Public health impact of nuisance biting blackfly (Simulium damnosum s.l.) along the Asejire dam in Southwest, Nigeria

Black flies remain a global public health concern, particularly through their biting behaviour which is a crucial risk factor in disease transmission. The present study seeks to investigate the public health implications of the biting behaviour of Simulium damnosum s.l along the Asejire dam, bordering Oyo and Osun State, Nigeria. Simulium damnosum s.l were collected using the standard human landing collection (HLC) between 0700 and 1800 across four study areas within first-line communities around the Asejire dam between December, 2024 and November, 2025. Collection was recorded hourly while the daily, monthly, and annual biting rate (ABR) were calculated using standard formulas. A total of 9857 blackflies were collected with variations in abundance across the sites ( P -value = 0.325). Osun had the higher flies collection 6685 (67.82%). The hourly catches varied in locations and bimodal biting peak was observed. Also, Simulium damnosum s.l abundance was high upstream of the dam than mid- and downstream. The monthly biting rate was more than 1000 bites/person/month in each of the study locations. The biting intensity (99,939.03) along the Oyo-Osun border is high, causing serious biting nuisance in the communities. The presence and persistence of black fly bites across the study communities along the border poses a great threat to disease transmission. Therefore, there is the need for an effective vector control measure targeted at preventing human-vector contact by the government of both states with a view to decimating fly abundance and reducing transmission risk.