Transmission of onchocerca volvulus by simulium damnosum S.L. in four villages in the Gorama Chiefdom; Kono district; Sierra Leone

ABSTRACT

Quantitative studies on the transmission of onchocerca volvulus; including monthly and annual biting densities; age composition; parity rates; infection and infective rates of the similium damnosum s.l. population; were carried out for a year in a tropical rain-forest zone in Sierra Leone. In all 19;432 s. damnosum s.l. female flies were acught and 8;755 dissected; of which 6.307 were parous. The annual biting rate (ABR) varied between 20;787 and 39;188; 5.4 per cent of all flies were infected with O. volvulus; 3.6 per cent carried infective larvae in the head capsule; with mean of 2.5 per fly. The annual transmission potential (ATP) varied between 1;138 and 2;081. The ATPs for Bunabu; Matama; Kangama and Moimandu villages were 2;081; 1;403; 1;138 and 1;498 respectively; with most of the infection occuring during the months of May and August. The prevalences of skin microfilariae (mf) in Bunabu; Matama; Kangama and Moimandu villages were 79.0 per cent; 51.3 per cent; 78.0 per cent and 80.0 per cent respectively