Seasonal Abundance and Diurnal Activities of Simulium damnosum Theobald (Diptera Simuliidae) Complex in Gurara River of Kagarko Local Government Area of Kaduna State

Abstract

Black flies (Diptera: Simuliidae) are medically and ecologically significant insects of importance and are the sole vectors of onchocerciasis. This study aimed to assess the abundance and diurnal activities of blackflies at the Gurara River in the Kagarko Local Government Area of Kaduna State. Blackflies were collected through the Human Landing Catch (HLC) method following WHO protocols between 7:00 am and 6:50 pm over twelve months (July 2019 – June 2020). Three human collectors sat at the banks of breeding sites, wore shirts and trousers rolled up to the knees, and constantly watched their lower legs for landing blackflies, which were caught individually before procuring a blood meal. Blackflies were caught by being trapped in a polypropylene tube inverted over them. Temperature and relative humidity were recorded using the whirling hygrometer. Data was analyzed using SPSS software statistical package version 25.0. A total of 3512 adult Simulium damnosum were caught. The highest number of blackflies caught was in August 2019 (28.5%). Relative humidity and temperatures were 89% and 260 °C, respectively. The abundance of blackflies and weather showed a significant correlation (p < 0.05). Seasonal blackfly abundance was higher in the rainy season (93.4%) than in the dry season (6.6%). The diurnal biting activity of the blackflies showed a bimodal biting pattern. The study showed a profusion of black flies in the study area, with black fly activities showing morning and afternoon peaks.