Abstract: The histochemical characterization of rain-forest strain of Onchocerca volvulus isolated in Akamkpa of Cross River State, Nigeria was studied. In a preliminary survey of 350 persons from eight villages, 75(21.4%) were found to be positive for the parasite. Males (23.6%) were more infected than the females but there ...
Lagoro, David Kitara; Arony, Denis Anywar
Nodding Syndrome (NS) is a childhood neurological disorder characterized by atonic seizures, cognitive decline, school dropout, muscle weakness, thermal dysfunction, wasting and stunted growth. There are recent published information suggesting associations between Nodding Syndrome (NS) with cerebrospinal fluid (CSF) VGKC antibodies and serum leiomidin-1 antibody cross reacting with Onchocerca Volvulus ( OV ). These findings suggest a neuro-inflammatory cause of NS and they are important findings in the search for the cause of Nodding Syndrome. These observations perhaps provide further, the unique explanation for the association between Nodding Syndrome and Onchocerca Volvulus . Many clinical and epidemiological studies had shown a significant correlation between NS and infestation with a nematode, Onchocerca volvulus which causes a disease, Onchocerciasis , some of which when left untreated can develop visual defect ("River Blindness"). While these studies conducted in Northern Uganda and Southern Sudan indicate a statistically significant association with ( OV infection (using positive skin snips), we observe that ( OV is generally endemic in many parts of Sub Saharan Africa and Latin America and that to date, no NS cases have been recorded in those regions. This letter to the Editor is to provide additional information on the current view about the relationship between Nodding Syndrome and Onchocerca Volvulus as seen in Northern Uganda.
A.P. Plaisier (Anton); G.J. van Oortmarssen (Gerrit); J.H.F. Remme (Jan); J.D.F. Habbema (Dik)
markdownabstractAbstract The epidemiological model ONCHOSIM — a model and computer simulation program for the transmission and control of onchocerciasis — has been used to determine the range of plausible values for the reproductive lifespan of Onchocerca volvulus. Model predictions based on
James L Crainey
Full Text Available We report here the first complete mitochondria genome of Onchocerca volvulus from a focus outside of Africa. An O. volvulus mitogenome from the Brazilian Amazonia focus was obtained using a combination of high-throughput and Sanger sequencing technologies. Comparisons made between this mitochondrial genome and publicly available mitochondrial sequences identified 46 variant nucleotide positions and suggested that our Brazilian mitogenome is more closely related to Cameroon-origin mitochondria than West African-origin mitochondria. As well as providing insights into the origins of Latin American onchocerciasis, the Brazilian Amazonia focus mitogenome may also have value as an epidemiological resource.
Convit, Jacinto; Schuler, Harland; Borges, Rafael; Olivero, Vimerca; Domínguez-Vázquez, Alfredo; Frontado, Hortencia; Grillet, María E
Onchocerciasis is caused by Onchocerca volvulus and transmitted by Simulium species (black flies). In the Americas, the infection has been previously described in 13 discrete regional foci distributed among six countries (Brazil, Colombia, Ecuador, Guatemala, Mexico and Venezuela) where more than 370,000 people are currently considered at risk. Since 2001, disease control in Venezuela has relied on the mass drug administration to the at-risk communities. This report provides empirical evidence of interruption of Onchocerca volvulus transmission by Simulium metallicum in 510 endemic communities from two Northern foci of Venezuela, after 10-12 years of 6-monthly Mectizan (ivermectin) treatment to all the eligible residents. In-depth entomologic and epidemiologic surveys were serially conducted from 2001-2012 in selected (sentinel and extra-sentinel) communities from the North-central (NC) and North-east (NE) onchocerciasis foci of Venezuela in order to monitor the impact of ivermectin treatment. From 2007-2009, entomological indicators in both foci confirmed that 0 out of 112,637 S. metallicum females examined by PCR contained L3 infection in insect heads. The upper bound of the 95% confidence intervals of the infective rate of the vector reached values below 1% by 2009 (NC) and 2012 (NE). Additionally, after 14 (NC) and 22 (NE) rounds of treatment, the seasonal transmission potential (±UL CIs) of S. metallicum was under the critical threshold of 20 L3 per person per season. Serological analysis in school children Venezuela.
Background Onchocerciasis is caused by Onchocerca volvulus and transmitted by Simulium species (black flies). In the Americas, the infection has been previously described in 13 discrete regional foci distributed among six countries (Brazil, Colombia, Ecuador, Guatemala, Mexico and Venezuela) where more than 370,000 people are currently considered at risk. Since 2001, disease control in Venezuela has relied on the mass drug administration to the at-risk communities. This report provides empirical evidence of interruption of Onchocerca volvulus transmission by Simulium metallicum in 510 endemic communities from two Northern foci of Venezuela, after 10–12 years of 6-monthly Mectizan® (ivermectin) treatment to all the eligible residents. Methods In-depth entomologic and epidemiologic surveys were serially conducted from 2001–2012 in selected (sentinel and extra-sentinel) communities from the North-central (NC) and North-east (NE) onchocerciasis foci of Venezuela in order to monitor the impact of ivermectin treatment. Results From 2007–2009, entomological indicators in both foci confirmed that 0 out of 112,637 S. metallicum females examined by PCR contained L3 infection in insect heads. The upper bound of the 95% confidence intervals of the infective rate of the vector reached values below 1% by 2009 (NC) and 2012 (NE). Additionally, after 14 (NC) and 22 (NE) rounds of treatment, the seasonal transmission potential (±UL CIs) of S. metallicum was under the critical threshold of 20 L3 per person per season. Serological analysis in school children < 15 years-old demonstrated that 0 out of 6,590 individuals were harboring antibodies to Ov-16. Finally, epidemiological surveys made during 2010 (NC) and 2012 (NE) showed no evidence of microfilariae in the skin and eyes of the population. Conclusions These results meet the WHO criteria for absence of parasite transmission and disease morbidity in these endemic areas which represent 91% of the population previously at
Alho, Ana Margarida; Cruz, Luís; Coelho, Ana; Martinho, Filipe; Mansinho, Mário; Annoscia, Giada; Lia, Riccardo P; Giannelli, Alessio; Otranto, Domenico; de Carvalho, Luís Madeira
Onchocerca lupi (Spirurida, Onchocercidae) is an emerging vector-borne helminth that causes nodular lesions associated with acute or chronic ocular disease in dogs and cats. Since its first description in dogs in 1991, this zoonotic filarioid has been increasingly reported in Europe and the United States. An 8-year-old outdoor mixed-breed female dog from the Algarve (southern Portugal) was presented with a history of severe dyspnoea. Cervical and thoracic radiographs revealed a slight reduction in the diameter of the cervical trachea and a moderate increase in radiopacity of the laryngeal soft tissue. An exploratory laryngoscopy was performed, revealing filiform worms associated with stenosis of the thyroid cartilage and a purulent necrotic tissue in the larynx lumen. A single sessile nodule, protruding from the dorsal wall of the laryngeal lumen caused a severe reduction of the glottis and tracheal diameter. Fragments of the worms were morphologically and molecularly identified as O. lupi. Histological examination of the nodule showed a granulomatous reaction with sections of coiled gravid female nematodes. Following laryngoscopy, a tracheostomy tube was inserted to relieve dyspnoea and ivermectin (300 μg/kg, once a week, for 8 weeks) combined with prednisolone was prescribed. The dog showed a complete recovery. Although O. lupi has been isolated in human patients from the spinal cord, this is the first report of an aberrant migration of O. lupi in a dog. The veterinary medical community should pay attention to aberrant location of O. lupi and consider onchocercosis as a differential diagnosis for airway obstruction in dogs. Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.
Otranto, Domenico; Dantas-Torres, Filipe; Papadopoulos, Elias; Petrić, Dušan; Ćupina, Aleksandra Ignjatović; Bain, Odile
During a hot Mediterranean summer, an expedition brought parasitologists from Brazil, France, Greece, Italy, and Serbia to a wooded area near Xanthi, Thrace, northeastern Greece, near the Turkish border, on the track of the vector of the little-known nematode Onchocerca lupi. The scientific purposes of the expedition blended then with stories of humans, animals, and parasites in this rural area.
Chloroqunie is a well-known anti-malaria drug commonly used in the tropics. Chloroquine was in this study, tested on adult male worms of Onchocerca volvulus to assess its possible effect. Male worms were mechanically isolated from nodules of untreated onchocerciasis patients. After 24hours incubation in a drug-free ...
Mowlavi, G; Farzbod, F; Kheirkhah, A; Mobedi, I; Bowman, D D; Naddaf, S R
Cases of canine onchocerciasis caused by Onchocerca lupi are increasingly reported from Europe and the western United States of America. The zoonotic role of this parasite had already been suspected in Europe as the clinical signs and histopathology seen in two ocular cases from Albania and the Crimean region were very similar to those of canine ocular onchocerciasis. In the most recent reports of human onchocerciasis, O. lupi has been morphologically and molecularly identified as the causative agent of ocular infestation in two patients from Turkey, and one patient from Tunisia. Here, we report an additional case of nodular lesions involving two, and possibly more, immature worms in a patient from Iran. The parasite was found to belong to the genus Onchocerca based on morphological features and the species was confirmed as O. lupi from a partial sequence analysis of 12S ribosomal DNA.
Full Text Available Microfilariae of five Onchocerca species, O. dewittei japonica (the causative agent of zoonotic onchocerciasis in Oita, Kyushu, Japan from wild boar (Sus scrofa, O. skrjabini and O. eberhardi from sika deer (Cervus nippon, O. lienalis from cattle, and an as yet unnamed Onchocerca sp. from wild boar, were injected intrathoracically into newly-emerged black flies of several species from Oita to search the potential vector(s of these parasites and identify their infective larvae. Development of O. dewittei japonica microfilariae to the infective larvae occurred in Simulium aokii, S. arakawae, S. bidentatum, S. japonicum, S. quinquestriatum, and S. rufibasis while development of infective larvae of O. skrjabini, O. eberhardi, and the unnamed Onchocerca sp. was observed in S. aokii, S. arakawae, and S. bidentatum. Development of O. lienalis microfilaria to infective larvae occurred in S. arakawae. Based on the morphology of infective larvae obtained, we proposed a key of identification of Onchocerca infective larvae found in Oita. We also reconsider the identification of three types of infective larvae previously recovered from Simulium species captured at cattle sheds: the large type I larvae that may be an undescribed species; the small type III identified as O. lienalis may include O. skrjabini too; the intermediary type II that may be O. gutturosa, or O. dewittei japonica, or the unnamed Onchocerca sp. of wild boar.
Manchang, T K; Ajonina-Ekoti, I; Ndjonka, D; Eisenbarth, A; Achukwi, M D; Renz, A; Brattig, N W; Liebau, E; Breloer, M
Onchocerca volvulus is a tissue-dwelling, vector-borne nematode parasite of humans and is the causative agent of onchocerciasis or river blindness. Natural infections of BALB/c mice with Litomosoides sigmodontis and of cattle with Onchocerca ochengi were used as models to study the immune responses to O. volvulus-derived recombinant proteins (OvALT-2, OvNLT-1, Ov103 and Ov7). The humoral immune response of O. volvulus-infected humans against OvALT-2, OvNLT-1 and Ov7 revealed pronounced immunoglobulin G (IgG) titres which were, however, significantly lower than against the lysate of O. volvulus adult female worms. Sera derived from patients displaying the hyperreactive form of onchocerciasis showed a uniform trend of higher IgG reactivity both to the single proteins and the O. volvulus lysate. Sera derived from L. sigmodontis-infected mice and from calves exposed to O. ochengi transmission in a hyperendemic area also contained IgM and IgG1 specific for O. volvulus-derived recombinant proteins. These results strongly suggest that L. sigmodontis-specific and O. ochengi-specific immunoglobulins elicited during natural infection of mice and cattle cross-reacted with O. volvulus-derived recombinant antigens. Monitoring O. ochengi-infected calves over a 26-month period, provided a comprehensive kinetic of the humoral response to infection that was strictly correlated with parasite load and occurrence of microfilariae.
Full Text Available The genus Onchocerca encompasses parasitic nematodes including Onchocerca volvulus, causative agent of river blindness in humans, and the zoonotic Onchocerca lupi infecting dogs and cats. In dogs, O. lupi adult worms cause ocular lesions of various degrees while humans may bear the brunt of zoonotic onchocercosis with patients requiring neurosurgical intervention because of central nervous system localization of nematodes. Though the zoonotic potential of O. lupi has been well recognized from human cases in Europe, the United States and the Middle East, a proper therapy for curing this parasitic infection in dogs is lacking. To evaluate the efficacy of oxfendazole, 11 out of the 21 client-owned dogs (21/123; 17.1% positive for skin-dwelling O. lupi microfilariae (mfs, were enrolled in the efficacy study and were treated with oxfendazole (50 mg/kg per OS once a day for 5 (G2 or 10 (G3 consecutive days or were left untreated (G1. The efficacy of oxfendazole in the reduction of O. lupi mfs was evaluated by microfilarial count and by assessing the percentage of mfs reduction and mean microfilaricidal efficacy, whereas the efficacy in the reduction of ocular lesions was evaluated by ultrasound imaging. All dogs where subjected to follow-ups at 30 (D30, 90 (D90 and 180 (D180 days post-treatment. The percentage of reduction of mfs was 78% for G2 and 12.5% for G3 at D180. The mean microfilaricidal efficacy of oxfendazole in the treatment of canine onchocercosis by O. lupi at D30, D90 and D180 was 41%, 81% and 90%, in G2 and 40%, 65% and 70%, in G3, respectively. Retrobulbar lesions did not reduce from D0 to D180 in control group (dogs in G1, whereas all treated dogs (in G2 and G3 had slightly decreased ocular lesions. Percentage of reduction of ocular lesions by ultrasound examination was 50% and 47.5% in G2 and G3 at D180, respectively. Despite the decrease in ocular lesions in all treated dogs (G2 and G3, oxfendazole was ineffective in reducing ocular
Tudor, Poliana; Turcitu, Mihai; Mateescu, Cosmin; Dantas-Torres, Filipe; Tudor, Niculae; Bărbuceanu, Florica; Ciuca, Lavinia; Burcoveanu, Ioana; Acatrinei, Dumitru; Rinaldi, Laura; Mateescu, Romanița; Bădicu, Adina; Ionașcu, Iuliana; Otranto, Domenico
Onchocerca lupi is a filarial nematode, which infects the scleral conjunctival tissue of dogs, wolves and cats. Whilst adult nematodes localize in the conjunctive tissue of sclera or in the retrobulbar, microfilariae are found in the skin, and they are rarely diagnosed in asymptomatic animals. Since the first report of human ocular infection 5 years ago, up to 10 zoonotic cases have been identified in patients worldwide. We report, for the first time in Romania, three cases of canine ocular onchocercosis in dogs. Fragments of the harvested worms were characterized morphologically and molecularly. This article expands knowledge on the distribution of this parasite in Eastern Europe and sounds an alarm bell for ophthalmologists about the possible occurrence of human cases of O. lupi infection.
Cho-Ngwa, Fidelis; Monya, Elvis; Azantsa, Boris K; Manfo, Faustin Pascal T; Babiaka, Smith B; Mbah, James A; Samje, Moses
Onchocerciasis is the world's second leading infectious cause of blindness. Its control is currently hampered by the lack of a macrofilaricidal drug and by severe adverse events observed when the lone recommended microfilaricide, ivermectin is administered to individuals co-infected with Loa loa. Therefore, there is the need for a safe and effective macrofilaricidal drug that will be able to cure the infection and break transmission cycles, or at least, an alternative microfilaricide that does not kill L. loa microfilariae (mf). Fourteen extracts from two medicinal plants, Tragia benthami and Piper umbellatum were screened in vitro against Onchocerca ochengi parasite and L. loa mf. Activities of extracts on male worms and microfilariae were assessed by motility reduction, while MTT/Formazan assay was used to assess biochemically the death of female worms. Cytotoxicity and acute toxicity of active extracts were tested on monkey kidney cells and Balb/c mice, respectively. At 500 μg/mL, all extracts showed 100 % activity on Onchocerca ochengi males and microfilariae, while 9 showed 100 % activity on female worms. The methylene chloride extract of Piper umbellatum leaves was the most active on adult male and female worms (IC50s: 16.63 μg/mL and 35.65 μg/mL, respectively). The three most active extracts on Onchocerca ochengi females were also highly active on Loa loa microfilariae, with IC50s of 35.12 - 13.9 μg/mL. Active extracts were generally more toxic to the worms than to cells and showed no acute toxicity to Balb/c mice. Phytochemical screening revealed the presence of saponins, steroids, tannins and flavanoids in the promising extracts. These results unfold potential sources of novel anti-Onchocerca lead compounds and validate the traditional use of the plants in onchocerciasis treatment.
Full Text Available BACKGROUND: Among the arthropod-borne nematodes infesting dogs, Onchocerca lupi (Spirurida: Onchocercidae is of increasing zoonotic concern, with new human cases of infection diagnosed in Turkey, Tunisia, Iran and the USA. Knowledge of the biology of this nematode is meagre. This study aimed at assessing the distribution and periodicity of O. lupi microfilariae from different body regions in naturally infested dogs. METHODOLOGY/PRINCIPAL FINDINGS: Skin samples were collected from six dogs infested with O. lupi but without apparent clinical signs. Two skin samples were collected from 18 anatomical regions of dog 1 at necropsy. In addition, single skin biopsies were performed from the forehead, inter-scapular and lumbar regions of dogs 2-6, in the morning, afternoon, and at night. Two aliquots of the sediment of each sample were microscopically observed, microfilariae counted and morphologically and molecularly identified. Most of the 1,667 microfilariae retrieved from dog 1 were in the right ear (59.6%, nose (26.5%, left ear (6.7%, forehead (3.0%, and inter-scapular (2.9% regions. In dogs 2-6, the overall mean number of microfilariae was larger on the head (n = 122.8, followed by the inter-scapular (n = 119.0 and lumbar (n = 12.8 regions. The overall mean number of microfilariae was larger in the afternoon (153.4, followed by night (75.4 and morning (25.8. CONCLUSIONS: Onchocerca lupi microfilariae were more common in the head (i.e., ears and nose than in the remaining part of the dog's body, indicating they tend to aggregate in specific body regions, which are the best sites to collect skin samples for diagnostic purposes. The periodicity pattern of microfilariae of O. lupi and their concentration in specific body regions is most likely a result of the co-evolution with their as-yet-unknown vector. The detection of skin microfilariae in asymptomatic animals, suggests the potential role of these animals as carriers and reservoirs of O. lupi.
Full Text Available Abstract Background Onchocerca volvulus, the causative agent of river blindness, is transmitted through the black fly Simulium damnosum s.l., which breeds in turbulent river waters. To date, the number of flies attacking humans has only been determined by standard fly collectors near the river or the village. In our study, we counted the actual number of attacking and successfully feeding S. damnosum s.l. flies landing on individual villagers during their routine day-time activities in two villages of the Sudan-savannah and rainforest of Cameroon. We compared these numbers to the number of flies caught by a standard vector-collector, one positioned near the particular villager during his/her daily activity and the other sitting at the nearest Simulium breeding site. Results Using these data obtained by the two vector-collectors, we were able to calculate the Actual Index of Exposure (AIE. While the AIE in the savannah was on average 6,3%, it was 34% in the rainforest. The Effective Annual Transmission Potential (EATP for individual villagers was about 20 fold higher in the rainforest compared to the savannah. Conclusions Here we show for the first time that it is possible to determine the EATP. Further studies with more subjects are needed in the future. These data are important for the development of future treatment strategies.
Rodríguez-Pérez, Mario A.; Unnasch, Thomas R.; Domínguez-Vázquez, Alfredo; Morales-Castro, Alba L.; Richards, Frank; Peña-Flores, Graciela P.; Orozco-Algarra, María Eugenia; Prado-Velasco, Gibert
The northern Chiapas onchocerciasis focus has undergone 11 years of ivermectin mass treatment. No evidence of microfilariae in the cornea and/or anterior chamber of the eye or in skin snips was seen in residents examined in 2006 in two sentinel communities (upper limit of the 95% confidence interval [UL 95% CI] = 0.5% and 0.3%, respectively). In children 10 and under, 0 of 305 were found to harbor antibodies to Ov16, a marker of parasite exposure; 0 of 4,400 Simulium ochraceum s.l. collected in 2005 contained parasite DNA, giving an UL 95% CI for the infective rate of 0.9/2,000, and an UL 95% CI of the seasonal transmission potential of 1.2 L3/person. These data, assumed to be representative of the focus as a whole, suggest that there is no ongoing transmission of Onchocerca volvulus in the northern Chiapas focus. Community-wide treatments with ivermectin were halted in 2008, and a post-treatment surveillance phase was initiated. PMID:20595471
Rodríguez-Pérez, Mario A; Katholi, Charles R; Hassan, Hassan K; Unnasch, Thomas R
To study the impact of mass Mectizan treatment on Onchocerca volvulus transmission in Mexico, entomological surveys were carried out in the endemic foci of Oaxaca, Southern Chiapas, and Northern Chiapas. Collected flies were screened by polymerase chain reaction (PCR) for O. volvulus parasites. The prevalence of infected and infective flies was estimated using the PoolScreen algorithm and with a novel probability-based method. O. volvulus infective larvae were not detected in flies from 6/13 communities. In 7/13 communities, infective flies were detected, with prevalences ranging from 1.6/10,000 to 29.0/10,000 and seasonal transmission potentials ranging from 0.4 to 3.3. Infected and infective flies were found in a community in Northern Chiapas, suggesting that, according to World Health Organization criteria, autochthonous transmission exists in this focus. These data suggest that O. volvulus transmission in Mexico has been suppressed or brought to a level that may be insufficient to sustain the parasite population.
Marchon-Silva, Verônica; Caër, Julien Charles; Post, Rory James; Maia-Herzog, Marilza; Fernandes, Octavio
Detection of Onchocerca volvulus in Simulium populations is of primary importance in the assessment of the effectiveness of onchocerciasis control programs. In Brazil, the main focus of onchocerciasis is in the Amazon region, in a Yanomami reserve. The main onchocerciasis control strategy in Brazil is the semi-annually mass distribution of the microfilaricide ivermectin. In accordance with the control strategy for the disease, polymerase chain reaction (PCR) was applied in pools of simuliids from the area to detect the helminth infection in the vectors, as recommended by the Onchocerciasis Elimination Program for the Americas and the World Health Organization. Systematic sampling was performed monthly from September 1998 to October 1999, and a total of 4942 blackflies were collected from two sites (2576 from Balawaú and 2366 from Toototobi). The molecular methodology was found to be highly sensitive and specific for the detection of infected and/or infective blackflies in pools of 50 blackflies. The results from the material collected under field conditions showed that after the sixth cycle of distribution of ivermectin, the prevalence of infected blackflies with O. volvulus had decreased from 8.6 to 0.3% in Balawaú and from 4 to 0.1% in Toototobi.
Full Text Available Detection of Onchocerca volvulus in Simulium populations is of primary importance in the assessment of the effectiveness of onchocerciasis control programs. In Brazil, the main focus of onchocerciasis is in the Amazon region, in a Yanomami reserve. The main onchocerciasis control strategy in Brazil is the semi-annually mass distribution of the microfilaricide ivermectin. In accordance with the control strategy for the disease, polymerase chain reaction (PCR was applied in pools of simuliids from the area to detect the helminth infection in the vectors, as recommended by the Onchocerciasis Elimination Program for the Americas and the World Health Organization. Systematic sampling was performed monthly from September 1998 to October 1999, and a total of 4942 blackflies were collected from two sites (2576 from Balawaú and 2366 from Toototobi. The molecular methodology was found to be highly sensitive and specific for the detection of infected and/or infective blackflies in pools of 50 blackflies. The results from the material collected under field conditions showed that after the sixth cycle of distribution of ivermectin, the prevalence of infected blackflies with O. volvulus had decreased from 8.6 to 0.3% in Balawaú and from 4 to 0.1% in Toototobi.
Miró, Guadalupe; Montoya, Ana; Checa, Rocío; Gálvez, Rosa; Mínguez, Juan José; Marino, Valentina; Otranto, Domenico
Onchocerca lupi causes ocular pathology of varying severity in dogs from south-western United States, western Europe and northern Asia. This filarioid has also been recognized as a zoonotic agent in Tunisia, Turkey, Iran and the USA, though the information about the biology and epidemiology of this infection is largely unknown. In Europe, O. lupi has been reported in dogs from Germany, Greece, Hungary, Portugal and Romania and in a cat from Portugal. The present study was designed to establish the occurrence of O. lupi in dogs in southwestern Spain. In the present study a total of 104 dogs of different breed, sex, and age living in a shelter in Huelva (SW Spain) were examined. Skin snip samples were collected using a disposable scalpel in the forehead and inter-scapular regions and stored as aliquots in saline solution (0.5 ml) before light microscopy observation of individual sediments (20 μl) and molecular examination. Of the 104 dogs examined, 5 (4.8 %) were skin snip-positive for O. lupi: two by microscopy and three by PCR. One of the O. lupi infected dogs showed neurological signs but ocular ultrasonography and/or MRI detected no abnormalities. This first report of O. lupi infection in dogs in southern Spain expands the range of geographical distribution of this parasite and sounds an alarm bell for practitioners and physicians working in that area.
Full Text Available In Latin America, onchocerciasis is targeted for elimination by 2012 through twice-yearly mass treatment of the eligible population with ivermectin. In Guatemala, two of the four historical endemic foci have demonstrated elimination of transmission, following World Health Organization guidelines. Using established guidelines ophthalmological, serological, and entomological evaluations were conducted in 2007-8 to determine the transmission status of onchocerciasis in the Huehuetenango focus. The prevalence of Onchocerca volvulus microfilariae in the anterior segment of the eye in 365 residents was 0% (95% confidence interval [CI] 0–0.8%, the prevalence of infection of O. volvulus in Simulium ochraceum among 8252 flies collected between November 2007 and April 2008 was 0% (95% CI 0–0.02%, and the prevalence of antibodies to a recombinant O. volvulus antigen in 3118 school age children was 0% (95% CI 0–0.1%. These results showed transmission interruption; thus, in 2009 mass treatment was halted and posttreatment surveillance began. To verify for potential recrudescence an entomological evaluation (from December 2010 to April 2011 was conducted during the 2nd and 3rd year of posttreatment surveillance. A total of 4587 S. ochraceum were collected, and the prevalence of infection of O. volvulus was 0% (95% CI 0–0.04%. Transmission of onchocerciasis in the Huehuetenango focus has been eliminated.
Mario A Rodríguez-Pérez
Full Text Available BACKGROUND: The Southern Chiapas focus of onchocerciasis in Southern Mexico represents one of the major onchocerciasis foci in Latin America. All 559 endemic communities of this focus have undergone semi-annual mass treatment with ivermectin since 1998. In 50 communities of this focus, ivermectin frequency shifted from twice to four times a year in 2003; an additional 113 communities were added to the quarterly treatment regimen in 2009 to achieve a rapid suppression of transmission. METHODOLOGY/PRINCIPAL FINDINGS: In-depth epidemiologic and entomologic assessments were performed in six sentinel communities (which had undergone 2 rounds of ivermectin treatment per year and three extra-sentinel communities (which had undergone 4 rounds of ivermectin treatment per year. None of the 67,924 Simulium ochraceum s.l. collected from this focus during the dry season of 2011 were found to contain parasite DNA when tested by polymerase chain reaction-enzyme-linked immunosorbent assay (PCR-ELISA, resulting in an upper bound of the 95% confidence interval (95%-ULCI of the infective rate in the vectors of 0.06/2,000 flies examined. Serological assays testing for Onchocerca volvulus exposure conducted on 4,230 children 5 years of age and under (of a total population of 10,280 in this age group revealed that 2/4,230 individuals were exposed to O. volvulus (0.05%; one sided 95% confidence interval = 0.08%. CONCLUSIONS/SIGNIFICANCE: The in-depth epidemiological and entomological findings from the Southern Chiapas focus meet the criteria for interruption of transmission developed by the international community.
Gonzalez, Rodrigo J.; Cruz-Ortiz, Nancy; Rizzo, Nidia; Richards, Jane; Zea-Flores, Guillermo; Domínguez, Alfredo; Sauerbrey, Mauricio; Catú, Eduardo; Oliva, Orlando; Richards, Frank O.; Lindblade, Kim A.
Background Elimination of onchocerciasis (river blindness) through mass administration of ivermectin in the six countries in Latin America where it is endemic is considered feasible due to the relatively small size and geographic isolation of endemic foci. We evaluated whether transmission of onchocerciasis has been interrupted in the endemic focus of Escuintla-Guatemala in Guatemala, based on World Health Organization criteria for the certification of elimination of onchocerciasis. Methodology/Principal Findings We conducted evaluations of ocular morbidity and past exposure to Onchocerca volvulus in the human population, while potential vectors (Simulium ochraceum) were captured and tested for O. volvulus DNA; all of the evaluations were carried out in potentially endemic communities (PEC; those with a history of actual or suspected transmission or those currently under semiannual mass treatment with ivermectin) within the focus. The prevalence of microfilariae in the anterior segment of the eye in 329 individuals (≥7 years old, resident in the PEC for at least 5 years) was 0% (one-sided 95% confidence interval [CI] 0–0.9%). The prevalence of antibodies to a recombinant O. volvulus antigen (Ov-16) in 6,432 school children (aged 6 to 12 years old) was 0% (one-sided 95% IC 0–0.05%). Out of a total of 14,099 S. ochraceum tested for O. volvulus DNA, none was positive (95% CI 0–0.01%). The seasonal transmission potential was, therefore, 0 infective stage larvae per person per season. Conclusions/Significance Based on these evaluations, transmission of onchocerciasis in the Escuintla-Guatemala focus has been successfully interrupted. Although this is the second onchocerciasis focus in Latin America to have demonstrated interruption of transmission, it is the first focus with a well-documented history of intense transmission to have eliminated O. volvulus. PMID:19333366
Globisch, Daniel; Moreno, Amira Y; Hixon, Mark S; Nunes, Ashlee A K; Denery, Judith R; Specht, Sabine; Hoerauf, Achim; Janda, Kim D
Onchocerciasis, also known as "river blindness", is a neglected tropical disease infecting millions of people mainly in Africa and the Middle East but also in South America and Central America. Disease infectivity initiates from the filarial parasitic nematode Onchocerca volvulus, which is transmitted by the blackfly vector Simulium sp. carrying infectious third-stage larvae. Ivermectin has controlled transmission of microfilariae, with an African Program elimination target date of 2025. However, there is currently no point-of-care diagnostic that can distinguish the burden of infection--including active and/or past infection--and enable the elimination program to be effectively monitored. Here, we describe how liquid chromatography-MS-based urine metabolome analysis can be exploited for the identification of a unique biomarker, N-acetyltyramine-O,β-glucuronide (NATOG), a neurotransmitter-derived secretion metabolite from O. volvulus. The regulation of this tyramine neurotransmitter was found to be linked to patient disease infection, including the controversial antibiotic doxycycline treatment that has been shown to both sterilize and kill adult female worms. Further clues to its regulation have been elucidated through biosynthetic pathway determination within the nematode and its human host. Our results demonstrate that NATOG tracks O. volvulus metabolism in both worms and humans, and thus can be considered a host-specific biomarker for onchocerciasis progression. Liquid chromatography-MS-based urine metabolome analysis discovery of NATOG not only has broad implications for a noninvasive host-specific onchocerciasis diagnostic but provides a basis for the metabolome mining of other neglected tropical diseases for the discovery of distinct biomarkers and monitoring of disease progression.
Rodríguez-Pérez, Mario A.; Domínguez-Vázquez, Alfredo; Unnasch, Thomas R.; Hassan, Hassan K.; Arredondo-Jiménez, Juan I.; Orozco-Algarra, María Eugenia; Rodríguez-Morales, Kristel B.; Rodríguez-Luna, Isabel C.; Prado-Velasco, Francisco Gibert
Background The Southern Chiapas focus of onchocerciasis in Southern Mexico represents one of the major onchocerciasis foci in Latin America. All 559 endemic communities of this focus have undergone semi-annual mass treatment with ivermectin since 1998. In 50 communities of this focus, ivermectin frequency shifted from twice to four times a year in 2003; an additional 113 communities were added to the quarterly treatment regimen in 2009 to achieve a rapid suppression of transmission. Methodology/Principal findings In-depth epidemiologic and entomologic assessments were performed in six sentinel communities (which had undergone 2 rounds of ivermectin treatment per year) and three extra-sentinel communities (which had undergone 4 rounds of ivermectin treatment per year). None of the 67,924 Simulium ochraceum s.l. collected from this focus during the dry season of 2011 were found to contain parasite DNA when tested by polymerase chain reaction-enzyme-linked immunosorbent assay (PCR-ELISA), resulting in an upper bound of the 95% confidence interval (95%-ULCI) of the infective rate in the vectors of 0.06/2,000 flies examined. Serological assays testing for Onchocerca volvulus exposure conducted on 4,230 children 5 years of age and under (of a total population of 10,280 in this age group) revealed that 2/4,230 individuals were exposed to O. volvulus (0.05%; one sided 95% confidence interval = 0.08%). Conclusions/Significance The in-depth epidemiological and entomological findings from the Southern Chiapas focus meet the criteria for interruption of transmission developed by the international community. PMID:23556018
Full Text Available Onchocerca eberhardi n. sp. from the sika deer, Cervus nippon, in Japan is described. Adult worms lived in the carpal ligament; infection reached high levels (up to 25 female and 16 male worms in a single carpal limb. Skin dwelling microfilariae were mainly found in the ears. Prevalence of infection was 81 % at the type locality, Mt. Sobo, in Kyushu. The new material was compared to the 31 species of Onchocerca presently known. Onchocerca eberhardi n. sp. females were characterized by a long slender anterior end and a thin esophagus ≤ 1 mm long with no or only a slight glandular region. The vulva was located near the level of the mid-esophagus and the cuticle had transverse external ridges and internal striae (two striae between adjoining ridges. The most similar species were O. stilesi (re-examined, O. lienalis, and to a lesser extent O. gutturosa, all from bovids (cattle. Two main lineages of Onchocerca are recognized in cervids with either primitive or with derived characteristics (as exemplified by the new species. The species in both lineages are not restricted to cervids but are also found in bovids in the Holarctic region, suggesting that the species diversified in the two host groups simultaneously, when these host groups lived in the same geographic area.
Full Text Available Wild female black flies attracted to a man or an idling automobile were collected at Oita, Japan where five cases of zoonotic onchocerciasis had occurred. Among the five Simulium species captured, 2% of Simulium bidentatum, the predominant species, were infected with filarial larvae. There were at least two types of infective larvae, types A and B, based on morphometric observation. Moreover, molecular analysis of the mitochondrial cytochrome c oxidase subunit 1 (CO1 gene revealed that types A and B were represented by a single unknown species of Onchocerca and two species, i.e., Onchocerca dewittei japonica from wild boar, the causative agent of zoonotic onchocerciasis in Japan, and an undescribed Onchocerca sp. from wild boar, respectively. Phylogenetic analysis based on the sequences of the mitochondrial 12S ribosomal RNA (12S rRNA gene also showed that type A is likely to be an unknown species of Onchocerca. Natural infection of black flies with infective larvae of O. dewittei japonica and O. sp. was demonstrated for the first time. The present study strongly suggests that S. bidentatum plays a role as a vector in the transmission of zoonotic onchocerciasis due to O. dewittei japonica in Japan.
Yarzàbal, L; Petralanda, I; Arango, M; Lobo, L; Botto, C
The patterns of acid phosphatase in strains of Onchocerca volvulus s.l. which parasitize an Amerindian population (Yanomami) in Venezuela's Upper Orinoco Basin were examined by using the naphthol AS-TR phosphate method. The study sample consisted of 40 Yanomami inhabiting a savannah area at 950 m above sea level and 21 Yanomami residents of a tropical rainforest area at an altitude of 250 m. Stained intrauterine microfilariae, still within the egg case, exhibited a diffuse distribution of the enzyme in the early stages of embryonic development and a negative reaction at a more developed stage. Four of the five enzyme staining patterns described by Omar (1978) were found in the 3157 microfilariae examined from skin snips. Their distribution was: Type I--17.2%, Type III--0.5%, Type IV--75.6% and Type V--6.6%. No examples of Type II were observed. The results indicate that acid phosphatase patterns of the Upper Orinoco Onchocerca strain most resemble those of strains from Guatemala and Yemen, and are different from the African strains found in Upper Volta and Liberia. The relative frequency of acid phosphatase patterns was modified by cryopreservation of microfilariae.
deC Bronsvoort Barend M
Full Text Available Abstract Background Human onchocerciasis or river blindness, caused by the filarial nematode Onchocerca volvulus, is currently controlled using the microfilaricidal drug, ivermectin. However, ivermectin does not kill adult O. volvulus, and in areas with less than 65% ivermectin coverage of the population, there is no effect on transmission. Therefore, there is still a need for a macrofilaricidal drug. Using the bovine filarial nematode O. ochengi (found naturally in African cattle, the macrofilaricidal efficacy of the modified flubendazole, UMF-078, was investigated. Methods Groups of 3 cows were treated with one of the following regimens: (a a single dose of UMF-078 at 150 mg/kg intramuscularly (im, (b 50 mg/kg im, (c 150 mg/kg intraabomasally (ia, (d 50 mg/kg ia, or (e not treated (controls. Results After treatment at 150 mg/kg im, nodule diameter, worm motility and worm viability (as measured by metabolic reduction of tetrazolium to formazan declined significantly compared with pre-treatment values and concurrent controls. There was abrogation of embryogenesis and death of all adult worms by 24 weeks post-treatment (pt. Animals treated at 50 mg/kg im showed a decline in nodule diameter together with abrogated reproduction, reduced motility, and lower metabolic activity in isolated worms, culminating in approximately 50% worm mortality by 52 weeks pt. Worms removed from animals treated ia were not killed, but exhibited a temporary embryotoxic effect which had waned by 12 weeks pt in the 50 mg/kg ia group and by 24 weeks pt in the 150 mg/kg ia group. These differences could be explained by the different absorption rates and elimination half-lives for each dose and route of administration. Conclusion Although we did not observe any signs of mammalian toxicity in this trial with a single dose, other studies have raised concerns regarding neuro- and genotoxicity. Consequently, further evaluation of this compound has been suspended. Nonetheless
Bah, Germanus S; Ward, Emma L; Srivastava, Abhishek; Trees, Alexander J; Tanya, Vincent N; Makepeace, Benjamin L
Onchocerciasis (river blindness), caused by the filarial nematode Onchocerca volvulus, is a major cause of visual impairment and dermatitis in sub-Saharan Africa. As O. volvulus contains an obligatory bacterial symbiont (Wolbachia), it is susceptible to antibiotic chemotherapy, although current regimens are considered too prolonged for community-level control programs. The aim of this study was to compare the efficacies of oxytetracycline and rifampin, administered separately or in combination, against a close relative of O. volvulus (Onchocerca ochengi) in cattle. Six animals per group were treated with continuous or intermittent oxytetracycline regimens, and effects on adult worm viability, dermal microfilarial loads, and Wolbachia density in worm tissues were assessed. Subsequently, the efficacies of 3-week regimens of oxytetracycline and rifampin alone and a combination regimen were compared, and rifampin levels in plasma and skin were quantified. A 6-month regimen of oxytetracycline with monthly dosing was strongly adulticidal, while 3-week and 6-week regimens exhibited weaker adulticidal effects. However, all three regimens achieved >2-log reductions in microfilarial load. In contrast, rifampin monotherapy and oxytetracycline-rifampin duotherapy failed to induce substantive reductions in either adult worm burden or microfilarial load, although a borderline effect on Wolbachia density was observed following duotherapy. Dermal rifampin levels were maintained above the MIC for >24 h after a single intravenous dose. We conclude that oxytetracycline-rifampin duotherapy is less efficacious against O. ochengi than oxytetracycline alone. Further studies will be required to determine whether rifampin reduces oxytetracycline bioavailability in this system, as suggested by human studies using other tetracycline-rifampin combinations.
Full Text Available Several Simulium species were investigated as to their biting habits and natural infections with filarial larvae at Ban Pan Fan, Chiang Mai Province, in northern Thailand. Female adults flies landing on or flighting around a human and a water buffalo were collected during the daytime from 06.00 to 19.00 hours on 22 June 2001. As a result, 217 S. nodosum, 86 S. asakoae and two S. nigrogilvum were obtained from a human attractant, and 416 S. nodosum, 25 S. nakhonense, 16 S. asakoae, four 5. fenestratum and two S. nigrogilvum, from a water buffalo. The blood-feeding was confirmed only for S. nodosum and S. nigrogilvum on humans, and for S. nodosum and S. nakhonense on water buffalos. Dissections of these simuliids showed that S. nodosum was naturally infected with developing filarial larvae. Two types of microfilariae were distinguished but only one type of infective larvae. These larvae resembled Onchocerca suzukii, a parasite from a wild Japanese bovid, suggesting that an unknown Onchocerca species from ruminants was transmitted in Thailand. Infection rates with all stages of larvae and third-stage larvae were 2.3 % (14/608 and 1 .0 % (6/608, respectively. This is the first report of natural infections of black flies with Onchocerca larvae in Southeast Asia, and the involved black fly species is shown to be not only anthropophilic but also zoophilic in this region.
Bah, Germanus S; Tanya, Vincent N; Makepeace, Benjamin L
Human onchocerciasis (river blindness), caused by the filarial nematode Onchocerca volvulus, has been successfully controlled by a single drug, ivermectin, for over 25 years. Ivermectin prevents the disease symptoms of severe itching and visual impairment by killing the microfilarial stage, but does not eliminate the adult parasites, necessitating repeated annual treatments. Mass drug administration with ivermectin does not always break transmission in forest zones and is contraindicated in individuals heavily co-infected with Loa loa, while reports of reduced drug efficacy in Ghana and Cameroon may signal the development of resistance. An alternative treatment for onchocerciasis involves targeting the essential Wolbachia symbiont with tetracycline or its derivatives, which are adulticidal. However, implementation of antibiotic therapy has not occurred on a wide scale due to the prolonged treatment regimen required (several weeks). In the bovine Onchocerca ochengi system, it has been shown previously that prolonged oxytetracycline therapy increases eosinophil counts in intradermal nodules, which kill the adult worms by degranulating on their surface. Here, in an "immunochemotherapeutic" approach, we sought to enhance the efficacy of a short, sub-lethal antibiotic regimen against O. ochengi by prior immunotherapy targeting onchocystatin, an immunomodulatory protein located in the adult female worm cuticle. A key asparagine residue in onchocystatin was mutated to ablate immunomodulatory activity, which has been demonstrated previously to markedly improve the protective efficacy of this vaccine candidate when used as an immunoprophylactic. The immunochemotherapeutic regimen was compared with sub-lethal oxytetracycline therapy alone; onchocystatin immunotherapy alone; a gold-standard prolonged, intermittent oxytetracycline regimen; and no treatment (negative control) in naturally infected Cameroonian cattle. Readouts were collected over one year and comprised adult
Attah, Simon K; Ayeh-Kumi, Patrick F; Sittie, Archibald A; Oppong, Isaac V; Nyarko, Alexander K
Onchocerciasis transmitted by Onchocerca volvulus is the second major cause of blindness in the world and it impacts negatively on the socio-economic development of the communities affected. Currently, ivermectin, a microfilaricidal drug is the only drug recommended for treating this disease. There have been speculations, of late, concerning O. volvulus resistance to ivermectin. Owing to this, it has become imperative to search for new drugs. World-wide, ethnomedicines including extracts of Euphorbia hirta and Rauvolfia vomitoria are used for treating various diseases, both infectious and non-infectious. In this study extracts of the two plants were evaluated in vitro in order to determine their effect against O. volvulus microfilariae. The toxicity of the E. hirta extracts on monkey kidney cell (LLCMK2) lines was also determined. The investigations showed that extracts of both plants immobilised microfilariae at different levels in vitro and, therefore, possess antifilarial properties. It was found that all the E. hirta extracts with the exception of the hexane extracts were more effective than those of R. vomitoria. Among the extracts of E. hirta the ethyl acetate fraction was most effective, and comparable to that of dimethanesulphonate salt but higher than that of Melarsoprol (Mel B). However, the crude ethanolic extract of E. hirta was found to be the least toxic to the LLCMK2 compared to the fractionated forms. Extracts from both plants possess antifilarial properties; however, the crude extract of E. hirta was found to be least toxic to LLCMK2.
Bennuru, Sasisekhar; Cotton, James A.; Ribeiro, Jose M. C.; Grote, Alexandra; Harsha, Bhavana; Holroyd, Nancy; Mhashilkar, Amruta; Molina, Douglas M.; Randall, Arlo Z.; Shandling, Adam D.; Unnasch, Thomas R.; Ghedin, Elodie; Berriman, Matthew
ABSTRACT Onchocerciasis (river blindness) is a neglected tropical disease that has been successfully targeted by mass drug treatment programs in the Americas and small parts of Africa. Achieving the long-term goal of elimination of onchocerciasis, however, requires additional tools, including drugs, vaccines, and biomarkers of infection. Here, we describe the transcriptome and proteome profiles of the major vector and the human host stages (L1, L2, L3, molting L3, L4, adult male, and adult female) of Onchocerca volvulus along with the proteome of each parasitic stage and of its Wolbachia endosymbiont (wOv). In so doing, we have identified stage-specific pathways important to the parasite’s adaptation to its human host during its early development. Further, we generated a protein array that, when screened with well-characterized human samples, identified novel diagnostic biomarkers of O. volvulus infection and new potential vaccine candidates. This immunomic approach not only demonstrates the power of this postgenomic discovery platform but also provides additional tools for onchocerciasis control programs. PMID:27881553
Full Text Available Control of onchocerciasis as a public health problem in Africa relies on annual mass ivermectin distribution. New tools are needed to achieve elimination of infection. This study determined in a small number of Onchocerca volvulus infected individuals whether moxidectin, a veterinary anthelminthic, is safe enough to administer it in a future large study to further characterize moxidectin's safety and efficacy. Effects on the parasite were also assessed.Men and women from a forest area in South-eastern Ghana without ivermectin mass distribution received a single oral dose of 2 mg (N = 44, 4 mg (N = 45 or 8 mg (N = 38 moxidectin or 150 µg/kg ivermectin (N = 45 with 18 months follow up. All ivermectin and 97%-100% of moxidectin treated participants had Mazzotti reactions. Statistically significantly higher percentages of participants treated with 8 mg moxidectin than participants treated with ivermectin experienced pruritus (87% vs. 56%, rash (63% vs. 42%, increased pulse rate (61% vs. 36% and decreased mean arterial pressure upon 2 minutes standing still after ≥5 minutes supine relative to pre-treatment (61% vs. 27%. These reactions resolved without treatment. In the 8 mg moxidectin and ivermectin arms, the mean±SD number of microfilariae/mg skin were 22.9±21.1 and 21.2±16.4 pre-treatment and 0.0±0.0 and 1.1±4.2 at nadir reached 1 and 3 months after treatment, respectively. At 6 months, values were 0.0±0.0 and 1.6±4.5, at 12 months 0.4±0.9 and 3.4±4.4 and at 18 months 1.8±3.3 and 4.0±4.8, respectively, in the 8 mg moxidectin and ivermectin arm. The reduction from pre-treatment values was significantly higher after 8 mg moxidectin than after ivermectin treatment throughout follow up (p<0.01.The 8 mg dose of moxidectin was safe enough to initiate the large study. Provided its results confirm those from this study, availability of moxidectin to control programmes could help them achieve onchocerciasis elimination
Eisenbarth, Albert; Achukwi, Mbunkah Daniel; Renz, Alfons
Background Recent reports of transmission interruption of Onchocerca volvulus, the causing agent of river blindness, in former endemic foci in the Americas, and more recently in West and East Africa, raise the question whether elimination of this debilitating disease is underway after long-term treatment of the population at risk with ivermectin. The situation in Central Africa has not yet been clearly assessed. Methods and findings Entomologic data from two former endemic river basins in North Cameroon were generated over a period of 43 and 48 months to follow-up transmission levels in areas under prolonged ivermectin control. Moreover, epidemiologic parameters of animal-borne Onchocerca spp. transmitted by the same local black fly vectors of the Simulium damnosum complex were recorded and their impact on O. volvulus transmission success evaluated. With mitochondrial DNA markers we unambiguously confirmed the presence of infective O. volvulus larvae in vectors from the Sudan savannah region (mean Annual Transmission Potential 2009–2012: 98, range 47–221), but not from the Adamawa highland region. Transmission rates of O. ochengi, a parasite of Zebu cattle, were high in both foci. Conclusions/significance The high cattle livestock density in conjunction with the high transmission rates of the bovine filaria O. ochengi prevents the transmission of O. volvulus on the Adamawa plateau, whereas transmission in a former hyperendemic focus was markedly reduced, but not completely interrupted after 25 years of ivermectin control. This study may be helpful to gauge the impact of the presence of animal-filariae for O. volvulus transmission in terms of the growing human and livestock populations in sub-Saharan countries. PMID:26926855
Richards, Frank; Rizzo, Nidia; Diaz Espinoza, Carlos Enrique; Monroy, Zoraida Morales; Crovella Valdez, Carol Guillermina; de Cabrera, Renata Mendizabal; de Leon, Oscar; Zea-Flores, Guillermo; Sauerbrey, Mauricio; Morales, Alba Lucia; Rios, Dalila; Unnasch, Thomas R; Hassan, Hassan K; Klein, Robert; Eberhard, Mark; Cupp, Ed; Domínguez, Alfredo
We report the elimination of Onchocerca volvulus transmission from the Central Endemic Zone (CEZ) of onchocerciasis in Guatemala, the largest focus of this disease in the Americas and the first to be discovered in this hemisphere by Rodolfo Robles Valverde in 1915. Mass drug administration (MDA) with ivermectin was launched in 1988, with semiannual MDA coverage reaching at least 85% of the eligible population in > 95% of treatment rounds during the 12-year period, 2000-2011. Serial parasitological testing to monitor MDA impact in sentinel villages showed a decrease in microfilaria skin prevalence from 70% to 0%, and polymerase chain reaction (PCR)-based entomological assessments of the principal vector Simulium ochraceum s.l. showed transmission interruption by 2007. These assessments, together with a 2010 serological survey in children 9-69 months of age that showed Ov16 IgG4 antibody prevalence to be Guatemala declared onchocerciasis transmission as having been eliminated from the CEZ. © The American Society of Tropical Medicine and Hygiene.
Wanji, Samuel; Amvongo-Adjia, Nathalie; Njouendou, Abdel Jelil; Kengne-Ouafo, Jonas Arnaud; Ndongmo, Winston Patrick Chounna; Fombad, Fanny Fri; Koudou, Benjamin; Enyong, Peter A; Bockarie, Moses
The immunochromatographic test (ICT) for lymphatic filariasis is a serological test designed for unequivocal detection of circulating Wuchereria bancrofti antigen. It was validated and promoted by WHO as the primary diagnostic tool for mapping and impact monitoring for disease elimination following interventions. The initial tests for specificity and sensitivity were based on samples collected in areas free of loiasis and the results suggested a near 100% specificity for W. bancrofti. The possibility of cross-reactivity with non-Wuchereria bancrofti antigens was not investigated until recently, when false positive results were observed in three independent studies carried out in Central Africa. Associations were demonstrated between ICT positivity and Loa loa microfilaraemia, but it was not clearly established if these false positive results were due to L. loa or can be extended to other filarial nematodes. This study brought further evidences of the cross-reactivity of ICT card with L. loa and Onchocerca ochengi (related to O. volvulus parasite) using in vivo and in vitro systems. Two filarial/host experimental systems (L. loa-baboon and O. ochengi-cattle) and the in vitro maintenance of different stages (microfilariae, infective larvae and adult worm) of the two filariae were used in three experiments per filarial species. First, whole blood and sera samples were prepared from venous blood of patent baboons and cattle, and applied on ICT cards to detect circulating filarial antigens. Secondly, larval stages of L. loa and O. ochengi as well as O. ochengi adult males were maintained in vitro. Culture supernatants were collected and applied on ICT cards after 6, 12 and 24 h of in vitro maintenance. Finally, total worm extracts (TWE) were prepared using L. loa microfilariae (Mf) and O. ochengi microfilariae, infective larvae and adult male worms. TWE were also tested on ICT cards. For each experiment, control assays (whole blood and sera from uninfected babon
Joseph D Turner
Full Text Available The risk of severe adverse events following treatment of onchocerciasis with ivermectin in areas co-endemic with loiasis currently compromises the development of control programmes and the treatment of co-infected individuals. We therefore assessed whether doxycycline treatment could be used without subsequent ivermectin administration to effectively deliver sustained effects on Onchocerca volvulus microfilaridermia and adult viability. Furthermore we assessed the safety of doxycycline treatment prior to ivermectin administration in a subset of onchocerciasis individuals co-infected with low to moderate intensities of Loa loa microfilaraemia.A double-blind, randomized, field trial was conducted of 6 weeks of doxycycline (200 mg/day alone, doxycycline in combination with ivermectin (150 microg/kg at +4 months or placebo matching doxycycline + ivermectin at +4 months in 150 individuals infected with Onchocerca volvulus. A further 22 individuals infected with O. volvulus and low to moderate intensities of Loa loa infection were administered with a course of 6 weeks doxycycline with ivermectin at +4 months. Treatment efficacy was determined at 4, 12 and 21 months after the start of doxycycline treatment together with the frequency and severity of adverse events.One hundred and four (60.5% participants completed all treatment allocations and follow up assessments over the 21-month trial period. At 12 months, doxycycline/ivermectin treated individuals had lower levels of microfilaridermia and higher frequency of amicrofilaridermia compared with ivermectin or doxycycline only groups. At 21 months, microfilaridermia in doxycycline/ivermectin and doxycycline only groups was significantly reduced compared to the ivermectin only group. 89% of the doxycycline/ivermectin group and 67% of the doxycycline only group were amicrofilaridermic, compared with 21% in the ivermectin only group. O. volvulus from doxycycline groups were depleted of Wolbachia and all
Jessica A Hess
Full Text Available In some regions in Africa, elimination of onchocerciasis may be possible with mass drug administration, although there is concern based on several factors that onchocerciasis cannot be eliminated solely through this approach. A vaccine against Onchocerca volvulus would provide a critical tool for the ultimate elimination of this infection. Previous studies have demonstrated that immunization of mice with Ov-103 and Ov-RAL-2, when formulated with alum, induced protective immunity. It was hypothesized that the levels of protective immunity induced with the two recombinant antigens formulated with alum would be improved by formulation with other adjuvants known to enhance different types of antigen-specific immune responses.Immunizing mice with Ov-103 and Ov-RAL-2 in conjunction with alum, Advax 2 and MF59 induced significant levels of larval killing and host protection. The immune response was biased towards Th2 with all three of the adjuvants, with IgG1 the dominant antibody. Improved larval killing and host protection was observed in mice immunized with co-administered Ov-103 and Ov-RAL-2 in conjunction with each of the three adjuvants as compared to single immunizations. Antigen-specific antibody titers were significantly increased in mice immunized concurrently with the two antigens. Based on chemokine levels, it appears that neutrophils and eosinophils participate in the protective immune response induced by Ov-103, and macrophages and neutrophils participate in immunity induced by Ov-RAL-2.The mechanism of protective immunity induced by Ov-103 and Ov-RAL-2, with the adjuvants alum, Advax 2 and MF59, appears to be multifactorial with roles for cytokines, chemokines, antibody and specific effector cells. The vaccines developed in this study have the potential of reducing the morbidity associated with onchocerciasis in humans.
Full Text Available Onchocerciasis is a neglected tropical disease caused by infection with the parasite Onchocerca volvulus (Ov. An estimated 180 million people are at risk for Ov infection, and 37 million people are infected, mostly in Africa. A lateral flow-based assay to detect human IgG4 antibodies to the Ov-specific antigen Ov-16 was developed as a rapid tool to detect exposure to Ov. The test, when performed on 449 sera specimens from patients with microfiladermia and Ov-negative patients, has a sensitivity of 89.1% (95% confidence interval: 86.2%-92.0%, and specificity of 97% (95% confidence interval: 95.4%-98.6%. Because the intended use of the test is for surveillance, it is highly desirable to have a stable, long-lasting result. An extended read window is thus desirable for a high-volume, busy workflow and facilitates post-surveillance quality assurance. The main restriction on achieving an extended read window for this assay was the erythrocyte lysis that can alter the signal-to-noise ratio, especially in those with low IgG4 levels (weak positives. We describe a test housing that incorporates a user-independent feature driven by assay fluid and an expanding wick that detaches the blood separation membrane from the nitrocellulose used in the assay, but before hemolysis occurs. We demonstrated material functionality at extreme operational conditions (37°C, 80% relative humidity and a read window of a minimum of 70 days. The fluid-driven assay device performs equally as well with whole blood as with plasma, as demonstrated with 100 spiked clinical specimens (with a correlation coefficient of 0.96. We show a novel, inexpensive, and simple approach to actuating the detachment of the blood separation membrane from the nitrocellulose test with no impact on the performance characteristics of the test.
Stephen R Doyle
Full Text Available Treatment of onchocerciasis using mass ivermectin administration has reduced morbidity and transmission throughout Africa and Central/South America. Mass drug administration is likely to exert selection pressure on parasites, and phenotypic and genetic changes in several Onchocerca volvulus populations from Cameroon and Ghana-exposed to more than a decade of regular ivermectin treatment-have raised concern that sub-optimal responses to ivermectin's anti-fecundity effect are becoming more frequent and may spread.Pooled next generation sequencing (Pool-seq was used to characterise genetic diversity within and between 108 adult female worms differing in ivermectin treatment history and response. Genome-wide analyses revealed genetic variation that significantly differentiated good responder (GR and sub-optimal responder (SOR parasites. These variants were not randomly distributed but clustered in ~31 quantitative trait loci (QTLs, with little overlap in putative QTL position and gene content between the two countries. Published candidate ivermectin SOR genes were largely absent in these regions; QTLs differentiating GR and SOR worms were enriched for genes in molecular pathways associated with neurotransmission, development, and stress responses. Finally, single worm genotyping demonstrated that geographic isolation and genetic change over time (in the presence of drug exposure had a significantly greater role in shaping genetic diversity than the evolution of SOR.This study is one of the first genome-wide association analyses in a parasitic nematode, and provides insight into the genomics of ivermectin response and population structure of O. volvulus. We argue that ivermectin response is a polygenically-determined quantitative trait (QT whereby identical or related molecular pathways but not necessarily individual genes are likely to determine the extent of ivermectin response in different parasite populations. Furthermore, we propose that genetic
Nana-Djeunga, Hugues C.; Kengne-Ouafo, Jonas A.; Pion, Sébastien D. S.; Bopda, Jean; Kamgno, Joseph; Wanji, Samuel; Che, Hua; Kuesel, Annette C.; Walker, Martin; Basáñez, Maria-Gloria; Boakye, Daniel A.; Osei-Atweneboana, Mike Y.; Boussinesq, Michel; Prichard, Roger K.; Grant, Warwick N.
Background Treatment of onchocerciasis using mass ivermectin administration has reduced morbidity and transmission throughout Africa and Central/South America. Mass drug administration is likely to exert selection pressure on parasites, and phenotypic and genetic changes in several Onchocerca volvulus populations from Cameroon and Ghana—exposed to more than a decade of regular ivermectin treatment—have raised concern that sub-optimal responses to ivermectin's anti-fecundity effect are becoming more frequent and may spread. Methodology/Principal findings Pooled next generation sequencing (Pool-seq) was used to characterise genetic diversity within and between 108 adult female worms differing in ivermectin treatment history and response. Genome-wide analyses revealed genetic variation that significantly differentiated good responder (GR) and sub-optimal responder (SOR) parasites. These variants were not randomly distributed but clustered in ~31 quantitative trait loci (QTLs), with little overlap in putative QTL position and gene content between the two countries. Published candidate ivermectin SOR genes were largely absent in these regions; QTLs differentiating GR and SOR worms were enriched for genes in molecular pathways associated with neurotransmission, development, and stress responses. Finally, single worm genotyping demonstrated that geographic isolation and genetic change over time (in the presence of drug exposure) had a significantly greater role in shaping genetic diversity than the evolution of SOR. Conclusions/Significance This study is one of the first genome-wide association analyses in a parasitic nematode, and provides insight into the genomics of ivermectin response and population structure of O. volvulus. We argue that ivermectin response is a polygenically-determined quantitative trait (QT) whereby identical or related molecular pathways but not necessarily individual genes are likely to determine the extent of ivermectin response in different
Segura-Cabrera, Aldo; Bocanegra-García, Virgilio; Lizarazo-Ortega, Cristian; Guo, Xianwu; Correa-Basurto, José; Rodríguez-Pérez, Mario A.
Onchocerciasis is a leading cause of blindness with at least 37 million people infected and more than 120 million people at risk of contracting the disease; most (99%) of this population, threatened by infection, live in Africa. The drug of choice for mass treatment is the microfilaricidal Mectizan® (ivermectin); it does not kill the adult stages of the parasite at the standard dose which is a single annual dose aimed at disease control. However, multiple treatments a year with ivermectin have effects on adult worms. The discovery of new therapeutic targets and drugs directed towards the killing of the adult parasites are thus urgently needed. The chitinase of filarial nematodes is a new drug target due to its essential function in the metabolism and molting of the parasite. Closantel is a potent and specific inhibitor of chitinase of Onchocerca volvulus (OvCHT1) and other filarial chitinases. However, the binding mode and specificity of closantel towards OvCHT1 remain unknown. In the absence of a crystallographic structure of OvCHT1, we developed a homology model of OvCHT1 using the currently available X-ray structures of human chitinases as templates. Energy minimization and molecular dynamics (MD) simulation of the model led to a high quality of 3D structure of OvCHIT1. A flexible docking study using closantel as the ligand on the binding site of OvCHIT1 and human chitinases was performed and demonstrated the differences in the closantel binding mode between OvCHIT1 and human chitinase. Furthermore, molecular dynamics simulations and free-energy calculation were employed to determine and compare the detailed binding mode of closantel with OvCHT1 and the structure of human chitinase. This comparative study allowed identification of structural features and properties responsible for differences in the computationally predicted closantel binding modes. The homology model and the closantel binding mode reported herein might help guide the rational development of
. Detection of the parasites in the vector was attained by dissection of flies under dissecting microscope. The result revealed that the prevalence of microfilariae among insects collected in the months July and August was 23.08% and 21.47%.
As an alternative to vector control, chemotherapy – based control has been revolutionized by the finding that ivermectin, a novel semi synthetic macrocyclic lactone, is safe and acceptable for mass ... The prevalence rate of infection obtained at post-treatment 2 was 9.1% while the intensity rate was 1.1mf/mg skin snip.
West African Journal of Medicine. Journal Home · ABOUT THIS JOURNAL · Advanced Search · Current Issue · Archives · Journal Home > Vol 24, No 1 (2005) >. Log in or Register to get access to full text downloads.
Annual mass treatment with ivermectin for 12 – 15 years in endemic communities is the control strategy adopted by the African Programme for Onchocerciasis Control (APOC) for the control of onchocerciasis in Nigeria. This long-term treatment necessitates the use of Polymerase Chain Reaction (PCR) for the proper ...
Epidemiological, entomological and serological assessments were conducted. Results: Freshwater crabs (n = 14,391) caught from monitoring sites (n = 41) since 2008 were negative for immature stages of S. neavei. The S.neavei population was reduced following trial and initiation of ground larviciding. No adult S. neavei ...
Simon J O'Hanlon
Full Text Available The initial endemicity (pre-control prevalence of onchocerciasis has been shown to be an important determinant of the feasibility of elimination by mass ivermectin distribution. We present the first geostatistical map of microfilarial prevalence in the former Onchocerciasis Control Programme in West Africa (OCP before commencement of antivectorial and antiparasitic interventions.Pre-control microfilarial prevalence data from 737 villages across the 11 constituent countries in the OCP epidemiological database were used as ground-truth data. These 737 data points, plus a set of statistically selected environmental covariates, were used in a Bayesian model-based geostatistical (B-MBG approach to generate a continuous surface (at pixel resolution of 5 km x 5km of microfilarial prevalence in West Africa prior to the commencement of the OCP. Uncertainty in model predictions was measured using a suite of validation statistics, performed on bootstrap samples of held-out validation data. The mean Pearson's correlation between observed and estimated prevalence at validation locations was 0.693; the mean prediction error (average difference between observed and estimated values was 0.77%, and the mean absolute prediction error (average magnitude of difference between observed and estimated values was 12.2%. Within OCP boundaries, 17.8 million people were deemed to have been at risk, 7.55 million to have been infected, and mean microfilarial prevalence to have been 45% (range: 2-90% in 1975.This is the first map of initial onchocerciasis prevalence in West Africa using B-MBG. Important environmental predictors of infection prevalence were identified and used in a model out-performing those without spatial random effects or environmental covariates. Results may be compared with recent epidemiological mapping efforts to find areas of persisting transmission. These methods may be extended to areas where data are sparse, and may be used to help inform the feasibility of elimination with current and novel tools.
Rodríguez-Pérez, Mario A.; Unnasch, Thomas R.; Domínguez-Vázquez, Alfredo; Morales-Castro, Alba L.; Peña-Flores, Graciela P.; Orozco-Algarra, María E.; Arredondo-Jiménez, Juan I.; Richards, Frank; Vásquez-Rodríguez, Miguel A.; Rendón, Vidal García
All endemic communities of the Oaxaca focus of onchocerciasis in southern Mexico have been treated annually or semi-annually with ivermectin since 1994. In-depth epidemiologic assessments were performed in communities during 2007 and 2008. None of the 52,632 Simulium ochraceum s.l. collected in four sentinel communities was found to contain parasite DNA when tested by polymerase chain reaction-enzyme-linked immunosorbent assay (PCR-ELISA), resulting in an upper bound of the infection rate in the vectors of 0.07/2,000. The prevalence of microfilariae (mf) in the cornea and/or anterior chamber of the eye was also zero (0 of 1,039 residents examined; 95%-UL = 0.35%). Similarly, all 1,164 individuals examined by skin biopsy were mf negative (95%-UL = 0.31%), and sera collected from 3,569 children from 25 communities did not harbor Ov16 IgG4-antibodies (95%-UL = 0.09%). These meet the criteria for absence of morbidity and parasite transmission in the Oaxaca focus. As a result mass treatments with ivermectin were halted in 2009. PMID:20595472
Atti, Miska Elyemen; TR, Unnasch; Mukhtar, M.M.
Onchcerciasis is endemic in three geographical regions in Sudan, and presented with variable clinical reactions. The current diagnosis of onchocerciasis is based on detection of live microflaraie in skin snips in addition to clinical signs and history of living in endemic regions. Different serological diagnostic trials using crude soluble antigens of O. volvulus have shown variable degrees of cross reaction with other nematodes co-endemic in the same area. We have studied the sensitivity and specificity of RAL-2, calreticulin and PDI O. volvulus cloned antigens using the ELISA techniques. Eighty serum samples of Onchocerciasis patients, 20 non endemic normal controls and 42 samples of patients of other endemic deseas including Leishmanoasis, malaria, tuberculosis and shestosomiasis were tested RAL-2 gave the best Ig G response, with 83.75% sensitivity and 91. 66% specificity. PDI sensitivity was 20% and specificity 91.66%, while calreticulum showed sensitivity of 37.5% and specificity of 73.30%. IgG3 subclasses was not significantly different from controls while IgG4 was significantly higher in patients. The sensitivity of RAL-2 for IgG4 was 90% with a specificity of 100%. For PDI sensitivity was 25% and 100% specificity while calreticulin resulted in sensitivity of 75% and specificity of 100%. Low levels of circulating IgE to RAL-2 antigen were detected. For all antigens there was significant correlation with gender, age, microflarial load or presence of nodules. (Author)
Isam M A Zarroug
Full Text Available The abundance of onchocerciasis vectors affects the epidemiology of disease in Sudan, therefore, studies of vector dynamics are crucial for onchocerciasis control/elimination programs. This study aims to compare the relative abundance, monthly biting-rates (MBR and hourly-based distribution of onchocerciasis vectors in Abu-Hamed and Galabat foci. These seasonally-based factors can be used to structure vector control efforts to reduce fly-biting rates as a component of onchocerciasis elimination programs.A cross-sectional study was conducted in four endemic villages in Abu-Hamed and Galabat foci during two non-consecutive years (2007-2008 and 2009-2010. Both adults and aquatic stages of the potential onchocerciasis vector Simulium damnosum sensu lato were collected following standard procedures during wet and dry seasons. Adult flies were collected using human landing capture for 5 days/month. The data was recorded on handheld data collection sheets to calculate the relative abundance, MBR, and hourly-based distribution associated with climatic factors. The data analysis was carried out using ANOVA and Spearman rank correlation tests.Data on vector surveillance revealed higher relative abundance of S. damnosum s.l. in Abu- Hamed (39,934 flies than Galabat (8,202 flies. In Abu-Hamed, vector populations increased in January-April then declined in June-July until they disappeared in August-October. Highest black fly density and MBR were found in March 2007 (N = 9,444, MBR = 58,552.8 bites/person/month, and March 2010 (N = 2,603, MBR = 16,138.6 bites/person/month while none of flies were collected in August-October (MBR = 0 bites/person/month. In Galabat, vectors increased in September-December, then decreased in February-June. The highest vector density and MBR were recorded in September 2007 (N = 1,138, MBR = 6,828 bites/person/month and September 2010 (N = 1,163, MBR = 6,978 bites/person/month, whereas, none appeared in collection from April to June. There was a significant difference in mean monthly density of S. damnosum s.l. across the two foci in 2007-2008 (df = 3, F = 3.91, P = 0.011. Minimum temperature showed significant correlation with adult flies counts in four areas sampled; the adult counts were increased in Nady village (rs = 0.799 and were decreased in Kalasecal (rs = -0.676, Gumaiza (rs = -0.585, and Hilat Khateir (rs = -0.496. Maximum temperature showed positive correlation with black fly counts only in Galabat focus. Precipitation was significantly correlated with adult flies counts in Nady village, Abu-Hamed, but no significance was found in the rest of the sampled villages in both foci. Hourly-based distribution of black flies showed a unimodal pattern in Abu-Hamed with one peak (10:00-18:00, while a bimodal pattern with two peaks (07:00-10:00 and (14:00-18:00 was exhibited in Galabat.Transmission of onchocerciasis in both foci showed marked differences in seasonality, which may be attributed to ecology, microclimate and proximity of breeding sites to collection sites. The seasonal shifts between the two foci might be related to variations in climate zones. This information on black fly vector seasonality, ecology, distribution and biting activity has obvious implications in monitoring transmission levels to guide the national and regional onchocerciasis elimination programs in Sudan.
Lakwo Thomson Luroni
Full Text Available Few studies have documented the interruption of onchocerciasis and Lymphatic Filariasis (LF by integrated chemotherapy in Uganda. The study describes the interruption of transmission of the two diseases co-endemic in Obongi focus, north western Uganda. Base line data for Onchocerciasis and LF were collected in 1994 and 2006, respectively. Annual mass drug administration for onchocerciasis (Ivermectin and Lymphatic Filariasis (Ivermectin + albendazole was conducted for 20 and 6 years, respectively. Thereafter, assessments by skin snip, larval searches in rivers and human landing catches were performed. Children 65% was achieved in the six treatment rounds. Household ownership of ITN's and utilization was 96% and 72.4%., respectively.Parasitological examinations conducted for onchocerciasis among 807 adults and children, revealed a reduction in mf prevalence from 58% in 1994 to 0% in 2012. Entomological monitoring conducted at the two sites had no single Simulium damnosum fly caught. Serological analysis using Ov16 ELISA for onchocerciasis revealed that out of the 3,308 children <10 years old screened in 2013, only 3/3308 (0.091% positive cases were detected. All Ov16 positive children were negative when tested for patent infection by skin snip PCR. A reduction in LF microfilaria prevalence from 2.5% (n = 13/522 in 2006 to 0.0% (n = 602 in 2014 was observed. LF TAS1 conducted in 2015 among 1,532 children 6-7 years, all were negative for antigens of W. bancrofti.The results concluded that interruption of onchocerciasis and LF has been achieved.
subunits from other eukaryotic organisms (Aplysia californica, S. japonicum, Caenorhabditis 143 elegans Mus musculus, Onchocerca volvulus , and Homo...Caenorhabditis elegans PKA-R (J05220); OvR, Onchocerca volvulus PKA-R (AY159364). 156 157 Figure 19: RNAi of Sm04765 in...PKA cancer chemotherapeutics . Interestingly, the PKA-R subunit homologue in Onchocerca volvulus , causative agent of river blindness, is being
prevalence of nodules of Onchocerca volvulus in Guatemala over the last four decades. Trop Med Parasitol 37: 28-34 CHAPTER 2 Manuscript 1 33 Mapping...Onchocerca volvulus in Guatemala over the last four decades. Trop Med Parasitol 37: 28-34 53 Figure 1: Villages (represented as blue dots) in Belize
Full Text Available Japan is a country of high specific diversity of Onchocerca with eight species, the adults of two not yet known. Onchocerca dewittei japonica, a common filarial parasite of wild boar, had been proved to be the agent of five zoonotic onchocerciasis in Kyushu island with morphological and molecular studies. The sixth case, at Hiroshima in the main island, was identified to the same Onchocerca species, based on adult characters observed on histological sections. To consolidate the identification, mitochondrial cytochrome c oxidase subunit 1 (CO1 gene analysis was attempted with the formalin-fixed, paraffin-embedded parasite specimen. The sequence (196 bp of a CO1 gene fragment of the parasite successfully PCR-amplified agreed well with those of O. dewittei japonica registered in GenBank, confirming the morphological identification. Moreover a comparison with the CO1 gene sequences of six other Onchocerca species in GenBank excluded the possibility that Onchocerca sp. from wild boar and Onchocerca sp. type A from cattle in Japan, were the causative agents in this case. Mitochondrial DNA analysis proved to be a valuable tool to support the morphological method for the discrimination of zoonotic Onchocerca species in a histological specimen.
...): Strongylus vulgaris (also early forms in blood vessels), S. edentatus (also tissue stages), S. equinus..., Onchocerca sp. (B) Large Strongyles (Strongylus equinus (adult), S. vulgaris (adult and arterial larval...
the disease bring about the need to control onchocerciasis by understanding the mechanism of the host's ... The insect vector of Onchocerca is the black fly, Simulium. The larvae ...... D. immitis infection in dogs (WHO, 1987). Introduction of.
Histochemical Characterization of Rain-Forest Strain of Onchocerca Volvulus Microfilariae Isolated in Akamkpa, Cross River State, Nigeria. EMAIL FULL TEXT EMAIL FULL TEXT DOWNLOAD FULL TEXT DOWNLOAD FULL TEXT. AW Essien, PC Inyang-Etoh, GC Ejezie ...
... an infection caused by the parasitic worm Onchocerca volvulus , spread by the bite of an infected Simulium ... indicate that you are still infected with O. volvulus . What is the treatment for onchocerciasis? There are ...
L.E. Coffeng (Luc)
markdownabstract__Abstract__ Onchocerciasis is a tropical disease endemic to Sub-Saharan Africa, Yemen, and parts of Latin America, and is caused by the filarial nematode Onchocerca volvulus, which is found exclusively in humans. Adult specimens of this roundworm reside in subcutaneous and
Onchocerciasis is a chronic parasitic disease with a wide range of cutaneous and ocular manifestations. It is caused by the tissue nematode, Onchocerca volvulus, and it is transmitted by the bite of a female black fly, Simulium damnosum. Onchocerciasis is a serious public health and socio-economic problem with 95% of all ...
Department of Paediatrics and Child Health Makerere University, Kampala, Uganda. 2. Department of ... several times each day, often during meals, and in ..... Figure 2: The smaller patient has Nodding syndrome and is the same age as the taller adolescent who is of the ... Onchocerca volvulus in the CSF confirms our lack.
Their fragments elicit host inflammatory responses with bystander effects believed to underlie dermal and ocular changes (5,. 6). Immunological mechanisms are believed to play a major role in the broad range of dermal and ocular pathologies complicating Onchocerca volvulus infections. These have therefore prompted.
Nov 24, 2015 ... Abstract. Onchocerciasis is a severe parasitic infestation caused by Onchocerca volvulus which causes disabling skin and subcutaneous tissue changes and ultimately leads to blindness. It has a huge public health impact due to its socioeconomic burden and the vast number of people it affects in.
Urinary tract parasites, which included Trichomonas. vaginalis and Schistosoma haematobium, were found in 330(6.87%) of the study population and hemoparasites (P. falciparum and Onchocerca spp.) in 1260(26.25%). Mixed infections of gastrointestinal and hemoparasites, gastrointestinal and urinary tract parasites, ...
This implied that treatment with ivermectin has a significant impact on the microfilaria load of Onchocerca volvulus therefore long term treatment with ivermectin after more than 15 years there is hope that there will be total elimination of onchocercoaisis in the study-area because many villages are having zero prevalence of ...
Factors affecting the transmission of human onchocerciasis by Simulium damnosum s l. in a fringe savanna village in Cross River State, Nigeria Abstract · Vol 9, No 1 (2009) - Articles Histochemical Characterization of Rain-Forest Strain of Onchocerca Volvulus Microfilariae Isolated in Akamkpa, Cross River State, Nigeria.
The study which was conducted between March and June 2015 also investigated the sero prevalence of Onchocerca volvulus using onchocerciasis IgG4 RDT. Data were analysed using SPSS 20 software. Demographic information revealed that 43.3% (939/2,169) were males while 56.7% (1,230/2,169) were females.
Indirect sandwich enzyme-linked immunosorbent assay (ELISA) was used to measure serum antibody responses in onchocerciasis patients. Apparently, IgG antibody class was more sensitive than IgG1, IgG3 and IgG4 responses to Onchocerca volvulus adult worms sodium duodecyl sulphate (SDS) extracted crude ...
Full Text Available Histological examination of a nodule removed from the back of the hand of a 58-year-old woman from Oita, Kyushu, Japan showed an Onchocerca female sectioned through the posterior region of the worm (ovaries identifiable and young (thin cuticle. Six Onchocerca species are enzootic in that area: O. gutturosa and O. lienalis in cattle, O. suzukii in serows (Capricornis crispus, O. skrjabini and an Onchocerca sp. in Cervus nippon nippon, and O. dewittei japonica in wild boar (Sus scrofa leucomystax. Diagnostic charactets of female Onchocerca species, such as the cuticle and its ridges, change along the body length. Tables of the histologic morphology of the mid- and posterior body-regions of the local species are presented. In addition, it was observed that transverse ridges arose and thickened during the adult stage (examination of fourth stage and juvenile females of O. volvulus. The specimen described in this report, with its prominent and widely spaced ridges, was identified as O. d. japonica. Four of the 10 zoonotic cases of onchocerciasis reported worldwide were from Oita, three of them being caused by O. d. japonica, the prevalence of which in local wild boar was 22 of 24 (92 %.
Pippione, Agnese C.; Dosio, Franco; Ducime, Alex
the distal (S)-glutamic acid carboxyl group using the 4-hydroxy-1,2,3-triazole moiety is applied, to obtain two promising glutamate analogs. In the second example, a scaffold hopping approach is applied, replacing the phenolic moiety present in MDG-1-33A, a potent inhibitor of Onchocerca volvulus chitinase...
disturbances and blindness. The parasite is a filarial nematode worm, Onchocerca volvulus . A related species, O. fasciata, occurs in camels but does...which O. volvulus multiplies. Microfilariae in human skin are ingested by vector black flies when they suck blood. In the Middle East, vectors are
Background: Onchocerciasis has been implicated in the pathogenesis of epilepsy. The debate on a potential causal relationship between Onchocerca volvulus and epilepsy has taken a new direction in the light of the most recent epidemic of nodding syndrome. Objective: To document MRI changes in people with different ...
methods of diagnosis, 7,144 consenting individuals aged 5 years and above were examined for Onchocerca volvulus microfilaria and clinical ... of onchocerciasis in the rain-forest. Their chronic and irreversible nature however creates a strong imperative for their prevention/control by the use of an annual dose of ivermectin.
Vargas, L; Díaz-Nájera, A
The entomological resources utilized for a better understanding of Onchocerca volvulus transmission are discussed in this paper. Vector density, anthropohilia, gonotrophic cycyle, parous condition longevity and probability of survival in days after the infectious meal are assessed here in order to integrate an overall picture. The concept of vectorial capacity is developed stressing the quantitative aspects. Parasitism of the black-flies by filariae that are doubtfully identified as O. volvulus is also mentioned here.
Christina A Bulman
Full Text Available Two major human diseases caused by filariid nematodes are onchocerciasis, or river blindness, and lymphatic filariasis, which can lead to elephantiasis. The drugs ivermectin, diethylcarbamazine (DEC, and albendazole are used in control programs for these diseases, but are mainly effective against the microfilarial stage and have minimal or no effect on adult worms. Adult Onchocerca volvulus and Brugia malayi worms (macrofilariae can live for up to 15 years, reproducing and allowing the infection to persist in a population. Therefore, to support control or elimination of these two diseases, effective macrofilaricidal drugs are necessary, in addition to current drugs. In an effort to identify macrofilaricidal drugs, we screened an FDA-approved library with adult worms of Brugia spp. and Onchocerca ochengi, third-stage larvae (L3s of Onchocerca volvulus, and the microfilariae of both O. ochengi and Loa loa. We found that auranofin, a gold-containing drug used for rheumatoid arthritis, was effective in vitro in killing both Brugia spp. and O. ochengi adult worms and in inhibiting the molting of L3s of O. volvulus with IC50 values in the low micromolar to nanomolar range. Auranofin had an approximately 43-fold higher IC50 against the microfilariae of L. loa compared with the IC50 for adult female O. ochengi, which may be beneficial if used in areas where Onchocerca and Brugia are co-endemic with L. loa, to prevent severe adverse reactions to the drug-induced death of L. loa microfilariae. Further testing indicated that auranofin is also effective in reducing Brugia adult worm burden in infected gerbils and that auranofin may be targeting the thioredoxin reductase in this nematode.
Botto, C; Arango, M; Yarzábal, L
Data are presented on microfilaraemia in 191 Yanomami Amerindians from two areas of Venezuela's Upper Orinoco Basin, where an endemic focus of onchocerciasis has been recently detected. Onchocerca microfilariae were found in the blood of 12.6% of the persons examined. In the village with the higher number of examined individuals (N = 162), the prevalence of microfilaraemia in the age groups covaried with the prevalence of microfilariae in the skin and with the parasite load (mf/mg of skin). A positive correlation was found between age and these three variables. The prevalence of Onchocerca microfilaraemia in the Upper Orinoco focus is high, and may be related to the ability of the strain to invade the blood stream. Morphobiometric characteristics of the Onchocerca microfilariae isolated from human blood are similar to those of O. volvulus fixed in formalin from skin and from the uterus of female O. volvulus worms. All have a very short cephalic space. Comparisons with the entity from the Upper Caura river designated as Microfilaria bolivarensis were also made. It was concluded that there are no valid biometric differences in thick blood smears between microfilaria bolivarensis and microfilaria of O. volvulus from the Upper Orinoco deme. A more striking difference may be in the concentration of microfilariae observed in the blood, which in one case of mf. bolivarensis was more than forty times the highest number recorded for microfilaria O. volvulus in Parima.
Georg G. Duscher
The role of wild ungulates, especially ruminants, as reservoirs for zoonotic disease on the other hand seems to be negligible, although the deer filaroid Onchocerca jakutensis has been described to infect humans. Deer may also harbour certain Anaplasma phagocytophilum strains with so far unclear potential to infect humans. The major role of deer as reservoirs is for ticks, mainly adults, thus maintaining the life cycle of these vectors and their distribution. Wild boar seem to be an exception among the ungulates as, in their interaction with the fox, they can introduce food-borne zoonotic agents such as Trichinella britovi and Alaria alata into the human food chain.
Full Text Available Achievements obtained by the onchocerciasis control programmes should not lead to a relaxation in the biological research on Onchocerca volvulus. Issues such as the Loa loa-related postivermectin serious adverse events, the uncertainties as to whether onchocerciasis can be eliminated by ivermectin treatments, and the possible emergence of ivermectin-resistant O. volvulus populations should be addressed proactively. Doxycycline, moxidectin and emodepside appear to be promising as alternative drugs against onchocerciasis but support to researches in immunology and genomics should also be increased to develop new control tools, including both vaccines and macrofilaricidal drugs.
Higazi, Tarig B.; Zarroug, Isam M. A.; Mohamed, Hanan A.; Mohamed, Wigdan A.; Deran, Tong Chor M.; Aziz, Nabil; Katabarwa, Moses; Hassan, Hassan K.; Unnasch, Thomas R.; Mackenzie, Charles D.; Richards, Frank
Onchocerciasis remains an important debilitating disease in many areas of Africa, including Sudan. The status of infection transmission in 2007 was assessed in the vectors of two disease foci in Sudan: Abu Hamed in northern Sudan, which has received at least 10 years of annual treatment and Galabat focus in eastern Sudan, where only minor, largely undocumented treatment activity has occurred. Assessment of more than 30,000 black flies for Onchocerca volvulus infectious stage L3 larvae by using an O-150 polymerase chain reaction protocol showed that black fly infectivity rates were 0.84 (95% confidence interval = 0.0497–1.88) per 10,000 flies for Abu Hamed and 6.9 (95% confidence interval = 1.1–16.4) infective flies per 10,000 for Galabat. These results provide entomologic evidence for suppressed Onchocerca volvulus transmission in the Abu Hamed focus and a moderate transmission rate of the parasite in the Galabat focus. PMID:21540385
A. J. Shelley
Full Text Available Factors that affect the propensity of a simuliid species to act as a host to Onchocerca volvulus and to naturally transmit this filarial worm in nature are discussed. Presence or absence of a cibarial armature is believed to be a major factor that has been previously overlooked and this is considered in relation to the choice of control methods currently advocated for onchocerciasis. The current epidemiological studies, transmission dynamics and relevant control measures are discussed for each onchocerciasis focus in Latin America.Neste trabalho são discutidos os fatores que interferem na suscetibilidade de espécies de simulídeos atuarem como hospedeiros do Onchocerca volvulus e de transmitir a filária em condições naturais. Acredita-se que a presença ou não da armadura do cibário pode ser um fator central, que anteriormente foi subestimado. Este aspecto é discutido em relação às opções em voga de métodos de controle na oncocercose. São também discutidos os estudos epidemiológicos correntes, a dinâmica de transmissão e principais medidas de controle para cada foco de oncocercose na América Latina.
Full Text Available Se presenta tres casos de filariosis de pacientes varones procedentes de la selva peruana (Junín, San Martín y Pucallpa. Un caso presentó filarias en el globo ocular y frotís sanguíneo, que según morfología, serología y biología molecular se determinó como un posible caso de filariosis zoonótica por Onchocerca spp. Los otros dos casos fueron causados por Dirofilaria spp. uno presentó un nódulo en el pómulo y sensación de movilidad en la zona y fue diagnosticado por serología y el último caso se le extrajo una filaria del dedo pulgar de la mano y fue identificado como tal por morfología y biología molecular. Estos casos son los primeros reportes en el Perú por Dirofilaria spp. y Onchocerca spp.
Poppy H L Lamberton
Full Text Available The World Health Organization (WHO aims at eliminating onchocerciasis by 2020 in selected African countries. Current control focuses on community-directed treatment with ivermectin (CDTI. In Ghana, persistent transmission has been reported despite long-term control. We present spatial and temporal patterns of onchocerciasis transmission in relation to ivermectin treatment history.Host-seeking and ovipositing blackflies were collected from seven villages in four regions of Ghana with 3-24 years of CDTI at the time of sampling. A total of 16,443 flies was analysed for infection; 5,812 (35.3% were dissected for parity (26.9% parous. Heads and thoraces of 12,196 flies were dissected for Onchocerca spp. and DNA from 11,122 abdomens was amplified using Onchocerca primers. A total of 463 larvae (0.03 larvae/fly from 97 (0.6% infected and 62 (0.4% infective flies was recorded; 258 abdomens (2.3% were positive for Onchocerca DNA. Infections (all were O. volvulus were more likely to be detected in ovipositing flies. Transmission occurred, mostly in the wet season, at Gyankobaa and Bosomase, with transmission potentials of, respectively, 86 and 422 L3/person/month after 3 and 6 years of CDTI. The numbers of L3/1,000 parous flies at these villages were over 100 times the WHO threshold of one L3/1,000 for transmission control. Vector species influenced transmission parameters. At Asubende, the number of L3/1,000 ovipositing flies (1.4, 95% CI = 0-4 also just exceeded the threshold despite extensive vector control and 24 years of ivermectin distribution, but there were no infective larvae in host-seeking flies.Despite repeated ivermectin treatment, evidence of O. volvulus transmission was documented in all seven villages and above the WHO threshold in two. Vector species influences transmission through biting and parous rates and vector competence, and should be included in transmission models. Oviposition traps could augment vector collector methods for
Full Text Available This review stresses the importance of studies that will provide a basic understanding of the pathology of parasite-infected vector insects. This knowledge should be a vital component of the very focussed initiatives currently being funded in the areas of vector control. Vector fecundity reduction is discussed as an example of such pathology. Underlying mechanisms are being investigated in a model system, Hymenolepis diminuta-infected Tenebrio molitor and in Onchocerca-infected blackflies and Plasmodium-infected Anopheles stephensi. In all cases, host vitellogenesis is disrupted by the parasite and, in the tapeworm/beetle model, interaction between the parasite and the endocrine control of the insect's reproductive physiology has been demonstrated.
Molehin, Adebayo J; Gobert, Geoffrey N; McManus, Donald P
Serine protease inhibitors (serpins) are a superfamily of structurally conserved proteins that inhibit serine proteases and play key physiological roles in numerous biological systems such as blood coagulation, complement activation and inflammation. A number of serpins have now been identified in parasitic helminths with putative involvement in immune regulation and in parasite survival through interference with the host immune response. This review describes the serpins and smapins (small serine protease inhibitors) that have been identified in Ascaris spp., Brugia malayi, Ancylostoma caninum Onchocerca volvulus, Haemonchus contortus, Trichinella spiralis, Trichostrongylus vitrinus, Anisakis simplex, Trichuris suis, Schistosoma spp., Clonorchis sinensis, Paragonimus westermani and Echinococcus spp. and discusses their possible biological functions, including roles in host-parasite interplay and their evolutionary relationships.
Nuss, K.; Muggli, E.; Hässig, M.; Räber, M.; Sydler, T.; Guscetti, F.
In 21 animals, chronic swelling on the lateral aspect of the stifle also known as perigonitis, stable-syndrome or bursitis bicipitalis femoris were evaluated. Ultrasonography showed increased fluid in the distal subtendinous bursa of the biceps femoris muscle and structural changes in the tendons, muscles, subcutis and fasciae. Soft tissue swelling and an irregular contour of the lateral tibial condyle were typical signs on radiographs. Macroscopic changes were found at the insertion of the biceps femoris muscle, the distal subtendinous bursa of the biceps femoris muscle, the lateral collateral ligament of the stifle, the origin of muscles on the lateral femoral condyle and the lateral tibial condyle. They mainly consisted of tendon and muscle tissue necrosis with granulation tissue. Histology revealed areas of coagulation necrosis in tendons and ligaments, in which occasionally Onchocerca spp. were seen. The severity of lesions correlated well with the clinical signs, which were associated with a poor prognosis in advanced cases
Makepeace, Benjamin L.; Jensen, Siv Aina; Laney, Sandra J.; Nfon, Charles K.; Njongmeta, Leo M.; Tanya, Vincent N.; Williams, Steven A.; Bianco, Albert E.; Trees, Alexander J.
Human onchocerciasis, caused by the filarial nematode Onchocerca volvulus, is controlled almost exclusively by the drug ivermectin, which prevents pathology by targeting the microfilariae. However, this reliance on a single control tool has led to interest in vaccination as a potentially complementary strategy. Here, we describe the results of a trial in West Africa to evaluate a multivalent, subunit vaccine for onchocerciasis in the naturally evolved host-parasite relationship of Onchocerca ochengi in cattle. Naïve calves, reared in fly-proof accommodation, were immunised with eight recombinant antigens of O. ochengi, administered separately with either Freund's adjuvant or alum. The selected antigens were orthologues of O. volvulus recombinant proteins that had previously been shown to confer protection against filarial larvae in rodent models and, in some cases, were recognised by serum antibodies from putatively immune humans. The vaccine was highly immunogenic, eliciting a mixed IgG isotype response. Four weeks after the final immunisation, vaccinated and adjuvant-treated control calves were exposed to natural parasite transmission by the blackfly vectors in an area of Cameroon hyperendemic for O. ochengi. After 22 months, all the control animals had patent infections (i.e., microfilaridermia), compared with only 58% of vaccinated cattle (P = 0.015). This study indicates that vaccination to prevent patent infection may be an achievable goal in onchocerciasis, reducing both the pathology and transmissibility of the infection. The cattle model has also demonstrated its utility for preclinical vaccine discovery, although much research will be required to achieve the requisite target product profile of a clinical candidate. PMID:19901988
Cladistic analysis of the Neotropical genera Cerqueirellum Py-Daniel, 1983, Coscaroniellum Py-Daniel, 1983 and Shelleyellum Py-Daniel & Pessoa, 2005 (Diptera: Simuliidae Análise cladística dos gêneros neotropicais Cerqueirellum Py-Daniel, 1983, Coscaroniellum Py-Daniel, 1983 e Shelleyellum Py-Daniel & Pessoa, 2005 (Diptera: Simuliidae
Felipe Arley Costa Pessoa
Full Text Available Females of simuliid black flies are haematophagous insects and vectors of several pathogenic agents of human diseases such as the filarial worms Mansonella ozzardi and Onchocerca volvulus. The genus Cerqueirellum is one of the most important groups of vectors of mansonellosis and onchocerciasis diseases in South America, and the genera Coscaroniellum and Shelleyellum are phylogenetically close to Cerqueirellum. There is not yet an agreement among authors about the generic classification of the species which compose these three genera, being all lumped by some taxonomists within Psaroniocompsa. A cladistic analysis of all species of Coscaroniellum, Cerqueirellum, and Shelleyellum, based on 41 morphological characters were done. Species closely related to Cerqueirellum were included in the analysis. The genera Cerqueirellum, Coscaroniellum and Shelleyellum were demonstrated as consistent basal entities and well-defined monophyletic clades.As fêmeas de piuns ou borrachudos da família Simuliidae são hematófagas e vetoras de diversos patógenos, destacando-se os vermes filarióides Mansonella ozzardi e Onchocerca volvulus. Dentre os grupos supra-específicos que são vetores de mansonelose e oncocercose na América do Sul, destaca-se o gênero Cerqueirellum. Os gêneros Coscaroniellum e Shelleyellum são filogeneticamente muito próximos a Cerqueirellum. Não existia concordância quanto à validade de Cerqueirellum e Coscaroniellum como clados supra-específicos, sendo ambos os gêneros incluídos, por uma escola taxonômica, como grupos de espécies em Psaroniocompsa. Neste trabalho é feita uma análise filogenética baseada em caracteres morfológicos dos três gêneros.. Os gêneros Cerqueirellum, Coscaroniellum e Shelleyellum. apresentaram-se como entidades basais válidas, consistentes e monofiléticas.
Magali Romero Sá
Full Text Available A oncocercose é causada por um verme parasita, a Onchocerca, e transmitida pelo mosquito borrachudo, simuliídeo, podendo causar cegueira em seu estado agudo. Oriunda do continente africano onde é disseminada, foi descoberta na América Latina, na Guatemala, em 1917, com registros posteriores no México, Venezuela, Colômbia e Brasil. O estabelecimento da doença nas Américas tem intrigado os especialistas, e ainda hoje é uma questão em aberto. O projeto multidisciplinar descrito nesta nota de pesquisa objetiva investigar os aspectos históricos da introdução e disseminação da doença na América Latina, e realizar estudos comparativos sobre a história da doença nos dois continentes. A importância que adquiriu acarretou a revalorização das coleções de simuliídeos, cujas espécies brasileiras começaram a ser estudadas por Adolpho Lutz no início do século XX.Round worm is a parasite, Onchocerca, and is transmitted by a black fly, simuliídeo; it can cause blindness. Originally from the African continent, where it is widespread, in Latin America it was first discovered in Guatemala in 1917; later instances were recorded in Mexico, Venezuela, Colombia and Brazil. The establishment of this disease in the Americas has intrigued scientists since then and today it is an open question. The multidisciplinary project described in this research note aims to investigate historical aspects of the arrival and spread of the disease in Latin America and, to make comparative studies of the history of the disease on both continents. The increasing importance of the disease has meant greater value being attributed to collections of simuliídeo, whose Brazilian species were first studied by Adolpho Lutz at the beginning of the 20th century.
Duscher, Georg G.; Leschnik, Michael; Fuehrer, Hans-Peter; Joachim, Anja
Austria's mammalian wildlife comprises a large variety of species, acting and interacting in different ways as reservoir and intermediate and definitive hosts for different pathogens that can be transmitted to pets and/or humans. Foxes and other wild canids are responsible for maintaining zoonotic agents, e.g. Echinococcus multilocularis, as well as pet-relevant pathogens, e.g. Hepatozoon canis. Together with the canids, and less commonly felids, rodents play a major role as intermediate and paratenic hosts. They carry viruses such as tick-borne encephalitis virus (TBEV), bacteria including Borrelia spp., protozoa such as Toxoplasma gondii, and helminths such as Toxocara canis. The role of wild ungulates, especially ruminants, as reservoirs for zoonotic disease on the other hand seems to be negligible, although the deer filaroid Onchocerca jakutensis has been described to infect humans. Deer may also harbour certain Anaplasma phagocytophilum strains with so far unclear potential to infect humans. The major role of deer as reservoirs is for ticks, mainly adults, thus maintaining the life cycle of these vectors and their distribution. Wild boar seem to be an exception among the ungulates as, in their interaction with the fox, they can introduce food-borne zoonotic agents such as Trichinella britovi and Alaria alata into the human food chain. PMID:25830102
Rodríguez-Pérez, Mario A.; Adeleke, Monsuru A.; Burkett-Cadena, Nathan D.; Garza-Hernández, Javier A.; Reyes-Villanueva, Filiberto; Cupp, Eddie W.; Toé, Laurent; Salinas-Carmona, Mario C.; Rodríguez-Ramírez, Américo D.; Katholi, Charles R.; Unnasch, Thomas R.
Background Human landing collections are currently the standard method for collecting onchocerciasis vectors in Africa and Latin America. As part of the efforts to develop a trap to replace human landing collections for the monitoring and surveillance of onchocerciasis transmission, comprehensive evaluations of several trap types were conducted to assess their ability to collect Simulium ochraceum sensu lato, one of the principal vectors of Onchocerca volvulus in Latin America. Methodology/Principal Findings Diverse trap designs with numerous modifications and bait variations were evaluated for their abilities to collect S. Ochraceum s.l. females. These traps targeted mostly host seeking flies. A novel trap dubbed the “Esperanza window trap” showed particular promise over other designs. When baited with CO2 and BG-lure (a synthetic blend of human odor components) a pair of Esperanza window traps collected numbers of S. Ochraceum s.l. females similar to those collected by a team of vector collectors. Conclusions/Significance The Esperanza window trap, when baited with chemical lures and CO2 can be used to collect epidemiologically significant numbers of Simulium ochraceum s.l., potentially serving as a replacement for human landing collections for evaluation of the transmission of O. volvulus. PMID:24116169
Barbazan, P; Escaffre, H; Mbentengam, R; Boussinesq, M
An entomological study was conducted in the basin area of middle Sanaga (Cameroon) in order to document the pattern of onchocerciasis transmission in a region where a high prevalence of infection had been recorded in villages located 30 km from the main rivers. The main vector of O. volvulus was found to be S. squamosum s.s. No breeding site was found in the small tributaries of the Sanaga and Mbam Rivers, and the dispersal of S. damnosum s.l. in the area thus appeared to be particularly high. The highest blackfly population densities were recorded during the long rainy season, and a second peak of density occurred along the Mbam River during the short rainy season. A seasonal variation in dispersal patterns was found at three of the four transects studied. The transmission of Onchocerca volvulus in the area occurred principally between January and May (i.e. at the end of the long dry season and the beginning of the short rainy season). Vector control operations might well reinforce the effect of ivermectin distributions in this onchocerciasis focus.
Michalski, Michelle L; Bain, Odile; Fischer, Kerstin; Fischer, Peter U; Kumar, Sanjay; Foster, Jeremy M
Dirofilaria ursi is a filarial nematode of American black bears (Ursus americanus Pallas, 1780) that is vectored by black flies (Simuliidae) in many parts of the United States. In northwestern Wisconsin, the prevalence of microfilaremic bears during the fall hunting season was 21% (n = 47). Unsheathed blood microfilariae from Wisconsin bears possess characters consistent with the original description of D. ursi, as do adult worms observed histologically and grossly. Immunohistochemistry was used to identify the Wolbachia endosymbiont in the hypodermis and lateral cords of an adult female D. ursi. Amplification of wsp, gatB, coxA, fbpA, and ftsZ bacterial sequences from parasite DNA confirmed the presence of Wolbachia, and molecular phylogenetic analysis of the Wolbachia ftsZ gene groups the endosymbiont with Wolbachia from D. immitis and D. repens. Phylogenetic analysis of D. ursi 5s rDNA sequence confirms the morphological observations grouping this parasite as a member of Dirofilaria, and within the Dirofilaria - Onchocerca clade of filarial nematodes. This is the first report of Wolbachia characterization and molecular phylogeny information for D. ursi.
Nuss, K; Räber, M; Sydler, T; Muggli, E; Hässig, M; Guscetti, F
In 21 animals, chronic swelling on the lateral aspect of the stifle also known as «perigonitis», «stable-syndrome» or «bursitis bicipitalis femoris» were evaluated. Ultrasonography showed increased fluid in the distal subtendinous bursa of the biceps femoris muscle and structural changes in the tendons, muscles, subcutis and fasciae. Soft tissue swelling and an irregular contour of the lateral tibial condyle were typical signs on radiographs. Macroscopic changes were found at the insertion of the biceps femoris muscle, the distal subtendinous bursa of the biceps femoris muscle, the lateral collateral ligament of the stifle, the origin of muscles on the lateral femoral condyle and the lateral tibial condyle. They mainly consisted of tendon and muscle tissue necrosis with granulation tissue. Histology revealed areas of coagulation necrosis in tendons and ligaments, in which occasionally Onchocerca spp. were seen. The severity of lesions correlated well with the clinical signs, which were associated with a poor prognosis in advanced cases.
Full Text Available Parasitic diseases of camels are major causes of impaired milk and meat production, decreases in performance or even death. Some camel parasites also represent a threat to human health. About 171,500 one-humped camels (Camelus dromedarius and 100–300 two-humped camels (Camelus bactrianus live in Iran. Knowledge of the biodiversity of their parasites is still limited. The present review covers all information about camel parasitic diseases in Iran published as dissertations and in both Iranian and international journals from 1931 to February 2017. Ten genera of Protozoa (Trypanosoma, Eimeria, Cryptosporidium, Toxoplasma, Neospora, Sarcocystis, Besnoitia, Theileria, Babesia and Balantidium, 48 helminth species detected in the digestive system, including three species of Trematoda, four species of Cestoda, and 41 species of Nematoda, as well as helminths from other organs – Echinococcus spp., Dictyocaulus filaria, Thelazia leesei, Dipetalonema evansi and Onchocerca fasciata – have so far been described in Iranian camels. Furthermore, 13 species of hard ticks, mange mites, the myiasis flies Cephalopina titillator and Wohlfahrtia magnifica, and immature stages of the Pentastomida Linguatula serrata have also been reported from camels of Iran. Camel parasitic diseases are a major issue in Iran in terms of economics and public health. The present review offers information for an integrated control programme against economically relevant parasites of camels.
Full Text Available Nodding syndrome (NS is an unexplained neurological illness that mainly affects children aged between 5 and 15 years. NS has so far been reported from South Sudan, northern Uganda, and Tanzania, but in spite of extensive investigations, the aetiology remains unknown. We hypothesize that blackflies (Diptera: Simuliidae infected with Onchocerca volvulus microfilariae may also transmit another pathogen. This may be a novel neurotropic virus or an endosymbiont of the microfilariae, which causes not only NS, but also epilepsy without nodding. This hypothesis addresses many of the questions about NS that researchers have previously been unable to answer. An argument in favour of the hypothesis is the fact that in Uganda, the number of new NS cases decreased (with no new cases reported since 2013 after ivermectin coverage was increased and with the implementation of a programme of aerial spraying and larviciding of the large rivers where blackflies were breeding. If confirmed, our hypothesis will enable new strategies to control NS outbreaks.
Onchocerciasis (river blindness) is caused by the parasitic worm Onchocerca volvulus, transmitted to humans by the bite of infected black flies of the genus Simulium, and is characterized by chronic skin disease, severe itching, and eye lesions that can progress to complete blindness. Currently, among approximately 123 million persons at risk for infection in 38 endemic countries, at least 25.7 million are infected, and 1 million are blinded or have severe visual impairment. Periodic, communitywide mass drug administration (MDA) with ivermectin (Mectizan, Merck) prevents eye and skin disease and might interrupt transmission of the infection, depending on the coverage, duration, and frequency of MDA. The Onchocerciasis Elimination Program for the Americas (OEPA) was launched in response to a 1991 resolution of the Pan American Health Organization (PAHO) calling for the elimination of onchocerciasis from the Americas. By the end of 2012, transmission of the infection, judged by surveys following World Health Organization (WHO) guidelines, had been interrupted or eliminated in four of the six endemic countries in the WHO Americas Region. Thus, in 2013, only 4% (23,378) of the 560,911 persons originally at risk in the Americas will be under ivermectin MDA. Active transmission currently is limited to two foci among Yanomami indigenes in adjacent border areas of Venezuela and Brazil.
Catherine B Poole
Full Text Available In this study we developed and evaluated a Brugia Hha I repeat loop-mediated isothermal amplification (LAMP assay for the rapid detection of Brugia genomic DNA. Amplification was detected using turbidity or fluorescence as readouts. Reactions generated a turbidity threshold value or a clear visual positive within 30 minutes using purified genomic DNA equivalent to one microfilaria. Similar results were obtained using DNA isolated from blood samples containing B. malayi microfilariae. Amplification was specific to B. malayi and B. timori, as no turbidity was observed using DNA from the related filarial parasites Wuchereria bancrofti, Onchocerca volvulus or Dirofilaria immitis, or from human or mosquito. Furthermore, the assay was most robust using a new strand-displacing DNA polymerase termed Bst 2.0 compared to wild-type Bst DNA polymerase, large fragment. The results indicate that the Brugia Hha I repeat LAMP assay is rapid, sensitive and Brugia-specific with the potential to be developed further as a field tool for diagnosis and mapping of brugian filariasis.
Sérgio Luiz Bessa Luz
Full Text Available In a recent issue of Memórias do Instituto Oswaldo Cruz, published in Rio de Janeiro in February 2014 (109: 87-92, Adami et al. have published a survey reporting Mansonella parasite prevalence in the Amazon Region. This report makes a useful contribution to the existing knowledge of filarial parasite distribution within the Amazon area, parasite prevalence rates in relation to age and occupation and provides observations on the possible clinical impact of Mansonella ozzardi. Their publication also provides an account of what appears to be a novel ELISA that has recently been used in the Simuliidae and Onchocerciasis Laboratory of the Oswaldo Cruz Institute, Rio de Janeiro, Brazil. We are concerned that the publication of this ELISA may have created an excessively positive impression of the effectiveness of the onchocerciasis recrudescence serological surveillance tools that are presently available for use in the Amazonia onchocerciasis focus. In this letter we have, thus, sought to highlight some of the limitations of this ELISA and suggest how continuing insecurities concerning the detection of antibodies to Onchocerca volvulus within the Amazonia onchocerciasis focus might be minimised.
Yara Leite Adami
Full Text Available Mansonella ozzardi infections are common in the riverside communities along the Solimões, Negro and Purus Rivers in the state of Amazonas (AM. However, little is known about the presence of this parasite in communities located in regions bordering AM and the state of Acre. The prevalence rate of M. ozzardi infections was determined in blood samples from volunteers according to the Knott method. A total of 355 volunteers from six riverine communities were enrolled in the study and 65 (18.3% were found to be infected with M. ozzardi. As expected, most of the infections (25% occurred in individuals involved in agriculture, cattle rearing and fishing and an age/sex group analysis revealed that the prevalence increased beginning in the 40-50-years-of-age group and reached 33% in both sexes in individuals over 50 years of age. Based on the described symptomatology, articular pain and headache were found to be significantly higher among infected individuals (56 and 65% prevalence, respectively, p < 0.05. Sera from volunteers were subjected to ELISA using a cocktail of recombinant proteins from Onchocerca volvulus to evaluate the specificity of the test in an endemic M. ozzardi region. No cross-reactions between M. ozzardi-infected individuals and recombinant O. volvulus proteins were detected, thus providing information on the secure use of this particular cocktail in areas where these parasites are sympatric.
Karbowiak, Grzegorz; Demiaszkiewicz, Aleksander W; Pyziel, Anna M; Wita, Irena; Moskwa, Bożena; Werszko, Joanna; Bień, Justyna; Goździk, Katarzyna; Lachowicz, Jacek; Cabaj, Władysław
During the current century, 88 species of parasites have been recorded in Bison bonasus. These are 22 species of protozoa (Trypanosoma wrublewskii, T. theileri, Giardia sp., Sarcocystis cruzi, S. hirsuta, S. hominis, S. fusiformis, Neospora caninum, Toxoplasma gondii, Cryptosporidium sp., Eimeria cylindrica, E. subspherica, E. bovis, E. zuernii, E. canadensis, E. ellipsoidalis, E. alabamensis, E. bukidnonensis, E. auburnensis, E. pellita, E. brasiliensis, Babesia divergens), 4 trematodes species (Dicrocoelium dendriticum, Fasciola hepatica, Parafasciolopsis fasciolaemorpha, Paramphistomum cervi), 4 cestodes species (Taenia hydatigena larvae, Moniezia benedeni, M. expansa, Moniezia sp.), 43 nematodes species (Bunostomum trigonocephalum, B. phlebotomum, Chabertia ovina, Oesophagostomum radiatum, O. venulosum, Dictyocaulus filaria, D.viviparus, Nematodirella alcidis, Nematodirus europaeus, N. helvetianus, N. roscidus, N. filicollis, N. spathiger, Cooperia oncophora, C. pectinata, C. punctata, C. surnabada, Haemonchus contortus, Mazamastrongylus dagestanicus, Ostertagia lyrata, O. ostertagi, O. antipini, O. leptospicularis, O. kolchida, O. circumcincta, O. trifurcata, Spiculopteragia boehmi, S. mathevossiani, S. asymmetrica, Trichostrongylus axei, T. askivali, T. capricola, T. vitrinus, Ashworthius sidemi, Onchocerca lienalis, O. gutturosa, Setaria labiatopapillosa, Gongylonema pulchrum, Thelazia gulosa, T. skrjabini, T. rhodesi, Aonchotheca bilobata, Trichuris ovis), 7 mites (Demodex bisonianus, D. bovis, Demodex sp., Chorioptes bovis, Psoroptes equi, P. ovis, Sarcoptes scabiei), 4 Ixodidae ticks (Ixodes ricinus, I. persulcatus, I. hexagonus, Dermacentor reticulatus), 1 Mallophaga species (Bisonicola sedecimdecembrii), 1 Anoplura (Haematopinus eurysternus), and 2 Hippoboscidae flies (Lipoptena cervi, Melophagus ovinus). There are few monoxenous parasites, many typical for cattle and many newly acquired from Cervidae.
Lynch, N R; Eddy, K; Hodgen, A N; Lopez, R I; Turner, K J
An enzyme-linked immunosorbent assay (ELISA) was used to determine the seroprevalence of Toxocara canis infection in different socio-economic groups of the tropical population of Venezuela. The lack of definitive independent diagnostic criteria for toxocariasis required the establishment of operational upper limits of normality for Toxocara ELISA values, based upon their log-normalized distribution in a presumptive "non-toxocariasis" sub-population. Only 1.8% of urban subjects of medium-high socio-economic level were considered to be clearly positive in Toxocara ELISA, compared to 20.0% of urban slum dwellers, 25.6% rural subsistence farmers and 34.9% Amazon Indians. As the test was performed using excretory-secretory antigen, and under conditions of competitive inhibition by soluble extracts of non-homologous parasites, co-infection by common intestinal helminths, protozoa or other organisms did not give rise to false positive results. However, strong cross-reactivity with Onchocerca volvulus may have influenced the prevalence figure obtained for the Amazon Indians. These results indicate that T. canis is yet another parasite that is widely distributed in economically underprivileged tropical populations.
Nana O Wilson
Full Text Available In Africa, onchocerciasis and lymphatic filariasis (LF are co-endemic in many areas. Current efforts to eliminate both diseases are through ivermectin-based mass drug administration (MDA. Years of ivermectin distribution for onchocerciasis may have interrupted LF transmission in certain areas. The Kédougou region, Senegal, is co-endemic for LF and onchocerciasis. Though MDA for onchocerciasis started in 1988, in 2014 albendazole had not yet been added for LF. The objective of this study was to assess in an integrated manner the LF and onchocerciasis status in the three districts of the Kédougou region after ≥10 years of ivermectin-based MDA. The study employed an African Programme for Onchocerciasis Control (APOC onchocerciasis-related methodology. In the three districts, 14 villages close to three rivers that have Simulium damnosum breeding sites were surveyed. Convenience sampling of residents ≥5 years old was performed. Assessment for LF antigenemia by immunochromatographic testing (ICT was added to skin snip microscopy for onchocerciasis. Participants were also tested for antibodies against Wb123 (LF and Ov16 (onchocerciasis antigens. In two districts, no participants were ICT or skin snip positive. In the third district, 3.5% were ICT positive and 0.7% were skin snip positive. In all the three districts, Wb123 prevalence was 0.6%. Overall, Ov16 prevalence was 6.9%. Ov16 prevalence among children 5-9 years old in the study was 2.5%. LF antigenemia prevalence was still above treatment threshold in one district despite ≥10 years of ivermectin-based MDA. The presence of Ov16 positive children suggested recent transmission of Onchocerca volvulus. This study showed the feasibility of integrated evaluation of onchocerciasis and LF but development of integrated robust methods for assessing transmission of both LF and onchocerciasis are needed to determine where MDA can be stopped safely in co-endemic areas.
Mawson, Anthony R; Makunde, Williams H; Penman, Alan D; Hernandez Morales, Veronica de Los Angeles; Kalinga, Akili K; Francis, Filbert; Rubinchik, Semyon; Kibweja, Addow
Based on the observation that the parasite Onchocerca volvulus selectively absorbs vitamin A from the host, and the known toxicity of vitamin A in higher concentration, it was hypothesized that dying microfilariae (mf) release their stores of vitamin A (retinoids) into the host circulation in toxic concentrations, inducing the signs and symptoms of onchocerciasis. We conducted a pilot study to test the hypothesis in Songea communities in Southern Tanzania, where mass drug administration with ivermectin had not been implemented by the time of the survey. The specific aim was to evaluate the correlation between the diagnosis of onchocerciasis and increased levels of retinoic acid at infection sites. The analysis was performed by determining copy numbers of a genome of O volvulus present in skin snip samples of persons with onchocerciacis, and correlating these numbers with expression levels of retinoic acid receptor-α (RAR-α), which is inducible by retinoic acid. Total DNA and RNA were extracted from each of 25 mf-positive and 25 mf-negative skin samples and evaluated using quantitative polymerase chain reaction with appropriate negative controls. Analysis of the samples, adjusted with glyceraldehyde 3-phosphate dehydrogenase gene levels, revealed that most samples with detectable RAR-α transcripts had higher levels of RAR-α expression than the assay control. However, the quality and number of samples were insufficient for statistical analysis. Fold data on the expression levels of both O volvulus DNA and RAR RNA suggested a possible trend toward higher relative RAR-α expression in samples with higher levels of O volvulus DNA ( r 2 = 0.25, P = .079). Evidence of a contribution of vitamin A to the pathology of onchocerciasis thus remains elusive. Future studies on the role of retinoids in onchocerciasis will require larger groups of participants as well as careful monitoring of the cold chain and tissue storage procedures in view of the sensitivity of
Rodríguez-Pérez, Mario A.; Fernández-Santos, Nadia A.; Orozco-Algarra, María E.; Rodríguez-Atanacio, José A.; Domínguez-Vázquez, Alfredo; Rodríguez-Morales, Kristel B.; Real-Najarro, Olga; Prado-Velasco, Francisco G.; Cupp, Eddie W.; Richards, Frank O.; Hassan, Hassan K.; González-Roldán, Jesús F.; Kuri-Morales, Pablo A.; Unnasch, Thomas R.
Background Mexico is one of the six countries formerly endemic for onchocerciasis in Latin America. Transmission has been interrupted in the three endemic foci of that country and mass drug distribution has ceased. Three years after mass drug distribution ended, post-treatment surveillance (PTS) surveys were undertaken which employed entomological indicators to check for transmission recrudescence. Methodology/Principal findings In-depth entomologic assessments were performed in 18 communities in the three endemic foci of Mexico. None of the 108,212 Simulium ochraceum s.l. collected from the three foci were found to contain parasite DNA when tested by polymerase chain reaction-enzyme-linked immunosorbent assay (PCR-ELISA), resulting in a maximum upper bound of the 95% confidence interval (95%-ULCI) of the infective rate in the vectors of 0.035/2,000 flies examined. This is an order of magnitude below the threshold of a 95%-ULCI of less than one infective fly per 2,000 flies tested, the current entomological criterion for interruption of transmission developed by the international community. The point estimate of seasonal transmission potential (STP) was zero, and the upper bound of the 95% confidence interval for the STP ranged from 1.2 to 1.7 L3/person/season in the different foci. This value is below all previous estimates for the minimum transmission potential required to maintain the parasite population. Conclusions/Significance The results from the in-depth entomological post treatment surveillance surveys strongly suggest that transmission has not resumed in the three foci of Mexico during the three years since the last distribution of ivermectin occurred; it was concluded that transmission remains undetectable without intervention, and Onchocerca volvulus has been eliminated from Mexico. PMID:26161558
Young, Ryan M.; Burkett-Cadena, Nathan D.; McGaha, Tommy W.; Rodriguez-Perez, Mario A.; Toé, Laurent D.; Adeleke, Monsuru A.; Sanfo, Moussa; Soungalo, Traore; Katholi, Charles R.; Noblet, Raymond; Fadamiro, Henry; Torres-Estrada, Jose L.; Salinas-Carmona, Mario C.; Baker, Bill; Unnasch, Thomas R.; Cupp, Eddie W.
Background Entomological indicators are considered key metrics to document the interruption of transmission of Onchocerca volvulus, the etiological agent of human onchocerciasis. Human landing collection is the standard employed for collection of the vectors for this parasite. Recent studies reported the development of traps that have the potential for replacing humans for surveillance of O. volvulus in the vector population. However, the key chemical components of human odor that are attractive to vector black flies have not been identified. Methodology/Principal Findings Human sweat compounds were analyzed using GC-MS analysis and compounds common to three individuals identified. These common compounds, with others previously identified as attractive to other hematophagous arthropods were evaluated for their ability to stimulate and attract the major onchocerciasis vectors in Africa (Simulium damnosum sensu lato) and Latin America (Simulium ochraceum s. l.) using electroantennography and a Y tube binary choice assay. Medium chain length carboxylic acids and aldehydes were neurostimulatory for S. damnosum s.l. while S. ochraceum s.l. was stimulated by short chain aliphatic alcohols and aldehydes. Both species were attracted to ammonium bicarbonate and acetophenone. The compounds were shown to be attractive to the relevant vector species in field studies, when incorporated into a formulation that permitted a continuous release of the compound over time and used in concert with previously developed trap platforms. Conclusions/Significance The identification of compounds attractive to the major vectors of O. volvulus will permit the development of optimized traps. Such traps may replace the use of human vector collectors for monitoring the effectiveness of onchocerciasis elimination programs and could find use as a contributing component in an integrated vector control/drug program aimed at eliminating river blindness in Africa. PMID:25569240
Full Text Available Background: This study was carried out in Opi-Agu a tropical semi-urban autonomous community comprising of three villages in Enugu State, Nigeria, between the months of April and June 2010. It was designed to determine the prevalence of Onchocerca volvulus infection and assess the perception of the disease among the inhabitants of this community.Methods: A total number of 305 individuals comprising of 148 males and 157 females were examined for various manifestations of onchocerciasis symptoms using rapid epidemiological assessment (REA method.Results: Out of this number, 119 (39.02% individuals were infected. Prevalence of infection among age groups and villages varied. Age group 41 yr and above had the highest (31.00% prevalence, while among the villages, Ogbozalla village ranked higher (45.71% than the other villages. Overall the prevalence of infection among the sexes revealed that males were more infected (43.24% than the females (35.03%. Lichenified onchodermatitis (LOD was the most prevalent (35.29% onchocerciasis symptom among others identified in the area, while leopard skin (LS had the lowest (20.17% occurrence and blindness (0.00% which is the most devastating effect of O. volvulus infection was not observed. Questionnaire responses from 410 individuals revealed that 34.8% respondent from Idi village and 28.1% from Ibeku village believed that O. volvulus infection occurs through poor personal hygiene. Bite of blackfly ranked least (10.6% among the respondent’s knowledge of the causes of onchocerciasis in Opi-Agu community.Conclusion: Opi-Agu community members had poor knowledge of onchocerciasis, the vector and of its etiologic organism. There is need for integration of community health education with mass chemotherapy
Full Text Available INTRODUCTION: A clinically significant endemic focus of onchocerciasis existing in Esmeraldas Province, coastal Ecuador has been under an ivermectin mass drug administration program since 1991. The main transmitting vector in this area is the voracious blackfly, Simulium exiguum. This paper describes the assessments made that support the decision to cease mass treatment. METHODOLOGY AND PRINCIPLE FINDINGS: Thirty-five rounds of ivermectin treatment occurred between 1991-2009 with 29 of these carrying >85% coverage. Following the guidelines set by WHO for ceasing ivermectin distribution the impact on parasite transmission was measured in the two vector species by an O-150 PCR technique standard for assessing for the presence of Onchocerca volvulus. Up to seven collection sites in three major river systems were tested on four occasions between 1995 and 2008. The infectivity rates of 65.0 (CI 39-101 and 72.7 (CI 42-116 in 1995 dropped to zero at all seven collection sites by 2008. Assessment for the presence of antibodies against O. volvulus was made in 2001, 2006, 2007 and 2008 using standard ELISA assays for detecting anti-Ov16 antibodies. None of total of 1810 children aged 1-15 years (between 82 and 98% of children present in the surveyed villages tested in the above years were found to be carrying antibodies to this antigen. These findings were the basis for the cessation of mass drug treatment with ivermectin in 2009. SIGNIFICANCE: This fulfillment of the criteria for cessation of mass distribution of ivermectin in the only known endemic zone of onchocerciasis in Ecuador moves the country into the surveillance phase of official verification for national elimination of transmission of infection. These findings indicate that ivermectin given twice a year with greater than 85% of the community can move a program to the final stages of verification of transmission interruption.
Lovato, Raquel; Guevara, Angel; Guderian, Ronald; Proaño, Roberto; Unnasch, Thomas; Criollo, Hipatia; Hassan, Hassan K; Mackenzie, Charles D
A clinically significant endemic focus of onchocerciasis existing in Esmeraldas Province, coastal Ecuador has been under an ivermectin mass drug administration program since 1991. The main transmitting vector in this area is the voracious blackfly, Simulium exiguum. This paper describes the assessments made that support the decision to cease mass treatment. Thirty-five rounds of ivermectin treatment occurred between 1991-2009 with 29 of these carrying >85% coverage. Following the guidelines set by WHO for ceasing ivermectin distribution the impact on parasite transmission was measured in the two vector species by an O-150 PCR technique standard for assessing for the presence of Onchocerca volvulus. Up to seven collection sites in three major river systems were tested on four occasions between 1995 and 2008. The infectivity rates of 65.0 (CI 39-101) and 72.7 (CI 42-116) in 1995 dropped to zero at all seven collection sites by 2008. Assessment for the presence of antibodies against O. volvulus was made in 2001, 2006, 2007 and 2008 using standard ELISA assays for detecting anti-Ov16 antibodies. None of total of 1810 children aged 1-15 years (between 82 and 98% of children present in the surveyed villages) tested in the above years were found to be carrying antibodies to this antigen. These findings were the basis for the cessation of mass drug treatment with ivermectin in 2009. This fulfillment of the criteria for cessation of mass distribution of ivermectin in the only known endemic zone of onchocerciasis in Ecuador moves the country into the surveillance phase of official verification for national elimination of transmission of infection. These findings indicate that ivermectin given twice a year with greater than 85% of the community can move a program to the final stages of verification of transmission interruption.
Young, Ryan M; Burkett-Cadena, Nathan D; McGaha, Tommy W; Rodriguez-Perez, Mario A; Toé, Laurent D; Adeleke, Monsuru A; Sanfo, Moussa; Soungalo, Traore; Katholi, Charles R; Noblet, Raymond; Fadamiro, Henry; Torres-Estrada, Jose L; Salinas-Carmona, Mario C; Baker, Bill; Unnasch, Thomas R; Cupp, Eddie W
Entomological indicators are considered key metrics to document the interruption of transmission of Onchocerca volvulus, the etiological agent of human onchocerciasis. Human landing collection is the standard employed for collection of the vectors for this parasite. Recent studies reported the development of traps that have the potential for replacing humans for surveillance of O. volvulus in the vector population. However, the key chemical components of human odor that are attractive to vector black flies have not been identified. Human sweat compounds were analyzed using GC-MS analysis and compounds common to three individuals identified. These common compounds, with others previously identified as attractive to other hematophagous arthropods were evaluated for their ability to stimulate and attract the major onchocerciasis vectors in Africa (Simulium damnosum sensu lato) and Latin America (Simulium ochraceum s. l.) using electroantennography and a Y tube binary choice assay. Medium chain length carboxylic acids and aldehydes were neurostimulatory for S. damnosum s.l. while S. ochraceum s.l. was stimulated by short chain aliphatic alcohols and aldehydes. Both species were attracted to ammonium bicarbonate and acetophenone. The compounds were shown to be attractive to the relevant vector species in field studies, when incorporated into a formulation that permitted a continuous release of the compound over time and used in concert with previously developed trap platforms. The identification of compounds attractive to the major vectors of O. volvulus will permit the development of optimized traps. Such traps may replace the use of human vector collectors for monitoring the effectiveness of onchocerciasis elimination programs and could find use as a contributing component in an integrated vector control/drug program aimed at eliminating river blindness in Africa.
Somo, R M; Enyong, P A; Fobi, G; Dinga, J S; Lafleur, C; Agnamey, P; Ngosso, A; Ngolle, E M
Prior to the initiation of an onchocerciasis control program based on the mass administration of ivermectin in the rain forest of southwestern Cameroon, a preliminary baseline study of the area was conducted. The results of this study showed that onchocerciasis was hyperendemic in the area. Skin symptoms and signs were observed including pruritus (67.4% of the population examined), onchocerca nodules (51.6%), skin depigmentation (18.5%), and hanging groins (5.7%). Except for pruritus, the prevalence of these symptoms increased with age. Of the eyes examined, 44.9% had microfilariae in the anterior chamber, 33.5% had choroidoretinitis, 28.0% had punctate keratitis, 8.3% had papillary abnormalities, and 3.6% had sclerosing keratitis. Vision in 10.5% of the eyes examined was classified as blind or very poor (visual acuity = 0-0.10), in 15.7% as poor (visual acuity = 0.11-0.39), and in 73.8% as good (visual acuity = 0.4-1.00). Unlike previous reports that have linked serious ocular damage mainly to savanna onchocerciasis, the present study showed that forest onchocerciasis also caused significant ocular pathology, including blindness. Parasitologically, positive skin snips were recorded for 92.7% of the persons examined, with both sexes being equally infected. The parasite load, expressed as the geometric mean number of microfilariae per skin snip, was 53.6, and was much higher in males than in females. The flv vector, Simulium squamosum, had a high infection rate of 7.5% infective females in Bakumba and 6.8% infective females in Ngbandi, the two fly-catching points. The transmission potential was 266 infective larvae per person per month in Bakumba and 189 in Ngbandi.
Mario A Rodríguez-Pérez
Full Text Available Mexico is one of the six countries formerly endemic for onchocerciasis in Latin America. Transmission has been interrupted in the three endemic foci of that country and mass drug distribution has ceased. Three years after mass drug distribution ended, post-treatment surveillance (PTS surveys were undertaken which employed entomological indicators to check for transmission recrudescence.In-depth entomologic assessments were performed in 18 communities in the three endemic foci of Mexico. None of the 108,212 Simulium ochraceum s.l. collected from the three foci were found to contain parasite DNA when tested by polymerase chain reaction-enzyme-linked immunosorbent assay (PCR-ELISA, resulting in a maximum upper bound of the 95% confidence interval (95%-ULCI of the infective rate in the vectors of 0.035/2,000 flies examined. This is an order of magnitude below the threshold of a 95%-ULCI of less than one infective fly per 2,000 flies tested, the current entomological criterion for interruption of transmission developed by the international community. The point estimate of seasonal transmission potential (STP was zero, and the upper bound of the 95% confidence interval for the STP ranged from 1.2 to 1.7 L3/person/season in the different foci. This value is below all previous estimates for the minimum transmission potential required to maintain the parasite population.The results from the in-depth entomological post treatment surveillance surveys strongly suggest that transmission has not resumed in the three foci of Mexico during the three years since the last distribution of ivermectin occurred; it was concluded that transmission remains undetectable without intervention, and Onchocerca volvulus has been eliminated from Mexico.
Opara, Kenneth N; Fagbemi, Olakunle B; Ekwe, Asuquo; Okenu, Daniel M N
In the Lower Cross River basin in Nigeria, no pre-control entomologic profile of Onchocerca volvulus infection in the local Simulium damnosum population was available prior to the initiation of an ivermectin control program in 1995. A longitudinal entomologic study was therefore carried out over a 12-month period (January-December 2001) at the Agbokim waterfalls and Afi River, which are breeding sites of S. damnosum in the river basin. A total of 9,287 adult S. damnosum were caught on human bait; 9,048 (97.43%) were dissected, of which 313 (3.46%) were infected. Annual biting rates (ABRs) of 42,419 and 28,346 bites per persons per year were recorded at the Agbokim Waterfalls and Afi River, respectively. The annual transmission potential (ATP) was 419 infective larvae per person per year at the Agbokim Waterfalls and 427 at the Afi River. Monthly biting rate and monthly transmission potential varied significantly (P < 0.05) at the two sites. Transmission was highly seasonal from April to September, corresponding to the peak biting period of the vector. The high ATP and ABR values are a measure of the mesoendemicity of onchocerciasis in the river basin. There was a significant F(0).05 (1, 10) (P < 0.05) variation in the relative fly abundance from both sites. It was observed that human activities such as farming, fishing, timber cutting, and hunting are done in the early morning and late afternoon, which corresponds to the peak diurnal biting period of the vector. Changes in these practices and attitudes may markedly affect the disease intensity and transmission.
Colebunders, Robert; Mandro, Michel; Njamnshi, Alfred K; Boussinesq, Michel; Hotterbeekx, An; Kamgno, Joseph; O'Neill, Sarah; Hopkins, Adrian; Suykerbuyk, Patrick; Basáñez, Maria-Gloria; Post, Rory J; Pedrique, Belén; Preux, Pierre-Marie; Stolk, Wilma A; Nutman, Thomas B; Idro, Richard
Recently, several epidemiological studies performed in Onchocerca volvulus-endemic regions have suggested that onchocerciasis-associated epilepsy (OAE) may constitute an important but neglected public health problem in many countries where onchocerciasis is still endemic. On October 12-14 th 2017, the first international workshop on onchocerciasis-associated epilepsy (OAE) was held in Antwerp, Belgium. The workshop was attended by 79 participants from 20 different countries. Recent research findings strongly suggest that O. volvulus is an important contributor to epilepsy, particularly in meso- and hyperendemic areas for onchocerciasis. Infection with O. volvulus is associated with a spectrum of epileptic seizures, mainly generalised tonic-clonic seizures but also atonic neck seizures (nodding), and stunted growth. OAE is characterised by an onset of seizures between the ages of 3-18 years. Multidisciplinary working groups discussed topics such as how to 1) strengthen the evidence for an association between onchocerciasis and epilepsy, 2) determine the burden of disease caused by OAE, 3) prevent OAE, 4) improve the treatment/care for persons with OAE and affected families, 5) identify the pathophysiological mechanism of OAE, and 6) deal with misconceptions, stigma, discrimination and gender violence associated with OAE. An OAE Alliance was created to increase awareness about OAE and its public health importance, stimulate research and disseminate research findings, and create partnerships between OAE researchers, communities, advocacy groups, ministries of health, non-governmental organisations, the pharmaceutical industry and funding organizations. Although the exact pathophysiological mechanism underlying OAE remains unknown, there is increasing evidence that by controlling and eliminating onchocerciasis, OAE will also disappear. Therefore, OAE constitutes an additional argument for strengthening onchocerciasis elimination efforts. Given the high numbers of
Lovato, Raquel; Guevara, Angel; Guderian, Ronald; Proaño, Roberto; Unnasch, Thomas; Criollo, Hipatia; Hassan, Hassan K.; Mackenzie, Charles D.
Introduction: A clinically significant endemic focus of onchocerciasis existing in Esmeraldas Province, coastal Ecuador has been under an ivermectin mass drug administration program since 1991. The main transmitting vector in this area is the voracious blackfly, Simulium exiguum. This paper describes the assessments made that support the decision to cease mass treatment. Methodology and Principle Findings: Thirty-five rounds of ivermectin treatment occurred between 1991–2009 with 29 of these carrying >85% coverage. Following the guidelines set by WHO for ceasing ivermectin distribution the impact on parasite transmission was measured in the two vector species by an O-150 PCR technique standard for assessing for the presence of Onchocerca volvulus. Up to seven collection sites in three major river systems were tested on four occasions between 1995 and 2008. The infectivity rates of 65.0 (CI 39–101) and 72.7 (CI 42–116) in 1995 dropped to zero at all seven collection sites by 2008. Assessment for the presence of antibodies against O. volvulus was made in 2001, 2006, 2007 and 2008 using standard ELISA assays for detecting anti-Ov16 antibodies. None of total of 1810 children aged 1–15 years (between 82 and 98% of children present in the surveyed villages) tested in the above years were found to be carrying antibodies to this antigen. These findings were the basis for the cessation of mass drug treatment with ivermectin in 2009. Significance: This fulfillment of the criteria for cessation of mass distribution of ivermectin in the only known endemic zone of onchocerciasis in Ecuador moves the country into the surveillance phase of official verification for national elimination of transmission of infection. These findings indicate that ivermectin given twice a year with greater than 85% of the community can move a program to the final stages of verification of transmission interruption. PMID:24853587
Traore, Mamadou O.; Sarr, Moussa D.; Badji, Alioune; Bissan, Yiriba; Diawara, Lamine; Doumbia, Konimba; Goita, Soula F.; Konate, Lassana; Mounkoro, Kalifa; Seck, Amadou F.; Toe, Laurent; Toure, Seyni; Remme, Jan H. F.
Background Mass treatment with ivermectin controls onchocerciasis as a public health problem, but it was not known if it could also interrupt transmission and eliminate the parasite in endemic foci in Africa where vectors are highly efficient. A longitudinal study was undertaken in three hyperendemic foci in Mali and Senegal with 15 to 17 years of annual or six-monthly ivermectin treatment in order to assess residual levels of infection and transmission, and test whether treatment could be safely stopped. This article reports the results of the final evaluations up to 5 years after the last treatment. Methodology/Principal Findings Skin snip surveys were undertaken in 131 villages where 29,753 people were examined and 492,600 blackflies were analyzed for the presence of Onchocerca volvulus larva using a specific DNA probe. There was a declining trend in infection and transmission levels after the last treatment. In two sites the prevalence of microfilaria and vector infectivity rate were zero 3 to 4 years after the last treatment. In the third site, where infection levels were comparatively high before stopping treatment, there was also a consistent decline in infection and transmission to very low levels 3 to 5 years after stopping treatment. All infection and transmission indicators were below postulated thresholds for elimination. Conclusion/Significance The study has established the proof of principle that onchocerciasis elimination with ivermectin treatment is feasible in at least some endemic foci in Africa. The study results have been instrumental for the current evolution from onchocerciasis control to elimination in Africa. PMID:23029586
Catherine B Poole
Full Text Available Accurate detection of filarial parasites in humans is essential for the implementation and evaluation of mass drug administration programs to control onchocerciasis and lymphatic filariasis. Determining the infection levels in vector populations is also important for assessing transmission, deciding when drug treatments may be terminated and for monitoring recrudescence. Immunological methods to detect infection in humans are available, however, cross-reactivity issues have been reported. Nucleic acid-based molecular assays offer high levels of specificity and sensitivity, and can be used to detect infection in both humans and vectors. In this study we developed loop-mediated isothermal amplification (LAMP tests to detect three different filarial DNAs in human and insect samples using pH sensitive dyes for enhanced visual detection of amplification. Furthermore, reactions were performed in a portable, non-instrumented nucleic acid amplification (NINA device that provides a stable heat source for LAMP. The efficacy of several strand displacing DNA polymerases were evaluated in combination with neutral red or phenol red dyes. Colorimetric NINA-LAMP assays targeting Brugia Hha I repeat, Onchocerca volvulus GST1a and Wuchereria bancrofti LDR each exhibit species-specificity and are also highly sensitive, detecting DNA equivalent to 1/10-1/5000th of one microfilaria. Reaction times varied depending on whether a single copy gene (70 minutes, O. volvulus or repetitive DNA (40 min, B. malayi and W. bancrofti was employed as a biomarker. The NINA heater can be used to detect multiple infections simultaneously. The accuracy, simplicity and versatility of the technology suggests that colorimetric NINA-LAMP assays are ideally suited for monitoring the success of filariasis control programs.
Yatawara, Lalani; Wickramasinghe, Susiji; Rajapakse, R P V J; Agatsuma, Takeshi
In the present study, we determined the complete mitochondrial (mt) genome sequence (13,839bp) of parasitic nematode Setaria digitata and its structure and organization compared with Onchocerca volvulus, Dirofilaria immitis and Brugia malayi. The mt genome of S. digitata is slightly larger than the mt genomes of other filarial nematodes. S. digitata mt genome contains 36 genes (12 protein-coding genes, 22 transfer RNAs and 2 ribosomal RNAs) that are typically found in metazoans. This genome contains a high A+T (75.1%) content and low G+C content (24.9%). The mt gene order for S. digitata is the same as those for O. volvulus, D. immitis and B. malayi but it is distinctly different from other nematodes compared. The start codons inferred in the mt genome of S. digitata are TTT, ATT, TTG, ATG, GTT and ATA. Interestingly, the initiation codon TTT is unique to S. digitata mt genome and four protein-coding genes use this codon as a translation initiation codon. Five protein-coding genes use TAG as a stop codon whereas three genes use TAA and four genes use T as a termination codon. Out of 64 possible codons, only 57 are used for mitochondrial protein-coding genes of S. digitata. T-rich codons such as TTT (18.9%), GTT (7.9%), TTG (7.8%), TAT (7%), ATT (5.7%), TCT (4.8%) and TTA (4.1%) are used more frequently. This pattern of codon usage reflects the strong bias for T in the mt genome of S. digitata. In conclusion, the present investigation provides new molecular data for future studies of the comparative mitochondrial genomics and systematic of parasitic nematodes of socio-economic importance. 2010 Elsevier B.V. All rights reserved.
Laura Moya Alonso
Full Text Available Background: Onchocerciasis or river blindness is a chronic parasitic disease caused by the filarial nematode Onchocerca Volvulus. It occurs in 38 countries in the world, including Africa, Latin America and the Arabian Peninsula. The infection predominantly causes visual impairment and blindness and skin disease. Objectives: The aim of this project is to review the literature on the psycho-social and economic consequences of onchocerciasis in endemic areas. Economic evaluation studies on onchocerciasis and its control programmes were also reviewed. Methods: Electronic searches of PUBMED and Google were made. In addition, the Cochrane Library and WHO website were searched. Different types of economic analysis were reviewed to quantify the relationship between the programme costs and impacts. Results: Eighty papers were identified from different sources, most of which are quantitative studies or literature reviews, and only two were clinical trials. Onchocerciasis has severe socio-economic and psychological consequences. The stigma associated with the disease may reduce marital prospects among affected individuals, disrupt social relationships and cause loss of self-confidence. Also among agricultural workers onchocerciasis has been associated with increased time away from work and reduced productivity, leading to lower income. Discussion: Most of the papers analysed were cross-sectional studies based on data collection through questionnaires. Although there is an increasing number of published papers about the importance of the psycho-social and economic perspective of onchocerciasis, further research is still necessary to quantify and control its consequences. Conclusion: Onchocerciasis is still a serious problem in poor countries. Infected people face physical disability and social stigma that can dramatically reduce the quality of life and land productivity. Control programmes, though costly, have been very successful and cost
Full Text Available Ed W Cupp1, Charles D Mackenzie2, Thomas R Unnasch31Department of Entomology and Plant Pathology, Auburn University, Auburn, AL, USA; 2Department of Pathobiology, Michigan State University, East Lansing, MI, USA; 3Department of Global Health, University of South Florida, Tampa, FL, USAAbstract: Ivermectin (registered for human use as Mectizan® was donated by Merck & Co Inc in 1987 for the treatment and control of human onchocerciasis ("river blindness". This philanthropic gesture has had a remarkable effect in reducing the incidence and prevalence of this serious ocular and dermatological disease, while changing health system support for millions of people worldwide. Over 800 million doses have been given to more than 80 million people for onchocerciasis during the past 23 years. As a result, onchocerciasis has been significantly reduced in more than 25 countries, transmission has been interrupted in foci in at least 10 countries, and the disease is no longer seen in children in many formerly endemic foci. Recent communications have suggested that the drug's efficacy as the major therapeutic agent for these control and elimination programs may be threatened, but alternative interpretations for suboptimal response/resistance suggest otherwise. Current research needs and control methods by which the public health community in endemic countries may respond to resistance, should it occur in their area, are discussed, along with the continuing importance of this anthelmintic as the mainstay in onchocerciasis control programs.Keywords: Ivermectin, Onchocerca volvulus, river blindness, resistance, African Programme for Onchocerciasis Control, Onchocerciasis Elimination Program for the Americas
Puente, Sabino; Ramirez-Olivencia, German; Lago, Mar; Subirats, Mercedes; Perez-Blazquez, Eugenio; Bru, Fernando; Garate, Teresa; Vicente, Belén; Belhassen-Garcia, Moncef; Muro, Antonio
Onchocerciasis is caused by Onchocerca volvulus and mainly leads to pruritus and skin and visual disorders, including blindness. Seventeen million people are infected in 38 countries; 31 of these are in sub-Saharan Africa, six in Latin America and one on the Arabian Peninsula. More than 99% of cases occur in sub-Saharan Africa where 120 million people are at risk of infection. Eye disorders have been well-documented; however, skin disorders have not been described accurately. The objective of our study was to describe the epidemiology, main skin manifestations and treatment of imported onchocerciasis. A retrospective study was thus conducted by analysing the main demographic, clinical and treatment data regarding a cohort of 400 patients attending a reference clinical unit over a 17-year period. Most patients were female (55%) with mean age 37.5±16.7 years. All the migrants came from sub-Saharan countries. The most frequently occurring dermatological symptom was pruritus. Ivermectin had been used as first-line therapy and adverse reactions had been described in 11 patients (3.2%). The results indicate the fact that there should be a clinical suspicion of onchocerciasis regarding immigrants from endemic areas having skin lesions compatible with the disease's profile or asymptomatic patients having eosinophilia or unexplained high IgE. Moreover, skin snips from the buttocks region were very fruitful and treatment with ivermectin was seen to be safe. This is the largest case series regarding imported onchocerciasis described up to the present time. Copyright © 2017 Elsevier España, S.L.U. and Sociedad Española de Enfermedades Infecciosas y Microbiología Clínica. All rights reserved.
Vivas-Martinez, S; Basáñez, M G; Grillet, M E; Weiss, H; Botto, C; García, M; Villamizar, N J; Chavasse, D C
In preparation for an ivermectin distribution programme, the prevalence and intensity of infection due to Onchocerca volvulus as well as the species composition and abundance of Simulium vectors were investigated in 22 Yanomami communities situated along 2 altitudinal transects in the southern Venezuelan onchocerciasis focus. These transects corresponded to the Ocamo-Putaco and Orinoco-Orinoquito river systems, covering a range of elevation between 50 m and 740 m above sea level (asl). A total of 831 people underwent parasitological examination in this survey and an additional 196 patients from a previous study, at an altitude of 950 m, were included in the analysis. A total of 92,659 man-biting blackflies were collected and identified to morphospecies. S. oyapockense s.l. was the predominant simuliid up to 150 m asl, whereas S. guianense s.l. and S. incrustatum s.l. prevailed above 150 m. Communities located below 150 m were found to range from hypo- to mesoendemic; all villages above 150 m proved to be hyperendemic (> 60% microfilarial prevalence) and mass ivermectin treatment should be implemented. Age above 10-14 years, altitude of the village and biting rate of S. guianense s.l. up to 200 m asl were found to be statistically significant independent predictors of infection by multivariate logistic regression using a spline model. There were no differences in infection status according to sex. Above 200 m, microfilarial rate and density remained approximately constant, prevalence averaging 79% regardless of blackfly abundance. For the implementation of ivermectin-based onchocerciasis control programmes in the Amazonian focus, altitude and species composition of the blackfly population might be adopted as useful indicators aiding selection of the most affected communities. However, below 200 m additional parasitological indicators may also be necessary. As a direct result of this study, regular mass-ivermectin delivery to meso- and hyperendemic communities is now
Moraes, M A; Shelley, A J; Luna Dias, A P
A recent survey for onchocerciasis conducted among the Yanomami Indians living on the middle reaches of the Mucajaí and Catrimâni Rivers (Territory of Roraima) has failed to show any alteration in the local pattern of the disease. In fact, after a decade from the first surveys in these areas located at the periphery of the Yanomami focus, the prevalence and the intensity of infection have not experienced a significant change. Considering only the residents in the villages inside the surveyed areas, the prevalence varied from zero in the neighbourhood of the Catrimâni mission to 3.1 per cent near the Mucajaí mission. Had there been a competent vector of Onchocerca volvulus in the region higher rates might be expected due to the Yanomami custom of periodic visits among the groups of the tribe. In some of these visits, numbers of highly infected Indians from the central and mountainous part of the Yanomami territory--where more than 90 per cent of the adults have onchocerciasis--come to the villages in the lowland area, attracted by the facilities offered by the mission posts. As the visitors stay in the host villages for several days or weeks, the residents could become exposed to the disease. Simulium oyapockense s.1., a man-biting species of black fly, widely distributed in Northern Brazil, is the only possible vector of O. volvulus in the investigated areas, on the grounds of its local abundance.(ABSTRACT TRUNCATED AT 250 WORDS)
Vivas-Martínez, S; Basáñez, M G; Botto, C; Rojas, S; García, M; Pacheco, M; Curtis, C F
This paper describes, for the human onchocerciasis focus of southern Venezuela, the age profiles of Onchocerca volvulus microfilarial (mf) and nodule prevalence, mf intensity, and mf aggregation for the whole examined population (836 Yanomami people) living in 20 villages, and for these communities classified according to endemicity levels (hypoendemic: < or = 20 %; mesoendemic: 21-59 %; hyperendemic: < or = 60 % infected). Mf prevalence and intensity increased with age, particularly in the hyperendemic areas, and there were no marked differences between the sexes. The prevalence of nodules followed the same age pattern. Fifty percent mf prevalence was reached in the 15-19 year age-class when the population was taken as a whole; nearly in the 10 to 14-year-olds for the hyperendemic level, in those aged 20-29 years in mesoendemic areas, and not reached at all in hypoendemic villages. The degree of mf aggregation was measured by the k value of the negative binomial distribution and by the variance to mean ratio (VMR). The relationship between the standard deviation (S.D.) of mf counts and the mean mf density was also explored. These 3 indices (k, VMR, and S.D.) showed a tendency to increase with both mean mf load and host age. Since infection intensity and host age were themselves positively related, it was not possible to draw definite conclusions about age-specific changes of parasite aggregation. There was not a significant decrease of mf intensity after an earlier peak neither was there a shift towards younger ages of the maximum no. of mf/mg reached as the endemicity level increased. These results are discussed in relation to detection of density dependence in the human host, selection of an indicator age-group for rapid epidemiological assessment (REA) methods, and strategies of ivermectin distribution in the Amazonian focus. It is recommended that, for the Amazonian onchocerciasis focus, the indicator group for REA consists of all those aged 15 years and over.
Basáñez, M G; Yarzábal, L; Takaoka, H; Suzuki, H; Noda, S; Tada, I
Experimental and natural infections with Onchocerca volvulus were studied in several anthropophilic blackfly species present in the endemic area of the Upper Orinoco region of Venezuela. When fed on four different Yanomami volunteers in the Sierra Parima, the total infection rate was 31.4% for Simulium guianense in comparison with 7.5% for S. limbatum. The proportion of ingested microfilariae that entered the thorax during the first 24 hours and completed development to the infective stage was also much lower in the latter than in the former species. There was no larval development of O. volvulus in S. antillarum, but one female harboured in its head six infective larvae of a zoonotic filaria. When S. oyapokense s.l. was fed on an infected volunteer in the Upper Orinoco most flies ingested few microfilariae, and further development reached only the L1 stage. Natural infection and infectivity rates for S. guianense in two localities of the Sierra Parima were 0.2-4.0% and 1.3-10.2%, respectively, more than 50% of the L3 larvae being in the head. The corresponding data for S. oyapockense s.l. in the Upper Orinoco were 0.1-0.5%, although the only L3 larva found did not correspond to O. volvulus. It is suggested that S. guianense is the main vector of onchocerciasis in the Sierra Parima and that S. limbatum could play a secondary role. Simulium oyapockense s.l. replaces them in the Upper Orinoco and may maintain a degree of transmission, but its epidemiological importance remains to be assessed.
Botto, Carlos; Basañez, María-Gloria; Escalona, Marisela; Villamizar, Néstor J; Noya-Alarcón, Oscar; Cortez, José; Vivas-Martínez, Sarai; Coronel, Pablo; Frontado, Hortencia; Flores, Jorge; Graterol, Beatriz; Camacho, Oneida; Tovar, Yseliam; Borges, Daniel; Morales, Alba Lucia; Ríos, Dalila; Guerra, Francisco; Margeli, Héctor; Rodriguez, Mario Alberto; Unnasch, Thomas R; Grillet, María Eugenia
The World Health Organization (WHO) has set goals for onchocerciasis elimination in Latin America by 2015. Most of the six previously endemic countries are attaining this goal by implementing twice a year (and in some foci, quarterly) mass ivermectin (Mectizan®) distribution. Elimination of transmission has been verified in Colombia, Ecuador and Mexico. Challenges remain in the Amazonian focus straddling Venezuela and Brazil, where the disease affects the hard-to-reach Yanomami indigenous population. We provide evidence of suppression of Onchocerca volvulus transmission by Simulium guianense s.l. in 16 previously hyperendemic Yanomami communities in southern Venezuela after 15 years of 6-monthly and 5 years of 3-monthly mass ivermectin treatment. Baseline and monitoring and evaluation parasitological, ophthalmological, entomological and serological surveys were conducted in selected sentinel and extra-sentinel communities of the focus throughout the implementation of the programme. From 2010 to 2012-2015, clinico-parasitological surveys indicate a substantial decrease in skin microfilarial prevalence and intensity of infection; accompanied by no evidence (or very low prevalence and intensity) of ocular microfilariae in the examined population. Of a total of 51,341 S. guianense flies tested by PCR none had L3 infection (heads only). Prevalence of infective flies and seasonal transmission potentials in 2012-2013 were, respectively, under 1% and 20 L3/person/transmission season. Serology in children aged 1-10 years demonstrated that although 26 out of 396 (7%) individuals still had Ov-16 antibodies, only 4/218 (2%) seropositives were aged 1-5 years. We report evidence of recent transmission and morbidity suppression in some communities of the focus representing 75% of the Yanomami population and 70% of all known communities. We conclude that onchocerciasis transmission could be feasibly interrupted in the Venezuelan Amazonian focus.
Full Text Available Filarial nematodes cause chronic and profoundly debilitating diseases in both humans and animals. Applications of novel technology are providing unprecedented opportunities to improve diagnosis and our understanding of the molecular basis for host-parasite interactions. As a first step, we investigated the presence of circulating miRNAs released by filarial nematodes into the host bloodstream. miRNA deep-sequencing combined with bioinformatics revealed over 200 mature miRNA sequences of potential nematode origin in Dirofilaria immitis-infected dog plasma in two independent analyses, and 21 in Onchocerca volvulus-infected human serum. Total RNA obtained from D. immitis-infected dog plasma was subjected to stem-loop RT-qPCR assays targeting two detected miRNA candidates, miR-71 and miR-34. Additionally, Brugia pahangi-infected dog samples were included in the analysis, as these miRNAs were previously detected in extracts prepared from this species. The presence of miR-71 and miR-34 discriminated infected samples (both species from uninfected samples, in which no specific miRNA amplification occurred. However, absolute miRNA copy numbers were not significantly correlated with microfilaraemia for either parasite. This may be due to the imprecision of mf counts to estimate infection intensity or to miRNA contributions from the unknown number of adult worms present. Nonetheless, parasite-derived circulating miRNAs are found in plasma or serum even for those species that do not live in the bloodstream.
Full Text Available Initially planned for a 20 year life time, the Onchocerciasis Control Programme in West Africa (OCP will have finally continued its activities for nearly three decades (vector control alone from 1975 to 1989, then vector control and/or therapeutic treatment until 2002. Although onchocerciasis is no longer a problem of public health importance nor an obstacle to socioeconomic development in the OCP area, the control of this filariasis is not over because OCP never aimed at eradication, neither of the parasite (Onchocerca volvulus, nor of its vector (Simulium damnosum s.l.. In 2003, the eleven Participating countries of OCP will take over the responsibility of carrying out the residual activities of monitoring and the control of this disease. This mission is of great importance because any recrudescence of the transmission could lead in the long run to the reappearance of the clinical signs of onchocerciasis, if not its most serious manifestations. For epidemiological and operational reasons, and given the disparity in national health policies and infrastructures, the capacities of the countries to take over the residual activities of monitoring and control of onchocerciasis are very unequal. Indeed, the interventions to be carried out are very different from one country to another and the process of integrating the residual activities into the national health systems is not taking place at the same pace. This inequality among the countries vis-a-vis the challenges to be met does not, however, prejudge the epidemiological situation after 2002 whose evolution will also depend on the effectiveness of the provisions made before that date by OCP, then after 2002, by the Regional Office for Africa of the World Health Organization which is currently setting up a sub-regional multidisease surveillance centre.
Neglected Tropical Diseases: Treatment of Dermatological Manifestation of Filariasis with Combination Regimen of Albendazole, Ivermectin, and Loratadine: A Case Report from a Suburban Community in Nigeria
Osede Ignis Iribhogbe
Full Text Available Threadlike filarial nematodes have been identified as the causative agent of filariasis. Cutaneous filariasis is caused primarily by Loa loa, Onchocerca volvulus, and Mansonella streptocerca. These parasites occupy the subcutaneous layer of the skin. However, other filarial parasites are usually associated with varying degrees of dermatological manifestations. In the present discourse, two cases of cutaneous filariasis were diagnosed in two female patients (21 and 40 years old, respectively in Remitch Clinic and Maternity located in a nonriverine community in Ekpoma, Edo State, Nigeria. In this report, patients with body mass index (BMI of 18.97 and 23.45 kg/m2, respectively, presented on two different occasions at least 6 months apart with hyperpigmented skin lesions in the upper and lower limbs, respectively. There was associated intense pruritus with no evidence of lymphadenopathy and lymphoedema. Following laboratory confirmation of filariasis, the patients were placed on a single oral dose combination of albendazole (400 mg + ivermectin (200 mcg/kg, while oral doses of loratadine 10 mg were administered daily for 5 days. Patients were carefully followed up for 6 weeks during which recession of the lesion and untoward reactions were monitored. It was observed that within 6 weeks of treatment, there was a dramatic recession of skin lesion. Adverse effect reported from use of the combination was mild. This case report revealed that cutaneous filariasis is not an uncommon presentation of filariasis infestation in Nigeria. The report also validates the safety and efficacy of the combination in the management of cutaneous manifestation of the disease.
Full Text Available Onchocerciasis or "river blindness" is a chronic parasitic neglected tropical disease which is endemic both in mainland and insular Equatorial Guinea. We aim to estimate the current epidemiological situation of onchocerciasis in Bioko Island after vector elimination in 2005 and more than sixteen years of Community Directed Treatment with Ivermectin (CDTI by using molecular and serological approaches for onchocerciasis diagnosis. A community-based cross-sectional study was carried out in Bioko Island from mid-January to mid-February 2014. A total of 544 study participants were recruited. A complete dermatological examination was performed and three skin snips were performed in every participant for parasitological and molecular assessments. Blood spots were also taken for determination of Ov16 IgG4 antibodies trough an "in-house" ELISA assay. Overall, we found 15 out of 522 individuals suffering any onchocerciasis specific cutaneous lesions and 16 out of 528 (3.0% with onchocercal nodules in the skin. Nodules were significantly associated with age, being more common in subjects older than 10 years than in younger people (3.9% vs. 0%, p = 0.029. Regarding the onchocerciasis laboratory assessment, no positive parasitological test for microfilaria detection was found in the skin snips. The calculated seroprevalence through IgG4 serology was 7.9%. No children less than 10 years old were found to be positive for this test. Only one case was positive for Onchocerca volvulus (O. volvulus after skin PCR. The present study points out that the on-going mass ivermectin treatment has been effective in reducing the prevalence of onchocerciasis and corroborates the interruption of transmission in Bioko Island. To our knowledge, this is the first time that accurate information through molecular and serological techniques is generated to estimate the onchocerciasis prevalence in this zone. Sustained support from the national program and appropriate communication
Full Text Available Abstract Background Studying mitochondrial (mt genomics has important implications for various fundamental areas, including mt biochemistry, physiology and molecular biology. In addition, mt genome sequences have provided useful markers for investigating population genetic structures, systematics and phylogenetics of organisms. Toxocara canis, Toxocara cati and Toxocara malaysiensis cause significant health problems in animals and humans. Although they are of importance in human and animal health, no information on the mt genomes for any of Toxocara species is available. Results The sizes of the entire mt genome are 14,322 bp for T. canis, 14029 bp for T. cati and 14266 bp for T. malaysiensis, respectively. These circular genomes are amongst the largest reported to date for all secernentean nematodes. Their relatively large sizes relate mainly to an increased length in the AT-rich region. The mt genomes of the three Toxocara species all encode 12 proteins, two ribosomal RNAs and 22 transfer RNA genes, but lack the ATP synthetase subunit 8 gene, which is consistent with all other species of Nematode studied to date, with the exception of Trichinella spiralis. All genes are transcribed in the same direction and have a nucleotide composition high in A and T, but low in G and C. The contents of A+T of the complete genomes are 68.57% for T. canis, 69.95% for T. cati and 68.86% for T. malaysiensis, among which the A+T for T. canis is the lowest among all nematodes studied to date. The AT bias had a significant effect on both the codon usage pattern and amino acid composition of proteins. The mt genome structures for three Toxocara species, including genes and non-coding regions, are in the same order as for Ascaris suum and Anisakis simplex, but differ from Ancylostoma duodenale, Necator americanus and Caenorhabditis elegans only in the location of the AT-rich region, whereas there are substantial differences when compared with Onchocerca volvulus
Mekonnen, Solomon A; Beissner, Marcus; Saar, Malkin; Ali, Solomon; Zeynudin, Ahmed; Tesfaye, Kassahun; Adbaru, Mulatu G; Battke, Florian; Poppert, Sven; Hoelscher, Michael; Löscher, Thomas; Bretzel, Gisela; Herbinger, Karl-Heinz
Onchocerciasis is a parasitic disease caused by the filarial nematode Onchocerca volvulus. In endemic areas, the diagnosis is commonly confirmed by microscopic examination of skin snip samples, though this technique is considered to have low sensitivity. The available melting-curve based quantitative real-time PCR (qPCR) using degenerated primers targeting the O-150 repeat of O. volvulus was considered insufficient for confirming the individual diagnosis, especially in elimination studies. This study aimed to improve detection of O. volvulus DNA in clinical samples through the development of a highly sensitive qPCR assay. A novel hydrolysis probe based qPCR assay was designed targeting the specific sequence of the O. volvulus O-5S rRNA gene. A total of 200 clinically suspected onchocerciasis cases were included from Goma district in South-west Ethiopia, from October 2012 through May 2013. Skin snip samples were collected and subjected to microscopy, O-150 qPCR, and the novel O-5S qPCR. Among the 200 individuals, 133 patients tested positive (positivity rate of 66.5%) and 67 negative by O-5S qPCR, 74 tested positive by microscopy (37.0%) and 78 tested positive by O-150 qPCR (39.0%). Among the 133 O-5S qPCR positive individuals, microscopy and O-150 qPCR detected 55.6 and 59.4% patients, respectively, implying a higher sensitivity of O-5S qPCR than microscopy and O-150 qPCR. None of the 67 individuals who tested negative by O-5S qPCR tested positive by microscopy or O-150 qPCR, implying 100% specificity of the newly designed O-5S qPCR assay. The novel O-5S qPCR assay is more sensitive than both microscopic examination and the existing O-150 qPCR for the detection of O. volvulus from skin snip samples. The newly designed assay is an important step towards appropriate individual diagnosis and control of onchocerciasis.
Nicholls, Rubén Santiago; Duque, Sofía; Olaya, Luz Adriana; López, Myriam Consuelo; Sánchez, Sol Beatriz; Morales, Alba Lucía; Palma, Gloria Inés
Onchocerciasis is a chronic parasitic infection originally endemic in 13 discrete regional foci distributed among six countries of Latin America (Brazil, Colombia, Ecuador, Guatemala, Mexico and Venezuela). In Colombia, this disease was discovered in 1965 in the Pacific Coast of the country. The National Onchocerciasis Elimination Program was established in 1993 with the aim of eliminating disease morbidity and infection transmission. In 2013, the World Health Organization (WHO) verified Colombia as free of onchocerciasis, becoming the first country in the world to reach such a goal. This report provides the empirical evidence of the elimination of Onchocerca volvulus transmission by Simulium exiguum (s.l.) after 12 years of 6-monthly mass drug administration of Mectizan® (ivermectin) to all the eligible residents living in this endemic area. From 1996 onwards, a biannual community-based mass ivermectin administration programme was implemented, complemented by health education and community participation. In-depth parasitological, serological and entomological surveys were conducted periodically between 1998 and 2007 to evaluate the impact of ivermectin treatment according to the 2001 WHO guidelines. When the interruption of parasite transmission was demonstrated, the drug distribution ceased and a three-year post-treatment surveillance (PTS) period (2008-2010) was initiated. After 23 rounds of treatment, parasitological and ophthalmological assessments showed absence of microfilariae in skin and anterior chamber of the eyes. Serological tests proved lack of antibodies against O. volvulus in children under 10 years-old. A total of 10,500 S. exiguum flies tested by PCR had no L3 infection (infectivity rate = 0.0095%; 95% CI: 0.0029-0.049) during 2004, indicating interruption of parasite transmission. However, biannual ivermectin treatments continued until 2007 followed by a 3-year PTS period at the end of which 13,481 flies were analyzed and no infective flies were
Full Text Available Filarial parasites (e.g., Brugia malayi, Onchocerca volvulus, and Wuchereria bancrofti are causative agents of lymphatic filariasis and onchocerciasis, which are among the most disabling of neglected tropical diseases. There is an urgent need to develop macro-filaricidal drugs, as current anti-filarial chemotherapy (e.g., diethylcarbamazine [DEC], ivermectin and albendazole can interrupt transmission predominantly by killing microfilariae (mf larvae, but is less effective on adult worms, which can live for decades in the human host. All medically relevant human filarial parasites appear to contain an obligate endosymbiotic bacterium, Wolbachia. This alpha-proteobacterial mutualist has been recognized as a potential target for filarial nematode life cycle intervention, as antibiotic treatments of filarial worms harboring Wolbachia result in the loss of worm fertility and viability upon antibiotic treatments both in vitro and in vivo. Human trials have confirmed this approach, although the length of treatments, high doses required and medical counter-indications for young children and pregnant women warrant the identification of additional anti-Wolbachia drugs.Genome sequence analysis indicated that enzymes involved in heme biosynthesis might constitute a potential anti-Wolbachia target set. We tested different heme biosynthetic pathway inhibitors in ex vivo B. malayi viability assays and report a specific effect of N-methyl mesoporphyrin (NMMP, which targets ferrochelatase (FC, the last step. Our phylogenetic analysis indicates evolutionarily significant divergence between Wolbachia heme genes and their human homologues. We therefore undertook the cloning, overexpression and analysis of several enzymes of this pathway alongside their human homologues, and prepared proteins for drug targeting. In vitro enzyme assays revealed a approximately 600-fold difference in drug sensitivities to succinyl acetone (SA between Wolbachia and human 5
Full Text Available Seasonal and daily biting activity patterns, and natural filarial infections of adult black flies attracted to human bait were investigated at Ban Pang Faen, a rural area in Chiang Mai Province in northern Thailand. Collections were carried out twice a month from 06-00 to 18-00 hours from January 2005 to February 2006. Among ten Simulium species collected, S. nodosum and S. asakoae were predominant occupying 57.3% and 37.2% of the total 16, 553 females, respectively. These two predominant species showed different patterns in seasonal abundance: majority of S. nodosum (86.7% were collected in hot season (from mid February to mid May, while most of S. asakoae (74.5% were collected in rainy season (from mid May to mid October. For the daily biting activity, S. nodosum had two patterns: the main one was unimodal with a peak from 17-00 to 18-00, and the other was bimodal and had the major peak from 16-00 to 18-00 and the minor one from 07-00 to 09-00. The pattern of S. asakoae was mostly unimodal with a peak from 06-00 to 10-00. The filarial larvae found in S. nodosum and S. asakoae were morphologically different from each other. The short and thick infective larvae found in S. asakoae differed from all known filarial larvae; it is suggested that they might be a bird parasite, Splendidofilariinae or Lemdaninae. The infection of the mammophilic S. nodosum with large Onchocerca type infective larvae was confirmed in this area. Natural filarial infections were found in each month (except December in either S. nodosum or S. asakoae or in both. Monthly infection rates with all stages of larvae were 0.6-5.0% for S. nodosum, and 1.0-4.0% for S. asakoae. It is suggested that people in this village are exposed to the risk of infection with zoonotic filariae throughout the year.
New molecular identifiers for Simulium limbatum and Simulium incrustatum s.l. and the detection of genetic substructure with potential implications for onchocerciasis epidemiology in the Amazonia focus of Brazil.
Conceição, Priscila A; Crainey, James L; Almeida, Tatiana P; Shelley, Anthony J; Luz, Sergio L B
still remains unanswered as the data presented here also suggest that S. limbatum found in the savannahs adjacent to, but outside the Amazonia focus (and which represent the only S. limbatum population to be unambiguously incriminated as a host of Onchocerca volvulus), are genetically distinct from those living inside the focus. These findings highlight the need for a clearer picture of the vector taxonomy inside the Amazonia onchocerciasis focus. Copyright © 2013 Elsevier B.V. All rights reserved.
Full Text Available OBJECTIVE: A systematic review and meta-analysis of all available case-control studies on the relationship between onchocerciasis and epilepsy. Because age and level of onchocerciasis endemicity in the area of residence are major determinants for infection, an additional analysis was performed, restricted to studies achieving control of these confounding factors. DATA SOURCES: Medical databases, the "African Neurology Database, Institute of Neuroepidemiology and Tropical Neurology, Limoges," reference lists of relevant articles, commercial search engines, up to May 2012. METHODS: We searched for studies examining infection status with Onchocerca volvulus in persons with epilepsy (PWE and without epilepsy (PWOE providing data suitable for the calculation of pooled odds ratios (ORp and/or standardized mean differences (SMD using random-effects models. RESULTS: Eleven studies providing data of qualitative skin biopsies for diagnosis of onchocerciasis were identified. Combined analysis on the total sample of 876 PWE and 4712 PWOE resulted in an ORp of 2.49 (95% confidence interval (95%CI: 1.61-3.86, p<0.001. When this analysis was restricted to those studies achieving control for age, residence and sex (367 PWE, 624 PWOE, an ORp of 1.29 (95% CI: 0.93-1.79; p = 0.139 was found. Presence of nodules for diagnosis of onchocerciasis was analyzed in four studies (225 PWE, 189 PWOE; ORp 1.74; 95%CI: 0.94-3.20; p<0.076, including two studies of the restricted analysis (106 PWE, 106 PWOE; ORp 2.81; 95%CI: 1.57-5.00; p<0.001. One study examined quantitative microfilariae counts in patients without preceding microfilaricidal treatment and demonstrated significantly higher counts in PWE than in PWOE. INTERPRETATION: Our results strengthen the hypothesis that, in onchocerciasis foci, epilepsy and infection with O. volvulus are associated. Analysis of indicators giving information on infection intensity, namely nodule palpation and quantitative microfilaria
O foco brasileiro de oncocercose: novas observações feitas nas áreas dos rios Mucajaí e Catrimâni, Território de Roraima The brazilian focus of onchocerciasis: new observations in areas of the Mucajaí and Catrimâni, Territory of Roraima
Mário Augusto Pinto de Moraes
Full Text Available Um novo inquérito para oncocercose, realizado em 1984, entre índios Yanomami da parte média dos rios Mucajaí e Catrimâni (Território de Roraima, mostrou que, decorridos vários anos das primeiras investigações - uma década no caso do rio Mucajaí - os índices de prevalência, nesses dois locais da periferia do foco brasileiro, não haviam sofrido alteração significativa. Levando-se em conta apenas os residentes nas aldeias ou malocas abrangidas pelo inquérito, a prevalência atingiu 3,1% nos índios do rio Mucajaí, enquanto ficou em zero nos do rio Catrimâni. Dada a presença contínua, nas referidas aldeias, de índios visitantes, altamente infectados, oriundos da parte central e mais elevada do território indígena - onde cerca de 90% doa adultos têm oncocercose - seria de esperar o achado de valores bem maiores (acima pelo menos daqueles encontrados anteriormente, caso um vetor apropiado estivesse presente na região. Simulium oyapockense s.1. é a única espécie antropofílica de simulídeo, em toda zona inferior da área ocupada pelos Yanomami (altitude ao redor de 200 metros, abundante o suficiente para constituir-se em transmissor da oncocercose. Sem dúvida, no entanto, trata-se de um mau vetor (como aliás já foi demonstrado experimentalmente para Mansonella ozzardi ou, até mesmo, de espécie não vetora de Onchocerca volvulus, pois, de outra forma, os índices de prevalência na parte média dos rios Mucajaí e Catrimâni já teriam crescido durante o período assinalado. Para explicar as altas taxas alcançadas pela endemia na porção central e cheia de acidentes (altitude superior a 900 metros do território Yanomami, há que se admitir a presença aí de um outro vetor, muito eficiente, cujos hábitos estariam ligados à região montanhosa da fronteira entre o Brasil e a Venezuela.A recent survey for onchocerciasis conducted among the Yanomami Indians living on the middle reaches of the Mucajaí and Catrim
Rodríguez-Pérez, Mario A; Unnasch, Thomas R; Real-Najarro, Olga
Onchocerciasis has historically been one of the leading causes of infectious blindness worldwide. It is endemic to tropical regions both in Africa and Latin America and in the Yemen. In Latin America, it is found in 13 foci located in 6 different countries. The epidemiologically most important focus of onchocerciasis in the Americas is located in a region spanning the border between Guatemala and Mexico. However, the Amazonian focus straddling the border of Venezuela and Brazil is larger in overall area because the Yanomami populations are scattered over a very large geographical region. Onchocerciasis is caused by infection with the filarial parasite Onchocerca volvulus. The infection is spread through the bites of an insect vector, black flies of the genus Simulium. In Africa, the major vectors are members of the S. damnosum complex, while numerous species serve as vectors of the parasite in Latin America. Latin America has had a long history of attempts to control onchocerciasis, stretching back almost 100 years. The earliest programmes used a strategy of surgical removal of the adult parasites from affected individuals. However, because many of the adult parasites lodge in undetectable and inaccessible areas of the body, the overall effect of this strategy on the prevalence of infection was relatively minor. In 1988, a new drug, ivermectin, was introduced that effectively killed the larval stage (microfilaria) of the parasite in infected humans. As the microfilaria is both the stage that is transmitted by the vector fly and the cause of most of the pathologies associated with the infection, ivermectin opened up a new strategy for the control of onchocerciasis. Concurrent with the use of ivermectin for the treatment of onchocerciasis, a number of sensitive new diagnostic tools were developed (both serological and nucleic acid based) that provided the efficiency, sensitivity and specificity necessary to monitor the decline and eventual elimination of
Dadzie, Yankum; Neira, Maria; Hopkins, Donald
onchocerciasis (REMO) and Geographic Information Systems (GIS). In the Americas, through support of the Onchocerciasis Elimination Program in the Americas (OEPA), a strategy of bi-annual ivermectin treatment of at least 85% of the eligible populations in all endemic communities is showing very good results and promises to be effective in eliminating onchocerciasis in the region.The Conference concluded that onchocerciasis is not eradicable using current tools due to the major barriers to eradication in Africa. However, the Conference also concluded that in most if not all the Americas, and possibly Yemen and some sites in Africa, transmission of onchocerciasis can be eliminated using current tools. The Conference recommended that where interruption of transmission is feasible and cost effective, programs should aim for that goal using all appropriate and available interventions so that the Onchocerca volvulus can eventually be eliminated and interventions halted. Although interruption of transmission of onchocerciasis cannot currently be achieved in most of Africa, the Conference recommended that efforts be made to preserve areas in West Africa made free of onchocerciasis transmission through the Onchocerciasis Control Program over the past 25 years. In the remaining hyper and mesoendemic foci in Africa, continued annual distribution of ivermectin will keep onchocerciasis controlled to a point where it is no longer a public health problem or constraint to economic development.