Background and Aim: Vector-borne diseases are the major causes of morbidity and mortality in several regions, especially in tropical and subtropical countries. This study aimed to compare the relative abundance, diversity, monthly biting rates, and parity rate of onchocerciasis vector collected from three small rivers in Southwest Ethiopia.

Materials and Methods: Adult Simulium were collected using human landing catch with protected by the Mosq Tent for 4 consecutive days per month from 7 a.m. to 6 p.m. from January 2018 to December 2018 at three communities: Dizi, Agalo Uka, and Haro Magela. Chi-square test was used to determine the association between study site villages and abundances of the Simulium diversity.

Results: During the study period, a total of 15,264 Simulium belong to two species Simulium damnosum sensu lato and Simulium neavei were collected. The monthly dynamics of S. damnosum sensu lato shows that the highest density of flies was observed in August, followed by July, whereas the lowest was observed in April. On the other hand, the highest peak biting hour was observed between 4 p.m. and 6 p.m., while the lowest hourly activity of the fly was recorded from 7 a.m. to 8 a.m. Furthermore, the highest parity rate was observed 82.2% in July followed by 80.9% in August while the lowest rate was observed 43.7% in January.

Conclusion: This information on onchocerciasis vectors seasonal variation, diversity, parity, and biting time are important factors that to be considered for noticeable suggestions in monitoring transmission levels to guide the regional and national onchocerciasis elimination programs in Ethiopia.

Keywords: onchocerciasis, parity, Simulium damnosum s.l., Simulium neavei, vector.