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Background: An epilepsy prevalence of 4.4% was documented in onchocerciasis-endemic villages close to the Maridi River in South Sudan. We investigated the role of the Maridi dam in causing an onchocerciasis-associated epilepsy epidemic in these villages. Methods: Affected communities were visited in November 2019 to conduct focus group discussions with village elders and assess the OV16 seroprevalence in 3- to 9-year-old children. Entomological assessments to map blackfly breeding sites and determine biting rates around the Maridi River were conducted. Historical data regarding various activities at the Maridi dam were obtained from the administrative authorities. Results: The Maridi dam was constructed in 1954-1955. Village elders reported an increasing number of children developing epilepsy, including nodding syndrome, from the early 1990s. Kazana 2 (the village closest to the dam; epilepsy prevalence 11.9%) had the highest OV16 seroprevalence: 40.0% among children 3-6 years old and 66.7% among children 7-9 years old. The Maridi dam spillway was found to be the only Simulium damnosum breeding site along the river, with biting rates reaching 202 flies/man/h. Conclusion: Onchocerciasis transmission rates are high in Maridi. Suitable breeding conditions at the Maridi dam, coupled with suboptimal onchocerciasis control measures, have probably played a major role in causing an epilepsy (including nodding syndrome) epidemic in the Maridi area.

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The Itwara onchocerciasis focus is located around the Itwara forest reserve in western Uganda. In 1991, annual treatments with ivermectin started in the focus. They were supplemented in 1995 by the control of the vector Simulium neavei, which was subsequently eliminated from the focus. The impact of the two interventions on the disease was assessed in 2010 by nodule palpations, examinations of skin snips by microscopy and PCR, and Ov16 recombinant ELISA. There was no evidence of any microfilaria in 688 skin snips and only 2 (0.06%) of 3316 children examined for IgG4 were slightly above the arbitrary cut off of 40. A follow up of the same children 21 months later in 2012 confirmed that both were negative for diagnostic antigen Ov-16, skin snip microscopy and PCR. Based on the World Health Organization (WHO) elimination criteria of 2001 and the Uganda onchocerciasis certification guidelines, it was concluded that the disease has disappeared from the Itwara focus after 19 years of ivermectin treatments and the elimination of the vector around 2001. Ivermectin treatments were recommended to be halted.

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An evaluation study on reversibility of Schistosoma mansoni induced periportal fibrosis (PF) morbidity following treatment with praziquantel, 40mg/kg body weight after one year, was carried out in Rhino Camp and Obongi all are West Nile districts in northern Uganda. To assess the reversibility of Schistosoma (S) mansoni induced PFs morbidity following treatment with praziquantel, 40mg/kg body weight after one year. The design was a Prospective cohorts study; and the setting was a busy canoe landing sites along Albert Nile in Schistosoma (S) mansoni hyperendemic areas of Rhino Camp and Obongi fishing village were selected for the study. Previously in 2005, 1562 people including fishermen and women, school pupils, teachers, and civil servants were studied in both fishing villages for S. mansoni using Kato/Katz stool smear method. Abdominal ultrasonography and sonomorphological abnormalities of periportal fibrosis were performed with Aloka portable ultrasound machine (Hellige, Freiburg, Germany) fitted with a convex probe of 3.5 mega Hertz was also performed in the field clinic on all patients who had S. mansoni eggs in their faeces. The sonomorphological abnormalities of periportal fibrosis were categorised and organomorphometry of liver and spleen was done. One thousand two hundred and seventy three 1273 (81.5%) patients in Rhino Camp and Obongi fishing villages were found to be excreting from 100 to ≥ 500 eggs per gram (epg) of faeces of S. mansoni eggs. Two hundred and eighty nine (18.5%) did not have eggs of S.mansoni in their faeces. All the 1273 patients secreting eggs of S.mansoni in their stool in Rhino Camp and Obongi fishing villages had abdominal ultrasonography and sonomorphological abnormalities of periportal fibrosis. Eight hundred and forty 840 (66%) although excreted S. mansoni eggs in their stool had Pf (0); Pf grade (I), n=259 (20.3%); Pf grade (II) n =147 (11.5%); and Pf grade (III) n=27 (2.1%) were observed.

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The Itwara focus of onchocerciasis covers an area of approximately 600 km(2) in western Uganda about 20 km north of Fort Portal. The vector is Simulium neavei, whose larvae and pupae live in a phoretic association on freshwater crabs. The phoretic host in the Itwara focus is the crab Potamonautes aloysiisabaudiae. Before any onchocerciasis control, ATPs were estimated to reach between 4500 and 6500 infective larvae per person per year. S. neavei was found to be a very efficient vector with 40% of parous flies harbouring developing larvae of Onchocerca volvulus. After 4 years of community-based distribution of ivermectin transmission was still considerable and in 1995 monthly treatment of streams with the larvicide temephos commenced in the first of three sub-foci, and was gradually extended to the whole focus. Biting S. neavei disappeared from the first sub-focus (Itwara main) in June 1996, and the last infested crab was caught in November 1996. In the second sub-focus (Siisa) treatment commenced towards the end of 1995, and the last biting fly was caught in March 1997, but a deterioration in the security situation interrupted the programme (after only three treatments in the third sub-focus). Monthly treatments restarted in the second and third sub-foci (Aswa) in September 1998, and when the situation was reassessed in 2003 no biting flies were found anywhere, and the flies had not reinvaded the first sub-focus, but infected crabs were found in the second and third sub-foci. The last treatments were carried out in April-June 2003, and since then no infested crabs have been found. In summary, no S. neavei-infested crabs have been found anywhere in the focus since June 2003 and the vector is considered eliminated from that date. However, transmission had already been halted since February 2001, when the last biting flies had been collected. The parasite reservoir should die out in the human population by 2016.

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BACKGROUND: Community directed treatment with ivermectin (CDTI) for onchocerciasis control was developed as a strategy for achieving sustained high coverage in endemic communities. This strategy for over a short period of time has radically altered the consequences of infection with Onchocerca volvulus. The present challenge is maintaining the high therapeutic coverage especially in some of the impoverished endemic countries. One of these challenges is non-adherence to ivermectin treatment and this provides compelling reason for data collection at community level. OBJECTIVE: To describe the factors associated with non-adherence to CDTI. DESIGN: Cross-sectional descriptive study. SETTING: Communities participating in CDTI activities in Ndubi village, Rungwe district, southwest Tanzania. RESULTS: A high proportion (66%) of respondents were aware of onchocerciasis, and this was more significant in males than females (X2 = 9.17; p< 0.002). Knowledge on causes of the disease was low, only 29.3% associated it with the bite of Simulium fly, 17% associated it with mosquitoes, 17.1% to houseflies, and 30% had completely no idea. Knowledge on signs and symptoms of onchocerciasis was also observed to be equally low (20.4%) among the respondents. Similarly, only 35.4% of the respondents knew itching, swelling of the body, diarrhoea and vomiting as associated side effects of ivermectin. There was, however, no sex difference in knowledge levels (X2 = 0.01; p>0.939). Low knowledge levels on causes of the disease, signs and symptoms and side effects of ivermectin were attributed to inadequate health education in the communities. However, some other factors associated with non-adherence were local beliefs and the lifestyle of alcoholism. CONCLUSIONS: Factors identified to affect programme implementation and associated with non-adherence were inadequate knowledge on causes of the disease and sign/symptoms, side effects of ivermectin, local beliefs and lifestyle of alcoholism in the communities.

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The transmission of Onchocerca volvulus Leuckart (Spirudida: Onchocercidae) and the prospects of Simulium neavei Roubaud (Diptera: Simuliidae) vector elimination through ground larviciding were investigated in the Mpamba-Nkusi focus, western Uganda. Transmission levels and the initiated vector elimination activities were assessed to supplement the ongoing ivermectin mass distribution programme. Searches for breeding sites, adult fly catches, dissection of flies, river treatment with temephos (Abate) and a review of annual ivermectin treatment data were conducted. High levels of crab infestation with S. neavei sensu stricto immature stages were recorded; 57.9% and 100% for the Mpamba and Nyabugando river systems, respectively. The mean numbers of larvae/pupae per crab were 3.6 +/- 0.5 in the Mpamba and 20.6 +/- 1.8 in the Nyabugando systems. Pre-intervention mean biting densities were 39 and 32 flies/(man day) in 2001 and 2002, respectively, and an annual biting rate in 2001 of > 14 000. The bimodal biting pattern of S. neavei s.s. consisted of two peaks; one in the morning (09.00-10.00 hours) and one in the afternoon (14.00-15.00 hours) with a mid-day lull in biting. The infection/infective rates were 13.3%/2.8% and 16.6%/2.9% in the dissected parous flies from the Mpamba and Nyabugando river systems, respectively. Out of approximately 1000 parous flies, 129 and 109 were found to be harbouring infective larvae of Onchocerca volvulus in their heads from the Mpamba and Nyabugando river systems, respectively. In spite of the > 10 years of ivermectin treatment, at a mean coverage of 71.3%, infection remained relatively high. Ground larviciding with temephos (Abate) initiated in June and October 2002 had a significant impact. In the Mpamba river system there was a significant (P < 0.001) reduction in positive crabs from 57.9% in 2001 to 0.06% in 2003 and a decrease in the mean number of larvae/pupae per crab from 3.6 +/- 0.5 in 2001 to 0.0007 +/- 0.0001 (P < 0.002) in 2003. Similarly, in the Nyabugando river system, a significant (P < 0.001) reduction in crab infestation from 100% in 2001 to 0.06% in 2003 and a decrease in the mean number of larvae/pupae per crab from 20.6 +/- 1.8 in 2001 to 0.06 +/- 0.03 in 2003. Drastic reductions were observed in the mean number of biting flies from 3 flies/h in 2001 to 0 flies/h in 2003 and the annual biting rates fell from 14,235 flies/year in 2001 to only 730 flies/year in 2003. These data suggest that substantial progress towards the goal of S. neavei s.s. vector elimination has been made and this will enhance the ongoing ivermectin treatment in this isolated focus.

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OBJECTIVE: To determine the biting activity and onchocerciasis transmission in Kashoya-Kitomi focus, Western Uganda. DESIGN: Cross-sectional survey in randomly selected sites. SETTING: Three districts in Western Uganda. METHOD: Crab trapping and examination for immature stages of Simulium neavei and full day human bait catches and dissections were conducted at three sites. RESULTS: A total of 338 crabs were caught and out of this 372 (95.9%) were positive with immature stages of S. neavei with mean S. neavei/crab of 6.9. High biting density of S. neavei was observed in the two sites in Kabarole and Mbarara districts whereas an extremely low density was observed at a site in Bushenyi. Diurnal biting pattern revealed two peaks in the morning (09:00-10:00 hours.) and in the late afternoon (14:00-15:00 hours.) with a mid-day lull. The infection/infective rates were 53.3/11.0%, 30.7% to 7.8% and 20.0/0% for sites in Mbarara, Kabarole and Bushenyi districts, respectively. Monthly biting rates/ Transmission potentials for Mbarara, Kabarole and Bushenyi districts were 6231/5437, 9244/2916 and 247/0. CONCLUSION: There was high transmission of onchocerciasis observed in Kashoya-Kitomi focus despite the ongoing ivermectin treatment. The need for improved chemotherapeutic coverage and instituting other control measures may be necessary.

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Four hundred and fifty one human strata living in the three fishing villages of Ndiaga, Kabukanga and Rwabikongoro along Lake Albert shore in Kibale District were examined for S. mansoni infection using Kato/Katz method. Of the 451 people, 409 (90.7%) were found infected with S. mansoni with geometric mean egg count of 561.3 eggs per gram (epg) faeces. Males had significantly higher mean egg counts than females, 608.3 epg and 415.6 epg respectively. All S. mansoni infected individuals were treated with praziquantel at 40 mg/kg body weight. Other common parasites observed were Asaris lumbricoides, Trichuris trichiura and hookworms. These were treated with mebendazole. Snail infection rate among the 115 Biomphalaria sudanica and the 56 B. stanleyi were 5.2% and 3.6% respectively. All the 66 Bulinus (B) tropicus found, were negative for cercariae shedding. The main pulmonate snails were 250 Lymnae natalensis, 500 Pila ovata and 375 Bellamya spp were the commonest prosobranchs followed by Bivalves (101).

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Using the Kato Katz technique, 600 people living in Nakiwogo fishing village at Lake Victoria, Uganda, were examined for Schistosoma mansoni infection. The total population of this village was estimated between 1,000 and 1,500 mainly consisting of migrants from western Uganda. Of the 600 individuals in the study group, 328 people (54.7%) were found to be infected with S. mansoni. The geometric mean egg count was 422 eggs per gramme of stool. A survey of the snail intermediate hosts for S. mansoni and S. haematobium at Nakiwogo was carried out. The collected snails were tested for cercariae shedding. A significant decrease in the number of Biomphalaria choanomphala and Biomphalaria pfeifferi (52%) which both still shed cercariae and Bulinus tropicus (52.5%) could be observed. There was a lower none-significant decrease of 13.3% of the Bulinus globosus population. With a combined approach including community participation in control measures in the form of health education, sanitation, environmental management and chemotherapy, the prevalence of S. mansoni infection was reduced from 54.7% to 14.6% in the period of one year.

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Using the Kato katzi technique; 600 people living in Nakiwogo fishing village at Lake Victoria; Uganda; were examined for schistosoma mansoni infection. The total population of this village was estimated between 1;00 and 1;500 mainly consisting of migrants from Western Uganda. Of the 600 individuals in the study group; 328 people (54.7) were found to be infected with S. mansoni. The geometric mean egg count was 422 eggs per gramme of stool. a survey of the snail intermediate hosts for S. mansoni and S. haematobium at Nakiwogo was carried out. The collected snails were tested for cercariae shedding. A significant decrease in the number of Biomphalaria choanomphala and Biomphalaria pfeifferi (52) which both still shed cercariae and Bulinus (52.5) could be observed. There was a lower none-significant decrease of 13.3of the Bulinus globosus population. With a combined approach including community participation in control measures in the form of health education; sanitation; environmental management and chemotherapy; the prevalence of S. mansoni infection was reduced from 54.7to 14.6 in the period of one year

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Four hundred and fifty one human strata living in the three fishing villages of Ndiaga; kabukanga and Rwabikongoro along Lake Albert shore in Kibale District were examined for S. mansoni infection using Kata/Katz method. Of the 451 people; 409(90.7) were found infected with S. mansoni with geometric mean egg count of 561.3 eggs per gram (epg) faeces. Males had significantly higher mean egg counts than females; 608.e epg and 415.6 epg respectively. All S. mansoni infected individuals were treated with praziquantel at 40mg/kg body weight. Other common parasites observed were Ascaris lumbricoides; Trichuris trichiura and hookworms. These were treated with mebandazole. Snail infection rate among the 115 Biomphalaria sudanica and the 56 B. stanleyi were 5.2and 3.6respectively. All the 66 Bulinus (B) tropicus found; were negative for cercariae shedding. The main pulmonate snails were 250 Lymnae natalensis; 500 Pila ovata and 375 Bellamya spp were the commonest prosobranchs followed by Bivalves (101)

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Using the Kato Katz method for quantification of parasitic eggs in faeces, 500 individuals aged between 4 and 50 years, living along River Enyau, half a kilometre from Arua town, were studied to assess the prevalence of Schistosoma mansoni in the population. The overall prevalence of Schistosoma mansoni infection was 62%. The infection was highest among school children (71.1%, i.e. 199 out of 280). Villagers who lived along the immediate vicinity of the river had a 62.8% prevalence of infection (98 out of 156). School teachers and the members of their families had the lowest infection rate (20.3% i.e. 13 out of 64). The geometric mean egg output for males and females in the community studied was 203 and 179 eggs per gram of stool, respectively. 206 (41%) out of 500 individuals had mixed infections of S. mansoni and hookworms. The rate of orally transmitted intestinal helminths like Trichuris trichiura was very low (0.8%). Ascaris lumbricoides eggs were not found.

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The intensity of Schistosoma mansoni infection in the fishing villages of Bugonga and Kitubulu, and the occurrence of snail intermediate host population in the two villages are described and compared. A total of five hundred and six faecal samples from both villages were examined by modified Kato's technique and the prevalence infection rate at Kitubulu was 40.3% with mean egg count of 187 eggs per gram(epg) while in Bugonga it was 32.4% and 126 epg respectively. The snail intermediate host for S. mansoni in the two villages was 2,750 Biomphalaria choanomphala at Kitubulu and 1,268 at Bugonga. But at Kitubulu in the vicinity of the village 185 Biomphalaria peifferi occurred in small localized population. The cercarial screening test conducted on 4,018 B. choanomphala and 185 B. peifferi from the two villages revealed higher snail infection rate for both mammalian and non-mammalian cercariae at Kitubulu than Bugonga. Variations in infection rates both among the inhabitants and host snail populations in the two villages are discussed.

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The intensity of Schistosoma mansoni infection in the fishing villages of Bugonga and Kitubulu; and the occurrence of snail intermediate host population in the two villages are described and compared. A total of five hundred and six faecal samples from both villages were examined by modified Kato's technique and the prevalence infection rate at Kitubulu was 40.3with mean egg count of 187 eggs per gram (epg) while in Bugonga it was 32.4and 126 egg respectively. The snail intermediate host for S. mansoni in the two villages was 2;750 Biomphalaria choanomphala at Kitubulu and 1;268 at Bugonga. But at Kitubulu in the vicinity of the village 185 Biomphalaria peifferi occurred in small localized population. The cercarial screening test conducted on 4;018 B. choanomphala and 185 B. peifferi from the two villages revealed higher snail infection rate for both mammalian and non-mammalian cercariae at Kitubulu than Bugonga. Variations in infection rates both among the inhabitants and host snail populations in the two villages are discussed

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The intensity of Schistosoma mansoni infection in the fishing villages of Bugonga and Kitubulu; and the occurrence of snail intermediate host population in the two villages are described and compared. A total of five hundred and six faecal samples from both villages were examined by modified Kato's technique and the prevalence infection rate at Kitubulu was 40.3pc with mean egg count of 187 eggs per gram(epg) while in Bugonga it was 32.4pc and 126 epg respectively. The snail intermediate host for S. mansoni in the two villages was 2;750 Biomphalaria choanomphala at Kitubulu and 1;268 at Bugonga. But at Kitubulu in the vicinity of the village 185 Biomphalaria peifferi occurred in small localized population. The cercarial screening test conducted on 4;018 B. choanomphala and 185 B. peifferi from the two villages revealed higher snail infection rate for both mammalian and non-mammalian cercariae at Kitubulu than Bugonga. Variations in infection rates both among the inhabitants and host snail populations in the two villages are discussed

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A comparative study of the prevalence of Schistosoma mansoni and their intermediate host in the fishing villages of Nakiwogo and Kigungu is reported. A total of 520 inhabitants from the two villages were examined for Schistosoma mansoni. Their age varied from 4 to 40 and the infection was found to be higher at Nakiwogo 95(36.6%) than at Kigungu 40(15.4%). The snails collected were 1,345 Biomphalaria choanomphala, 237 Biomphalaria pfeifferi, 180 Bulinus (Bulinus) tropicus, 56 Bulinus (physopsis) globosus and other snails of non-medical importance like Pila ovata, Melanoides tuberculata and Bellamya species. Biomphalaria choanomphala was found to be the major intermediate host for Schistosoma mansoni in the two villages. The intermediate hosts for S. mansoni were screened for cercarial shedding, 2 Biomphalaria pfeifferi shed furcocercous cercariae and 9 Leptocercous cercariae while Biomphalaria choanomphala were an negative. The water contact activities related to infection in the two villages are discussed.

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