Genetic Structure of Simulium Damnosum S.L. Populations in Three Epidemiological Patterns of Onchocerciasis in Cote D’ivoire

The Simulium damnosum sensu lato complex comprises several species that act as vectors for onchocerciasis, which differ in terms of geographical distribution, ecology, dispersal capacity and vector competence. Understanding their genetic structure is essential for assessing connectivity between populations. The objective of this study was to characterise the genetic structure of S. damnosum s.l. populations in three epidemiological regions affected by onchocerciasis in Côte d’Ivoire (Soubré, Bouaflé and Touba), using microsatellite markers. Simuliids were collected between December 2024 and October 2025 using human bait, and were then genotyped using four microsatellite loci. Factor analysis of correspondences highlighted two genetic groups, whilst classification analyses identified three to four genetic groups comprising individuals from the three study sites. The fact that individuals are not grouped according to their geographical origin reflects a low level of genetic differentiation between populations. These results indicate the existence of significant gene flow, which supports the hypothesis of active dispersal of black flies in the areas studied. Such connectivity could facilitate the spread of genetic variants between regions and influence the transmission dynamics of onchocerciasis. This study therefore provides new insights into the genetic organisation of S. damnosum s.l. populations in Côte d’Ivoire.