Abstract:
This doctoral thesis, titled “Taxonomy and Control of Simulium Black Flies, Vectors of Onchocerciasis in Cameroon,” focuses on a neglected tropical disease that poses significant public health challenges in many regions of Cameroon. Onchocerciasis, commonly known as river blindness, is caused by the filarial worm Onchocerca volvulus and transmitted by black flies of the genus Simulium. Despite over two decades of mass ivermectin distribution, limited means of effective vector control has allowed the disease to persist in endemic communities. The aim of the study was to identify and genetically analyse the diversity of Simulium species, and to assess the efficacy of commonly used insecticides, Temephos and Bacillus thuringiensis var. israelensis (Bti) to control the aquatic larval stages of the flies. Surveys conducted in four endemic communities (Mawong, Befang, Soramboum, Galim) revealed that while 90% of respondents perceived black flies as a nuisance, only 9.3% associated their bites with the risk of blindness. Over 1,100 Simulium larvae and pupae were collected and analysed using morphological characteristics and molecular markers (ITS2 and Cox1 genes). The study identified 19 Simulium species, including two previously undetermined ones, with S. vorax and S. dentulosum reported for the first time in Cameroon as potential vectors. Larvicidal tests showed that black fly larvae in Cameroon were more susceptible to Temephos and Bti than European species, though continuous resistance monitoring is recommended. The study emphasizes the need for integrated vector control strategies, especially in areas where ivermectin cannot be used due to co-endemicity with Loa loa, which poses serious health risks. Combining morphological and molecular tools significantly advances the understanding of black fly diversity and provides critical data for improving onchocerciasis control efforts in Cameroon and similar endemic regions.
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