Abundance, Biting Rates, and Molecular Detection of Onchocerca volvulus in Simulium damnosum s.l. in N’Golodougou, Bafing Region, Côte d’Ivoire

Abstract

Aim: This study aimed to assess the abundance, biting activity, and transmission potential of O. volvulus in S. damnosum s.l. in N’Golodougou, Bafing Region, Côte d’Ivoire. Study Design: A descriptive cross-sectional entomological study. Place and Duration of Study: Blackflies were collected in western Côte d’Ivoire in February 2025. Methodology: Adult blackflies were collected using human landing catches over three days at two sites in N’Golodougou: S1 (Field) and S2 (Bridge). Blackfly abundance and hourly biting activity were determined from the collectors’ catches. Vectorial aggressiveness was estimated based on the biting rate per person per day. Molecular detection of O. volvulus was performed by PCR on 15 pools of blackflies. Results: A total of 2,409 blackflies were collected, including 1,750 (72.6%) at S1 and 659 (27.4%) at S2. Biting activity was predominantly diurnal, with a peak between 2:00 p.m. and 4:00 p.m. The biting rate was higher at S1 (194.44 bites/person/day) than at S2 (73.22 bites/person/day). None of the 15 pools tested positive for O. volvulus. Conclusion: N’Golodougou exhibits high abundance and substantial biting activity of S. damnosum s.l., indicating significant exposure of local populations to blackfly bites. However, the absence of O. volvulus detection in the analysed pools does not allow transmission interruption to be concluded. Longitudinal and enhanced entomological surveillance is therefore needed to document the potential for residual transmission in the Bafing region.