Dataset Information

On-going transmission of human onchocerciasis in the Massangam health district in the West Region of Cameroon: Better understanding transmission dynamics to inform changes in programmatic interventions.

ABSTRACT:

Background

Massangam health district (HD), in the West Region of Cameroon, has received ivermectin mass drug administration (MDA) for 20 years, however there is evidence of continued high transmission of Onchocerca volvulus. In order to better understand the transmission dynamics in the HD and inform intervention strategies there is a need to delineate the boundaries of the suspected area of high transmission within the wider transmission zone.

Methodology/principal findings

Parasitological and entomological surveys were conducted to map out the breeding sites of Simulium damnosum and evaluate the prevalence of onchocerciasis in neighbouring communities, including Makouopsap sentinel community. Potential rapids were prospected for identification of S. damnosum larvae and black flies collected to determine infectivity rates. Adults were assessed for the presence of O. volvulus microfilariae through a skin snip biopsy and examined for the presence of nodules. Anti Ov-16 antibodies were tested for in children. Four perennial breeding sites were identified on the Rivers Mbam and Nja. Large number of flies were collected along the River Mbam, especially in the rainy season, with up to 955 flies per day, suggesting this river is a perennial source of black flies. A total of 0.8% of parous flies were infective across the study area. Parasitological studies provided evidence of high rates of infection in the sentinel community and three neighbouring communities, with 37.1% of adults microfilariae positive in Makouopsap. High Ov-16 seropositivity in children also provided evidence of recent on-going transmission. In comparison, communities sampled further away from the sentinel community and neighbouring breeding sites were much closer to reaching onchocerciasis elimination targets.

Conclusions/significance

This study provides evidence of a particular geographic area of high transmission in an approximate 12 km range around the sentinel community of Makouopsap and the neighbouring breeding sites on the River Nja. To eliminate onchocerciasis by 2025, there is a need to explore alternative intervention strategies in this area of high transmission.

SUBMITTER: Bakajika D

PROVIDER: S-EPMC6261645 | biostudies-literature | 2018 Nov

REPOSITORIES: biostudies-literature

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Publications

On-going transmission of human onchocerciasis in the Massangam health district in the West Region of Cameroon: Better understanding transmission dynamics to inform changes in programmatic interventions.

Bakajika Didier D Senyonjo Laura L Enyong Peter P Oye Joseph J Biholong Benjamin B Elhassan Elizabeth E Boakye Daniel D Dixon Ruth R Schmidt Elena E

PLoS neglected tropical diseases 20181114 11

<h4>Background</h4>Massangam health district (HD), in the West Region of Cameroon, has received ivermectin mass drug administration (MDA) for 20 years, however there is evidence of continued high transmission of Onchocerca volvulus. In order to better understand the transmission dynamics in the HD and inform intervention strategies there is a need to delineate the boundaries of the suspected area of high transmission within the wider transmission zone.<h4>Methodology/principal findings</h4>Paras ...[more]

PMID: 30427830

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Project description:BackgroundIvermectin-based preventive chemotherapy (PC) is distributed annually to all at-risk populations eligible for ivermectin treatment to control and/or eliminate onchocerciasis. Information on the impact of mass ivermectin administration on onchocerciasis transmission is scanty, and it is tricky to appreciate the progress towards elimination and engage corrective measures. To fill that gap in the Centre Region in Cameroon, the current onchocerciasis endemicity level in the Ndikinimeki Health District after about two decades of mass treatments was assessed.MethodsA cluster-based cross-sectional survey was carried out in the Ndikinimeki Health District and all volunteers aged ≥ 5 years were (i) interviewed on their compliance to ivermectin over the past five years and (ii) underwent clinical (nodule palpation and visual search for onchocercal lesions) and parasitological examinations (skin snip) for onchocerciasis.ResultsThe overall Onchocerca volvulus prevalence was 7.0% (95% CI: 5.2-9.3%). The prevalence of the disease was significantly higher in the communities Kiboum 1 and Kiboum 2 compared to the other communities (highest prevalence in Makénéné Town Water: 8.5%; 95% CI: 2.3-20.4%) (χ2 = 51.314, df = 11, P = 0.0001). The proportion of systematic non-compliers to ivermectin was 23.3% (95% CI: 19.9-27.1%) among individuals interviewed. In the sentinel sites (Kiboum communities), onchocerciasis prevalence decreased from 95.2% (95% CI: 88.3-98.1%) to 23.7% (95% CI: 14.7-36.0%).ConclusionsThis study has revealed that the Ndikinimeki Health District is hypo-endemic for onchocerciasis after about two decades of preventive chemotherapy. However, transmission is ongoing, with potential hotspots in the Kiboum 1 and Kiboum 2 communities, which are known as first-line communities (closest to the breeding sites of the vector). Alternative or complementary strategies to annual ivermectin appear compulsory to accelerate the momentum towards onchocerciasis elimination.

Project description:IntroductionThe CDTI model is known to have enhanced community participation in planning and resource mobilization toward the control of onchocerciasis. These effects were expected to translate into better individual acceptance of the intervention and hence high Treatment Coverage, leading to a sustainable community-led strategy and reduction in the disease burden. A survey revealed that after 10-12 rounds of treatment, prevalence of onchocerciasis was still high in three drainage basins of South West Cameroon and transmission was going on.MethodsWe designed a three (3)-year retrospective (2012, 2013 and 2014), descriptive cross-sectional study to explore the roles of operational challenges in the failure of CDTI to control the disease as expected. We administered 83 semi-structured questionnaires and conducted 12 in-depth interviews with Chiefs of Bureau Health, Chiefs of Centers, CDDs and Community Heads. Descriptive statistics was used to explore indicators of performance which were supported with views from in-depth interviews.ResultsWe found that community participation was weak; communities were not deciding time and mode of distributions. Only 6 (15.0%) of 40 Community Drug Distributors reported they were selected at general community meetings as required. The health service was not able to meet and discuss Community-Directed Treatment with Ivermectin activities with individual communities partly due to transportation challenges; this was mostly done through letters. Funding was reported to be inadequate and not timely. Funds were not available to conduct Community-Self Monitoring after the 2014 Mass Drug Administration. There was inadequate health staff at the frontline health facility levels, and some Chiefs of Center reported that Community-Directed Treatment with Ivermectin work was too much for them. The mean operational Community Drug Distributor-population ratio was 1 Community Drug Distributor per 317 populations (range: 194-464, expected is 1:250). Community Drug Distributor attrition rate was 14% (2012), 11% (2013) and 12% (2014) of total Community Drug Distributors trained in the region. Lack of incentive for Community Drug Distributor was primary reason for Community Drug Distributor attrition. Number of Community Drug Distributors trained together by health area ranged from 14 to 127 (mean ± SD = 51 ±32) with duration of training ranging from 4-7 hours (mean ± SD = 5.05 ± 1.09). The trainings were conducted at the health centers. Community Drug Distributors always conducted census during the past three distributions (Mean ± SD = 2.85 ± 0.58). Community-Self Monitoring was facing challenge. Several of the community heads, Chiefs of Bureau Health and Chiefs of Center agreed that Community-Self Monitoring was not being carried out effectively due to lack of incentives for monitors in the communities.ConclusionInadequate human resource, funding issues and transportation challenges during distribution periods reduced the ability of the health service to thoroughly sensitize communities and supervise CDTI activities. This resulted in weak community understanding, acceptance and participation in the process. CDTI in our study area did not achieve sustainable community-led campaign and this may have led to the reduced impact on Onchocerciasis.

Project description:The main onchocerciasis elimination strategy is annual Community-Directed Treatment with ivermectin (CDTi). However, as a response to persistent high infection prevalence in Massangam Health District in Cameroon, two rounds of alternative treatments including biannual CDTi, ground larviciding and test and treat with doxycycline (TTd) were implemented. This led to a significant prevalence reduction from 35.7% to 12.3% (p<0.001) as reported by Atekem and colleagues. Here we report on the acceptability of TTd component based on qualitative and quantitative data. The TTd involved microscopic examination for microfilaria in skin biopsy and those infected were offered doxycycline 100 mg daily for 35 days by community-directed distributors (CDDs). Participation level was significantly high with 54% of eligible population (age > 8, not pregnant, not breastfeeding, not severely ill,) participating in the test in each round, increasing to 83% over the two rounds. Factors associated with non-participation included mistrust, being female; being younger than 26 years; short stay in the community; and belonging to semi-nomadic sub population due to their remote and disperse settlement, discrimination, their non selection as CDD, and language and cultural barriers. Treatment coverage was high -71% in round 1 and 83% in round 2. People moving away between testing and treatment impacted treatment coverage. Some participants noted mismatch between symptoms and test result; and that ivermectin is better than doxycycline, while others favoured doxycycline. CDD worried about work burden with unmatching compensation. Overall, TTd participation was satisfactory. But can be improved through reinforcing sensitisation, reducing time between test and treatment; combining TTd and CDTi in one outing; augmenting CDDs compensation and/or weekly visit; exploring for frequently excluded populations and adapting strategies to reach them; and use of a sensitive less invasive test.

Project description:After more than a decade of community-directed treatment with ivermectin (CDTI) in the West Region of Cameroon, epidemiological evaluation conducted in 2011 showed that onchocerciasis endemicity was still high in some communities. The conceptual framework for onchocerciasis elimination recommends in such case, to conduct additional phase 1A surveys at intervals of three to four years. Therefore, to assess the progress made towards the elimination of onchocerciasis in the West CDTI projects, we conducted a cross-sectional survey in May 2015 in 15 unevaluated communities where the highest baseline endemicity level were found in 1996. All volunteers living for at least five years in the community, aged five years or more, underwent clinical and parasitological examinations. Individual adherence to ivermectin treatment was also assessed. Analyses of data were weighted proportionally to age and gender distribution in the population.The mean age was 28.4 ± 22.2 years and there were 55% of women among the 2058 individuals examined. The weighted prevalences were 5.5%, 2.1% and 1.7% for microfilaridermia, nodule and cutaneous signs, respectively. The weighted microfilaridermia prevalences varied from 4.0 in 5-9 years old to 11.6% in 40-49 years old. In the 30 children under 10 years examined in Makouopsap, the weighted prevalences were 49.9% for microfilaridermia and 13.3% for nodule. In surveyed communities, the weighted prevalences varied from 0 to 41.6% for microfilaridermia, with 11 (73.3%) communities having <5%. Except Makouopsap which had 41.6%, all the surveyed communities were below 15% for microfilaridermia prevalence. The community microfilarial load (CMFL) expressed in microfilariae/skin snip (mf/ss), also significantly dropped by 98-100%, from 3.75-33.16 mf/ss in 1996 to 0-0.94 mf/ss in 2015. The weighted therapeutic coverage in 2014 was 69.4% and the 5 years' adherence was only 39.3% among participants.After more than 15 years of CDTI, there is an important progress towards the elimination of onchocerciasis in the communities surveyed. Innovative strategy like semi-annual ivermectin treatment plus vector control or the adjunction of a vector control strategy to the current annual treatment should be implemented in the bordering districts of the Centre and West Regions, as well as in other parts of the country with persistent high prevalences in the sight of onchocerciasis elimination.

Project description:BackgroundA strong association between epilepsy and onchocerciasis endemicity has been reported. We sought to document the epidemiology of epilepsy in onchocerciasis-endemic villages of the Ntui Health District in Cameroon and investigate how this relates to the prevalence of onchocerciasis.MethodsIn March 2022, door-to-door epilepsy surveys were conducted in four villages (Essougli, Nachtigal, Ndjame, and Ndowe). Ivermectin intake during the 2021 session of community-directed treatment with ivermectin (CDTI) was investigated in all participating village residents. Persons with epilepsy (PWE) were identified through a two-step approach: administration of a 5-item epilepsy screening questionnaire followed by clinical confirmation by a neurologist. Epilepsy findings were analyzed together with onchocerciasis epidemiological data previously obtained in the study villages.ResultsWe surveyed 1663 persons in the four study villages. The 2021 CDTI coverage for all study sites was 50.9%. Overall, 67 PWE were identified (prevalence of 4.0% (IQR: 3.2-5.1) with one new-onset case during the past 12 months (annual incidence of 60.1 per 100,000 persons). The median age of PWE was 32 years (IQR: 25-40), with 41 (61.2%) being females. The majority (78.3%) of PWE met the previously published criteria for onchocerciasis-associated epilepsy (OAE). Persons with a history of nodding seizures were found in all villages and represented 19.4% of the 67 PWE. Epilepsy prevalence was positively correlated with onchocerciasis prevalence (Spearman Rho = 0.949, p = 0.051). Meanwhile, an inverse relationship was observed between distance from the Sanaga river (blackfly breeding site) and the prevalence of both epilepsy and onchocerciasis.ConclusionThe high epilepsy prevalence in Ntui appears to be driven by onchocerciasis. It is likely that decades of CDTI have likely contributed to a gradual decrease in epilepsy incidence, as only one new case occurred in the past year. Therefore, more effective elimination measures are urgently needed in such endemic areas to curb the OAE burden.

Project description:BackgroundThe impact of large scale Mass Drug Adminstration (MDA) of ivermectin on active onchocerciasis transmission by Simulium damnosum, which transmits the parasite O. volvulus is of great importance for onchocerciasis control programmes. We investigated in the Mbam river system area, the impact of MDA of ivermectin on entomological indices and also verify if there are river system factors that could have favoured the transmission of onchocerciasis in this area and contribute to the persistence of disease. We compared three independent techniques to detect Onchocerca larvae in blackflies and also analyzed the river system within 9 months post-MDA of ivermectin.MethodSimulium flies were captured before and after 1, 3, 6 and 9months of ivermectin-MDA. The biting rate was determined and 41% of the flies dissected while the rest were grouped into pools of 100 flies for DNA extraction. The extracted DNA was then subjected to O-150 LAMP and real-time PCR for the detection of infection by Onchocerca species using pool screening. The river system was analysed and the water discharge compared between rainy and dry seasons.Principal findingsWe used human landing collection method (previously called human bait) to collect 22,274 adult female Simulium flies from Mbam River System. Of this number, 9,134 were dissected while 129 pools constituted for molecular screening. Overall biting and parous rates of 1113 flies/man/day and 24.7%, respectively, were observed. All diagnostic techniques detected similar rates of O. volvulus infection (P = 0.9252) and infectivity (P = 0.4825) at all monitoring time points. Onchocerca ochengi larvae were only detected in 2 of the 129 pools. Analysis of the river drainage revealed two hydroelectric dams constructed on the tributaries of the Mbam river were the key contributing factor to the high-water discharge during both rainy and dry seasons.ConclusionResults from fly dissection (Microscopy), real-time PCR and LAMP revealed the same trends pre- and post-MDA. The infection rate with animal Onchocerca sp was exceptionally low. The dense river system generate important breeding sites that govern the abundance of Simulium during both dry and rainy seasons.

Project description:Community-Directed Treatment with Ivermectin (CDTI) is the main strategy adopted by the African Programme for Onchocerciasis control (APOC). Recent reports from onchocerciasis endemic areas of savannah zones have demonstrated the feasibility of disease elimination through CDTI. Such information is lacking in rain forest zones. In this study, we investigated the parasitological and entomological indices of onchocerciasis transmission in three drainage basins in the rain forest area of Cameroon [after over a decade of CDTI]. River basins differed in terms of river number and their flow rates; and were characterized by high pre-control prevalence rates (60-98%).Nodule palpation and skin snipping were carried out in the study communities to determine the nodule rates, microfilarial prevalences and intensity. Simulium flies were caught at capture points and dissected to determine the biting, parous, infection and infective rates and the transmission potential.The highest mean microfilaria (mf) prevalence was recorded in the Meme (52.7%), followed by Mungo (41.0%) and Manyu drainage basin (33.0%). The same trend was seen with nodule prevalence between the drainage basins. Twenty-three (23/39) communities (among which 13 in the Meme) still had mf prevalence above 40%. All the communities surveyed had community microfilarial loads (CMFL) below 10 mf/skin snip (ss). The infection was more intense in the Mungo and Meme. The intensity of infection was still high in younger individuals and children less than 10 years of age. Transmission potentials as high as 1211.7 infective larvae/person/month were found in some of the study communities. Entomological indices followed the same trend as the parasitological indices in the three river basins with the Meme having the highest values.When compared with pre-control data, results of the present study show that after over a decade of CDTI, the burden of onchocerciasis has reduced. However, transmission is still going on in this study site where loiasis and onchocerciasis are co-endemic and where ecological factors strongly favour the onchocerciasis transmission. The possible reasons for this persistent and differential transmission despite over a decade of control efforts using ivermectin are discussed.

Dataset Information

On-going transmission of human onchocerciasis in the Massangam health district in the West Region of Cameroon: Better understanding transmission dynamics to inform changes in programmatic interventions.

Background

Methodology/principal findings

Conclusions/significance

Publications

On-going transmission of human onchocerciasis in the Massangam health district in the West Region of Cameroon: Better understanding transmission dynamics to inform changes in programmatic interventions.

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