A survey of the distribution of Simulium species complex population and its infection rate with Onchocerca volvulus was carried out along River Muvir, Mubi between July and August 2009. Black flies were collected using baits, pooter and hand nets. Out of 310 flies collected, 89 (28.70%) were found to be infected with microflariae. Detection of the parasites in the vector was attained by dissection of flies under dissecting microscope. The result revealed that the prevalence of microfilariae among insects collected in the months July and August was 23.08% and 21.47% respectively. Statistical analysis using t-test and ANOVA revealed that there was no significant difference (p<0.05) in the prevalence between the months of collection. They also showed no significant differences in microfilariae load between the three anatomical parts (the head, thorax and abdomen). These investigations showed that Simulium damnosum is wide spread along the River Muvur and a large population of flies is infected with Onchocerca volvulus.
Keywords Onchocerca volvulus, infection, Simulium species, Muvur.