ArticleParasites & vectors2024
Onchocerciasis in the Cameroon-Chad border area after more than 20 years of annual mass ivermectin distribution.
Article in Parasites & vectors, 2024. The graph could read no effect estimate from its abstract, so it casts no vote on the map. Cited by 7 papers.
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7 citing papers in PubMed.
- Impact of seasonal changes on human onchocerciasis transmission and disease elimination.International health · 2026Review
- Comorbidities of onchocerciasis and non-communicable diseases, and determinants of continued transmission in Bafut Health District, Cameroon.BMC infectious diseases · 2026Article
- Spatio-temporal analysis and geostatistical modelling of onchocerciasis prevalence in Nigeria to support elimination efforts.PLoS neglected tropical diseases · 2026Article
- The risk of onchocerciasis infection by human population movements between high and low transmission settings in Ghana.PLoS neglected tropical diseases · 2026Article
- Modelling the effects of immigration on the re-introduction of onchocerciasis.Parasites & vectors · 2026Article
- Changes in cytoforms of Simulium damnosum sensu lato (Diptera: Simuliidae) and onchocerciasis transmission zones in northern Cameroon with possible implications for onchocerciasis transmission elimination.Journal of medical entomology · 2025Article
- Knowledge and Practices of Four Onchocerciasis-Endemic Communities in Cameroon.Microorganisms · 2025Article
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6 authors.
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Abstract
backgroundThe main vectors of onchocerciasis in Africa are Simulium damnosum sensu lato, which transmit the causative agent Onchocerca volvulus. The force of transmission is driven by the vector density, hence influencing the disease prevalence and intensity. Onchocerciasis is currently targeted for elimination using mass drug administration (MDA) of ivermectin, a potent microfilaricide. MDA in Cameroon began in 1987 in the Vina Valley, an endemic cross-border area with Chad, known for high vector densities and precontrol endemicity. Evaluations in 2008-2010 in this area showed ongoing transmission, while border areas in Chad were close to interrupting transmission. This study aimed to evaluate transmission in this area after several rounds of MDA since the last evaluation surveys.
methodsBlack flies were collected by human landing catches at seven border sites in Cameroon, twice a week, from August 2021 to March 2022. A fraction of the flies was dissected for parity assessment and identification of Onchocerca larval stages. The transmission indices were estimated. Black fly larvae were also collected from the breeding sites at the fly catching sites and identified to species level by cytotaxonomy.
resultsA total of 14,303 female flies were collected, and 6918 were dissected. Of these, 4421 (64.0%) were parous. The total biting rates were high, reaching up to 16,407 bites/person/study period, and transmission potential (third-stage larvae (L3) from head/all L3) were 367/702, 146/506, 51/55, 20/32, 0/3, 0/0, and 0/0 infective larvae/person, respectively, for Mbere-Tchad, Babidan, Hajam/V5, Gor, Djeing, Touboro, and Koinderi. Infectivity rates (L3 from head) were 16.00, 12.75, 5.15, and 4.07 infective females (L3H)/1000 parous flies for Haijam, Mbere-Tchad, Babidan, and Gor, respectively. These values exceed the World Health Organization (WHO) thresholds of ≤ 20 annual transmission potential (ATP) or < 1 infective female/1000 parous females. The major vectors identified were Simulium damnosum sensu stricto, S. squamosum, and for the first time in the area, S. yahense.
conclusionsMore than 20 years of MDA has not eliminated onchocerciasis in the study area; hence, this area is a potential source of reintroduction of onchocerciasis in Chad and would require alternative treatment strategies. Many factors such as MDA efficiency, effectiveness of ivermectin, and cytospecies composition may be contributing to transmission persistence.
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