Studies on the dynamics of transmission of onchocerciasis in a Sudan-savanna area of North Cameroon I. Prevailing Simulium vectors, their biting rates and age-composition at different distances from their breeding sites.
Along the main water courses in the sparsely populated areas of the Sous-Préfecture of Tcholliré, the vectors of onchocerciasis were mainly Simulium damnosum s. str. and S. sirbanum, together with a small proportion of S. squamosum. Over a period of one to three years, vector biting rates were measured at 23 fly-catching sites in the vicinities of nine villages with different endemicities of onchocerciasis. Annual Biting Rates (ABR) on man were estimated as 26,100-83,800 fly-bites per man per year along the rivers Mayo Rey and Vina du Nord, and 11,000-37,400 at rainy season tributaries. Biting rates decreased rapidly at increasing distances from the river, and were between 10,700 and 2400 at 2-10 km cross-country from the breeding site. Lowest biting rates (50-6000) were measured at the village centres. The ABR varied from year to year in relation to the water-discharge of the main rivers, the coefficient of variation of the mean being 34-49%. The parous rates were 64-73% at the perennial breeding sites and only 17-44% away from the breeding sites, indicating dispersal mainly of young nulliparous flies and a reduced flight-range after oviposition.
Renz
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A
Institute of Tropical Medicine, University of Tübingen, F.R.G.
Wenk
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P
D000367:Age Factors; D000818:Animals; D001947:Breeding; D002163:Cameroon; D005260:Female; D005618:Fresh Water; D006801:Humans; D007299:Insect Bites and Stings; D007303:Insect Vectors; D008297:Male; D009855:Onchocerciasis / Q000453:epidemiology / Q000635:transmission*; D012843:Simuliidae / Q000469:parasitology* / Q000502:physiology