiest to recover from.

  10. EPA's SHEDS-multimedia model: children's cumulative pyrethroid exposure estimates and evaluation against NHANES biomarker data

    Science.gov (United States)

    The U.S. EPA's SHEDS-Multimedia model was applied to enhance the understanding of children's exposures and doses to multiple pyrethroid pesticides, including major contributing chemicals and pathways. This paper presents combined dietary and residential exposure estimates and cum...

  11. Ownership and use of insecticide-treated nets during pregnancy in sub-Saharan Africa: a review.

    Science.gov (United States)

    Singh, Megha; Brown, Graham; Rogerson, Stephen J

    2013-08-01

    Over the past decade, significant gains have been made in the implementation of malaria prevention measures in pregnancy in sub-Saharan Africa, including the distribution of insecticide-treated nets (ITNs). These have been shown to cause a reduction in the incidence of malaria and its consequences such as maternal anaemia, stillbirths and intrauterine growth restriction. Currently most nations in Africa have policies for distributing ITNs to pregnant women through various mechanisms, however coverage remains well below the targets. This review summarizes recent evidence regarding the correlation between ownership and use of ITNs and the determinants of both, in pregnancy in sub-Saharan Africa, and reviews interventions directed at improving coverage. A review of the literature using Pubmed, CINAHL and scanning of reference lists was conducted in October 2012 and 59 articles were selected for final review. The research obtained was a mixture of national and district level surveys, and a narrative synthesis of the data was undertaken. Ownership of ITNs varied from as low as 3% to greater than 80%, and the main determinants were found to be education level, knowledge of malaria, community involvement, socio-economic status and parity, although the significance of each varied between the different settings and studies reviewed. In more than half the settings where data were available, the combination of lack of availability and lack of use of an available net meant that less than half of all pregnancies received the recommended intervention. Supply and cost remain major barriers to achieving optimal coverage, but the additional important contributor to reduced efficiency of intervention was the clear discrepancy between ownership and use, with available ITN use below 60% in several settings. Cited reasons for not using an ITN, where one was available, included discomfort, problems with hanging up nets and lack of space, low awareness of need, and seasonal variations in

  12. Dietary cumulative acute risk assessment of organophosphorus, carbamates and pyrethroids insecticides for the Brazilian population.

    NARCIS (Netherlands)

    Jardim, Andreia Nunes Oliveira; Brito, Alessandra Page; van Donkersgoed, Gerda; Boon, Polly E; Caldas, Eloisa Dutra

    Cumulative acute dietary risk assessments of organophosphorus (OPs), carbamates (CBs) and pyrethroids (PYs) were conducted for the Brazilian population. Residue data for 30786 samples of 30 foods were obtained from two national monitoring programs and one University laboratory, and consumption data

  13. Fluidized bed selective pyrolysis of coal

    Science.gov (United States)

    Shang, Jer Y.; Cha, Chang Y.; Merriam, Norman W.

    1992-01-01

    The present invention discloses a process for the pyrolysis of coal which comprises the effective utilization of two zonal inclined fluidized beds, where said zones can be selectively controlled as to temperature and heating rate. The first zonal inclined fluidized bed serves as a dryer for crushed coal and additionally is controlled to selectively pyrolyze said coal producing substantially carbon dioxide for recycle use. The second zonal inclined fluidized bed further pyrolyzes the coal to gaseous, liquid and char products under controlled temperature and heating rate zones designed to economically integrate the product mix. The gas and liquid products are recovered from the gaseous effluent stream while the char which remains can be further treated or utilized in a subsequent process step.

  14. Analytical method for urinary metabolites of the fluorine-containing pyrethroids metofluthrin, profluthrin and transfluthrin by gas chromatography/mass spectrometry.

    Science.gov (United States)

    Yoshida, Toshiaki

    2013-01-15

    An analytical method was developed for measurement of the major urinary metabolites in rats administered fluorine-containing pyrethroids (metofluthrin, profluthrin and transfluthrin) which are widely used recently as mosquito repellents or mothproof repellents. Eight metabolites, 2,3,5,6-tetrafluorobenzoic acid, 4-methyl-2,3,5,6-tetrafluorobenzoic acid, 2,2-dimethyl-3-(1-propenyl)-cyclopropanecarboxylic acid, 3-(2,2-dichlorovinyl)-2,2-dimethylcyclopropanecarboxylic acid (carboxylic metabolites), 2,3,5,6-tetrafluorobenzyl alcohol, 4-methyl-2,3,5,6-tetrafluorobenzyl alcohol, 4-methoxymethyl-2,3,5,6-tetrafluorobenzyl alcohol and 4-hydroxymethyl-2,3,5,6-tetrafluorobenzyl alcohol (alcoholic metabolites), were extracted from enzymatic hydrolyzed urine using toluene and then concentrated. After transformation to their tert-butyldimethylsilyl derivatives for carboxylic metabolites or their trimethylsilyl derivatives for alcoholic metabolites, analysis was conducted by gas chromatography/mass spectrometry in the electron impact ionization mode. The calibration curves for each metabolite were linear over the concentration range of 0-20μg/ml in urine, and the quantification limits were between 0.009 and 0.03μg/ml. The relative errors and the relative standard deviations on replicate assays were less than 6% and 5%, respectively, for all concentrations studied. The measurements were accurate and precise. The collected urine samples could be stored for up to 1 month at -20°C in a freezer. The proposed method was applied to the analysis of several urine samples collected from rats treated with these pyrethroids. Copyright © 2012 Elsevier B.V. All rights reserved.

  15. Distribution of Voltage-Gated Sodium Channel (Nav) Alleles among the Aedes aegypti Populations In Central Java Province and Its Association with Resistance to Pyrethroid Insecticides.

    Science.gov (United States)

    Sayono, Sayono; Hidayati, Anggie Puspa Nur; Fahri, Sukmal; Sumanto, Didik; Dharmana, Edi; Hadisaputro, Suharyo; Asih, Puji Budi Setia; Syafruddin, Din

    2016-01-01

    The emergence of insecticide resistant Aedes aegypti mosquitoes has hampered dengue control efforts. WHO susceptibility tests, using several pyrethroid compounds, were conducted on Ae. aegypti larvae that were collected and raised to adulthood from Semarang, Surakarta, Kudus and Jepara in Java. The AaNaV gene fragment encompassing kdr polymorphic sites from both susceptible and resistant mosquitoes was amplified, and polymorphisms were associated with the resistant phenotype. The insecticide susceptibility tests demonstrated Ae, aegypti resistance to the pyrethroids, with mortality rates ranging from 1.6%-15.2%. Three non-synonymous polymorphisms (S989P, V1016G and F1534C) and one synonymous polymorphism (codon 982) were detected in the AaNaV gene. Eight AaNaV alleles were observed in specimens from Central Java. Allele 3 (SGF) and allele 7 (PGF) represent the most common alleles found and demonstrated strong associations with resistance to pyrethroids (OR = 2.75, CI: 0.97-7.8 and OR = 7.37, CI: 2.4-22.5, respectively). This is the first report of 8 Ae. aegypti AaNaV alleles, and it indicates the development of resistance in Ae. aegypti in response to pyrethroid insecticide-based selective pressure. These findings strongly suggest the need for an appropriate integrated use of insecticides in the region. The 989P, 1016G and 1534C polymorphisms in the AaNaV gene are potentially valuable molecular markers for pyrethroid insecticide resistance monitoring.

  16. Measurement of pyrethroids and their environmental degradation products in fresh fruits and vegetables using a modification of the quick easy cheap effective rugged safe (QuEChERS) method

    Science.gov (United States)

    Pyrethroid insecticides are used extensively in agriculture, and they, as well as their environmental degradates, may remain as residues on foods such as fruits and vegetables. Since pyrethroid degradates can be identical to the urinary markers used in human biomonitoring, it is ...

  17. Do-it-yourself Bed Bug Control

    Science.gov (United States)

    ... Contact Us Share Do-it-yourself Bed Bug Control Información relacionada disponible en español Can you treat ... all of the residents to participate. Achieving complete control can take weeks to months, depending on the ...

  18. Genomic Footprints of Selective Sweeps from Metabolic Resistance to Pyrethroids in African Malaria Vectors Are Driven by Scale up of Insecticide-Based Vector Control.

    Science.gov (United States)

    Barnes, Kayla G; Weedall, Gareth D; Ndula, Miranda; Irving, Helen; Mzihalowa, Themba; Hemingway, Janet; Wondji, Charles S

    2017-02-01

    Insecticide resistance in mosquito populations threatens recent successes in malaria prevention. Elucidating patterns of genetic structure in malaria vectors to predict the speed and direction of the spread of resistance is essential to get ahead of the 'resistance curve' and to avert a public health catastrophe. Here, applying a combination of microsatellite analysis, whole genome sequencing and targeted sequencing of a resistance locus, we elucidated the continent-wide population structure of a major African malaria vector, Anopheles funestus. We identified a major selective sweep in a genomic region controlling cytochrome P450-based metabolic resistance conferring high resistance to pyrethroids. This selective sweep occurred since 2002, likely as a direct consequence of scaled up vector control as revealed by whole genome and fine-scale sequencing of pre- and post-intervention populations. Fine-scaled analysis of the pyrethroid resistance locus revealed that a resistance-associated allele of the cytochrome P450 monooxygenase CYP6P9a has swept through southern Africa to near fixation, in contrast to high polymorphism levels before interventions, conferring high levels of pyrethroid resistance linked to control failure. Population structure analysis revealed a barrier to gene flow between southern Africa and other areas, which may prevent or slow the spread of the southern mechanism of pyrethroid resistance to other regions. By identifying a genetic signature of pyrethroid-based interventions, we have demonstrated the intense selective pressure that control interventions exert on mosquito populations. If this level of selection and spread of resistance continues unabated, our ability to control malaria with current interventions will be compromised.

  19. Genomic Footprints of Selective Sweeps from Metabolic Resistance to Pyrethroids in African Malaria Vectors Are Driven by Scale up of Insecticide-Based Vector Control.

    Directory of Open Access Journals (Sweden)

    Kayla G Barnes

    2017-02-01

    Full Text Available Insecticide resistance in mosquito populations threatens recent successes in malaria prevention. Elucidating patterns of genetic structure in malaria vectors to predict the speed and direction of the spread of resistance is essential to get ahead of the 'resistance curve' and to avert a public health catastrophe. Here, applying a combination of microsatellite analysis, whole genome sequencing and targeted sequencing of a resistance locus, we elucidated the continent-wide population structure of a major African malaria vector, Anopheles funestus. We identified a major selective sweep in a genomic region controlling cytochrome P450-based metabolic resistance conferring high resistance to pyrethroids. This selective sweep occurred since 2002, likely as a direct consequence of scaled up vector control as revealed by whole genome and fine-scale sequencing of pre- and post-intervention populations. Fine-scaled analysis of the pyrethroid resistance locus revealed that a resistance-associated allele of the cytochrome P450 monooxygenase CYP6P9a has swept through southern Africa to near fixation, in contrast to high polymorphism levels before interventions, conferring high levels of pyrethroid resistance linked to control failure. Population structure analysis revealed a barrier to gene flow between southern Africa and other areas, which may prevent or slow the spread of the southern mechanism of pyrethroid resistance to other regions. By identifying a genetic signature of pyrethroid-based interventions, we have demonstrated the intense selective pressure that control interventions exert on mosquito populations. If this level of selection and spread of resistance continues unabated, our ability to control malaria with current interventions will be compromised.

  20. Immunotoxicity of the pyrethroid insecticides deltametrin and alpha-cypermetrin

    DEFF Research Database (Denmark)

    Madsen, Charlotte Bernhard; Claesson, M. H.; Ropke, C.

    1996-01-01

    The synthetic pyrethroids deltametrin and alpha-cypermetrin were studied for effects on the immune system in 28-day studies in F344 male rats. Sixteen rats per group were dosed with either deltametrin 0, 1, 5, or 10 mg/kg body wt./day or alpha-cypermetrin 0, 4, 8, or 12 mg/kg body wt./day in soy...... bean oil by gavage. Haematology, bone marrow cell counts, tests for natural killer (NK) cell activity and mitogen response (Con A and STM) as well as quantitation of lymphocyte subpopulations were performed. Spleen cells from immunized animals (six animals/group) were tested for antibody production...

  1. Nonproliferation and safeguard considerations: Pebble Bed reactor fuel cycle evaluation

    International Nuclear Information System (INIS)

    1978-09-01

    Nuclear fuel cycles were evaluated for the Pebble Bed Gas Cooled Reactor under development in the Federal Republic of Germany. The basic fuel cycle specified for the HTR-K and PNP is well qualified and will meet the requirements of these reactors. Twenty alternate fuel cycles are described, including high-conversion cycles, net-breeding cycles, and proliferation-resistant cycles. High-conversion cycles, which have a high probability of being successfully developed, promise a significant improvement in resource utilization. Proliferation-resistant cycles, also with a high probability of successful development, conpare very favorably with those for other types of reactors. Most of the advanced cycles could be adapted to first-generation pebble bed reactors with no significant modifications

  2. Petrology and geochemistry of samples from bed-contact zones in Tunnel Bed 5, U12g-Tunnel, Nevada Test Site

    International Nuclear Information System (INIS)

    Connolly, J.R.; Keil, K.; Mansker, W.L.; Allen, C.C.; Husler, J.; Lowy, R.; Fortney, D.R.; Lappin, A.R.

    1984-10-01

    This report summarizes the detailed geologic characterization of samples of bed-contact zones and surrounding nonwelded bedded tuffs, both within Tunnel Bed 5, that are exposed in the G-Tunnel complex beneath Rainier Mesa on the Nevada Test Site (NTS). Original planning studies treated the bed-contact zones in Tunnel Bed 5 as simple planar surfaces of relatively high permeability. Detailed characterization, however, indicates that these zones have a finite thickness, are depositional in origin, vary considerably over short vertical and horizontal distances, and are internally complex. Fluid flow in a sequence of nonwelded zeolitized ash-flow or bedded tuffs and thin intervening reworked zones appears to be a porous-medium phenomenon, regardless of the presence of layering. There are no consistent differences in either bulk composition or detailed mineralogy between bedded tuffs and bed-contact zones in Tunnel Bed 5. Although the original bulk composition of Tunnel Bed 5 was probably peralkaline, extensive zeolitization has resulted in a present peraluminous bulk composition of both bedded tuffs and bed-contact zones. The major zeolite present, clinoptilolite, is intermediate (Ca:K:Na = 26:35:39) and effectively uniform in composition. This composition is similar to that of clinoptilolite from the tuffaceous beds of Calico Hills above the static water level in hole USW G-1, but somewhat different from that reported for zeolites from below the static water level in USW G-2. Tunnel Bed 5 also contains abundant hydrous manganese oxides. The similarity in composition of the clinoptilolites from Tunnel Bed 5 and those above the static water level at Yucca Mountain indicates that many of the results of nuclide-migration experiments in Tunnel Bed 5 would be transferrable to zeolitized nonwelded tuffs above the static water level at Yucca Mountain

  3. Tritium recovery from helium purge stream of solid breeder blanket by cryogenic molecular sieve bed. 2. Regeneration operation of cryogenic molecular sieve bed

    Energy Technology Data Exchange (ETDEWEB)

    Kawamura, Yoshinori; Enoeda, Mikio; Nishi, Masataka [Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Tokai Research Establishment

    1998-03-01

    Regeneration operation is a very important operation, because it is the most influential factor for deciding the net operation cycle time and the minimum dimension of Cryogenic Molecular Sieve Bed (CMSB). However, the experimental data of CMSB regeneration operation was not so sufficient that even the optimum regeneration procedure could not be decided yet. This work was focused on getting the primary information about various regeneration procedures. (author)

  4. Reservoir evaluation of thin-bedded turbidites and hydrocarbon pore thickness estimation for an accurate quantification of resource

    Science.gov (United States)

    Omoniyi, Bayonle; Stow, Dorrik

    2016-04-01

    One of the major challenges in the assessment of and production from turbidite reservoirs is to take full account of thin and medium-bedded turbidites (succession, they can go unnoticed by conventional analysis and so negatively impact on reserve estimation, particularly in fields producing from prolific thick-bedded turbidite reservoirs. Field development plans often take little note of such thin beds, which are therefore bypassed by mainstream production. In fact, the trapped and bypassed fluids can be vital where maximising field value and optimising production are key business drivers. We have studied in detail, a succession of thin-bedded turbidites associated with thicker-bedded reservoir facies in the North Brae Field, UKCS, using a combination of conventional logs and cores to assess the significance of thin-bedded turbidites in computing hydrocarbon pore thickness (HPT). This quantity, being an indirect measure of thickness, is critical for an accurate estimation of original-oil-in-place (OOIP). By using a combination of conventional and unconventional logging analysis techniques, we obtain three different results for the reservoir intervals studied. These results include estimated net sand thickness, average sand thickness, and their distribution trend within a 3D structural grid. The net sand thickness varies from 205 to 380 ft, and HPT ranges from 21.53 to 39.90 ft. We observe that an integrated approach (neutron-density cross plots conditioned to cores) to HPT quantification reduces the associated uncertainties significantly, resulting in estimation of 96% of actual HPT. Further work will focus on assessing the 3D dynamic connectivity of the low-pay sands with the surrounding thick-bedded turbidite facies.

  5. Pyrethroid toxicity in silver catfish, Rhamdia quelen

    Directory of Open Access Journals (Sweden)

    Francisco P. Montanha

    2012-12-01

    Full Text Available This study aimed to determine both the lethal and sublethal concentrations of Cypermethrin in young Silver Catfish (Brazilian "Jundiá", Rhamdia quelen on aquatic environment during 96 hours, as well as to determine the Cypermethrin and Deltamethrin sublethal concentrations during the initial embryonic development period of Rhamdia quelen, and to verify their respective rates of fertilization, hatching and survival. Pyrethroid nowadays is a widely used insecticide, which presents a high toxicity to fish. In order to determine lethal and sublethal concentrations, 120 silver catfish were used; each one had an average weight of 59.58±4.50g and an average size of 20.33±2.34cm. Concentrations used were 0, 1.0, 1.5, 2.0, 2.5, 3.0, 5.0, 10.0, 15.0 and 20.0mg of Cypermethrin per liter of water (mg/L. Fish were exposed to the product in 30-liter fish tanks. In each fish tank there were four fishes and the product was applied three times, i.e., a total of twelve fish were exposed to the product at each application, and a total of 120 fish during the entire experiment (n=120. In order to determine the Cypermethrin and Deltamethrin sublethal concentrations during the initial embryonic development, ovulation induction was performed on female fishes using hormones, and then and egg collection was performed. The eggs were then hydrated and fertilized in Cypermethrin and Deltamethrin in different concentrations: 0.001, 0.01, 0.1, 1.0 and 10.0mg/L of Cypermethrin and 0.001, 0.01, 0.1, 0.5 and 1.0mg/L of Deltamethrin, in addition to the control group (0mg/L. After fertilization, the eggs were kept in containers with the respective pesticides of Cypermethrin and Deltamethrin until hatching, when hatching rate was verified. Then the alevins, from the hatching, were kept on their respective concentrations of Cypermethrin and Deltamethrin so that the survival rate could be analyzed regarding the tested insecticides, during both 12-hour and 24-hour periods

  6. Determination of Pyrethroids in Tea Brew by GC-MS Combined with SPME with Multiwalled Carbon Nanotube Coated Fiber

    Directory of Open Access Journals (Sweden)

    Dongxia Ren

    2018-01-01

    Full Text Available A new method has been developed to simultaneously determine 7 pyrethroid residues in tea brew using gas chromatography-mass spectrometry (GC-MS combined with solid phase microextraction (SPME with multiwalled carbon nanotubes (MWCNTs coated fiber. The MWCNTs coated fiber of SPME was homemade by using stainless steel wire as coating carrier and polyacrylonitrile (PAN solution as adhesive glue. Under the optimized conditions, a good linearity was shown for bifenthrin, fenpropathrin, permethrin, and cyfluthrin in 1–50 ng mL−1 and for cypermethrin, fenvalerate, and deltamethrin in 5–50 ng mL−1. The correlation coefficients were in the range of 0.9948–0.9999. The average recoveries of 7 pyrethroids were 94.2%–107.3% and the relative standard deviations (RSDs were less than 15%. The detection limit of the method ranged from 0.12 to 1.65 ng mL−1. The tea brew samples made from some commercial tea samples were analyzed. Among them, bifenthrin, fenpropathrin, and permethrin were found. The results show that the method is rapid and sensitive and requires low organic reagent consumption, which can be well used for the detection of the pyrethroids in tea brew.

  7. The sterilizing effect of pyriproxyfen on the malaria vector Anopheles gambiae: physiological impact on ovaries development.

    Science.gov (United States)

    Koama, Bayili; Namountougou, Moussa; Sanou, Roger; Ndo, Sévérin; Ouattara, Abdoulaye; Dabiré, Roch K; Malone, David; Diabaté, Abdoulaye

    2015-03-04

    Adult females An. gambiae were exposed in 3 min cone test to treated nets with PPF before or after they were blood fed. The effects of PPF on ovaries development, females oviposition and eggs hatching were assessed. Both unfed and fed mosquitoes exposed to PPF exhibited nearly complete inhibition of fecundity (70-100%) and fertility (90-100%). After females have been exposed once to PPF, the sterilizing effect on their fecundity was observed over 3 consecutive blood meals suggesting that PPF might have an irreversible sterilizing effect. Observation of the ovaries of exposed females to PPF under microscope revealed that the ovaries failed to develop even after several blood meals. The combination of PPF to pyrethroids on bednets could provide better malaria control tool and prevent the further development and spread of pyrethroid resistance in malaria vectors.

  8. Efficacy, Safety and Cost of Insecticide Treated Wall Lining, Insecticide Treated Bed Nets and Indoor Wall Wash with Lime for Visceral Leishmaniasis Vector Control in the Indian Sub-continent: A Multi-country Cluster Randomized Controlled Trial

    Science.gov (United States)

    Das, Pradeep; Ghosh, Debashis; Priyanka, Jyoti; Matlashewski, Greg; Kroeger, Axel; Upfill-Brown, Alexander

    2016-01-01

    Background We investigated the efficacy, safety and cost of lime wash of household walls plus treatment of sand fly breeding places with bleach (i.e. environmental management or EM), insecticide impregnated durable wall lining (DWL), and bed net impregnation with slow release insecticide (ITN) for sand fly control in the Indian sub-continent. Methods This multi-country cluster randomized controlled trial had 24 clusters in each three sites with eight clusters per high, medium or low sand fly density stratum. Every cluster included 45–50 households. Five households from each cluster were randomly selected for entomological measurements including sand fly density and mortality at one, three, nine and twelve months post intervention. Household interviews were conducted for socioeconomic information and intervention acceptability assessment. Cost for each intervention was calculated. There was a control group without intervention. Findings Sand fly mortality [mean and 95%CI] ranged from 84% (81%-87%) at one month to 74% (71%-78%) at 12 months for DWL, 75% (71%-79%) at one month to 49% (43%-55%) at twelve months for ITN, and 44% (34%-53%) at one month to 22% (14%-29%) at twelve months for EM. Adjusted intervention effect on sand fly density measured by incidence rate ratio ranged from 0.28 (0.23–0.34) at one month to 0.62 (0.51–0.75) at 12 months for DWL; 0.72 (0.62–0.85) at one month to 1.02 (0.86–1.22) at 12 months for ITN; and 0.89 (0.76–1.03) at one months to 1.49 (1.26–1.74) at 12 months for EM. Household acceptance of EM was 74% compared to 94% for both DWL and ITN. Operational cost per household in USD was about 5, 8, and 2 for EM, DWL and ITN, respectively. Minimal adverse reactions were reported for EM and ITN while 36% of households with DWL reported transient itching. Interpretation DWL is the most effective, durable and acceptable control method followed by ITN. The Visceral Leishmaniasis (VL) Elimination Program in the Indian sub

  9. ELISA AND SOL-GEL BASED IMMUNOAFFINITY PURIFICATION OF THE PYRETHROID BIOALLETHRIN IN FOOD AND ENVIRONMENTAL SAMPLES

    Science.gov (United States)

    The peer-reviewed article describes the development of a new sol-gel based immunoaffinity purification procedure and an immunoassay for the pyrethroid bioallethrin. The immunoaffinity chromatography procedure was applied to food samples providing an efficient cleanup prior to im...

  10. Magnetic solid-phase extraction of five pyrethroids from environmental water samples followed by ultrafast liquid chromatography analysis.

    Science.gov (United States)

    Yu, Xi; Sun, Ying; Jiang, Chunzhu; Sun, Xiumin; Gao, Yan; Wang, Yuanpeng; Zhang, Hanqi; Song, Daqian

    2012-08-30

    In this study, the polystyrene-coated magnetic nanoparticles (MNPs/PSt) were successfully prepared and characterized by Fourier transform infrared spectroscopy, transmission electron microscopy and vibrating sample magnetometry. The as-prepared MNPs/PSt were used as the adsorbent in magnetic solid phase extraction of five pyrethroids, including lambda-cyhalothrin, deltamethrin, esfenvalerate, permethrin, bifenthrin, in environmental water samples. The five pyrethroids were determined by ultra fast liquid chromatography-ultraviolet spectrometry. The influencing factors, including amount of MNPs/Pst, extraction time, pH value, type and volume of desorption solvent and desorption time, were examined and optimized. The extraction recoveries obtained with merely 50mg of MNPs/Pst were very satisfactory. The whole extraction process could be completed within 0.5h. The MNPs/PSt can be reused after an easy washing process. Thus, a simple, green, economical, time saving and effective method for pyrethroids analysis in environmental water samples was established. A high enrichment factor of 500 was achieved and the limits of detection for lambda-cyhalothrin, deltamethrin, esfenvalerate, permethrin, bifenthrin were 0.015±0.001 ng mL(-1), 0.012±0.001 ng mL(-1), 0.026±0.001 ng mL(-1), 0.020±0.001 ng mL(-1), 0.013±0.001 ng mL(-1), respectively. Recoveries obtained by analyzing spiked water samples at three concentration levels (0.100±0.001 ng mL(-1), 1.000±0.001 ng mL(-1), 10.000±0.001 ng mL(-1)) were between 78.97±8.38% and 96.05±8.38%. The standard curves for the five pyrethroids showed good linearity with the correlation coefficients in the range of 0.9994-0.9999. The intra-day and inter-day precision were satisfactory with the RSDs in the range of 2.05-5.52% and 2.73-8.38%, respectively. Copyright © 2012 Elsevier B.V. All rights reserved.

  11. Molecular and functional characterization of CYP6BQ23, a cytochrome P450 conferring resistance to pyrethroids in European populations of pollen beetle, Meligethes aeneus.

    Science.gov (United States)

    Zimmer, Christoph T; Bass, Chris; Williamson, Martin S; Kaussmann, Martin; Wölfel, Katharina; Gutbrod, Oliver; Nauen, Ralf

    2014-02-01

    The pollen beetle (Meligethes aeneus F.) is widespread throughout much of Europe where it is a major coleopteran pest of oilseed rape (Brassica napus). The reliance on synthetic insecticides for control, particularly the pyrethroid class, has led to the development of populations with high levels of resistance. Resistance to pyrethroids is now widespread throughout Europe and is thought to be mediated by enhanced detoxification by cytochrome P450ś and/or mutation of the pyrethroid target-site, the voltage-gated sodium channel. However, in the case of cytochrome P450 mediated detoxification, the specific enzyme(s) involved has (have) not yet been identified. In this study a degenerate PCR approach was used to identify ten partial P450 gene sequences from pollen beetle. Quantitative PCR was then used to examine the level of expression of these genes in a range of pollen beetle populations that showed differing levels of resistance to pyrethroids in bioassays. The study revealed a single P450 gene, CYP6BQ23, which is significantly and highly overexpressed (up to ∼900-fold) in adults and larvae of pyrethroid resistant strains compared to susceptible strains. CYP6BQ23 overexpression is significantly correlated with both the level of resistance and with the rate of deltamethrin metabolism in microsomal preparations of these populations. Functional recombinant expression of full length CYP6BQ23 along with cytochrome P450 reductase in an insect (Sf9) cell line showed that it is able to efficiently metabolise deltamethrin to 4-hydroxy deltamethrin. Furthermore we demonstrated by detection of 4-hydroxy tau-fluvalinate using ESI-TOF MS/MS that functionally expressed CYP6BQ23 also metabolizes tau-fluvalinate. A protein model was generated and subsequent docking simulations revealed the predicted substrate-binding mode of both deltamethrin and tau-fluvalinate to CYP6BQ23. Taken together these results strongly suggest that the overexpression of CYP6BQ23 is the primary

  12. Thermal-hydraulic tests on net divertor targets using swirl tubes

    International Nuclear Information System (INIS)

    Schlosser, J.; Chappuis, P.; Deschamps, P.; Massmann, P.; Falter, H.D.; Deschamps, G.H.

    1991-01-01

    Thermal-hydraulic tests have been carried out in collaboration between NET, CEA Cadarache and JET in order to find a cooling method capable of removing the high heat fluxes expected for the NET/ITER divertor. The goal was to evaluate by experiments the critical heat flux (CHF) and heat transfer in the subcooled boiling regime using twisted tapes as turbulence promoters and testing them under relevant thermal-hydraulic conditions. The CEA 200 kW Electron Beam (EB) facility and the 10 MW JET Neutral Beam (NB) test bed have been used to heat up the NET relevant test sections (TS) consisting of rectangular copper elements with circular internal channels. The TS have been exposed to the electron or ion beams under normal incidence. This paper reports the results of the experiments and of thermal analyses performed in support of the tests. The experimental CHF values have been benchmarked with the Tong-75 correlation

  13. Net currents in the wave bottom boundary layer: on waveshape streaming and progressive wave streaming

    NARCIS (Netherlands)

    Kranenburg, Wouter; Ribberink, Jan S.; Uittenbogaard, R.E.; Hulscher, Suzanne J.M.H.

    2012-01-01

    The net current (streaming) in a turbulent bottom boundary layer under waves above a flat bed, identified as potentially relevant for sediment transport, is mainly determined by two competing mechanisms: an onshore streaming resulting from the horizontal non-uniformity of the velocity field under

  14. Preventing childhood malaria in Africa by protecting adults from mosquitoes with insecticide-treated nets.

    Directory of Open Access Journals (Sweden)

    Gerry F Killeen

    2007-07-01

    Full Text Available Malaria prevention in Africa merits particular attention as the world strives toward a better life for the poorest. Insecticide-treated nets (ITNs represent a practical means to prevent malaria in Africa, so scaling up coverage to at least 80% of young children and pregnant women by 2010 is integral to the Millennium Development Goals (MDG. Targeting individual protection to vulnerable groups is an accepted priority, but community-level impacts of broader population coverage are largely ignored even though they may be just as important. We therefore estimated coverage thresholds for entire populations at which individual- and community-level protection are equivalent, representing rational targets for ITN coverage beyond vulnerable groups.Using field-parameterized malaria transmission models, we show that high (80% use but exclusively targeted coverage of young children and pregnant women (representing <20% of the population will deliver limited protection and equity for these vulnerable groups. In contrast, relatively modest coverage (35%-65% use, with this threshold depending on ecological scenario and net quality of all adults and children, rather than just vulnerable groups, can achieve equitable community-wide benefits equivalent to or greater than personal protection.Coverage of entire populations will be required to accomplish large reductions of the malaria burden in Africa. While coverage of vulnerable groups should still be prioritized, the equitable and communal benefits of wide-scale ITN use by older children and adults should be explicitly promoted and evaluated by national malaria control programmes. ITN use by the majority of entire populations could protect all children in such communities, even those not actually covered by achieving existing personal protection targets of the MDG, Roll Back Malaria Partnership, or the US President's Malaria Initiative.

  15. Pebble bed blanket design for deuterium burning tandem mirror reactors

    International Nuclear Information System (INIS)

    Grotz, S.P.; Dhir, V.K.

    1983-01-01

    The UCLA tandem mirror reactor, SATYR, was developed around the capability of tandem mirrors with thermal barriers to burn deuterium at reasonable efficiency levels. The pebble bed concept has been incorporated into our blanket design for the following reasons: 1) Large area-to-volume ratio for purposes of heat removal; 2) Large volume of structure for high thermal capacity thus increasing the safety margin during off-normal incidents; 3) Relatively inexpensive manufacturing costs because of large acceptable tolerances and lack of exotic materials (i.e., lithium). A simplified stress analysis of the blanket module was performed to optimize and simplify the design. The pre-specified stress intensity limitations used were based upon a 30-year predicted lifetime for each module. Along with stress analysis of the vessel a detailed thermal hydraulic analysis of the pebble bed has been completed. Parameters affecting the pebble bed design are fluidization velocity, pressure drop, heat transfer coefficient, thermally induced stress in the spheres and spatial variation of the power density. Although reasonable gross thermal efficiencies of the 2 designs has been achieved (28% for H 2 O and 39% for He) the high net recirculating power fraction for heating and neutral beams results in relatively low net plant efficiencies (21% and 27%). The results show that a blanket can be designed with good thermal efficiency and a relative-ly simple configuration. However, application of this concept to the high Q deuterium-tritium fuel cycle would have difficulties resulting from the need for continuous removal of the tritium. (orig./HP)

  16. Behavioral effects of type II pyrethroid cyhalothrin in rats

    International Nuclear Information System (INIS)

    Righi, D. Abbud; Palermo-Neto, J.

    2003-01-01

    Synthetic pyrethroids such as cyhalothrin are extensively used in agriculture for the control of a broad range of ectoparasites in farm animals. It has been suggested that type II pyrethroids might induce anxiogenic-like effects in laboratory animals. The present study was undertaken to investigate a possible anxiogenic-like outcome of cyhalothrin in rats. Adult male rats were orally dosed for 7 days with 1.0, 3.0, or 7.0 mg/kg/day of cyhalothrin, present in a commercial formulation (Grenade Coopers do Brazil S.A.). The neurobehavioral changes induced by cyhalothrin as well as those produced on corticosterone serum levels were measured 24 h after the last treatment. Picrotoxin (1.0 mg/kg) was also acutely used as a positive control for anxiety. Results showed that cyhalothrin: (1) induced some signs and symptoms of intoxication that included salivation, tremors, and liquid feces; (2) reduced total locomotor activity in the open-field; (3) reduced the percentage of time spent in open-field central zones; (4) increased immobility time in the open-field; (5) reduced the percentage of time spent in plus-maze open arms exploration; (6) reduced the time spent in social interactions, and (7) increased the levels of serum corticosterone. The behavioral changes reported for cyhalothrin (3.0 mg/kg/day) were similar of those induced by picrotoxin. The no effect level dose obtained for cyhalothrin in this study was 1.0 mg/kg/day. These results provide experimental evidence that cyhalothrin induces anxiety-like symptoms, with this effect being dose-related. Thus, anxiety must be included among the several signs and symptoms of pesticide intoxication

  17. Carbon Bed Mercury Emissions Control For Mixed Waste Treatment

    International Nuclear Information System (INIS)

    Soelberg, Nick; Enneking, Joe

    2010-01-01

    Mercury has had various uses in nuclear fuel reprocessing and other nuclear processes, and so is often present in radioactive and mixed (both radioactive and hazardous according to the Resource Conservation and Recovery Act) wastes. Depending on regulatory requirements, the mercury in the off-gas must be controlled with sometimes very high efficiencies. Compliance to the Hazardous Waste Combustor (HWC) Maximum Achievable Control Technology (MACT) standards can require off-gas mercury removal efficiencies up to 99.999% for thermally treating some mixed waste streams. Several test programs have demonstrated this level of off-gas mercury control using fixed beds of granular sulfur-impregnated activated carbon. Other results of these tests include: (a) The depth of the mercury control mass transfer zone was less than 15-30 cm for the operating conditions of these tests, (b) MERSORB(reg s ign) carbon can sorb Hg up to 19 wt% of the carbon mass, and (c) the spent carbon retained almost all (98-99.99%) of the Hg; but when even a small fraction of the total Hg dissolves, the spent carbon can fail the TCLP test when the spent carbon contains high Hg concentrations. Localized areas in a carbon bed that become heated through heat of adsorption, to temperatures where oxidation occurs, are referred to as 'bed hot spots.' Carbon bed hot spots must be avoided in processes that treat radioactive and mixed waste. Key to carbon bed hot spot mitigation are (a) designing for sufficient gas velocity, for avoiding gas flow maldistribution, and for sufficient but not excessive bed depth, (b) monitoring and control of inlet gas flowrate, temperature, and composition, (c) monitoring and control of in-bed and bed outlet gas temperatures, and (d) most important, monitoring of bed outlet CO concentrations. An increase of CO levels in the off-gas downstream of the carbon bed to levels about 50-100 ppm higher than the inlet CO concentration indicate CO formation in the bed, caused by carbon bed

  18. Co-occurrence of point mutations in the voltage-gated sodium channel of pyrethroid-resistant Aedes aegypti populations in Myanmar.

    Science.gov (United States)

    Kawada, Hitoshi; Oo, Sai Zaw Min; Thaung, Sein; Kawashima, Emiko; Maung, Yan Naung Maung; Thu, Hlaing Myat; Thant, Kyaw Zin; Minakawa, Noboru

    2014-01-01

    Single amino acid substitutions in the voltage-gated sodium channel associated with pyrethroid resistance constitute one of the main causative factors of knockdown resistance in insects. The kdr gene has been observed in several mosquito species; however, point mutations in the para gene of Aedes aegypti populations in Myanmar have not been fully characterized. The aim of the present study was to determine the types and frequencies of mutations in the para gene of Aedes aegypti collected from used tires in Yangon City, Myanmar. We determined high pyrethroid resistance in Aedes aegypti larvae at all collection sites in Yangon City, by using a simplified knockdown bioassay. We showed that V1016G and S989P mutations were widely distributed, with high frequencies (84.4% and 78.8%, respectively). By contrast, we were unable to detect I1011M (or I1011V) or L1014F mutations. F1534C mutations were also widely distributed, but with a lower frequency than the V1016G mutation (21.2%). High percentage of co-occurrence of the homozygous V1016G/S989P mutations was detected (65.7%). Additionally, co-occurrence of homozygous V1016G/F1534C mutations (2.9%) and homozygous V1016G/F1534C/S989P mutations (0.98%) were detected in the present study. Pyrethroid insecticides were first used for malaria control in 1992, and have since been constantly used in Myanmar. This intensive use may explain the strong selection pressure toward Aedes aegypti, because this mosquito is generally a domestic and endophagic species with a preference for indoor breeding. Extensive use of DDT for malaria control before the use of this chemical was banned may also explain the development of pyrethroid resistance in Aedes aegypti.

  19. Co-occurrence of Point Mutations in the Voltage-Gated Sodium Channel of Pyrethroid-Resistant Aedes aegypti Populations in Myanmar

    Science.gov (United States)

    Kawada, Hitoshi; Oo, Sai Zaw Min; Thaung, Sein; Kawashima, Emiko; Maung, Yan Naung Maung; Thu, Hlaing Myat; Thant, Kyaw Zin; Minakawa, Noboru

    2014-01-01

    Background Single amino acid substitutions in the voltage-gated sodium channel associated with pyrethroid resistance constitute one of the main causative factors of knockdown resistance in insects. The kdr gene has been observed in several mosquito species; however, point mutations in the para gene of Aedes aegypti populations in Myanmar have not been fully characterized. The aim of the present study was to determine the types and frequencies of mutations in the para gene of Aedes aegypti collected from used tires in Yangon City, Myanmar. Methodology/Principal Findings We determined high pyrethroid resistance in Aedes aegypti larvae at all collection sites in Yangon City, by using a simplified knockdown bioassay. We showed that V1016G and S989P mutations were widely distributed, with high frequencies (84.4% and 78.8%, respectively). By contrast, we were unable to detect I1011M (or I1011V) or L1014F mutations. F1534C mutations were also widely distributed, but with a lower frequency than the V1016G mutation (21.2%). High percentage of co-occurrence of the homozygous V1016G/S989P mutations was detected (65.7%). Additionally, co-occurrence of homozygous V1016G/F1534C mutations (2.9%) and homozygous V1016G/F1534C/S989P mutations (0.98%) were detected in the present study. Conclusions/Significance Pyrethroid insecticides were first used for malaria control in 1992, and have since been constantly used in Myanmar. This intensive use may explain the strong selection pressure toward Aedes aegypti, because this mosquito is generally a domestic and endophagic species with a preference for indoor breeding. Extensive use of DDT for malaria control before the use of this chemical was banned may also explain the development of pyrethroid resistance in Aedes aegypti. PMID:25077956

  20. [Malaria: knowledge, behaviour and practices among a rural population of Gossas, Senegal].

    Science.gov (United States)

    Ndour, C T; Ba, O; Manga, N M; Fortes, M L; Nyamwasa, D; Sow, P S

    2006-10-01

    Malaria remains a major public health problem in Sub-Saharian Africa, in terms of morbidity and mortality rate. To assess the knowledge and behaviour of population regarding the transmission, the treatment and the prevention of malaria, we conducted a cluster sample household survey in Gossas, a rural District in Senegal, from May 2nd to May 6th 2005. A questionnaire that focused on socioeconomic conditions, beliefs, knowledge about and behavior toward antimalarial medication and the prevention means used was given to 480 household owners. Overall, 107 pregnant women and 1,201 children aged less than 5 years old lived within these household. More than a half of the household owners (51%) were illiterate and 25.2% ignored how malaria is transmitted. Fever was the most common symptom suggesting malaria (61%). In 46.1% of febrile cases, people did not seek for treatment from a physician. Home treatment of febrile episodes was based on paracetamol or aspirin (84%), chloroquine (13%) and cotrimoxazole (2.9%). Overall, the proportion of insecticide treated nets users were 22.7%. This percentage was 14.9% and 11.4% for pregnant women and children younger than 5 years old, respectively. People having radio sets, regular access to television, and people aware of the transmission route of malaria were more likely to use bed nets. In most cases, organic material burning was used as repellent against mosquitoes. The low prevalence of bed net use was most often explained by participants' limited accessibility to and by the high cost of insecticide-treated nets. Knowledge about malaria prevention and treatment is low in the rural district of Gossas. The rate of insecticide-treated-bed nets use in vulnerable people is very low, far from the Abuja meeting objective. A sensibilization program and a social marketing plan for insecticide-treated-bed nets could improve this situation.

  1. Pyrethroids and Nectar Toxins Have Subtle Effects on the Motor Function, Grooming and Wing Fanning Behaviour of Honeybees (Apis mellifera).

    Science.gov (United States)

    Oliver, Caitlin J; Softley, Samantha; Williamson, Sally M; Stevenson, Philip C; Wright, Geraldine A

    2015-01-01

    Sodium channels, found ubiquitously in animal muscle cells and neurons, are one of the main target sites of many naturally-occurring, insecticidal plant compounds and agricultural pesticides. Pyrethroids, derived from compounds found only in the Asteraceae, are particularly toxic to insects and have been successfully used as pesticides including on flowering crops that are visited by pollinators. Pyrethrins, from which they were derived, occur naturally in the nectar of some flowering plant species. We know relatively little about how such compounds--i.e., compounds that target sodium channels--influence pollinators at low or sub-lethal doses. Here, we exposed individual adult forager honeybees to several compounds that bind to sodium channels to identify whether these compounds affect motor function. Using an assay previously developed to identify the effect of drugs and toxins on individual bees, we investigated how acute exposure to 10 ng doses (1 ppm) of the pyrethroid insecticides (cyfluthrin, tau-fluvalinate, allethrin and permethrin) and the nectar toxins (aconitine and grayanotoxin I) affected honeybee locomotion, grooming and wing fanning behaviour. Bees exposed to these compounds spent more time upside down and fanning their wings. They also had longer bouts of standing still. Bees exposed to the nectar toxin, aconitine, and the pyrethroid, allethrin, also spent less time grooming their antennae. We also found that the concentration of the nectar toxin, grayanotoxin I (GTX), fed to bees affected the time spent upside down (i.e., failure to perform the righting reflex). Our data show that low doses of pyrethroids and other nectar toxins that target sodium channels mainly influence motor function through their effect on the righting reflex of adult worker honeybees.

  2. Effects of the pyrethroid insecticide gamma-cyhalothrin on aquatic invertebrates in laboratory and outdoor microcosm tests

    NARCIS (Netherlands)

    Wijngaarden, van R.P.A.; Barber, I.; Brock, T.C.M.

    2009-01-01

    The sensitivity of a range of freshwater lentic invertebrates to gamma-cyhalothrin (GCH), a single enantiomer of the synthetic pyrethroid lambda-cyhalothrin, was assessed in single species laboratory tests and an outdoor multi-species ecosystem test. The most sensitive species in the laboratory

  3. The treatment and eradication of sheep lice and ked with cyhalothrin--a new synthetic pyrethroid.

    Science.gov (United States)

    Rundle, J C; Forsyth, B A

    1984-12-01

    A new synthetic pyrethroid, cyhalothrin, has been evaluated as both a sheep dip and a jetting fluid for the control of body lice (Damalinia ovis), face lice (Linognathus ovillus), foot lice (Linognathus pedalis) and the sheep ked (Melophagus ovinus). A dip wash concentration of 1.25 ppm cyhalothrin eradicated D. ovis from sheep. A jetting fluid at a concentration of 20 ppm also eradicated D. ovis. In the field cyhalothrin was evaluated at 20 ppm as a dip wash and at 50 ppm as a jetting fluid. These field trials confirmed the ability of cyhalothrin to eradicate D. ovis from short and long-woolled sheep. The sucking lice, L. ovillus and L. pedalis, were also found to be very susceptible to cyhalothrin at a dip wash concentration of 20 ppm, but it was necessary to treat the predilection sites infested by these parasites twice within a 3-week period to achieve their eradication. Sheep ked (M. ovinus) were eradicated from an infected flock of sheep after plunge dipping in cyhalothrin at 20 ppm.

  4. Malaria transmission in Bissau, Guinea-Bissau between 1995 and 2012

    DEFF Research Database (Denmark)

    Ursing, Johan; Rombo, Lars; Rodrigues, Amabelia

    2014-01-01

    of insecticide treated bed nets (ITN) amongst children chloroquine treatment regime was routinely used until artemisinin based combination therapy (ACT) was introduced in 2008. Long lasting insecticide treated bed nets (LLIN) were distributed in 2011. By 2012 there was 1 net...... (1995-2012) were considered incident cases. The mean annual malaria incidence per thousand children in 1995-1997, 1999-2003, 2007, 2011, 2012 were as follows; age use...... per 2 people and 97% usage. All-cause mortality decreased from post-war peaks in 1999 until 2012 in all age groups and was not negatively affected by malaria resurgence. CONCLUSION: The cause of decreasing malaria incidence (1995-2007) was probably multifactorial and coincident with the use...

  5. Insecticide-treated nets for the prevention of malaria in pregnancy: a systematic review of randomised controlled trials.

    Directory of Open Access Journals (Sweden)

    Carol Gamble

    2007-03-01

    Full Text Available BACKGROUND: Protection from malaria with insecticide-treated bednets (ITNs during pregnancy is widely advocated, but evidence of benefit has been inconsistent. We undertook a systematic review of randomised trials. METHODS AND FINDINGS: Three cluster-randomised and two individually randomised trials met the inclusion criteria; four from Africa (n = 6,418 and one from Thailand (n = 223. In Africa, ITNs compared to no nets increased mean birth weight by 55 g (95% confidence interval [CI] 21-88, reduced low birth weight by 23% (relative risk [RR] 0.77, 95% CI 0.61-0.98, and reduced miscarriages/stillbirths by 33% (RR 0.67, 0.47-0.97 in the first few pregnancies. Placental parasitaemia was reduced by 23% in all gravidae (RR 0.77, 0.66-0.90. The effects were apparent in the cluster-randomised trials and the one individually randomised trial in Africa. The trial in Thailand, which randomised individuals to ITNs or untreated nets, showed reductions in anaemia and fetal loss in all gravidae, but not reductions in clinical malaria or low birth weight. CONCLUSIONS: ITNs used throughout pregnancy or from mid-pregnancy onwards have a beneficial impact on pregnancy outcome in malaria-endemic Africa in the first few pregnancies. The potential impact of ITNs in pregnant women and their newborns in malaria regions outside Africa requires further research.

  6. A comparison of the fate and effects of two pyrethroid insecticides (lambda-cyhalothrin and cypermethrin) in pond mesocosms.

    Science.gov (United States)

    Farmer, D; Hill, I R; Maund, S J

    1995-08-01

    : The fate and effects of two pyrethroid insecticides (lambda-cyhalothrin and cypermethrin) were investigated in replicated 25 m(3) pond mesocosms. Three pesticide treatments which simulated spray drift deposition were examined: 0.7 g a.i. ha(-1) cypermethrin and 0.17 and 1.7 g a.i. ha(-1) lambda-cyhalothrin. Based on the use rate and pesticidal activity of the chemicals, the cypermethrin and lower lambda-cyhalothrin rates were approximately equivalent. After applications, pyrethroid residues in the water column declined rapidly. Treatment-related effects were observed on some macroinvertebrate taxa, most notably the Asellidae and Gammaridae. Surfacedwelling insects also suffered initial knock-down, particularly in the 1.7 g a.i. ha(-1) lambda-cyhalothrin treatment, but there was recovery after the spray period. No adverse effects occurred on algae, macrophytes or zooplankton, but there were occasional enhancements (e.g. algal biomass and abundances of copepod nauplii and Rotifera) which may have been indirect effects. An overall comparison of the treatments indicated that the higher lambda-cyhalothrin rate had the greatest effects, whilst the cypermethrin application had a somewhat greater impact than the lower lambda-cyhalothrin treatment rate (due to effects on peracarid crustaceans). The study indicated that should spray drift occur at the levels expected for either pyrethroid's normal use patterns, potential impacts on natural aquatic ecosystems would be minor and transient.

  7. Effect of Beauveria bassiana infection on detoxification enzyme transcription in pyrethroid resistant Anopheles arabiensis: a preliminary study.

    Science.gov (United States)

    Nardini, Luisa; Blanford, Simon; Coetzee, Maureen; Koekemoer, Lizette L

    2014-04-01

    Fungal biopesticides are of great interest to vector control scientists as they provide a novel and environmentally friendly alternative to insecticide use. The aim of this study was to determine whether genes associated with pyrethroid resistance in Anopheles arabiensis from Sudan and South Africa are further induced following exposure to the entomopathogenic fungus, Beauveria bassiana (strain GHA). Following B. bassiana bioassays, RNA was extracted from infected mosquitoes and the transcription of four important insecticide resistance genes, CYP9L1, CYP6M2 and CYP4G16 (cytochrome P450s) and TPX4 (thioredoxin peroxidase) was investigated using quantitative real-time PCR. Beauveria bassiana strain GHA was highly infective and virulent against An. arabiensis. In terms of changes in gene transcription, overall, the fold change (FC) values for each gene in the infected strains, were lower than 1.5. The FC values of CYP9L1, CYP6M2 and TPX4, were significantly lower than the FC values of the same genes in uninfected resistant An. arabiensis. These data suggest that B. bassiana does not enhance the pyrethroid resistant phenotype on a molecular level as the two An. arabiensis strains used here, with different pyrethroid resistance mechanisms, revealed no increase in pre-existing metabolic transcripts. This supports the fact that fungal pathogens are suitable candidates for vector control, particularly with regard to the development of novel vector control strategies.

  8. Baseline susceptibility to pyrethroid and organophosphate insecticides in two old world sand fly species (diptera: psychodidae)

    Science.gov (United States)

    A study was conducted with support from the Department of Defense’s Deployed Warfighter Protection (DWFP) Program to evaluate the susceptibility of two old world sand fly species, Phlebotomus papatasi and P. duboscqi, to a number of commonly used pyrethroid and organophosphate insecticides. A simpl...

  9. Polymer-coated magnetic nanospheres for preconcentration of organochlorine and pyrethroid pesticides prior to their determination by gas chromatography with electron capture detection

    International Nuclear Information System (INIS)

    Yang, Genggeng; He, Zeying; Liu, Xueke; Liu, Chang; Zhan, Jing; Liu, Donghui; Wang, Peng; Zhou, Zhiqiang

    2016-01-01

    Magnetic polymer nanospheres were prepared and used as adsorbents for the extraction of organochlorine and pyrethroid pesticides from water samples. The adsorbents were synthesized by mini emulsion polymerization of N-vinylimidazole and divinylbenzene and simultaneous encapsulation of oleic acid-coated Fe 3 O 4 nanoparticles. Following desorption with ethyl acetate, the target analytes β-hexachlorocyclohexane, δ-hexachlorocyclohexane, p,p’-DDE, heptachlor, trans-chlordan, cis-chlordan, bifenthrin, β-cypermethrin, δ-methrin, λ-cyhalothrin and esfenvalerate were determined by gas chromatography with electron capture detection. Desorption conditions, extraction times and sample volume were screened by Plackett-Burman design and optimized by Box-Behnken design. Under the optimum conditions, the organochlorines can be quantified in the 20 to 400 ng L −1 concentration range, and the pyrethroids in the 400 to 4000 ng L −1 concentration range. The recoveries of organochlorines and pyrethroids from spiked real water samples are between 77.6 and 97.3 %, with relative standard deviations between 0.9 and 10.0 %. The method for magnetic solid phase extraction described here is fast, simple and friendly to the environment. (author)

  10. Effect of the use of insecticide-treated bed nets on birth outcomes ...

    African Journals Online (AJOL)

    Each year in sub-Saharan Africa, where 80 to 90% of the world's malaria cases occur, approximately 19 to 24 million .... in winning the battle against malaria.16 .... tion group and given ITNs prepared in ... two doses of tetanus toxoid vaccine.

  11. Wash-resistance of pirimiphos-methyl insecticide treatments of window screens and eave baffles for killing indoor-feeding malaria vector mosquitoes: an experimental hut trial, South East of Zambia.

    Science.gov (United States)

    Chinula, Dingani; Sikaala, Chadwick H; Chanda-Kapata, Pascalina; Hamainza, Busiku; Zulu, Reuben; Reimer, Lisa; Chizema, Elizabeth; Kiware, Samson; Okumu, Fredros O; Killeen, Gerry

    2018-04-13

    The effectiveness of long-lasting insecticidal-treated nets (LLINs) and indoor residual spraying (IRS) for malaria control is threatened by resistance to commonly used pyrethroid insecticides. Rotations, mosaics, combinations, or mixtures of insecticides from different complementary classes are recommended by the World Health Organization (WHO) for mitigating against resistance, but many of the alternatives to pyrethroids are prohibitively expensive to apply in large national IRS campaigns. Recent evaluations of window screens and eave baffles (WSEBs) treated with pirimiphos-methyl (PM), to selectively target insecticides inside houses, demonstrated malaria vector mortality rates equivalent or superior to IRS. However, the durability of efficacy when co-applied with polyacrylate-binding agents (BA) remains to be established. This study evaluated whether WSEBs, co-treated with PM and BA have comparable wash resistance to LLINs and might therefore remain insecticidal for years rather than months. WHO-recommended wire ball assays of insecticidal efficacy were applied to polyester netting treated with or without BA plus 1 or 2 g/sq m PM. They were then tested for insecticidal efficacy using fully susceptible insectary-reared Anopheles gambiae mosquitoes, following 0, 5, 10, 15, then 20 washes as per WHO-recommended protocols for accelerated ageing of LLINs. This was followed by a small-scale field trial in experimental huts to measure malaria vector mortality achieved by polyester netting WSEBs treated with BA and 2 g/sq m PM after 0, 10 and then 20 standardized washes, alongside recently applied IRS using PM. Co-treatment with BA and either dosage of PM remained insecticidal over 20 washes in the laboratory. In experimental huts, WSEBs treated with PM plus BA consistently killed similar proportions of Anopheles arabiensis mosquitoes to PM-IRS (both consistently ≥ 94%), even after 20 washes. Co-treating WSEBs with both PM and BA results in wash

  12. Trends in DDT and pyrethroid resistance in Anopheles gambiae s.s. populations from urban and agro-industrial settings in southern Cameroon

    Directory of Open Access Journals (Sweden)

    Kerah-Hinzoumbé Clément

    2009-09-01

    Full Text Available Abstract Background Pyrethroid insecticides are widely used for insect pest control in Cameroon. In certain insect species, particularly the malaria vector Anopheles gambiae, resistance to this class of insecticides is a source of great concern and needs to be monitored in order to sustain the efficacy of vector control operations in the fields. This study highlights trends in DDT and pyrethroid resistance in wild An. gambiae populations from South Cameroon. Methods Mosquitoes were collected between 2001 and 2007 in four sites in South Cameroon, where insecticides are used for agricultural or personal protection purposes. Insecticide use was documented in each site by interviewing residents. Batches of 2-4 days old adult female mosquitoes reared from larval collections were tested for susceptibility to DDT, permethrin and deltamethrin using standard WHO procedures. Control, dead and survivors mosquitoes from bioassays were identified by PCR-RFLP and characterized for the kdr mutations using either the AS-PCR or the HOLA method. Results Four chemical insecticide groups were cited in the study sites: organochlorines, organophosphates, carbamates and pyrethroids. These chemicals were used for personal, crop or wood protection. In the four An. gambiae populations tested, significant variation in resistance levels, molecular forms composition and kdr frequencies were recorded in the time span of the study. Increases in DDT and pyrethroid resistance, as observed in most areas, were generally associated with an increase in the relative frequency of the S molecular form carrying the kdr mutations at higher frequencies. In Mangoum, however, where only the S form was present, a significant increase in the frequency of kdr alleles between 2003 to 2007 diverged with a decrease of the level of resistance to DDT and pyrethroids. Analyses of the kdr frequencies in dead and surviving mosquitoes showed partial correlation between the kdr genotypes and resistance

  13. Characterization of cell-free extracts from fenpropathrin-degrading strain Bacillus cereus ZH-3 and its potential for bioremediation of pyrethroid-contaminated soils.

    Science.gov (United States)

    Liu, Jie; Huang, Wenwen; Han, Haitao; She, Changchun; Zhong, Guohua

    2015-08-01

    Synthetic pyrethroid fenpropathrin has received increasing attention because of its environmental contamination and toxic effects on non-target organisms including human beings. Here we report the degradation characteristics of cell-free extracts from fenpropathrin-degrading strain Bacillus cereus ZH-3 and its potential for pyrethroid bioremediation in soils. 50mg·L(-1) of fenpropathrin was decreased to 20.6mg·L(-1) by the enzymatic extracts (869.4mg·L(-1)) within 30min. Kinetic constants Km and Vm were determined to be 1006.7nmol·L(-1) and 56.8nmol·min(-1), respectively. Degradation products were identified as 3-phenoxybenzaldehyde, α-hydroxy-3-phenoxy-benzeneacetonitrile and phenol by gas chromatography-mass spectrometry (GC-MS). In addition to degradation of fenpropathrin, the cell-free extracts could degrade other pyrethroids including beta-cypermethrin, cyfluthrin, deltamethrin and cypermethrin. Additionally, the reaction conditions were optimized. In the sterile and non-sterile soils, 50mg·kg(-1) of fenpropathrin was reduced to 15.3 and 13.9mg·L(-1) in 1d, respectively. Sprayed 100 and 300mg·kg(-1) of fenpropathrin emulsifiable concentrate (EC), up to 84.6% and 92.1% of soil fenpropathrin were removed from soils within 7d, respectively. Taken together, our results depict the biodegradation characteristics of cell-free extracts from B. cereus ZH-3, highlight its promising potential in bioremediation of pyrethroid-contaminated soils and also provide new insights into the utilization of degrading microbes. Copyright © 2015. Published by Elsevier B.V.

  14. Comparing Biofouling Control Treatments for Use on Aquaculture Nets

    Directory of Open Access Journals (Sweden)

    Geoffrey Swain

    2014-12-01

    Full Text Available Test panels comprised of uncoated, copper coated and silicone coated 7/8'' (22 mm mesh knitted nylon net were evaluated to compare their properties and the effectiveness to prevent biofouling. This paper describes test procedures that were developed to quantify the performance in terms of antifouling, cleanability, drag and cost. The copper treatment was the most effective at controlling fouling, however, the silicone treated nets were the easiest to clean. The drag forces on the net were a function of twine diameter, twine roughness and fouling. After immersion, the uncoated nets had the most drag followed by the silicone and copper treatments. The cost of applying silicone to nets is high; however, improved formulations may provide a non-toxic alternative to control fouling.

  15. Novel cytochrome P450 (CYP6D1) and voltage sensitive sodium channel (Vssc) alleles of the house fly (Musca domestica) and their roles in pyrethroid resistance.

    Science.gov (United States)

    Pan, Jing; Yang, Chan; Liu, Yan; Gao, Qi; Li, Mei; Qiu, Xinghui

    2018-04-01

    The house fly Musca domestica is an important disease vector. Point mutation-mediated target-site insensitivity of the voltage sensitive sodium channel (VSSC) and increased detoxification mediated by cytochrome P450 (CYP6D1) overexpression have been characterized as two major mechanisms of pyrethroid resistance. In this study, genetic mutations in the Vssc and CYP6D1 genes and their contribution to pyrethroid resistance were investigated. Twelve lines of house flies homozygous for four genotypes were established. House flies carrying the VSSC 1014F mutation and overexpressing CYP6D1 had higher resistance to pyrethroids than those carrying 1014F alone. The presence of the 15-bp insert in the promoter region of the CYP6D1 gene did not necessarily result in a significant increase in CYP6D1 mRNA and pyrethroid resistance levels. A novel Vssc allele carrying two mutations (G1924D and G2004S) in combination with the classic 1014F and a novel CYP6D1 allele that is very similar to CYP6D1v1 were identified in Chinese house flies. This work demonstrates the effect of genetic mutations in CYP6D1 and Vssc on the susceptibility of house flies to pyrethroids, and verifies that 15-bp insert-containing CYP6D1 alleles have a single origin. These findings offer insights into the evolution of insecticide resistance and have implications for house fly control. © 2017 Society of Chemical Industry. © 2017 Society of Chemical Industry.

  16. Using multiple bed load measurements: Toward the identification of bed dilation and contraction in gravel-bed rivers

    Science.gov (United States)

    Marquis, G. A.; Roy, A. G.

    2012-02-01

    This study examines bed load transport processes in a small gravel-bed river (Béard Creek, Québec) using three complementary methods: bed elevation changes between successive floods, bed activity surveys using tags inserted into the bed, and bed load transport rates from bed load traps. The analysis of 20 flood events capable of mobilizing bed material led to the identification of divergent results among the methods. In particular, bed elevation changes were not consistent with the bed activity surveys. In many cases, bed elevation changes were significant (1 to 2 times the D50) even if the bed surface had not been activated during the flood, leading to the identification of processes of bed dilation and contraction that occurred over 10% to 40% of the bed surface. These dynamics of the river bed prevent accurate derivation of bed load transport rates from topographic changes, especially for low magnitude floods. This paper discusses the mechanisms that could explain the dilation and contraction of particles within the bed and their implications in fluvial dynamics. Bed contraction seems to be the result of the winnowing of the fine sediments under very low gravel transport. Bed dilation seems to occur on patches of the bed at the threshold of motion where various processes such as fine sediment infiltration lead to the maintenance of a larger sediment framework volume. Both processes are also influenced by flood history and the initial local bed state and in turn may have a significant impact on sediment transport and morphological changes in gravel-bed rivers.

  17. Concentrations versus amounts of biomarkers in urine: a comparison of approaches to assess pyrethroid exposure

    Directory of Open Access Journals (Sweden)

    Bouchard Michèle

    2008-11-01

    Full Text Available Abstract Background Assessment of human exposure to non-persistent pesticides such as pyrethroids is often based on urinary biomarker measurements. Urinary metabolite levels of these pesticides are usually reported in volume-weighted concentrations or creatinine-adjusted concentrations measured in spot urine samples. It is known that these units are subject to intra- and inter-individual variations. This research aimed at studying the impact of these variations on the assessment of pyrethroid absorbed doses at individual and population levels. Methods Using data obtained from various adult and infantile populations, the intra and inter-individual variability in the urinary flow rate and creatinine excretion rate was first estimated. Individual absorbed doses were then calculated using volume-weighted or creatinine-adjusted concentrations according to published approaches and compared to those estimated from the amounts of biomarkers excreted in 15- or 24-h urine collections, the latter serving as a benchmark unit. The effect of the units of measurements (volume-weighted or creatinine adjusted concentrations or 24-h amounts on results of the comparison of pyrethroid biomarker levels between two populations was also evaluated. Results Estimation of daily absorbed doses of permethrin from volume-weighted or creatinine-adjusted concentrations of biomarkers was found to potentially lead to substantial under or overestimation when compared to doses reconstructed directly from amounts excreted in urine during a given period of time (-70 to +573% and -83 to +167%, respectively. It was also shown that the variability in creatinine excretion rate and urinary flow rate may introduce a bias in the case of between population comparisons. Conclusion The unit chosen to express biomonitoring data may influence the validity of estimated individual absorbed dose as well as the outcome of between population comparisons.

  18. Assessing the effects of Aedes aegypti kdr mutations on pyrethroid resistance and its fitness cost.

    Directory of Open Access Journals (Sweden)

    Luiz Paulo Brito

    Full Text Available Pyrethroids are the most used insecticide class worldwide. They target the voltage gated sodium channel (NaV, inducing the knockdown effect. In Aedes aegypti, the main dengue vector, the AaNaV substitutions Val1016Ile and Phe1534Cys are the most important knockdown resistance (kdr mutations. We evaluated the fitness cost of these kdr mutations related to distinct aspects of development and reproduction, in the absence of any other major resistance mechanism. To accomplish this, we initially set up 68 crosses with mosquitoes from a natural population. Allele-specific PCR revealed that one couple, the one originating the CIT-32 strain, had both parents homozygous for both kdr mutations. However, this pyrethroid resistant strain also presented high levels of detoxifying enzymes, which synergistically account for resistance, as revealed by biological and biochemical assays. Therefore, we carried out backcrosses between CIT-32 and Rockefeller (an insecticide susceptible strain for eight generations in order to bring the kdr mutation into a susceptible genetic background. This new strain, named Rock-kdr, was highly resistant to pyrethroid and presented reduced alteration of detoxifying activity. Fitness of the Rock-kdr was then evaluated in comparison with Rockefeller. In this strain, larval development took longer, adults had an increased locomotor activity, fewer females laid eggs, and produced a lower number of eggs. Under an inter-strain competition scenario, the Rock-kdr larvae developed even slower. Moreover, when Rockefeller and Rock-kdr were reared together in population cage experiments during 15 generations in absence of insecticide, the mutant allele decreased in frequency. These results strongly suggest that the Ae. aegypti kdr mutations have a high fitness cost. Therefore, enhanced surveillance for resistance should be priority in localities where the kdr mutation is found before new adaptive alleles can be selected for diminishing the

  19. A Locomotor Deficit Induced by Sublethal Doses of Pyrethroid and Neonicotinoid Insecticides in the Honeybee Apis mellifera.

    Science.gov (United States)

    Charreton, Mercédès; Decourtye, Axel; Henry, Mickaël; Rodet, Guy; Sandoz, Jean-Christophe; Charnet, Pierre; Collet, Claude

    2015-01-01

    The toxicity of pesticides used in agriculture towards non-targeted organisms and especially pollinators has recently drawn the attention from a broad scientific community. Increased honeybee mortality observed worldwide certainly contributes to this interest. The potential role of several neurotoxic insecticides in triggering or potentiating honeybee mortality was considered, in particular phenylpyrazoles and neonicotinoids, given that they are widely used and highly toxic for insects. Along with their ability to kill insects at lethal doses, they can compromise survival at sublethal doses by producing subtle deleterious effects. In this study, we compared the bee's locomotor ability, which is crucial for many tasks within the hive (e.g. cleaning brood cells, feeding larvae…), before and after an acute sublethal exposure to one insecticide belonging to the two insecticide classes, fipronil and thiamethoxam. Additionally, we examined the locomotor ability after exposure to pyrethroids, an older chemical insecticide class still widely used and known to be highly toxic to bees as well. Our study focused on young bees (day 1 after emergence) since (i) few studies are available on locomotion at this stage and (ii) in recent years, pesticides have been reported to accumulate in different hive matrices, where young bees undergo their early development. At sublethal doses (SLD48h, i.e. causing no mortality at 48 h), three pyrethroids, namely cypermethrin (2.5 ng/bee), tetramethrin (70 ng/bee), tau-fluvalinate (33 ng/bee) and the neonicotinoid thiamethoxam (3.8 ng/bee) caused a locomotor deficit in honeybees. While the SLD48h of fipronil (a phenylpyrazole, 0.5 ng/bee) had no measurable effect on locomotion, we observed high mortality several days after exposure, an effect that was not observed with the other insecticides. Although locomotor deficits observed in the sublethal range of pyrethroids and thiamethoxam would suggest deleterious effects in the field, the case of

  20. A Locomotor Deficit Induced by Sublethal Doses of Pyrethroid and Neonicotinoid Insecticides in the Honeybee Apis mellifera.

    Directory of Open Access Journals (Sweden)

    Mercédès Charreton

    Full Text Available The toxicity of pesticides used in agriculture towards non-targeted organisms and especially pollinators has recently drawn the attention from a broad scientific community. Increased honeybee mortality observed worldwide certainly contributes to this interest. The potential role of several neurotoxic insecticides in triggering or potentiating honeybee mortality was considered, in particular phenylpyrazoles and neonicotinoids, given that they are widely used and highly toxic for insects. Along with their ability to kill insects at lethal doses, they can compromise survival at sublethal doses by producing subtle deleterious effects. In this study, we compared the bee's locomotor ability, which is crucial for many tasks within the hive (e.g. cleaning brood cells, feeding larvae…, before and after an acute sublethal exposure to one insecticide belonging to the two insecticide classes, fipronil and thiamethoxam. Additionally, we examined the locomotor ability after exposure to pyrethroids, an older chemical insecticide class still widely used and known to be highly toxic to bees as well. Our study focused on young bees (day 1 after emergence since (i few studies are available on locomotion at this stage and (ii in recent years, pesticides have been reported to accumulate in different hive matrices, where young bees undergo their early development. At sublethal doses (SLD48h, i.e. causing no mortality at 48 h, three pyrethroids, namely cypermethrin (2.5 ng/bee, tetramethrin (70 ng/bee, tau-fluvalinate (33 ng/bee and the neonicotinoid thiamethoxam (3.8 ng/bee caused a locomotor deficit in honeybees. While the SLD48h of fipronil (a phenylpyrazole, 0.5 ng/bee had no measurable effect on locomotion, we observed high mortality several days after exposure, an effect that was not observed with the other insecticides. Although locomotor deficits observed in the sublethal range of pyrethroids and thiamethoxam would suggest deleterious effects in the field

  1. Divertor plate concept with carbon based armour for NET

    International Nuclear Information System (INIS)

    Moons, F.; Howard, R.; Kneringer, G.; Stickler, R.

    1989-01-01

    A series of tests has been performed on simulated divertor elements for NET at the JET neutral beam injector test bed. The test section consisted of a water cooled main structure, the surface of which was protected with a carbon based armour in the form of tiles. The scope of these was to study the thermal behaviour of mechanically attached tiles with the use of an intermediate soft carbon layer to improve the thermal contact under divertor relevant conditions. (author). 4 refs.; 4 figs.; 1 tab

  2. Assessment of the Efficacy of Deltamethrin Impregnated Bed Nets ...

    African Journals Online (AJOL)

    The impact of deltamethrin treated bednets and walls were assessed on school children aged 12-18 years, in a community secondary school in Ono, Nigeria. Children with body weights of 45-60kg were given 2 tablets of fansidar to clear parasites in their system while those with body weights of 60kg and above were given ...

  3. Effect of untreated bed nets on blood-fed Phlebotomus argentipes in kala-azar endemic foci in Nepal and India.

    Science.gov (United States)

    Picado, Albert; Kumar, Vijay; Das, Murari; Burniston, Ian; Roy, Lalita; Suman, Rijal; Dinesh, Diwakar; Coosemans, Marc; Sundar, Shyam; Shreekant, Kesari; Boelaert, Marleen; Davies, Clive; Cameron, Mary

    2009-12-01

    Observational studies in the Indian subcontinent have shown that untreated nets may be protective against visceral leishmaniasis (VL). In this study, we evaluated the effect of untreated nets on the blood feeding rates of Phlebotomus argentipes as well as the human blood index (HBI) in VL endemic villages in India and Nepal. The study had a 'before and after intervention' design in 58 households in six clusters. The use of untreated nets reduced the blood feeding rate by 85% (95% CI 76.5-91.1%) and the HBI by 42.2% (95% CI 11.1-62.5%). These results provide circumstantial evidence that untreated nets may provide some degree of personal protection against sand fly bites.

  4. Characterization of a Pyrethroid-Degrading Pseudomonas fulva Strain P31 and Biochemical Degradation Pathway of D-Phenothrin

    Directory of Open Access Journals (Sweden)

    Jingjing Yang

    2018-05-01

    Full Text Available D-phenothrin is one of the most popular pyrethroid insecticides for its broad spectrum and high insecticidal activity. However, continuous use of D-phenothrin has resulted in serious environmental contamination and raised public concern about its impact on human health. Biodegradation of D-phenothrin has never been investigated and its metabolic behaviors remain unknown. Here, a novel bacterial strain P31 was isolated from active sludge, which completely degraded (100% D-phenothrin at 50 mg⋅L-1 in 72 h. Based on the morphology, 16S rRNA gene and Biolog tests, the strain was identified as Pseudomonas fulva. Biodegradation conditions were optimized as 29.5°C and pH 7.3 by utilizing response surface methodology. Strain P31 depicted high tolerance and strong D-phenothrin degradation ability through hydrolysis pathway. Strain P31 degraded D-phenothrin at inhibition constant (Ki of 482.1673 mg⋅L-1 and maximum specific degradation constant (qmax of 0.0455 h-1 whereas critical inhibitor concentration remained as 41.1189 mg⋅L-1. The 3-Phenoxybenzaldehyde and 1,2-benzenedicarboxylic butyl dacyl ester were identified as the major intermediate metabolites of D-phenothrin degradation pathway through high-performance liquid chromatography and gas chromatography-mass spectrometry. Bioaugmentation of D-phenothrin-contaminated soils with strain P31 dramatically enhanced its degradation, and over 75% of D-phenothrin was removed from soils within 10 days. Moreover, the strain illustrated a remarkable capacity to degrade other synthetic pyrethroids, including permethrin, cyhalothrin, β-cypermethrin, deltamethrin, fenpropathrin, and bifenthrin, exhibiting great potential in bioremediation of pyrethroid-contaminated environment.

  5. Fenpropathrin biodegradation pathway in Bacillus sp. DG-02 and its potential for bioremediation of pyrethroid-contaminated soils.

    Science.gov (United States)

    Chen, Shaohua; Chang, Changqing; Deng, Yinyue; An, Shuwen; Dong, Yi Hu; Zhou, Jianuan; Hu, Meiying; Zhong, Guohua; Zhang, Lian-Hui

    2014-03-12

    The widely used insecticide fenpropathrin in agriculture has become a public concern because of its heavy environmental contamination and toxic effects on mammals, yet little is known about the kinetic and metabolic behaviors of this pesticide. This study reports the degradation kinetics and metabolic pathway of fenpropathrin in Bacillus sp. DG-02, previously isolated from the pyrethroid-manufacturing wastewater treatment system. Up to 93.3% of 50 mg L(-1) fenpropathrin was degraded by Bacillus sp. DG-02 within 72 h, and the degradation rate parameters qmax, Ks, and Ki were determined to be 0.05 h(-1), 9.0 mg L(-1), and 694.8 mg L(-1), respectively. Analysis of the degradation products by gas chromatography-mass spectrometry led to identification of seven metabolites of fenpropathrin, which suggest that fenpropathrin could be degraded first by cleavage of its carboxylester linkage and diaryl bond, followed by degradation of the aromatic ring and subsequent metabolism. In addition to degradation of fenpropathrin, this strain was also found to be capable of degrading a wide range of synthetic pyrethroids including deltamethrin, λ-cyhalothrin, β-cypermethrin, β-cyfluthrin, bifenthrin, and permethrin, which are also widely used insecticides with environmental contamination problems with the degradation process following the first-order kinetic model. Bioaugmentation of fenpropathrin-contaminated soils with strain DG-02 significantly enhanced the disappearance rate of fenpropathrin, and its half-life was sharply reduced in the soils. Taken together, these results depict the biodegradation mechanisms of fenpropathrin and also highlight the promising potentials of Bacillus sp. DG-02 in bioremediation of pyrethroid-contaminated soils.

  6. Analysing deltamethrin susceptibility and pyrethroid esterase activity variations in sylvatic and domestic Triatoma infestans at the embryonic stage

    Directory of Open Access Journals (Sweden)

    Pablo Luis Santo-Orihuela

    2013-12-01

    Full Text Available The aim of the present work was to study the deltamethrin susceptibility of eggs from Triatoma infestans populations and the contribution of pyrethroid esterases to deltamethrin degradation. Insects were collected from sylvatic areas, including Veinte de Octubre and Kirus-Mayu (Bolivia and from domiciliary areas, including El Palmar (Bolivia and La Pista (Argentina. Deltamethrin susceptibility was determined by dose-response bioassays. Serial dilutions of deltamethrin (0.0005-1 mg/mL were topically applied to 12-day-old eggs. Samples from El Palmar had the highest lethal dose ratio (LDR value (44.90 compared to the susceptible reference strain (NFS, whereas the Veinte de Octubre samples had the lowest value (0.50. Pyrethroid esterases were evaluated using 7-coumaryl permethrate (7-CP on individually homogenised eggs from each population and from NFS. The El Palmar and La Pista samples contained 40.11 and 36.64 pmol/min/mg protein, respectively, and these values were statistically similar to NFS (34.92 pmol/min/mg protein and different from Kirus-Mayu and Veinte de Octubre (27.49 and 22.69 pmol/min/mg protein, respectively. The toxicological data indicate that the domestic populations were resistant to deltamethrin, but no statistical contribution of 7-CP esterases was observed. The sylvatic populations had similar LDR values to NFS, but lower 7-CP esterase activities. Moreover, this is the first study of the pyrethroid esterases on T. infestans eggs employing a specific substrate (7-CP.

  7. In-situ ionic liquid dispersive liquid-liquid microextraction using a new anion-exchange reagent combined Fe3O4 magnetic nanoparticles for determination of pyrethroid pesticides in water samples.

    Science.gov (United States)

    Fan, Chen; Liang, You; Dong, Hongqiang; Ding, Guanglong; Zhang, Wenbing; Tang, Gang; Yang, Jiale; Kong, Dandan; Wang, Deng; Cao, Yongsong

    2017-07-04

    In this work, in-situ ionic liquid dispersive liquid-liquid microextraction combined ultrasmall Fe 3 O 4 magnetic nanoparticles was developed as a kind of pretreatment method to detect pyrethroid pesticides in water samples. New anion-exchange reagents including Na[DDTC] and Na[N(CN) 2 ] were optimized for in-situ extraction pyrethroids, which showed enhanced microextraction performance. Pyrethroids were enriched by hydrophilic ionic liquid [P 4448 ][Br] (aqueous solution, 200 μL, 0.2 mmol mL -1 ) reaction in-situ with anion-exchange reagent Na[N(CN) 2 ] (aqueous solution, 300 μL, 0.2 mmol mL -1 ) forming hydrophobic ionic liquid as extraction agent in water sample (10 mL). Ultrasmall superparamagnetic iron oxide nanoparticles (30 mg) were used to collect the mixture of ionic liquid and pyrethroids followed by elution with acetonitrile. The extraction of ionic liquid strategies was unique and efficiently fulfilled with high enrichment factors (176-213) and good recoveries (80.20-117.31%). The method was successively applied to the determination of pyrethroid pesticides in different kinds of water samples with the limits of detection ranged from 0.16 to 0.21 μg L -1 . The proposed method is actually nanometer-level microextraction (average size 80 nm) with the advantages of simplicity, rapidity, and sensitivity. Copyright © 2017 Elsevier B.V. All rights reserved.

  8. In-situ treatment of acid mine waters using fluidized bed ash: Field study

    International Nuclear Information System (INIS)

    Everett, J.W.; Canty, G.A.

    1999-01-01

    A slurry of mine water and fluidized bed ash (FBA) was injected into an abandoned coal mine in eastern Oklahoma in July 1997. Oil-field technology was used to inject 1.8 Gg (418 tons) of FBA through five wells in 15 hours. Prior to injection the seep water had a pH of 4.4, was net acidic (acidity over 400 mg/L as CaCO 3 ), and had relatively high metal concentrations (in mg/L: Fe-200; Mn-7; and Al-6). After injection, during the period of effective treatment, the seep water had a pH above 6.0, less net acidity, and had lower metals concentrations (in mg/L: Fe-120; Mn-5; and Al-< PQL). When the treated seep water exited the mine, the dissolved metals oxidized and hydrolyzed. As the metals precipitated, the alkalinity introduced by the FBA was consumed and the pH dropped. However, the seep water characteristics upon entering the receiving stream were improved, compared to pre-injection. The resulting seep water quality is such that it is more amenable to further treatment by passive treatment methods, such as anoxic limestone drains or wetlands. Alkaline injection is a finite treatment process. Eventually, the added alkalinity is exhausted, at which time the seep returns to pre-injection conditions, necessitating another injection of ash. For the study discussed in this paper, the treatment lasted approximately 15 months. While the amount of alkalinity added to the mine could have potentially treated much more than a year's volume of seep water, it is believed that much of the injected alkalinity was unavailable in backwater areas in the mine. This alkalinity contributed little, if any, to the treatment of water flowing through the mine. Mine hydrology, especially during injection are crucial to treatment longevity

  9. Expression of the cytochrome P450s, CYP6P3 and CYP6M2 are significantly elevated in multiple pyrethroid resistant populations of Anopheles gambiae s.s. from Southern Benin and Nigeria

    Directory of Open Access Journals (Sweden)

    Ranson Hilary

    2008-11-01

    Full Text Available Abstract Background Insecticide resistance in Anopheles mosquitoes is threatening the success of malaria control programmes. This is particularly true in Benin where pyrethroid resistance has been linked to the failure of insecticide treated bed nets. The role of mutations in the insecticide target sites in conferring resistance has been clearly established. In this study, the contribution of other potential resistance mechanisms was investigated in Anopheles gambiae s.s. from a number of localities in Southern Benin and Nigeria. The mosquitoes were sampled from a variety of breeding sites in a preliminary attempt to investigate the role of contamination of mosquito breeding sites in selecting for resistance in adult mosquitoes. Results All mosquitoes sampled belonged to the M form of An. gambiae s.s. There were high levels of permethrin resistance in an agricultural area (Akron and an urban area (Gbedjromede, low levels of resistance in mosquito samples from an oil contaminated site (Ojoo and complete susceptibility in the rural Orogun location. The target site mutation kdrW was detected at high levels in two of the populations (Akron f = 0.86 and Gbedjromede f = 0.84 but was not detected in Ojoo or Orogun. Microarray analysis using the Anopheles gambiae detox chip identified two P450s, CYP6P3 and CYP6M2 up regulated in all three populations, the former was expressed at particularly high levels in the Akron (12.4-fold and Ojoo (7.4-fold populations compared to the susceptible population. Additional detoxification and redox genes were also over expressed in one or more populations including two cuticular pre-cursor genes which were elevated in two of the three resistant populations. Conclusion Multiple resistance mechanisms incurred in the different breeding sites contribute to resistance to permethrin in Benin. The cytochrome P450 genes, CYP6P3 and CYP6M2 are upregulated in all three resistant populations analysed. Several additional potential

  10. Analysis of wall-packed-bed thermal interactions

    International Nuclear Information System (INIS)

    Gorbis, Z.R.; Tillack, M.S.; Tehranian, F.; Abdou, M.A.

    1995-01-01

    One of the major issues remaining for ceramic breeder blankets involves uncertainties in heat transfer and thermomechanical interactions within the breeder and multiplier regions. Particle bed forms are considered in many reactor blanket designs for both the breeder and Be multiplier. The effective thermal conductivity of beds and the wall-bed thermal conductance are still not adequately characterized, particularly under the influence of mechanical stresses. The problem is particularly serious for the wall conductance between Be and its cladding, where the uncertainty can be greater than 50%. In this work, we describe a new model for the wall-bed conductance that treats the near-wall region as a finite-width zone. The model includes an estimate of the region porosity based on the number of contact points, and the contact area for smooth surfaces. It solves the heat conduction in a near-wall unit cell. The model is verified with existing data and used to predict the range of wall conductances expected in future simulation experiments and in reactor applications. (orig.)

  11. Hiring a Pest Management Professional for Bed Bugs

    Science.gov (United States)

    If you hire someone to treat your bed bug infestation, make sure they use Integrated Pest Management (IPM) techniques, check credentials, and know they may need multiple visits, to take apart furniture, and to use vacuums, heat, and pesticides.

  12. Micronuclei induction in Rana catesbeiana tadpoles by the pyrethroid insecticide lambda-cyhalothrin

    OpenAIRE

    Campana, Marcela Alejandra; Panzeri, Ana María; Moreno, Víctor Jorge; Dulout, Fernando Noel

    2003-01-01

    Pyrethroid lambda-cyhalothrin genotoxicity was evaluated using the micronucleus test in Rana catesbeiana tadpoles. The effects of concentration and exposure time on the micronuclei frequency were studied in blood smears obtained from tadpoles exposed to four concentrations (0.02, 0.1, 0.2 and 0.4 mg/L) of the compound for 24, 48, 72 and 96 h and 8, 15, 20 and 30 days. As a positive control, tadpoles were exposed to cyclophosphamide (5 mg/L). The micronucleated cell frequency was expressed per...

  13. Scepticism towards insecticide treated mosquito nets for malaria control in rural community in north-western Tanzania.

    Science.gov (United States)

    Nnko, Soori E; Whyte, Susan R; Geissler, Wenzel P; Aagaard-Hansen, Jens

    2012-04-01

    Despite existence of effective tools for malaria control, malaria continues to be one of the leading killer diseases especially among under-five year children and pregnant women in poor rural populations of Sub Saharan Africa. In Tanzania Mainland the disease contributes to 39.4% of the total OPD attendances. In terms of mortality, malaria is known to be responsible for more than one third of deaths among children of age below 5 years and also contributes for up to one fifth of deaths among pregnant women. This paper is based on a study conducted in a rural community along the shores of Lake Victoria in Mwanza region, North-Western Tanzania. The study explores reasons for scepticism and low uptake of insecticide treated mosquito nets (ITNs) that were promoted through social marketing strategy for malaria control prior to the introduction of long lasting nets (LLN). The paper breaks from traditional approach that tend to study low uptake of health interventions in terms of structural practical constraints--cost, accessibility, everyday priorities--or in terms of cognition--insufficient knowledge of benefits e.g. ignorance of public health messages. This paper has shown that, the majority of people who could afford the prices of ITNs and who knew where to obtain the insecticides did not necessarily buy them. This suggests that, although people tend to report cost-related factors as a barrier against the use of ITNs, there are other critical concerns at work. Without underestimating the practical factors, our study have recommended to consider critical examinations of those other concerns that hinder optimal utilization of ITN for malaria control, and the basis for those concerns.

  14. A simplified high-throughput method for pyrethroid knock-down resistance (kdr) detection in Anopheles gambiae

    Science.gov (United States)

    Lynd, Amy; Ranson, Hilary; McCall, P J; Randle, Nadine P; Black, William C; Walker, Edward D; Donnelly, Martin J

    2005-01-01

    Background A single base pair mutation in the sodium channel confers knock-down resistance to pyrethroids in many insect species. Its occurrence in Anopheles mosquitoes may have important implications for malaria vector control especially considering the current trend for large scale pyrethroid-treated bednet programmes. Screening Anopheles gambiae populations for the kdr mutation has become one of the mainstays of programmes that monitor the development of insecticide resistance. The screening is commonly performed using a multiplex Polymerase Chain Reaction (PCR) which, since it is reliant on a single nucleotide polymorphism, can be unreliable. Here we present a reliable and potentially high throughput method for screening An. gambiae for the kdr mutation. Methods A Hot Ligation Oligonucleotide Assay (HOLA) was developed to detect both the East and West African kdr alleles in the homozygous and heterozygous states, and was optimized for use in low-tech developing world laboratories. Results from the HOLA were compared to results from the multiplex PCR for field and laboratory mosquito specimens to provide verification of the robustness and sensitivity of the technique. Results and Discussion The HOLA assay, developed for detection of the kdr mutation, gives a bright blue colouration for a positive result whilst negative reactions remain colourless. The results are apparent within a few minutes of adding the final substrate and can be scored by eye. Heterozygotes are scored when a sample gives a positive reaction to the susceptible probe and the kdr probe. The technique uses only basic laboratory equipment and skills and can be carried out by anyone familiar with the Enzyme-linked immunosorbent assay (ELISA) technique. A comparison to the multiplex PCR method showed that the HOLA assay was more reliable, and scoring of the plates was less ambiguous. Conclusion The method is capable of detecting both the East and West African kdr alleles in the homozygous and

  15. A simplified high-throughput method for pyrethroid knock-down resistance (kdr detection in Anopheles gambiae

    Directory of Open Access Journals (Sweden)

    Walker Edward D

    2005-03-01

    Full Text Available Abstract Background A single base pair mutation in the sodium channel confers knock-down resistance to pyrethroids in many insect species. Its occurrence in Anopheles mosquitoes may have important implications for malaria vector control especially considering the current trend for large scale pyrethroid-treated bednet programmes. Screening Anopheles gambiae populations for the kdr mutation has become one of the mainstays of programmes that monitor the development of insecticide resistance. The screening is commonly performed using a multiplex Polymerase Chain Reaction (PCR which, since it is reliant on a single nucleotide polymorphism, can be unreliable. Here we present a reliable and potentially high throughput method for screening An. gambiae for the kdr mutation. Methods A Hot Ligation Oligonucleotide Assay (HOLA was developed to detect both the East and West African kdr alleles in the homozygous and heterozygous states, and was optimized for use in low-tech developing world laboratories. Results from the HOLA were compared to results from the multiplex PCR for field and laboratory mosquito specimens to provide verification of the robustness and sensitivity of the technique. Results and Discussion The HOLA assay, developed for detection of the kdr mutation, gives a bright blue colouration for a positive result whilst negative reactions remain colourless. The results are apparent within a few minutes of adding the final substrate and can be scored by eye. Heterozygotes are scored when a sample gives a positive reaction to the susceptible probe and the kdr probe. The technique uses only basic laboratory equipment and skills and can be carried out by anyone familiar with the Enzyme-linked immunosorbent assay (ELISA technique. A comparison to the multiplex PCR method showed that the HOLA assay was more reliable, and scoring of the plates was less ambiguous. Conclusion The method is capable of detecting both the East and West African kdr alleles

  16. Synergistic potential of dillapiole-rich essential oil with synthetic pyrethroid insecticides against fall armyworm

    OpenAIRE

    Fazolin, Murilo; Estrela, Joelma Lima Vidal; Medeiros, André Fábio Monteiro; Silva, Iriana Maria da; Gomes, Luiara Paiva; Silva, Maria Samylla de Farias

    2016-01-01

    ABSTRACT: The objective of this study was to evaluate the synergy and response homogeneity of the Spodoptera frugiperda larvae population to the Piper aduncum essential oil in combination with pyrethroid insecticides (alpha-cypermethrin, beta-cypermethrin, fenpropathrin, and gamma-cyhalothrin) compared to piperonylbutoxide (PBO) as positive control. Synergism (SF) comparisons were obtained using lethal concentration (LC50) and lethal dose (LD50) ratios of insecticides individually and in thei...

  17. Triiodothyronine increases calcium loss in a bed rest antigravity model for space flight.

    Science.gov (United States)

    Smith, Steven R; Lovejoy, Jennifer C; Bray, George A; Rood, Jennifer; Most, Marlene M; Ryan, Donna H

    2008-12-01

    Bed rest has been used as a model to simulate the effects of space flight on bone metabolism. Thyroid hormones accelerate bone metabolism. Thus, supraphysiologic doses of this hormone might be used as a model to accelerate bone metabolism during bed rest and potentially simulate space flight. The objective of the study was to quantitate the changes in bone turnover after low doses of triiodothyronine (T(3)) added to short-term bed rest. Nine men and 5 women were restricted to bed rest for 28 days with their heads positioned 6 degrees below their feet. Subjects were randomly assigned to receive either placebo or oral T(3) at doses of 50 to 75 microg/d in a single-blind fashion. Calcium balance was measured over 5-day periods; and T(3), thyroxine, thyroid-stimulating hormone, immunoreactive parathyroid hormone, osteocalcin, bone alkaline phosphatase, and urinary deoxypyridinoline were measured weekly. Triiodothyronine increased 2-fold in the men and 5-fold in the women during treatment, suppressing both thyroxine and thyroid-stimulating hormone. Calcium balance was negative by 300 to 400 mg/d in the T(3)-treated volunteers, primarily because of the increased fecal loss that was not present in the placebo group. Urinary deoxypyridinoline to creatinine ratio, a marker of bone resorption, increased 60% in the placebo group during bed rest, but more than doubled in the T(3)-treated subjects (P < .01), suggesting that bone resorption was enhanced by treatment with T(3). Changes in serum osteocalcin and bone-specific alkaline phosphatase, markers of bone formation, were similar in T(3)- and placebo-treated subjects. Triiodothyronine increases bone resorption and fecal calcium loss in subjects at bed rest.

  18. The P450 CYP6Z1 confers carbamate/pyrethroid cross-resistance in a major African malaria vector beside a novel carbamate-insensitive N485I acetylcholinesterase-1 mutation.

    Science.gov (United States)

    Ibrahim, Sulaiman S; Ndula, Miranda; Riveron, Jacob M; Irving, Helen; Wondji, Charles S

    2016-07-01

    Carbamates are increasingly used for vector control notably in areas with pyrethroid resistance. However, a cross-resistance between these insecticides in major malaria vectors such as Anopheles funestus could severely limit available resistance management options. Unfortunately, the molecular basis of such cross-resistance remains uncharacterized in An. funestus, preventing effective resistance management. Here, using a genomewide transcription profiling, we revealed that metabolic resistance through upregulation of cytochrome P450 genes is driving carbamate resistance. The P450s CYP6P9a, CYP6P9b and CYP6Z1 were the most upregulated detoxification genes in the multiple resistant mosquitoes. However, in silico docking simulations predicted CYP6Z1 to metabolize both pyrethroids and carbamates, whereas CYP6P9a and CYP6P9b were predicted to metabolize only the pyrethroids. Using recombinant enzyme metabolism and inhibition assays, we demonstrated that CYP6Z1 metabolizes bendiocarb and pyrethroids, whereas CYP6P9a and CYP6P9b metabolize only the pyrethroids. Other upregulated gene families in resistant mosquitoes included several cuticular protein genes suggesting a possible reduced penetration resistance mechanism. Investigation of the target-site resistance in acetylcholinesterase 1 (ace-1) gene detected and established the association between the new N485I mutation and bendiocarb resistance (odds ratio 7.3; P resistance and improve the design of effective resistance management strategies to control this malaria vector. © 2016 The Authors. Molecular Ecology Published by John Wiley & Sons Ltd.

  19. Gas reactor international cooperative program interim report. Pebble bed reactor fuel cycle evaluation

    International Nuclear Information System (INIS)

    1978-09-01

    Nuclear fuel cycles were evaluated for the Pebble Bed Gas Cooled Reactor under development in the Federal Republic of Germany. The basic fuel cycle specified for the HTR-K and PNP is well qualified and will meet the requirements of these reactors. Twenty alternate fuel cycles are described, including high-conversion cycles, net-breeding cycles, and proliferation-resistant cycles. High-conversion cycles, which have a high probability of being successfully developed, promise a significant improvement in resource utilization. Proliferation-resistant cycles, also with a high probability of successful development, compare very favorably with those for other types of reactors. Most of the advanced cycles could be adapted to first-generation pebble bed reactors with no significant modifications

  20. Collembola and macroarthropod community responses to carbamate, organophosphate and synthetic pyrethroid insecticides: Direct and indirect effects

    Energy Technology Data Exchange (ETDEWEB)

    Frampton, Geoff K. [Ecology and Evolutionary Biology Group, School of Biological Sciences, University of Southampton, Bassett Crescent East, Southampton SO16 7PX (United Kingdom)]. E-mail: gkf@soton.ac.uk; Brink, Paul J. van den [Alterra, Wageningen University and Research Centre, P.O. Box 47, 6700 AA Wageningen (Netherlands); Wageningen University, Department of Aquatic Ecology and Water Quality Management, Wageningen University and Research Centre, P.O. Box 8080, 6700 DD Wageningen (Netherlands)

    2007-05-15

    Non-target effects on terrestrial arthropod communities of the broad-spectrum insecticides chlorpyrifos and cypermethrin and the selective insecticide pirimicarb were investigated in winter wheat fields in summer. Effects of chlorpyrifos on arthropod abundance and taxonomic richness were consistently negative whereas effects of cypermethrin were negative for predatory arthropods but positive for soil surface Collembola. Pirimicarb effects were marginal, primarily on aphids and their antagonists, with no effect on the Collembola community. Collembola-predator ratios were significantly higher following cypermethrin treatment, suggesting that cypermethrin-induced increases in collembolan abundance represent a classical resurgence. Observations in other studies suggest Collembola resurgences may be typical after synthetic pyrethroid applications. Collembola responses to insecticides differed among species, both in terms of effect magnitude and persistence, suggesting that coarse taxonomic monitoring would not adequately detect pesticide risks. These findings have implications for pesticide risk assessments and for the selection of indicator species. - Direct and indirect insecticide effects differ among closely-related arthropod taxa; resurgence of Collembola may occur widely after synthetic pyrethroid insecticide applications.

  1. Collembola and macroarthropod community responses to carbamate, organophosphate and synthetic pyrethroid insecticides: Direct and indirect effects

    International Nuclear Information System (INIS)

    Frampton, Geoff K.; Brink, Paul J. van den

    2007-01-01

    Non-target effects on terrestrial arthropod communities of the broad-spectrum insecticides chlorpyrifos and cypermethrin and the selective insecticide pirimicarb were investigated in winter wheat fields in summer. Effects of chlorpyrifos on arthropod abundance and taxonomic richness were consistently negative whereas effects of cypermethrin were negative for predatory arthropods but positive for soil surface Collembola. Pirimicarb effects were marginal, primarily on aphids and their antagonists, with no effect on the Collembola community. Collembola-predator ratios were significantly higher following cypermethrin treatment, suggesting that cypermethrin-induced increases in collembolan abundance represent a classical resurgence. Observations in other studies suggest Collembola resurgences may be typical after synthetic pyrethroid applications. Collembola responses to insecticides differed among species, both in terms of effect magnitude and persistence, suggesting that coarse taxonomic monitoring would not adequately detect pesticide risks. These findings have implications for pesticide risk assessments and for the selection of indicator species. - Direct and indirect insecticide effects differ among closely-related arthropod taxa; resurgence of Collembola may occur widely after synthetic pyrethroid insecticide applications

  2. Acidification of calf bedding reduces fly development and bacterial abundance.

    Science.gov (United States)

    Calvo, M S; Gerry, A C; McGarvey, J A; Armitage, T L; Mitloehner, F M

    2010-03-01

    Environmental stressors, such as high fly density, can affect calf well-being. Sodium bisulfate (SBS) is an acidifier that reduces the pH of flooring and bedding, creating a medium that neither bacteria nor immature flies (also known as larvae or maggots) can thrive in. Two experiments were conducted to investigate the application of SBS to a mixture of rice hull calf bedding and calf slurry (BED) to reduce house fly (Musca domestica L.) larval density and the abundance of bacteria. In experiment 1, dish pans containing 1L of BED and 3,000 house fly eggs were treated with SBS at concentrations of 0, 8.9, 17.7, and 26.5g of SBS/0.05m(2) of BED (CON, LOW, MED, and HIGH, respectively), with each SBS concentration applied to 4 individual pans (16 pans total). Reapplication of the same SBS concentrations in each pan occurred 3 times/wk throughout the 23-d trial. Larval house fly survival was significantly reduced in all pans with SBS relative to CON pans, with lowest survival rates in the MED and HIGH pans (99% and 100% reduction, respectively). The mean pH for each treatment was inversely related to the SBS concentration. In experiment 2, pans containing 1L of BED and 3,000 house fly eggs were treated with either 0g of SBS (CON), 8.9g of SBS/0.05m(2) of BED with reapplication of the acidifier 3 times/wk (SB3x), or 8.9g of SBS/0.05m(2) of BED applied only once at 48h before the end of the 8 d-trial (SB48). Larval house fly survival and bacterial concentrations were reduced (90% larval reduction and 68% bacterial reduction) in the SB3x treatment relative to the CON. Mean pH was also reduced in SB3x pans relative to CON or SB48 pans. Overall, acidification of calf BED using the acidifier SBS resulted in a reduction of bacteria and house fly larval survival. This form of fly control might be expected to reduce adult fly production and, therefore, fly-related stress in calves.

  3. Identification of mutations associated with pyrethroid resistance in the voltage-gated sodium channel of the tomato leaf miner (Tuta absoluta).

    Science.gov (United States)

    Haddi, Khalid; Berger, Madeleine; Bielza, Pablo; Cifuentes, Dina; Field, Linda M; Gorman, Kevin; Rapisarda, Carmelo; Williamson, Martin S; Bass, Chris

    2012-07-01

    The tomato leaf miner, Tuta absoluta (Lepidoptera) is a significant pest of tomatoes that has undergone a rapid expansion in its range during the past six years and is now present across Europe, North Africa and parts of Asia. One of the main means of controlling this pest is through the use of chemical insecticides. In the current study insecticide bioassays were used to determine the susceptibility of five T. absoluta strains established from field collections from Europe and Brazil to pyrethroids. High levels of resistance to λ cyhalothrin and tau fluvalinate were observed in all five strains tested. To investigate whether pyrethroid resistance was mediated by mutation of the para-type sodium channel in T. absoluta the IIS4-IIS6 region of the para gene, which contains many of the mutation sites previously shown to confer knock down (kdr)-type resistance to pyrethroids across a range of different arthropod species, was cloned and sequenced. This revealed that three kdr/super-kdr-type mutations (M918T, T929I and L1014F), were present at high frequencies within all five resistant strains at known resistance 'hot-spots'. This is the first description of these mutations together in any insect population. High-throughput DNA-based diagnostic assays were developed and used to assess the prevalence of these mutations in 27 field strains from 12 countries. Overall mutant allele frequencies were high (L1014F 0.98, M918T 0.35, T929I 0.60) and remarkably no individual was observed that did not carry kdr in combination with either M918T or T929I. The presence of these mutations at high frequency in T. absoluta populations across much of its range suggests pyrethroids are likely to be ineffective for control and supports the idea that the rapid expansion of this species over the last six years may be in part mediated by the resistance of this pest to chemical insecticides. Crown Copyright © 2012. Published by Elsevier Ltd. All rights reserved.

  4. Implications of bio-efficacy and persistence of insecticides when indoor residual spraying and long-lasting insecticide nets are combined for malaria prevention.

    Science.gov (United States)

    Okumu, Fredros O; Chipwaza, Beatrice; Madumla, Edith P; Mbeyela, Edgar; Lingamba, Geoffrey; Moore, Jason; Ntamatungro, Alex J; Kavishe, Deo R; Moore, Sarah J

    2012-11-19

    Bio-efficacy and residual activity of insecticides used for indoor residual spraying (IRS) and long-lasting insecticide nets (LLINs) were assessed against laboratory-reared and wild populations of the malaria vector, Anopheles arabiensis in south eastern Tanzania. Implications of the findings are examined in the context of potential synergies and redundancies where IRS and LLINs are combined. Bioassays were conducted monthly for six months on three LLIN types (Olyset® PermaNet 2.0®,and Icon Life®) and three IRS treatments (2 g/m2 pirimiphos-methyl, 2 g/m2 DDT and 0.03 g/m2 lambda-cyhalothrin, sprayed on mud walls and palm ceilings of experimental huts). Tests used susceptible laboratory-reared An. arabiensis exposed in cones (nets and IRS) or wire balls (nets only). Susceptibility of wild populations was assessed using WHO diagnostic concentrations and PCR for knock-down resistance (kdr) genes. IRS treatments killed ≥ 85% of mosquitoes exposed on palm ceilings and ≥ 90% of those exposed on mud walls, but up to 50% of this toxicity decayed within 1-3 months, except for DDT. By 6th month, only 7.5%, 42.5% and 30.0% of mosquitoes died when exposed to ceilings sprayed with pirimiphos-methyl, DDT or lambda-cyhalothrin respectively, while 12.5%, 36.0% and 27.5% died after exposure to mud walls sprayed with the same insecticides. In wire-ball assays, mortality decreased from 98.1% in 1st month to 92.6% in 6th month in tests on PermaNet 2.0®, from 100% to 61.1% on Icon Life® and from 93.2% to 33.3% on Olyset® nets. In cone bioassays, mortality reduced from 92.8% in 1st month to 83.3% in 6th month on PermaNet 2.0®, from 96.9% to 43.80% on Icon Life® and from 85.6% to 14.6% on Olyset®. Wild An. arabiensis were 100% susceptible to DDT, 95.8% to deltamethrin, 90.2% to lambda cyhalothrin and 95.2% susceptible to permethrin. No kdr gene mutations were detected. In bioassays where sufficient contact with treated surfaces is assured, LLINs and IRS kill high

  5. Are seagrass beds indicators of anthropogenic nutrient stress in the rocky intertidal?

    International Nuclear Information System (INIS)

    Honig, Susanna E.; Mahoney, Brenna; Glanz, Jess S.; Hughes, Brent B.

    2017-01-01

    It is well established that anthropogenic nutrient inputs harm estuarine seagrasses, but the influence of nutrients in rocky intertidal ecosystems is less clear. In this study, we investigated the effect of anthropogenic nutrient loading on Phyllospadix spp., a rocky intertidal seagrass, at local and regional scales. At sites along California, Washington, and Oregon, we demonstrated a significant, negative correlation of urban development and Phyllospadix bed thickness. These results were echoed locally along an urban gradient on the central California coast, where Phyllospadix shoot δ 15 N was negatively associated with Phyllospadix bed thickness, and experimentally, where nutrient additions in mesocosms reduced Phyllospadix shoot formation and increased epiphytic cover on Phyllospadix shoots. These findings provide evidence that coastal development can threaten rocky intertidal seagrasses through increased epiphytism. Considering that seagrasses provide vital ecosystem services, mitigating eutrophication and other factors associated with development in the rocky intertidal coastal zone should be a management priority. - Highlights: • The effect of nutrient loading on rocky intertidal seagrasses is not well studied. • Regionally, development was negatively associated with Phyllospadix bed thickness. • Locally, shoot δ 15 N was negatively associated with Phyllospadix bed thickness. • Mesocosms with added nutrients had a net loss in shoots and increased epiphytes. • Nutrient loading may have a negative effect on intertidal seagrass bed health.

  6. Numerical simulation of the knotted nylon netting panel

    Directory of Open Access Journals (Sweden)

    Li Yuwei

    2016-01-01

    Full Text Available A piece of netting, consists of the 8 8 meshes, fixed on a square frame, was simulated and the tensions and their distribution, the positions of knots and netting shape were calculated by means of MATLAB in computer. The dynamic mathematic model was developed based on lumped mass method, the netting was treated as spring-mass system, the Runge-Kutta fifth-order and sixth-order method was used to solve the differential equations for every step, then the displacement and tension of each mass point were obtained. For verify this model, the tests have been carried out in a flume tank. The results of the numerical simulation fully agreed with the experiments.

  7. Incineration of Sludge in a Fluidized-Bed Combustor

    OpenAIRE

    Chien-Song Chyang; Yu-Chi Wang

    2017-01-01

    For sludge disposal, incineration is considered to be better than direct burial because of regulations and space limitations in Taiwan. Additionally, burial after incineration can effectively prolong the lifespan of a landfill. Therefore, it is the most satisfactory method for treating sludge at present. Of the various incineration technologies, the fluidized bed incinerator is a suitable choice due to its fuel flexibility. In this work, sludge generated from industrial plants was treated in ...

  8. Production of bio-oil with low contents of copper and chlorine by fast pyrolysis of alkaline copper quaternary-treated wood in a fluidized bed reactor

    International Nuclear Information System (INIS)

    Koo, Won-Mo; Jung, Su-Hwa; Kim, Joo-Sik

    2014-01-01

    Fast pyrolysis of ACQ (alkaline copper quaternary)-treated wood was carried out in a bench-scale pyrolysis plant equipped with a fluidized bed reactor and char separation system. This study focused on the production of a bio-oil with low copper and chlorine contents, especially by adopting the fractional condensation of bio-oil using water condensers, an impact separator and an electrostatic precipitator. In addition, various analytical tools were applied to investigate the physicochemical properties of the pyrolysis products and the behavior of the preservative during pyrolysis. The bio-oil yield was maximized at 63.7 wt% at a pyrolysis temperature of 411 °C. Highly water-soluble holocellulose-derived components such as acetic acid and hydroxyacetone were mainly collected by the condensers, while lignin-derived components and levoglucosan were mainly observed in the oils collected by the impact separator and electrostatic precipitator. All the bio-oils produced in the experiments were almost free of copper and chlorine. Most copper in ACQ was transferred into the char. - Highlights: • ACQ(alkaline copper quaternary)-treated wood was successfully pyrolyzed in a bench-scale fluidized bed. • Bio-oils separately collected were different in their characteristics. • Bio-oils were free of didecyldimethylammonium chloride. • Bio oils were almost free of copper and chlorine. • The concentration of levoglucosan in a bio-oil was 24–31 wt%

  9. Biodegradation of 2,4,6-trichlorophenol in a packed-bed biofilm reactor equipped with an internal net draft tube riser for aeration and liquid circulation

    Energy Technology Data Exchange (ETDEWEB)

    Gomez-De Jesus, A.; Romano-Baez, F.J.; Leyva-Amezcua, L.; Juarez-Ramirez, C.; Ruiz-Ordaz, N. [Departamento de Ingenieria Bioquimica, Escuela Nacional de Ciencias Biologicas, IPN. Prol. Carpio y Plan de Ayala, Colonia Santo Tomas, s/n. CP 11340, Mexico, D.F. (Mexico); Galindez-Mayer, J. [Departamento de Ingenieria Bioquimica, Escuela Nacional de Ciencias Biologicas, IPN. Prol. Carpio y Plan de Ayala, Colonia Santo Tomas, s/n. CP 11340, Mexico, D.F. (Mexico)], E-mail: cmayer@encb.ipn.mx

    2009-01-30

    For the aerobic biodegradation of the fungicide and defoliant 2,4,6-trichlorophenol (2,4,6-TCP), a bench-scale packed-bed bioreactor equipped with a net draft tube riser for liquid circulation and oxygenation (PB-ALR) was constructed. To obtain a high packed-bed volume relative to the whole bioreactor volume, a high A{sub D}/A{sub R} ratio was used. Reactor's downcomer was packed with a porous support of volcanic stone fragments. PB-ALR hydrodynamics and oxygen mass transfer behavior was evaluated and compared to the observed behavior of the unpacked reactor operating as an internal airlift reactor (ALR). Overall gas holdup values {epsilon}{sub G}, and zonal oxygen mass transfer coefficients determined at various airflow rates in the PB-ALR, were higher than those obtained with the ALR. When comparing mixing time values obtained in both cases, a slight increment in mixing time was observed when reactor was operated as a PB-ALR. By using a mixed microbial community, the biofilm reactor was used to evaluate the aerobic biodegradation of 2,4,6-TCP. Three bacterial strains identified as Burkholderia sp., Burkholderia kururiensis and Stenotrophomonas sp. constituted the microbial consortium able to cometabolically degrade the 2,4,6-TCP, using phenol as primary substrate. This consortium removed 100% of phenol and near 99% of 2,4,6-TCP. Mineralization and dehalogenation of 2,4,6-TCP was evidenced by high COD removal efficiencies ({approx}95%), and by the stoichiometric release of chloride ions from the halogenated compound ({approx}80%). Finally, it was observed that the microbial consortium was also capable to metabolize 2,4,6-TCP without phenol as primary substrate, with high removal efficiencies (near 100% for 2,4,6-TCP, 92% for COD and 88% for chloride ions)

  10. Design of fluidized-bed, biological denitrification systems

    International Nuclear Information System (INIS)

    Patton, B.D.; Hancher, C.W.; Pitt, W.W.; Walker, J.F.

    1982-01-01

    Many commercial processes yield nitrate-containing wastewaters that are being discharged to the environment because traditional recovery or disposal methods are economically unacceptable. The anticipated discharge limits (i.e., 10 to 20 g (NO 3 - )/m 3 ) being considered by many states will not allow continued release of these wastewaters. The new discharge standards can be met economically by use of the fluidizied-bed, biological denitrification process. Research and development studies were conducted with 0.05-, 0.10-, 0.20-, and 0.50-m-diam fluidized-bed bioreactor systems. Feed nitrate concentrations were in the 0 to 10,000 g (NO 3 - )/m 3 range. Using the data from these studies, rate expressions were developed for the destruction of nitrate as a function of nitrate concentration. Methods were also developed for sizing bioreactors and biomass control systems. The sizing methods for fluidized-bed denitrification systems are described, and support systems such as sampling and analysis, instrumentation and controls, utilities, and bacteria storage are discussed. Operation of the process is also briefly discussed to aid the designer. Using the methods presented in this report, fluidized-bed, biological denitrification systems can be designed to treat nitrate wastewater streams

  11. Coverage of intermittent preventive treatment and insecticide-treated nets for the control of malaria during pregnancy in sub-Saharan Africa: a synthesis and meta-analysis of national survey data, 2009-11

    NARCIS (Netherlands)

    van Eijk, Anna Maria; Hill, Jenny; Larsen, David A.; Webster, Jayne; Steketee, Richard W.; Eisele, Thomas P.; ter Kuile, Feiko O.

    2013-01-01

    Pregnant women in malaria-endemic countries in sub-Saharan Africa are especially vulnerable to malaria. Recommended prevention strategies include intermittent preventive treatment with two doses of sulfadoxine-pyrimethamine and the use of insecticide-treated nets. However, progress with

  12. Status of the fluidized bed unit

    International Nuclear Information System (INIS)

    Williams, P.M.; Wade, J.F.

    1994-01-01

    Rocky Flats has a serious mixed waste problem. No technology or company has a license and available facilities to remedy this dilemma. One solution under study is to use a catalytic fluidized bed unit to destroy the combustible portion of the mixed waste. The fluidized bed thermal treatment program at Rocky Flats is building on knowledge gained over twenty years of successful development activity. The FBU has numerous technical advantages over other thermal technologies to treat Rocky Flats' mixed waste, the largest being the lower temperature (700 degrees C versus 1000 degrees C) which reduces acid corrosion and mechanical failures and obviates the need for ceramic lining. Successful demonstrations have taken place on bench, pilot, and full-scale tests using radioactive mixed wastes. The program is approaching implementation and licensing of a production-scale fluidized bed system for the safe treatment of mixed waste. The measure for success on this project is the ability to work closely with the community to jointly solve problems and respond to concerns of mixed waste treatment at Rocky Flats

  13. Infant's bed climate and bedding in the Japanese home.

    Science.gov (United States)

    Nakamura Ikeda, Rie; Fukai, Kiyoko; Okamoto Mizuno, Kazue

    2012-06-01

    to assess the bed climate of infants in their homes in Japan. descriptive, exploratory, non-experimental research design. the data were collected at the participants' homes under normal circumstances. nineteen healthy infants between the ages of two and five months. Their mothers, who joined a parenting class organised by a maternity clinic in Okayama, Japan, consented to participate in this study. we visited the infants' homes and interviewed their mothers concerning the types and use of bedding. The temperature and relative humidity of the bed climate at the back and foot of the bedding, and in the room were measured every minute for four consecutive days. Differences among the bed climates measured during three seasons (spring, summer, and autumn) were assessed by one-way analysis of variance. The bed temperature was higher for infants than for adults. No significant difference in temperature was noted among the three seasons. The bed temperature was about 36.0°C when waterproof sheets and futon mattresses for children or adult were used. The average relative humidity of the bed climate at the back was highest in summer, followed by that in spring and autumn; the differences were significant. The use of waterproof sheets and futon mattresses for children in summer increased the relative humidity to 80% or more. The use of infant beds, sunoko drainboards, and cotton futon mattresses in summer was effective in reducing the bed humidity. these results suggest that nurse-midwives should advise the parents on comfortable bed climates for their infants, as well as how to select and use bedding for them. Copyright © 2010 Elsevier Ltd. All rights reserved.

  14. Factors associated with falling in early, treated Parkinson's disease: The NET-PD LS1 cohort.

    Science.gov (United States)

    Chou, Kelvin L; Elm, Jordan J; Wielinski, Catherine L; Simon, David K; Aminoff, Michael J; Christine, Chadwick W; Liang, Grace S; Hauser, Robert A; Sudarsky, Lewis; Umeh, Chizoba C; Voss, Tiffini; Juncos, Jorge; Fang, John Y; Boyd, James T; Bodis-Wollner, Ivan; Mari, Zoltan; Morgan, John C; Wills, Anne-Marie; Lee, Stephen L; Parashos, Sotirios A

    2017-06-15

    Recognizing the factors associated with falling in Parkinson's disease (PD) would improve identification of at-risk individuals. To examine frequency of falling and baseline characteristics associated with falling in PD using the National Institute of Neurological Disorders and Stroke (NINDS) Exploratory Trials in PD Long-term Study-1 (NET-PD LS-1) dataset. The LS-1 database included 1741 early treated PD subjects (median 4year follow-up). Baseline characteristics were tested for a univariate association with post-baseline falling during the trial. Significant variables were included in a multivariable logistic regression model. A separate analysis using a negative binomial model investigated baseline factors on fall rate. 728 subjects (42%) fell during the trial, including at baseline. A baseline history of falls was the factor most associated with post-baseline falling. Men had lower odds of post-baseline falling compared to women, but for men, the probability of a post-baseline fall increased with age such that after age 70, men and women had similar odds of falling. Other baseline factors associated with a post-baseline fall and increased fall rate included the Unified PD Rating Scale (UPDRS) Activities of Daily Living (ADL) score, total functional capacity (TFC), baseline ambulatory capacity score and dopamine agonist monotherapy. Falls are common in early treated PD. The biggest risk factor for falls in PD remains a history of falling. Measures of functional ability (UPDRS ADL, TFC) and ambulatory capacity are novel clinical risk factors needing further study. A significant age by sex interaction may help to explain why age has been an inconsistent risk factor for falls in PD. Copyright © 2017 Elsevier B.V. All rights reserved.

  15. Subsidized sales of insecticide-treated nets in Afghan refugee camps demonstrate the feasibility of a transition from humanitarian aid towards sustainability

    Directory of Open Access Journals (Sweden)

    Kolaczinski Jan H

    2004-06-01

    Full Text Available Abstract Background Introducing sustainability and self-reliance is essential in chronic humanitarian emergencies before financial assistance is phased out. In Pakistan-based Afghan refugee camps, this was attempted through shifting from indoor residual spraying (IRS to the subsidized sale of insecticide-treated nets (ITNs for prevention of malaria and anthroponotic cutaneous leishmaniasis (ACL. Here we outline the strategy and document the progress to provide guidance for replication of similar approaches in other chronic refugee situations. Methods The operational monitoring data presented were collected through: (i two surveys of knowledge, attitude and practice (KAP; (ii routine sales reporting of health-care providers; (iii records completed during field visits; and (iv registers used during annual re-treatment campaigns. Results From 2000 until 2003, subsidized ITN sales expanded from 17 to 44 camps. Based on 2003 sales records, maximum coverage from subsidized sales exceeded 50% in 13 camps and 20% in an additional 14 camps. Free annual treatment campaigns showed that many refugees were in possession of non-programme nets, which were either locally-made or had leaked from an ITN programme in Afghanistan. Estimated re-treatment coverage of sold and existing nets through annual campaigns exceeded 43% in all camps and was above 70% in the majority. Conclusion Subsidized sales of ITNs have effectively introduced the components of sustainability and self-reliance to the prevention of malaria and ACL in Afghan refugee camps. Similar approaches should be investigated in other chronic refugee situations to discourage expectations of continuing humanitarian donations that cannot be fulfilled.

  16. Contact irritant responses of Aedes aegypti Using sublethal concentration and focal application of pyrethroid chemicals.

    Science.gov (United States)

    Manda, Hortance; Shah, Pankhil; Polsomboon, Suppaluck; Chareonviriyaphap, Theeraphap; Castro-Llanos, Fanny; Morrison, Amy; Burrus, Roxanne G; Grieco, John P; Achee, Nicole L

    2013-01-01

    Previous studies have demonstrated contact irritant and spatial repellent behaviors in Aedes aegypti following exposure to sublethal concentrations of chemicals. These sublethal actions are currently being evaluated in the development of a push-pull strategy for Ae. aegypti control. This study reports on mosquito escape responses after exposure to candidate chemicals for a contact irritant focused push-pull strategy using varying concentrations and focal application. Contact irritancy (escape) behavior, knockdown and 24 hour mortality rates were quantified in populations of female Ae. aegypti under laboratory conditions and validated in the field (Thailand and Peru) using experimental huts. Evaluations were conducted using varying concentrations and treatment surface area coverage (SAC) of three pyrethroid insecticides: alphacypermethrin, lambacyhalothrin and deltamethrin. Under laboratory conditions, exposure of Ae. aegypti to alphacypermethrin using the standard field application rate (FAR) resulted in escape responses at 25% and 50% SAC that were comparable with escape responses at 100% SAC. Significant escape responses were also observed at time of exit (by four hours) and 40% increase in escape using ½FAR of alphacypermethrin at 75% SAC compared to a matched chemical-free control. In Peru, however, the maximum increase in Ae. aegypti escape from alphacypermethrin-treated huts was 11%. Results presented here suggest a potential role for sublethal and focal application of contact irritant chemicals in an Ae. aegypti push-pull strategy to reduce human-vector contact inside treated homes. However, the impact of an increase in escape response on dengue virus transmission is currently unknown and will depend on rate of biting on human hosts prior to house exiting.

  17. Public-private delivery of insecticide-treated nets: a voucher scheme in Volta Region, Ghana

    Directory of Open Access Journals (Sweden)

    Taylor Ian

    2007-02-01

    Full Text Available Abstract Background Coverage of vulnerable groups with insecticide-treated nets (ITNs in Ghana, as in the majority of countries of sub-Saharan Africa is currently low. A voucher scheme was introduced in Volta Region as a possible sustainable delivery system for increasing this coverage through scale-up to other regions. Successful scale-up of public health interventions depends upon optimal delivery processes but operational research for delivery processes in large-scale implementation has been inadequate. Methods A simple tool was developed to monitor numbers of vouchers given to each health facility, numbers issued to pregnant women by the health staff, and numbers redeemed by the distributors back to the management agent. Three rounds of interviews were undertaken with health facility staff, retailers and pregnant women who had attended antenatal clinic (ANC. Results During the one year pilot 25,926 vouchers were issued to eligible women from clinics, which equates to 50.7% of the 51,658 ANC registrants during this time period. Of the vouchers issued 66.7% were redeemed by distributors back to the management agent. Initially, non-issuing of vouchers to pregnant women was mainly due to eligibility criteria imposed by the midwives; later in the year it was due to decisions of the pregnant women, and supply constraints. These in turn were heavily influenced by factors external to the programme: current household ownership of nets, competing ITN delivery strategies, and competition for the limited number of ITNs available in the country from major urban areas of other regions. Conclusion Both issuing and redemption of vouchers should be monitored as factors assumed to influence voucher redemption had an influence on issuing, and vice versa. More evidence is needed on how specific contextual factors influence the success of voucher schemes and other models of delivery of ITNs. Such an evidence base will facilitate optimal strategic decision making

  18. Utilizing the fluidized bed to initiate water treatment on site

    International Nuclear Information System (INIS)

    Ahmadvand, H.; Germann, G.; Gandee, J.P.; Buehler, V.T.

    1995-01-01

    Escalating wastewater disposal costs coupled with enforcement of stricter regulations push industrial sites previously without water treatment to treat on site. These sites, inexperienced in water treatment, require a treatment technology that is easily installed, operated, and maintained. The aerobic granular activated carbon (GAC) fluidized bed incorporates biological and adsorptive technologies into a simple, cost-effective process capable of meeting strict effluent requirements. Two case studies at industrial sites illustrate the installation and operation of the fluidized bed and emphasize the ability to use the fluidized bed singularly or as an integral component of a treatment system capable of achieving treatment levels that allow surface discharge and reinjection. Attention is focused on BTEX (benzene, toluene, ethylbenzene, and xylenes)

  19. Comparison of laboratory single species and field population-level effects of the pyrethroid insecticide lambda-cyhalothrin on freshwater invertebrates

    NARCIS (Netherlands)

    Schroer, A.F.W.; Belgers, J.D.M.; Brock, T.C.M.; Matser, A.M.; Maund, S.J.; Brink, van den P.J.

    2004-01-01

    The toxicity of the pyrethroid insecticide lambda-cyhalothrin to freshwater invertebrates has been investigated using data from short-term laboratory toxicity tests and in situ bioassays and population-level effects in field microcosms. In laboratory tests, patterns of toxicity were consistent with

  20. Mathematical model for solid fuel combustion in fluidized bed

    International Nuclear Information System (INIS)

    Kostikj, Zvonimir; Noshpal, Aleksandar

    1994-01-01

    A mathematical model for computation of the combustion process of solid fuel in fluidized bed is presented in this work. Only the combustor part of the plant (the fluidized bed and the free board) is treated with this model. In that manner, all principal, physical presumption and improvements (upon which this model is based) are given. Finally, the results of the numerical realisation of the mathematical model for combustion of minced straw as well as the results of the experimental investigation of a concrete physical model are presented. (author)

  1. Atmospheric fluidized bed coal combustion research, development and application

    CERN Document Server

    Valk, M

    1994-01-01

    The use of fluidized bed coal combustion technology has been developed in the past decade in The Netherlands with a view to expanding the industrial use of coal as an energy supply. Various research groups from universities, institutes for applied science and from boiler industries participated and contributed to this research area. Comprehensive results of such recent experimentation and development work on atmospheric fluidized bed combustion of coal are covered in this volume. Each chapter, written by an expert, treats one specific subject and gives both the theoretical background as well a

  2. Indoor residual spraying with a mixture of clothianidin (a neonicotinoid insecticide and deltamethrin provides improved control and long residual activity against pyrethroid resistant Anopheles gambiae sl in Southern Benin.

    Directory of Open Access Journals (Sweden)

    Corine Ngufor

    Full Text Available There is an urgent need for new insecticides for indoor residual spraying (IRS which can provide improved and prolonged control of malaria vectors that have developed resistance to existing insecticides. The neonicotinoid, clothianidin represents a class of chemistry new to public health. Clothianidin acts as an agonist on nicotinic acetyl choline receptors. IRS with a mixture of Clothianidin and another WHO approved insecticide such as deltamethrin could provide improved control of insecticide resistant malaria vector populations and serve as a tool for insecticide resistance management.The efficacy and residual activity of a novel IRS mixture of deltamethrin and clothianidin was evaluated against wild pyrethroid resistant An. gambiae sl in experimental huts in Cove, Benin. Two application rates of the mixture were tested and comparison was made with clothianidin and deltamethrin applied alone. To assess the residual efficacy of the treatments on different local wall substrates, the inner walls of the experimental huts were covered with either cement, mud or plywood.Clothianidin demonstrated a clear delayed expression in mortality of wild pyrethroid resistant An. gambiae sl in the experimental huts which reached its full effect 120 hours after exposure. Overall mortality over the 12-month hut trial was 15% in the control hut and 24-29% in the deltamethrin-treated huts. The mixture of clothianidin 200mg/m2 and deltamethrin 25mg/m2 induced high overall hut mortality rates (87% on mud walls, 82% on cement walls and 61% on wooden walls largely due to the clothianidin component and high hut exiting rates (67-76% mostly due to the deltamethrin component. Mortality rates remained >80% for 8-9 months on mud and cement walls. The residual activity trend was confirmed by results from monthly in situ cone bioassays with laboratory susceptible An. gambiae Kisumu strain.IRS campaigns with the mixture of clothianidin plus deltamethrin have the potential to

  3. Indoor residual spraying with a mixture of clothianidin (a neonicotinoid insecticide) and deltamethrin provides improved control and long residual activity against pyrethroid resistant Anopheles gambiae sl in Southern Benin.

    Science.gov (United States)

    Ngufor, Corine; Fongnikin, Augustin; Rowland, Mark; N'Guessan, Raphael

    2017-01-01

    There is an urgent need for new insecticides for indoor residual spraying (IRS) which can provide improved and prolonged control of malaria vectors that have developed resistance to existing insecticides. The neonicotinoid, clothianidin represents a class of chemistry new to public health. Clothianidin acts as an agonist on nicotinic acetyl choline receptors. IRS with a mixture of Clothianidin and another WHO approved insecticide such as deltamethrin could provide improved control of insecticide resistant malaria vector populations and serve as a tool for insecticide resistance management. The efficacy and residual activity of a novel IRS mixture of deltamethrin and clothianidin was evaluated against wild pyrethroid resistant An. gambiae sl in experimental huts in Cove, Benin. Two application rates of the mixture were tested and comparison was made with clothianidin and deltamethrin applied alone. To assess the residual efficacy of the treatments on different local wall substrates, the inner walls of the experimental huts were covered with either cement, mud or plywood. Clothianidin demonstrated a clear delayed expression in mortality of wild pyrethroid resistant An. gambiae sl in the experimental huts which reached its full effect 120 hours after exposure. Overall mortality over the 12-month hut trial was 15% in the control hut and 24-29% in the deltamethrin-treated huts. The mixture of clothianidin 200mg/m2 and deltamethrin 25mg/m2 induced high overall hut mortality rates (87% on mud walls, 82% on cement walls and 61% on wooden walls) largely due to the clothianidin component and high hut exiting rates (67-76%) mostly due to the deltamethrin component. Mortality rates remained >80% for 8-9 months on mud and cement walls. The residual activity trend was confirmed by results from monthly in situ cone bioassays with laboratory susceptible An. gambiae Kisumu strain. IRS campaigns with the mixture of clothianidin plus deltamethrin have the potential to provide

  4. 78 FR 72393 - Net Investment Income Tax

    Science.gov (United States)

    2013-12-02

    ... of Article 23 (Relief from Double Taxation) of the 2006 United States Model Income Tax Convention... taxation of ANSTs at the lowest individual tax rate. Furthermore, section 646 treats all distributions, to... of Net Investment Income. The regulations affect individuals, estates, and trusts whose incomes meet...

  5. Waste Water Treatment-Bed of Coal Fly Ash for Dyes and Pigments Industry

    Directory of Open Access Journals (Sweden)

    Syed Farman Ali Shah

    2015-12-01

    Full Text Available The highly porous power plant waste ashes have been utilized to treat toxic effluent of a dyes manufacturing plant. An attempt has been made for the first time in Pakistan, to generate an effective and economically sound treatment facility for the toxic effluent of a dyes manufacturing plant. This is an indigenous bed which could replace expensive treatment facilities, such as reverse osmosis (RO, granulated activated carbon (GAC bed, etc. The treatment efficiency was improved by coupling coagulants with fly ash adsorbent bed. The ash was collected from coal fired boilers of power plant at Lakhra Power Generation Company, Jamshoro, Pakistan. The use of this ash resolved the disposal and environmental issues by treating wastewater of chemical, dyes and pigment industry. The treatment bed comprised of briquettes of coal fly ash coupled with commercial coagulant ferrous sulfate-lime reduced COD, color, turbidity and TSS of effluent remarkably. An adsorption capacity and chemical behavior of fly ash bed was also studied. In coagulation treatment, coagulant FeSO4-lime influenced reduction of COD, color, turbidity and TSS by 32%, 48%, 50% and 51%, respectively. The CFAB coupled with coagulant, resulted an excessive removal of color, TSS, COD, and turbidity by 88%, 92%, 67% and89%, respectively.

  6. Waste Water Treatment-Bed of Coal Fly Ash for Dyes and Pigments Industry

    International Nuclear Information System (INIS)

    Shah, S.F.A.; Aftab, A.; Soomro, N.; Nawaz, M.S.; Vafai, K.

    2015-01-01

    The highly porous power plant waste ashes have been utilized to treat toxic effluent of a dyes manufacturing plant. An attempt has been made for the first time in Pakistan, to generate an effective and economically sound treatment facility for the toxic effluent of a dyes manufacturing plant. This is an indigenous bed which could replace expensive treatment facilities, such as reverse osmosis (RO), granulated activated carbon (GAC) bed, etc. The treatment efficiency was improved by coupling coagulants with fly ash adsorbent bed. The ash was collected from coal fired boilers of power plant at Lakhra Power Generation Company, Jamshoro, Pakistan. The use of this ash resolved the disposal and environmental issues by treating wastewater of chemical, dyes and pigment industry. The treatment bed comprised of briquettes of coal fly ash coupled with commercial coagulant ferrous sulfate-lime reduced COD, color, turbidity and TSS of effluent remarkably. An adsorption capacity and chemical behavior of fly ash bed was also studied. In coagulation treatment, coagulant FeSO/sun 4/-lime influenced reduction of COD, color, turbidity and TSS by 32 percentage, 48 percentage, 50 percentage and 51 percentage, respectively. The CFAB coupled with coagulant, resulted an excessive removal of color, TSS, COD, and turbidity by 88 percentage, 92 percentage, 67 percentage and 89 percentage, respectively. (author)

  7. Longlasting insecticidal nets for prevention of Leishmania donovani infection in India and Nepal: paired cluster randomised trial

    DEFF Research Database (Denmark)

    Picado, Albert; Singh, Shri Prakash; Rijal, Suman

    2010-01-01

    To test the effectiveness of large scale distribution of longlasting nets treated with insecticide in reducing the incidence of visceral leishmaniasis in India and Nepal.......To test the effectiveness of large scale distribution of longlasting nets treated with insecticide in reducing the incidence of visceral leishmaniasis in India and Nepal....

  8. Inter-compartmental transport of organophosphate and pyrethroid pesticides in South China: implications for a regional risk assessment.

    Science.gov (United States)

    Li, Huizhen; Wei, Yanli; Lydy, Michael J; You, Jing

    2014-07-01

    The dynamic flux of an organophosphate and four pyrethroid pesticides was determined in an air-(soil)-water-sediment system based on monitoring data from Guangzhou, China. The total air-water flux, including air-water gaseous exchange and atmospheric deposition, showed deposition from air to water for chlorpyrifos, bifenthrin and cypermethrin, but volatilization for lambda-cyhalothrin and permethrin. The transport of the pesticides from overlying water to sediment suggested that sediment acted as a sink for the pesticides. Additionally, distinct annual atmospheric depositional fluxes between legacy and current-use pesticides suggested the role of consumer usage in their transport throughout the system. Finally, pesticide toxicity was estimated from annual air-water-sediment flux within an urban stream in Guangzhou. A dynamic flux-based risk assessment indicated that inter-compartmental transport of chlorpyrifos decreased its atmospheric exposure, but had little influence on its aquatic toxicity. Instead, water-to-sediment transport of pyrethroids increased their sediment toxicity, which was supported by previously reported toxicity data. Copyright © 2014 Elsevier Ltd. All rights reserved.

  9. Pyrethroid resistance in Sitophilus zeamais is associated with a mutation (T929I) in the voltage-gated sodium channel.

    Science.gov (United States)

    Araújo, Rúbia A; Williamson, Martin S; Bass, Christopher; Field, Linda M; Duce, Ian R

    2011-08-01

    The maize weevil, Sitophilus zeamais, is the most important pest affecting stored grain in Brazil and its control relies heavily on the use of insecticides. The intensive use of compounds such as the pyrethroids has led to the emergence of resistance, and previous studies have suggested that resistance to both pyrethroids and 1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane (DDT) may result from reduced sensitivity of the insecticide target, the voltage-gated sodium channel. To identify the molecular mechanisms underlying pyrethroid resistance in S. zeamais, the domain II region of the voltage-gated sodium channel (para-orthologue) gene was amplified by PCR and sequenced from susceptible and resistant laboratory S. zeamais strains that were selected with a discriminating dose of DDT. A single point mutation, T929I, was found in the para gene of the resistant S. zeamais populations and its presence in individual weevils was strongly associated with survival after DDT exposure. This is the first identification of a target-site resistance mutation in S. zeamais and unusually it is a super-kdr type mutation occurring in the absence of the more common kdr (L1014F) substitution. A high-throughput assay based on TaqMan single nucleotide polymorphism genotyping was developed for sensitive detection of the mutation and used to screen field-collected strains of S. zeamais. This showed that the mutation is present at low frequency in field populations and is a useful tool for informing control strategies. © 2011 The Authors. Insect Molecular Biology © 2011 The Royal Entomological Society.

  10. Insecticidal activity and expression of cytochrome P450 family 4 genes in Aedes albopictus after exposure to pyrethroid mosquito coils.

    Science.gov (United States)

    Avicor, Silas W; Wajidi, Mustafa F F; El-Garj, Fatma M A; Jaal, Zairi; Yahaya, Zary S

    2014-10-01

    Mosquito coils are insecticides commonly used for protection against mosquitoes due to their toxic effects on mosquito populations. These effects on mosquitoes could induce the expression of metabolic enzymes in exposed populations as a counteractive measure. Cytochrome P450 family 4 (CYP4) are metabolic enzymes associated with a wide range of biological activities including insecticide resistance. In this study, the efficacies of three commercial mosquito coils with different pyrethroid active ingredients were assessed and their potential to induce the expression of CYP4 genes in Aedes albopictus analyzed by real-time quantitative PCR. Coils containing 0.3 % D-allethrin and 0.005 % metofluthrin exacted profound toxic effects on Ae. albopictus, inducing high mortalities (≥90 %) compared to the 0.2 % D-allethrin reference coil. CYP4H42 and CYP4H43 expressions were significantly higher in 0.3 % D-allethrin treated mosquitoes compared to the other treated populations. Short-term (KT50) exposure to mosquito coils induced significantly higher expression of both genes in 0.005 % metofluthrin exposed mosquitoes. These results suggest the evaluated products provided better protection than the reference coil; however, they also induced the expression of metabolic genes which could impact negatively on personal protection against mosquito.

  11. The impact of a hybrid social marketing intervention on inequities in access, ownership and use of insecticide-treated nets

    Directory of Open Access Journals (Sweden)

    Stallworthy Guy

    2007-01-01

    Full Text Available Abstract Background An ITN intervention was initiated in three predominantly rural districts of Eastern Province, Zambia, that lacked commercial distribution and communication infrastructures. Social marketing techniques were used for product and message development. Public sector clinics and village-based volunteers promoted and distributed subsidized ITNs priced at $2.5 per net. A study was conducted to assess the effects of the intervention on inequities in knowledge, access, ownership and use of ITNs. Methods A post-test only quasi-experimental study design was used to compare intervention and comparison districts. A total of 2,986 respondents were interviewed. Survey respondents were grouped into four socio-economic (SES categories: low, medium-low, medium and high. Knowledge, access, ownership and use indicators are compared. Concentration index scores are calculated. Interactions between intervention status and SES help determine how different SES groups benefited from the intervention. Results Although overall use of nets remained relatively low, post-test data show that knowledge, access, ownership and use of mosquito nets was higher in intervention districts. A decline in SES inequity in access to nets occurred in intervention districts, resulting from a disproportionately greater increase in access among the low SES group. Declines in SES inequities in net ownership and use of nets were associated with the intervention. The largest increases in net ownership and use occurred among medium and high SES categories. Conclusion Increasing access to nets among the poorest respondents in rural areas may not lead to increases in net use unless the price of nets is no longer a barrier to their purchase.

  12. The impact of a hybrid social marketing intervention on inequities in access, ownership and use of insecticide-treated nets.

    Science.gov (United States)

    Agha, Sohail; Van Rossem, Ronan; Stallworthy, Guy; Kusanthan, Thankian

    2007-01-29

    An ITN intervention was initiated in three predominantly rural districts of Eastern Province, Zambia, that lacked commercial distribution and communication infrastructures. Social marketing techniques were used for product and message development. Public sector clinics and village-based volunteers promoted and distributed subsidized ITNs priced at 2.5 dollars per net. A study was conducted to assess the effects of the intervention on inequities in knowledge, access, ownership and use of ITNs. A post-test only quasi-experimental study design was used to compare intervention and comparison districts. A total of 2,986 respondents were interviewed. Survey respondents were grouped into four socio-economic (SES) categories: low, medium-low, medium and high. Knowledge, access, ownership and use indicators are compared. Concentration index scores are calculated. Interactions between intervention status and SES help determine how different SES groups benefited from the intervention. Although overall use of nets remained relatively low, post-test data show that knowledge, access, ownership and use of mosquito nets was higher in intervention districts. A decline in SES inequity in access to nets occurred in intervention districts, resulting from a disproportionately greater increase in access among the low SES group. Declines in SES inequities in net ownership and use of nets were associated with the intervention. The largest increases in net ownership and use occurred among medium and high SES categories. Increasing access to nets among the poorest respondents in rural areas may not lead to increases in net use unless the price of nets is no longer a barrier to their purchase.

  13. Potentially toxic concentrations of synthetic pyrethroids associated with low density residential land use

    Directory of Open Access Journals (Sweden)

    Stephen Marshall

    2016-11-01

    Full Text Available Trace organic compounds associated with human activity are now ubiquitous in the environment. As the population becomes more urbanised and the use of pesticides and person care products continues to increase, urban waterways are likely to receive higher loads of trace organic contaminants with unknown ecological consequences. To establish the extent of trace organic contamination in urban runoff, concentrations of emerging chemicals of concern were determined in sediments from 99 urban wetlands in and around Melbourne, Australia between February and April, 2015. As a preliminary estimation of potential risks to aquatic biota, we compared measured concentrations with thresholds for acute and chronic toxicity, and modelled toxic units as a function of demographic and land use trends. The synthetic pyrethroid insecticide bifenthrin was common and widespread, and frequently occurred at concentrations likely to cause toxicity to aquatic life. Personal care products DEET and triclosan were common and widely distributed, while the herbicides diuron and prometryn, and the fungicides pyrimethanil and trifloxystrobin occurred less frequently. Toxic unit modelling using random forests found complex and unexpected associations between urban land uses and trace organic concentrations. Synthetic pyrethroid insecticides were identified as emerging compounds of concern, particularly bifenthrin. In contrast with previous surveys, the highest bifenthrin concentrations were associated with lower housing and population density, implicating low-density residential land use in bifenthrin contamination. We discuss the implications for pesticide regulation and urban wetland management in a global context.

  14. Bioaccumulation and enantioselectivity of type I and type II pyrethroid pesticides in earthworm.

    Science.gov (United States)

    Chang, Jing; Wang, Yinghuan; Wang, Huili; Li, Jianzhong; Xu, Peng

    2016-02-01

    In this study, the bioavailability and enantioselectivity differences between bifenthrin (BF, typeⅠpyrethroid) and lambad-cyhalothrin (LCT, type Ⅱ pyrethroid) in earthworm (Eisenia fetida) were investigated. The bio-soil accumulation factors (BSAFs) of BF was about 4 times greater than that of LCT. LCT was degraded faster than BF in soil while eliminated lower in earthworm samples. Compound sorption plays an important role on bioavailability in earthworm, and the soil-adsorption coefficient (K(oc)) of BF and LCT were 22 442 and 42 578, respectively. Metabolic capacity of earthworm to LCT was further studied as no significant difference in the accumulation of LCT between the high and low dose experiment was found. 3-phenoxybenzoic acid (PBCOOH), a metabolite of LCT produced by earthworm was detected in soil. The concentration of PBCOOH at high dose exposure was about 4.7 times greater than that of in low dose level at the fifth day. The bioaccumulation of BF and LCT were both enantioselective in earthworm. The enantiomer factors of BF and LCT in earthworm were approximately 0.12 and 0.65, respectively. The more toxic enantiomers ((+)-BF and (-)-LCT) had a preferential degradation in earthworm and leaded to less toxicity on earthworm for racemate exposure. In combination with other studies, a liner relationship between Log BSAF(S) and Log K(ow) was observed, and the Log BSAF(S) decreased with the increase of Log K(ow). Copyright © 2015 Elsevier Ltd. All rights reserved.

  15. Field evaluation of the bio-efficacy of three pyrethroid based coils against wild populations of anthropophilic mosquitoes in Northern Tanzania

    Directory of Open Access Journals (Sweden)

    Shandala Msangi

    2010-01-01

    Full Text Available Aims: This study aims to assess the feeding inhibition and repellency effect of three brands of mosquito coils in experimental huts (East African design. Evaluated products were all pyrethroid-based mosquito coils - Kiboko; , Total; and Risasi; . Mosfly (0.1% D-allethrin was a positive control. Indoor resting behavior, feeding inhibition and induced exophily were measured as responses of burnt coil smoke in huts. Materials and methods: Resting mosquitoes were collected inside the huts, in window traps and verandah traps using mechanical aspirators. Identified to species level and sex. Results: A total of 1460 mosquitoes were collected, 58.9% (n=860 were Anopheles gambiae s.l while 41.1% (n=600 Culex quinquefasciatus. Indoor resting mosquitoes in all treated huts were significantly reduced than in negative control (DF=4, F=18.6, P < 0.001. Species found to rest indoors were not statistical different between the positive control (Mosfly coil and other three treated huts (DF=3, F=1.068, P=0.408. Cx.quinquefasciatus had significantly higher induced exophily in all treatments comparing to An.gambiae s.l (DF=1, F=5.34, P=0.050. Comparison between species (An.gambiae s.l and Cx. quinquefasciatus for the feeding inhibition among treated huts was not statistically significant (DF=1, F=0.062, P=0.810. Conclusion: Introduction of several personal protection measures will be ideal to supplement the existing gap in reducing the man vector contacts hence lowering the disease transmission.

  16. Multi-country comparison of delivery strategies for mass campaigns to achieve universal coverage with insecticide-treated nets: what works best?

    Science.gov (United States)

    Zegers de Beyl, Celine; Koenker, Hannah; Acosta, Angela; Onyefunafoa, Emmanuel Obi; Adegbe, Emmanuel; McCartney-Melstad, Anna; Selby, Richmond Ato; Kilian, Albert

    2016-02-03

    The use of insecticide-treated nets (ITNs) is widely recognized as one of the main interventions to prevent malaria. High ITN coverage is needed to reduce transmission. Mass distribution campaigns are the fastest way to rapidly scale up ITN coverage. However, the best strategy to distribute ITNs to ensure household coverage targets are met is still under debate. This paper presents results from 14 post-campaign surveys in five African countries to assess whether the campaign strategy used had any effect on distribution outcome. Data from 13,901 households and 14 campaigns from Ghana, Nigeria, Senegal, South Sudan and Uganda, were obtained through representative cross-sectional questionnaire surveys, conducted three to 16 months after ITN distribution. All evaluations used a multi-stage sampling approach and similar methods for data collection. Key outcomes examined were the proportion of households having received a net from the campaign and the proportion of households with one net for every two people. Household registration rates proved to be the most important determinant of a household receiving any net from the campaign (adjusted odds ratio [OR] 74.8; 95 % confidence interval [CI]: 55.3-101.1) or had enough ITNs for all household members (adjusted OR 19.1; 95 % CI: 55.34-101.05). Factors that positively influenced registration were larger household size (adjusted OR 1.7; 95 % CI: 1.5-2.1) and families with children under five (adjusted OR 1.4; 95 % CI: 1.2-1.6). Urban residence was negatively associated with receipt of a net from the campaign (adjusted OR 0.73; 95 % CI: 0.58-0.92). Registration was equitable in most campaigns except for Uganda and South Sudan, where the poorest wealth quintiles were less likely to have been reached. After adjusting for other factors, delivery strategy (house-to-house vs. fixed point) and distribution approach (integrated versus stand-alone) did not show a systematic impact on registration or owning any ITN. Campaigns that

  17. System of treating flue gas

    International Nuclear Information System (INIS)

    Ziegler, D.L.

    1975-01-01

    A system is described for treating or cleaning incinerator flue gas containing acid gases and radioactive and fissionable contaminants. Flue gas and a quench solution are fed into a venturi and then tangentially into the lower portion of a receptacle for restricting volumetric content of the solution. The upper portion of the receptacle contains a scrub bed to further treat or clean the flue gas

  18. Hazard classification for the supercritical water oxidation test bed. Revision 1

    International Nuclear Information System (INIS)

    Ramos, A.G.

    1994-10-01

    A hazard classification of ''routinely accepted by the public'' has been determined for the operation of the supercritical water oxidation test bed at the Idaho National Engineering Laboratory. This determination is based on the fact that the design and proposed operation meet or exceed appropriate national standards so that the risks are equivalent to those present in similar activities conducted in private industry. Each of the 17 criteria for hazards ''routinely accepted by the public,'' identified in the EG and G Idaho, Inc., Safety Manual, were analyzed. The supercritical water oxidation (SCWO) test bed will treat simulated mixed waste without the radioactive component. It will be designed to operate with eight test wastes. These test wastes have been chosen to represent a broad cross-section of candidate mixed wastes anticipated for storage or generation by DOE. In particular, the test bed will generate data to evaluate the ability of the technology to treat chlorinated waste and other wastes that have in the past caused severe corrosion and deposition in SCWO reactors

  19. Field and laboratory experiements with Iridaea cordata (florideophyceae) grown on nylon netting

    Energy Technology Data Exchange (ETDEWEB)

    Mumford, T.F., Jr.

    1979-01-01

    Iridaea cordata (Turner) Bory (Giagatinales) is a carrageenophyte that has been seeded on nets placed directly over natural beds. This process results in only ca. 50% success and suffers from intense grazing by the snails Calliostoma and Lacuna. Ir Iridaea covers the nets, animals fouling does not occur, but further setting of the nets is prevented by fouling with Ulva and Monostroma. Yields of 6-8 kg dry matter m- /sup 2/ was obtained in 1975 and 3.3 kg dry matter m-/sup 2/ in 1976. Expected 1977 yields should be between these values. Comparison of strategies of harvesting nets is made. One harvest yields 461.4 g dry wt 0.25m/sup -2/; two harvests, the first performed early in the growing season yields 500.0 g dry wt 0.25m/sup -2/. Two harvests, one performed near the peak of the growing season yields 594.2 g dry wt 0.25m-/sup 2/, and three harvests yields 697.1 g dry wt 0.25m-/sup 2/. Peak growth occurs in April through July. Careful monitoring of biomass must be made to insure harvest before senescence and subsequent loss of biomass occurs. The potential for commerical use is discussed.

  20. Bed agglomeration characteristics of palm shell and corncob combustion in fluidized bed

    International Nuclear Information System (INIS)

    Chaivatamaset, Pawin; Sricharoon, Panchan; Tia, Suvit

    2011-01-01

    Bed particle agglomeration was studied experimentally in an atmospheric laboratory scale fluidized bed combustor using quartz sand as bed material. Palm shell and corncob were tested. The objectives of the study were (i) to describe the contributions of the biomass ash properties and the operating conditions on the bed agglomeration tendency in term of the bed defluidization time (t def ) and the extent of potassium accumulation in the bed (K/Bed) and (ii) to further elucidate the ash inorganic behaviors and the governing bed agglomeration mechanisms. Defluidization caused by the bed agglomeration was experienced in all experiments during combustion of these biomasses, as a consequence of the presence of potassium in biomass. The experimental results indicated that biomass ash characteristics were the significant influence on the bed agglomeration. The increasing bed temperature, bed particle size and static bed height and the decreasing fluidizing air velocity enhanced the bed agglomeration tendency. The SEM/EDS analyses on the agglomerates confirmed that the agglomeration was attributed to the formation of potassium silicate liquid enriched on the surface of quartz sand particles in conjunction with the high surface temperature of the burning biomass char particles. Thermodynamic examination based on the phase diagram analysis confirmed that the molten phase formation was responsible for the agglomeration. In this study, the high molten ash fraction resulting from the high potassium content in biomass promoted the agglomeration and thus defluidization. - Highlights: → Palm shell and corncob of Thailand are tested their bed agglomeration behaviors during fluidized bed combustion. → The increase of bed temperature, bed particle size and static bed height and the decrease of air velocity enhance bed agglomeration. → The formation of ash derived potassium silicate melts enriched on sand surface is the key process. → The collision between char and sand

  1. The characteristics of bed agglomeration during fluidized bed combustion of eucalyptus bark

    International Nuclear Information System (INIS)

    Chaivatamaset, Pawin; Tia, Suvit

    2015-01-01

    The bed agglomeration behaviors were investigated experimentally when eucalyptus bark was burning tested in a laboratory scale fluidized bed reactor. The focuses of this work were the influences of operating conditions and bed materials on the bed agglomeration tendency and the elucidation in the behaviors of fuel inorganic elements and the governing mode of the agglomeration. It was found that the defluidization caused by the bed agglomeration was clearly detectable from the decrease in measured bed pressure. The growth of bed particle and accumulation of agglomerates during combustion provided the partial to complete defluidization. The defluidization was promoted by the increase of bed temperature and bed particle size, and the decrease of fluidizing air velocity. The SEM-EDS analyses revealed that the bed agglomeration was mainly attributed to the formation of potassium silicate compounds as liquid phase during the combustion. This was initiated by the chemical reaction between the bed particle and the released ash constituents. In this study, the inorganic migration from fuel particle to bed particle was likely dominated by the condensation/reaction. The thermodynamic examination by ternary phase diagram analysis corroborated that the liquid phase formation of the ash derived materials controlled the agglomeration. The alumina sand prevented the bed agglomeration since it was inactive in the formation of viscous molten substances during combustion at the observed temperatures. - Highlights: • The behaviors of bed agglomeration were studied during the fluidized bed combustion of eucalyptus bark. • The increase in bed temperature and sand size, and the decrease of air velocity promoted bed defluidization. • The formation of molten potassium silicate compounds conduced to the bed agglomeration. • Condensation/reaction was the dominant inorganic migration mechanism from fuel particle to bed particle. • The alumina sand prevented effectively the bed

  2. Enantiomeric separation of type I and type II pyrethroid insecticides with different chiral stationary phases by reversed-phase high-performance liquid chromatography.

    Science.gov (United States)

    Zhang, Ping; Yu, Qian; He, Xiulong; Qian, Kun; Xiao, Wei; Xu, Zhifeng; Li, Tian; He, Lin

    2018-04-01

    The enantiomeric separation of type I (bifenthrin, BF) and type II (lambda-cyhalothrin, LCT) pyrethroid insecticides on Lux Cellulose-1, Lux Cellulose-3, and Chiralpak IC chiral columns was investigated by reversed-phase high-performance liquid chromatography. Methanol/water or acetonitrile/water was used as mobile phase at a flow rate of 0.8 mL/min. The effects of chiral stationary phase, mobile phase composition, column temperature, and thermodynamic parameters on enantiomer separation were carefully studied. Bifenthrin got a partial separation on Lux Cellulose-1 column and baseline separation on Lux Cellulose-3 column, while LCT enantiomers could be completely separated on both Lux Cellulose-1 and Lux Cellulose-3 columns. Chiralpak IC provided no separation ability for both BF and LCT. Retention factor (k) and selectivity factor (α) decreased with the column temperature increasing from 10°C to 40°C for both BF and LCT enantiomers. Thermodynamic parameters including ∆H and ∆S were also calculated, and the maximum R s were not always obtained at lowest temperature. Furthermore, the quantitative analysis methods for BF and LCT enantiomers in soil and water were also established. Such results provide a new approach for pyrethroid separation under reversed-phase condition and contribute to environmental risk assessment of pyrethroids at enantiomer level. © 2017 Wiley Periodicals, Inc.

  3. Thermal-hydraulic analysis techniques for axisymmetric pebble bed nuclear reactor cores

    International Nuclear Information System (INIS)

    Stroh, K.R.

    1979-03-01

    The pebble bed reactor's cylindrical core volume contains a random bed of small, spherical fuel-moderator elements. These graphite spheres, containing a central region of dispersed coated-particle fissile and fertile material, are cooled by high pressure helium flowing through the connected interstitial voids. A mathematical model and numerical solution technique have been developed which allow calculation of macroscopic values of thermal-hydraulic variables in an axisymmetric pebble bed nuclear reactor core. The computer program PEBBLE is based on a mathematical model which treats the bed macroscopically as a generating, conducting porous medium. The steady-state model uses a nonlinear Forchheimer-type relation between the coolant pressure gradient and mass flux, with newly derived coefficients for the linear and quadratic resistance terms. The remaining equations in the model make use of mass continuity, and thermal energy balances for the solid and fluid phases

  4. Widespread Pyrethroid and DDT Resistance in the Major Malaria Vector Anopheles funestus in East Africa Is Driven by Metabolic Resistance Mechanisms

    Science.gov (United States)

    Mulamba, Charles; Riveron, Jacob M.; Ibrahim, Sulaiman S.; Irving, Helen; Barnes, Kayla G.; Mukwaya, Louis G.; Birungi, Josephine; Wondji, Charles S.

    2014-01-01

    Background Establishing the extent, geographical distribution and mechanisms of insecticide resistance in malaria vectors is a prerequisite for resistance management. Here, we report a widespread distribution of insecticide resistance in the major malaria vector An. funestus across Uganda and western Kenya under the control of metabolic resistance mechanisms. Methodology/Principal Findings Female An. funestus collected throughout Uganda and western Kenya exhibited a Plasmodium infection rate between 4.2 to 10.4%. Widespread resistance against both type I (permethrin) and II (deltamethrin) pyrethroids and DDT was observed across Uganda and western Kenya. All populations remain highly susceptible to carbamate, organophosphate and dieldrin insecticides. Knockdown resistance plays no role in the pyrethroid and DDT resistance as no kdr mutation associated with resistance was detected despite the presence of a F1021C replacement. Additionally, no signature of selection was observed on the sodium channel gene. Synergist assays and qRT-PCR indicated that metabolic resistance plays a major role notably through elevated expression of cytochrome P450s. DDT resistance mechanisms differ from West Africa as the L119F-GSTe2 mutation only explains a small proportion of the genetic variance to DDT resistance. Conclusion The extensive distribution of pyrethroid and DDT resistance in East African An. funestus populations represents a challenge to the control of this vector. However, the observed carbamate and organophosphate susceptibility offers alternative solutions for resistance management. PMID:25333491

  5. Implications of bio-efficacy and persistence of insecticides when indoor residual spraying and long-lasting insecticide nets are combined for malaria prevention

    Directory of Open Access Journals (Sweden)

    Okumu Fredros O

    2012-11-01

    treated surfaces is assured, LLINs and IRS kill high proportions of susceptible An. arabiensis mosquitoes, though these efficacies decay gradually for LLINs and rapidly for IRS. It is, therefore, important to always add intact nets in sprayed houses, guaranteeing protection even after the IRS decays, and to ensure accurate timing, quality control and regular re-spraying in IRS programmes. By contrast, adding IRS in houses with intact LLINs is unlikely to improve protection relative to LLINs alone, since there is no guarantee that unfed vectors would rest long enough on the sprayed surfaces, and because of the rapid IRS decay. However, there is need to clarify these effects using data from observations of free flying mosquitoes in huts. Physiological susceptibility of An. arabiensis in the area remains 100% against DDT, but is slightly reduced against pyrethroids, necessitating caution over possible spread of resistance. The loss of LLIN toxicity, particularly Olyset® nets suggests that protection offered by these nets against An. arabiensis may be primarily due to physical bite prevention rather than insecticidal efficacy.

  6. Gastroenteropancreatic neuroendocrine tumors (GEP-NETS)

    International Nuclear Information System (INIS)

    Vargas Martinez, Cristian Camilo; Castano Llano, Rodrigo

    2010-01-01

    Gastroenteropancreatic neuroendocrine tumors (GEP-NETS) are rare neoplasms which can occur anywhere in the gastrointestinal tract. Their particular characteristics include uptake of silver salts, neuroendocrine cell marker expression and hormonal secretory granules. Depending on their size, anatomical location and upon whether or not metastasis has occurred, these tumors can show different clinical patterns and have different prognoses. Early diagnosis is essential for treating these lesions and improving the patients' prognoses, but it requires a high degree of suspicion and confirmation by special testing. Surgical treatment is the first choice, but other medical therapy can be helpful for patients who have unresectable disease. This review presents the most relevant aspects of classification, morphology, methods of locating tumors, diagnosis and treatment of GEP-NETS. It presents only the Colombian experience in the epidemiology and management of these tumors.

  7. Insecticide resistance in Anopheles gambiae from south-western Chad, Central Africa

    Directory of Open Access Journals (Sweden)

    Etang Josiane

    2008-09-01

    Full Text Available Abstract Background Indoor residual spraying and insecticide-treated nets (ITN are essential components of malaria vector control in Africa. Pyrethroids are the only recommended compounds for nets treatment because they are fast-acting insecticides with low mammalian toxicity. However, there is growing concern that pyrethroid resistance may threaten the sustainability of ITN scaling-up programmes. Here, insecticide susceptibility was investigated in Anopheles gambiae sensu lato from an area of large scale ITN distribution programme in south-western Chad. Methods Susceptibility to 4% DDT, 0.05% deltamethrin, 0.75% permethrin, 0.1% bendiocarb and 5% malathion was assessed using the WHO standard procedures for adult mosquitoes. Tests were carried out with two to four days-old, non-engorged female mosquitoes. The An. gambiae Kisumu strain was used as a reference. Knockdown effect was recorded every 5 min and mortality scored 24 h after exposure. Mosquitoes were identified to species and molecular form by PCR-RFLP and genotypes at the kdr locus were determined in surviving specimens by Hot Oligonucleotide Ligation Assay (HOLA. Results During this survey, full susceptibility to malathion was recorded in all samples. Reduced susceptibility to bendiocarb (mortality rate of 96.1% was found in one sample out of nine assayed. Increased tolerance to pyrethroids was detected in most samples (8/9 with mortality rates ranging from 70.2 to 96.6% for deltamethrin and from 26.7 to 96.3% for permethrin. Pyrethroid tolerance was not associated with a significant increase of knock-down times. Anopheles arabiensis was the predominant species of the An. gambiae complex in the study area, representing 75 to 100% of the samples. Screening for kdr mutations detected the L1014F mutation in 88.6% (N = 35 of surviving An. gambiae sensu stricto S form mosquitoes. All surviving An. arabiensis (N = 49 and M form An. gambiae s.s. (N = 1 carried the susceptible allele

  8. The Safety of Hospital Beds: Ingress, Egress, and In-Bed Mobility.

    Science.gov (United States)

    Morse, Janice M; Gervais, Pierre; Pooler, Charlotte; Merryweather, Andrew; Doig, Alexa K; Bloswick, Donald

    2015-01-01

    To explore the safety of the standard and the low hospital bed, we report on a microanalysis of 15 patients' ability to ingress, move about the bed, and egress. The 15 participants were purposefully selected with various disabilities. Bed conditions were randomized with side rails up or down and one low bed with side rails down. We explored the patients' use of the side rails, bed height, ability to lift their legs onto the mattress, and ability to turn, egress, and walk back to the chair. The standard bed was too high for some participants, both for ingress and egress. Side rails were used by most participants when entering, turning in bed, and exiting. We recommend that side rails be reconsidered as a means to facilitate in-bed movement, ingress, and egress. Furthermore, single deck height settings for all patients are not optimal. Low beds as a safety measure must be re-evaluated.

  9. Multiple causes of an unexpected malaria outbreak in a high-transmission area in Madagascar.

    Science.gov (United States)

    Kesteman, Thomas; Rafalimanantsoa, Solofoniaina A; Razafimandimby, Harimahefa; Rasamimanana, Heriniaina H; Raharimanga, Vaomalala; Ramarosandratana, Benjamin; Ratsimbasoa, Arsene; Ratovonjato, Jocelyn; Elissa, Nohal; Randrianasolo, Laurence; Finlay, Alyssa; Rogier, Christophe; Randrianarivelojosia, Milijaona

    2016-02-02

    pyrethroids. Two years after distribution, nearly all LLINs collected showed a loss of physical integrity and insecticide activity, Increased rainfall, decreasing use and reduced insecticide activity of long-lasting insecticide-treated nets, and drug shortages may have been responsible for, or contributed to, the outbreak observed in South-Eastern Madagascar in 2011-2012. Control interventions for malaria elimination must be sustained at the risk of triggering harmful epidemics, even in zones of high transmission.

  10. Horizontal ichthyoplankton tow-net system with unobstructed net opening

    Science.gov (United States)

    Nester, Robert T.

    1987-01-01

    The larval fish sampler described here consists of a modified bridle, frame, and net system with an obstruction-free net opening and is small enough for use on boats 10 m or less in length. The tow net features a square net frame attached to a 0.5-m-diameter cylinder-on-cone plankton net with a bridle designed to eliminate all obstructions forward of the net opening, significantly reducing currents and vibrations in the water directly preceding the net. This system was effective in collecting larvae representing more than 25 species of fish at sampling depths ranging from surface to 10 m and could easily be used at greater depths.

  11. Higher-moment measurements of net-kaon, net-charge and net-proton multiplicity distributions at STAR

    International Nuclear Information System (INIS)

    Sarkar, Amal

    2014-01-01

    In this paper, we report the measurements of the various moments, such as mean, standard deviation (σ), skewness (S) and kurtosis (κ) of the net-kaon, net-charge and net-proton multiplicity distributions at mid-rapidity in Au + Au collisions from √(s NN )=7.7 to 200 GeV with the STAR experiment at RHIC. This work has been done with the aim to locate the critical point on the QCD phase diagram. These moments and their products are related to the thermodynamic susceptibilities of conserved quantities such as net baryon number, net charge, and net strangeness as well as to the correlation length of the system which diverges in an ideal infinite thermodynamic system at the critical point. For a finite system, existing for a finite time, a non-monotonic behavior of these variables would indicate the presence of the critical point. Furthermore, we also present the moment products Sσ, κσ 2 of net-kaon, net-charge and net-proton multiplicity distributions as a function of collision centrality and energy. The energy and the centrality dependence of higher moments and their products have been compared with different models

  12. Dynamic behavior of tobacco waste in the coal-fired fluidized-bed boiler

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Kai; Chang, Jian; Chen, Honggang; Yang, Yongping [North China Electric Power Univ., Beijing (China). National Eng Lab for Biomass Power Generation Equipment; Yu, Bangting [China Univ. of Petroleum, Beijing (China). State Key Lab. of Heavy Oil Processing

    2013-07-01

    Circulating fluidized bed (CFB) technology is an advanced method for utilizing coal and other solid fuels in an environmentally acceptable manner. During the processing procedure in the nicotiana tabacum plants, lots of tobacco stem wastes are produced, which are normally being dumped to the landfill field. If this kind of waste can be used as a part of the fuel to be added into the coal in a CFB combustor, it will reduce the use of coal and then cut the net carbon emissions. To understand the complicated fluid dynamics of nicotiana tabacum wastes in the coal-fired CFB boiler, the mixing and segregation behavior of tobacco stalk are preliminary measured in a cylindrical fluidized bed. Obvious segregation behavior is found due to distinct differences in density and shape between tobacco stem and coal, which results in poor fluidization quality and bad combustion efficiency. To overcome this disadvantage, a jet with high gas velocity is introduced through the air distributor and a detailed experimental study is conducted in a fluidized bed made up of stem-sand mixture with different solid components at various jet velocities, which greatly improve the mixing performance of stem in the fluidized bed. The above findings are helpful for the technological upgrading of small- or middle-sized CFB boiler with adding tobacco stem into coal.

  13. Performance of a system with full- and pilot-scale sludge drying reed bed units treating septic tank sludge in Brazil.

    Science.gov (United States)

    Calderón-Vallejo, Luisa Fernanda; Andrade, Cynthia Franco; Manjate, Elias Sete; Madera-Parra, Carlos Arturo; von Sperling, Marcos

    2015-01-01

    This study investigated the performance of sludge drying reed beds (SDRB) at full- and pilot-scale treating sludge from septic tanks in the city of Belo Horizonte, Brazil. The treatment units, planted with Cynodon spp., were based on an adaptation of the first-stage of the French vertical-flow constructed wetland, originally developed for treating sewage. Two different operational phases were investigated; in the first one, the full-scale unit was used together with six pilot-scale columns in order to test different feeding strategies. For the second phase, only the full-scale unit was used, including a recirculation of the filtered effluent (percolate) to one of the units of the French vertical wetland. Sludge application was done once a week emptying a full truck, during 25 weeks. The sludge was predominantly diluted, leading to low solids loading rates (median values of 18 kgTS m(-2) year(-1)). Chemical oxygen demand removal efficiency in the full-scale unit was reasonable (median of 71%), but the total solids removal was only moderate (median of 44%) in the full-scale unit without recirculation. Recirculation did not bring substantial improvements in the overall performance. The other loading conditions implemented in the pilot columns also did not show statistically different performances.

  14. Characterization of biofilm in 200W fluidized bed reactors

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Michelle H. [Pacific Northwest National Laboratory (PNNL), Richland, WA (United States); Saurey, Sabrina D. [Pacific Northwest National Laboratory (PNNL), Richland, WA (United States); Lee, Brady D. [Pacific Northwest National Laboratory (PNNL), Richland, WA (United States); Parker, Kent E. [Pacific Northwest National Laboratory (PNNL), Richland, WA (United States); Eisenhauer, Emalee E. R. [Pacific Northwest National Laboratory (PNNL), Richland, WA (United States); Cordova, Elsa A. [Pacific Northwest National Laboratory (PNNL), Richland, WA (United States); Golovich, Elizabeth C. [Pacific Northwest National Laboratory (PNNL), Richland, WA (United States)

    2014-09-29

    Contaminated groundwater beneath the 200 West Area at the Hanford Site in Southeast Washington is currently being treated using a pump and treat system to remove organics, inorganics, radionuclides, and metals. A granular activated carbon-based fluidized bed reactor (FBR) has been added to remove nitrate, hexavalent chromium and carbon tetrachloride. Initial analytical results indicated the microorganisms effectively reduced many of the contaminants to less than cleanup levels. However shortly thereafter operational upsets of the FBR include carbon carry over, over production of microbial extracellular polymeric substance (biofilm) materials, and over production of hydrogen sulfide. As a result detailed investigations were undertaken to understand the functional diversity and activity of the microbial community present in the FBR over time. Molecular analyses including terminal restriction fragment length polymorphism analysis, quantitative polymerase chain reaction and fluorescent in situ hybridization analyses were performed on the microbial community extracted from the biofilm within the bed and from the inoculum, to determine functional dynamics of the FBR bed over time and following operational changes. Findings from these analyses indicated: 1) the microbial community within the bed was completely different than community used for inoculation, and was likely from the groundwater; 2) analyses early in the testing showed an FBR community dominated by a few Curvibacter and Flavobacterium species; 3) the final sample taken indicated that the microbial community in the FBR bed had become more diverse; and 4) qPCR analyses indicated that bacteria involved in nitrogen cycling, including denitrifiers and anaerobic ammonia oxidizing bacteria, were dominant in the bed. These results indicate that molecular tools can be powerful for determining functional diversity within FBR type reactors. Coupled with micronutrient, influent and effluent chemistry

  15. 7 CFR 2902.15 - Bedding, bed linens, and towels.

    Science.gov (United States)

    2010-01-01

    ... PROCUREMENT Designated Items § 2902.15 Bedding, bed linens, and towels. (a) Definition. (1) Bedding is that... minimum biobased content is 12 percent and shall be based on the amount of qualifying biobased carbon in..., and silk are not qualifying biobased feedstocks for the purpose of determining the biobased content of...

  16. A Multistage Fluidized Bed for the Deep Removal of Sour Gases : Proof of Concept and Tray Efficiencies

    NARCIS (Netherlands)

    Driessen, Rick T.; Bos, Martin J.; Brilman, Derk W. F.

    2018-01-01

    Currently there are significant amounts of natural gas that cannot be produced and treated to meet pipeline specifications, because that would not be economically viable. This work investigates a bench scale multistage fluidized bed (MSFB) with shallow beds for sour gas removal from natural gas

  17. Cardiac atrophy after bed rest and spaceflight

    Science.gov (United States)

    Perhonen, M. A.; Franco, F.; Lane, L. D.; Buckey, J. C.; Blomqvist, C. G.; Zerwekh, J. E.; Peshock, R. M.; Weatherall, P. T.; Levine, B. D.

    2001-01-01

    Cardiac muscle adapts well to changes in loading conditions. For example, left ventricular (LV) hypertrophy may be induced physiologically (via exercise training) or pathologically (via hypertension or valvular heart disease). If hypertension is treated, LV hypertrophy regresses, suggesting a sensitivity to LV work. However, whether physical inactivity in nonathletic populations causes adaptive changes in LV mass or even frank atrophy is not clear. We exposed previously sedentary men to 6 (n = 5) and 12 (n = 3) wk of horizontal bed rest. LV and right ventricular (RV) mass and end-diastolic volume were measured using cine magnetic resonance imaging (MRI) at 2, 6, and 12 wk of bed rest; five healthy men were also studied before and after at least 6 wk of routine daily activities as controls. In addition, four astronauts were exposed to the complete elimination of hydrostatic gradients during a spaceflight of 10 days. During bed rest, LV mass decreased by 8.0 +/- 2.2% (P = 0.005) after 6 wk with an additional atrophy of 7.6 +/- 2.3% in the subjects who remained in bed for 12 wk; there was no change in LV mass for the control subjects (153.0 +/- 12.2 vs. 153.4 +/- 12.1 g, P = 0.81). Mean wall thickness decreased (4 +/- 2.5%, P = 0.01) after 6 wk of bed rest associated with the decrease in LV mass, suggesting a physiological remodeling with respect to altered load. LV end-diastolic volume decreased by 14 +/- 1.7% (P = 0.002) after 2 wk of bed rest and changed minimally thereafter. After 6 wk of bed rest, RV free wall mass decreased by 10 +/- 2.7% (P = 0.06) and RV end-diastolic volume by 16 +/- 7.9% (P = 0.06). After spaceflight, LV mass decreased by 12 +/- 6.9% (P = 0.07). In conclusion, cardiac atrophy occurs during prolonged (6 wk) horizontal bed rest and may also occur after short-term spaceflight. We suggest that cardiac atrophy is due to a physiological adaptation to reduced myocardial load and work in real or simulated microgravity and demonstrates the plasticity

  18. Sorption of lambda-cyhalothrin, cypermethrin, deltamethrin and fenvalerate to quartz, corundum, kaolinite and montmorillonite.

    Science.gov (United States)

    Oudou, H Chaaieri; Hansen, H C Bruun

    2002-12-01

    Sorption to mineral surfaces may be important for retention and degradation of hydrophobic pesticides in subsoils and aquifers poor in organic matter. In this work the title pyrethroids have been used to investigate selective interactions with the surfaces of four minerals. Sorption of the four pyrethroids was quantified in batch experiments with initial pyrethroid concentrations of 1-100 microg/l. Sorption to centrifuge tubes used in the batch experiments accounted for 25-60% of total sorption. Net sorption was obtained from total sorption after subtracting the amounts of pyrethroids sorbed to centrifuge tubes used. All isotherms could be fitted by the Freundlich equation with n ranging between 0.9 and 1.1. Bonding affinities per unit surface area decreased in the order: corundum > quartz > montmorillonite approximately equal kaolinite. A similar sequence as found for the total surface tension of the minerals. All minerals showed the same selectivity order with respect to sorption affinity of the four pyrethroids: lambda-cyhalothrin > deltamethrin > cypermethrin > fenvalerate, which shows that the most hydrophobic compound is sorbed most strongly. Stereochemical properties of the four pyrethroid formulations may also contribute to the selectivity pattern.

  19. Biogas recirculation for simultaneous calcium removal and biogas purification within an expanded granular sludge bed system treating leachate.

    Science.gov (United States)

    Luo, Jinghuan; Lu, Xueqin; Liu, Jianyong; Qian, Guangren; Lu, Yongsheng

    2014-12-01

    Biogas, generated from an expanded granular sludge bed (EGSB) reactor treating municipal solid waste (MSW) leachate, was recirculated for calcium removal from the leachate via a carbonation process with simultaneous biogas purification. Batch trials were performed to optimize the solution pH and imported biogas (CO2) for CaCO3 precipitation. With applicable pH of 10-11 obtained, continuous trials achieved final calcium concentrations of 181-375 mg/L (removal efficiencies≈92.8-96.5%) in the leachate and methane contents of 87.1-91.4% (purification efficiencies≈65.4-82.2%) in the biogas. Calcium-balance study indicates that 23-986 mg Ca/d was released from the bio-system under the carbonized condition where CaCO3 precipitating was moved outside the bioreactor, whereas 7918-9517 mg Ca/d was trapped into the system for the controlled one. These findings demonstrate that carbonation removal of calcium by biogas recirculation could be a promising alternative to pretreat calcium-rich MSW leachate and synergistically to improve methane content. Copyright © 2014 Elsevier Ltd. All rights reserved.

  20. Development of net energy ratio and emission factor for quad-generation pathways

    DEFF Research Database (Denmark)

    Rudra, Souman; Rosendahl, Lasse; Kumar, Amit

    2014-01-01

    of this study was to evaluate the energy performance, reduce GHG and acid rain precursor emission, and use of biomass for different outputs based on demand. Finally, a sensitivity analysis and a comparative study ar conducted for expected technological improvements and factors that could increase the energy......, methanol and methane. Circulating fluidized bed gasifier and the gas technology institute (GTI) gasifier technologies are used for this quad-generation process. Two different biomass feedstocks are considered in this study. The net energy ratio for six different pathways having the range of between 1...