Seasonal biting rate and transmission potentials of host-seeking black flies (Diptera: Simulidae) and its implications for human onchocerciasis control in parts of Imo River Basin, Nigeria

Biting and parity status of black flies were evaluated between the transmission seasons (rainy and dry) after long-term Ivermectin treatments in Imo River Basin, Nigeria. Captured black flies were morphologically identified, dissected and assessed by standard protocol. Although more black flies were caught in the rainy season (54.3%) than dry season (45.3%), there was insignificant difference in the transmission parameters (P>0.05). Infection rate (0.2% versus 1.2%), parous rate (19.9% versus 22.4%), Infectivity rate (0.0% versus 0.0%), monthly biting rate (3,533.75 versus 3,095.5) bites/person/month, monthly parous biting rate (703.75 versus 771.5) bites and monthly transmission potential (0.0% versus 0.0%) were comparable for the seasons respectively. The data showed the existence of residual infection at the level of transmission likely to be insignificant to maintain parasite population.