An entomological study to prepare for a "slash and clear" community-based vector control intervention in onchocerciasis endemic South Sudan

Mvolo in Western Equatoria of South Sudan has been a hotspot for Onchocerca volvulus transmission since the 1940s. In Mvolo onchocerciasis is a disease of public health importance, associated with onchocerciasis-associated epilepsy including nodding syndrome.

This entomological study aimed to map the breeding sites of blackflies on the river Naam, to allow the removal of vegetation from vector breeding sites, the "slash and clear". Three blackfly catching sites were established along the river. Focus group discussions were also conducted to assess the willingness of the communities to support the "slash and clear" intervention and the semi-annual distribution of ivermectin.

A total of 2466 female black flies were caught in 14×11h catches. The highest biting density were observed in November 2023, and had reduced to zero in the intervention site by April 2024. Two diurnal biting peaks were observed, one from 9:00-10:00 and a prominent one from 14:00-15:00 in the two catching sites in Mvolo. Active breeding was identified along the river Naam in a stretch of 3-5 km close to human settlements. The "slash and clear" intervention was implemented at Dogoyabolu along the river Naam. Communities expressed willingness to support a "slash and clear" intervention and the semi-annual distribution of ivermectin.

Find out more about this study on the project page.