Vector Competence and Biting Habits of Simulium damnosum in Communities Around the Benue River, Benue State, North Central Nigeria

Simulium damnosum sensu lato, the black fly vector of Onchocerca volvulus, remains the focus of entomological surveillance and vector control programmes in West Africa, with biting rates and infectivity indices determining the risk of onchocerciasis transmission in riverine communities. This study examines the vector competence and biting habits of S. damnosum in communities around the Benue River in Benue State, North Central Nigeria. An entomological cross-sectional survey was conducted over eight weeks in three communities adjacent to the Benue River rapids in Makurdi and Agatu Local Government Areas. Adult female S. damnosum were collected using human landing catches under supervised conditions and CDC light traps. Collected flies were dissected to assess larval development stages of O. volvulus and calculate transmission potentials. Meteorological data on river flow velocity and rainfall were correlated with fly biting density. Literature from 2020 to 2024 confirms seasonal fluctuation in S. damnosum biting rates corresponding to rainfall patterns and river levels in the Benue basin. This study provides updated entomological transmission potential estimates for communities along the Benue River to guide the phasing of community-directed ivermectin treatment and prioritisation of vector control activities. Findings will be shared with the Benue State Ministry of Health and the Benue State NTD Control Team. Keywords: Simulium damnosum, black fly, vector competence, Benue River, onchocerciasis.