Onchocerciasis in Benue State of Nigeria III: a study of bionomics of Simulium damnosum (Theobald) complex at Manor.
Results of a 12-month study (January-December 1981) on the breeding sites, incidence and infection rates of Simulium damnosum in an area of Benue State of Nigeria endemic for human onchocerciasis are given. Natural and artificial breeding sites are described. Permanent and temporary breeding sites were recognized along the rivers in the study area and the intensity of rains was found to be the only factor which determined the permanency or temporary nature of a breeding site. All adult blackflies caught were S. damnosum "sensu lato" Greater numbers were caught during the rains with peak catches corresponding with peak of rainfall in September. The influence of shade temperature on daily biting activity was shown, peak activity being recorded at periods of day when temperature was low. Population density of blackflies increased with increasing distance from the main breeding sites on the river during the normal rains; at the peak of rains, the reverse was observed. April and September were the months of highest and lowest infection rates respectively among the catches while April to July were the most favourable period for onchocerciasis transmission because of the high infective bites per person per day in those months. The infective bites per person per day were estimated at 0.83 which, by comparison with values from endemic areas of Africa, confirmed the endemicity of the study area for human onchocerciasis. Dissected flies carried low number of developing larvae of Onchocerca volvulus with a mean of 3.9. Measurements of larvae are given and the relevance of the results to the epidemiology of human onchocerciasis in the study area is discussed.
D000818:Animals; D005260:Female; D006801:Humans; D007303:Insect Vectors / Q000469:parasitology; D009549:Nigeria; D009854:Onchocerca / Q000302:isolation & purification; D009855:Onchocerciasis / Q000635:transmission*; D010298:Parity; D012621:Seasons; D012843:Simuliidae / Q000469:parasitology*