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. 2025 Apr 15:7:100259.
doi: 10.1016/j.crpvbd.2025.100259. eCollection 2025.

Entomological surveillance of onchocerciasis in Burkina Faso: Progress towards interrupting transmission in blackflies in the main river basins of the country

Lassane Koala  1 , Achille S Nikièma  1   2 , Mathias Ouedraogo  3 , Justin Compaoré  3 , Clarisse Bougouma  3 , Karim Sanon  4 , Aimé G Adjami  4 , Moussa S Sanfo  4 , Inaki Tirados  5 , Philip McCall  5 , Paul Bessel  6 , Thomas R Unnasch  7 , Daniel A Boakye  8 , Soungalo Traore  1 , Roch K Dabire  1
Affiliations

Entomological surveillance of onchocerciasis in Burkina Faso: Progress towards interrupting transmission in blackflies in the main river basins of the country

Lassane Koala et al. Curr Res Parasitol Vector Borne Dis. .

Abstract

Current guidelines for onchocerciasis elimination rely heavily upon assessment of the presence of Onchocerca volvulus in the vector Simulium damnosum (sensu lato). This entomological study was conducted over four years in several regions of Burkina Faso to determine the progress made towards interrupting onchocerciasis transmission. Larvae and adult blackflies were collected in eight river basins (Comoé, Léraba, Dienkoa, Mouhoun, Bougouriba, Bambassou, Nakambé, Nazinon and Sissili). Larvae were analyzed by cytotaxonomy, and the adult blackflies analyzed for the presence of infective larvae of O. volvulus by PCR. Blackfly infectivity rates were first determined by year for each basin, then compared to the thresholds established by the WHO. The results indicate that the blackflies collected belong to the savannah group species Simulium damnosum (sensu stricto) and Simulium sirbanum. Hybrids of the two species were also identified. Overall, the prevalence of flies carrying infective larvae was below the threshold of 0.05% established by the WHO, indicating important progress towards the interruption of onchocerciasis transmission in Burkina Faso, although hotspots with infectivity rates well above the WHO's thresholds remain. Onchocerca volvulus continues to be transmitted in six of the nine basins evaluated, all of which border neighboring countries. These data indicate that it will be necessary to maintain entomological surveillance in these hotspot areas until transmission is interrupted throughout the region.

Keywords: Onchocerciasis; Persitence; Simulium; Surveillance; Transmission.

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Conflict of interest statement

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Figures

Image 1
Graphical abstract
Fig. 1
Fig. 1
Distribution of onchocerciasis-endemic rivers in Burkina Faso. The solid lines represent the geographical boundaries of the countries.
Fig. 2
Fig. 2
Distribution of Simulium damnosum (s.l.) capture points along the onchocerciasis-endemic river basins of Burkina Faso.
Fig. 3
Fig. 3
Map representing the results of molecular analyses of blackflies captured during 2017, 2018, 2019 and 2021 along the nine monitored river basins. Red circles indicate the capture points where O. volvulus was found in the flies analyzed; black circles indicate the capture points where O. volvulus was not found; empty circles indicate capture points where there was no survey in that year.
See this image and copyright information in PMC

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