Insecticide selection pressure extends to the secondary malaria vector Anopheles coustani in the Vallée du Kou, Burkina Faso

Abstract

Malaria remains a major public health problem in Burkina Faso, transmitted by several Anopheles species. The principal vectors include Anopheles gambiae, Anopheles arabiensis, Anopheles coluzzii, and Anopheles funestus, while Anopheles coustani, Anopheles rufipes, and Anopheles pharoensis are considered secondary vectors. Vector control, mainly through the use of insecticide-treated nets and indoor residual spraying, is increasingly threatened by the spread of insecticide resistance. Most studies on resistance mechanisms have focused on major vector species, leaving significant knowledge gaps regarding secondary vectors.

This study aimed to characterize the pyrethroid resistance profile of Anopheles coustani, a secondary malaria vector in the Vallée du Kou, Burkina Faso. Between September and October 2021, adult female mosquitoes were collected, reared under insectary conditions, and their first-generation progeny (F1) were tested using WHO bioassays with 0.75% permethrin. Molecular analyses were performed for specie identification and detection of the kdr L1014F mutation, a key genetic marker of pyrethroid resistance.

A total of 164 Anopheles coustani females were tested, showing a mortality rate of 79.79%, indicating moderate resistance. The frequency of the kdr L1014F mutation was 56.90% for resistant homozygotes, 37.93% for heterozygotes, and 5.17% for susceptible homozygotes, corresponding to an overall allele frequency of 0.76.

These results reveal that Anopheles coustani populations in the Vallée du Kou exhibit phenotypic resistance linked to a high prevalence of the kdr mutation. This finding suggests that insecticide selection pressure is acting not only on major malaria vectors but also on secondary ones, underscoring the need for comprehensive resistance monitoring in all vector species.