Spatial and temporal dynamics of insecticide resistance in the Anopheles gambiae complex, with a focus on Anopheles coluzzii, in Burkina Faso

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Insecticide resistance is widespread among malaria vectors in Burkina Faso. Although resistance in Anopheles coluzzii has been extensively documented, studies integrating spatial variation and long-term temporal trends in both field and laboratory populations remain limited in Burkina Faso. Understanding these dynamics is essential for evidence-based vector control strategies. Spatial variation in insecticide resistance was assessed using WHO susceptibility bioassays on Anopheles gambiae s.l. collected from four localities, combined with molecular species identification and genotyping of the kdr-L995F mutation in An. coluzzii . Temporal dynamics were investigated over five consecutive years in a sentinel site (Vallée du Kou) and over 2 years in a laboratory colony using the same methods. A total of 6,700 mosquitoes were tested in susceptibility bioassays and 1,264 An. coluzzii specimens were genotyped. Populations of An. gambiae s.l. and An. coluzzii were fully susceptible to pirimiphos-methyl (100% mortality), while responses to bendiocarb varied across localities (94.9–100%), years (96.1–100%), and laboratory generations (86.3–100%). In contrast, high levels of resistance were observed to pyrethroids and DDT, with mortality ranging from 0 to 18.4% for deltamethrin, 1–5.9% for permethrin, and 1–41.6% for DDT. Pre-exposure to PBO partially restored susceptibility to deltamethrin, increasing mortality by 27.5–68 percentage points across all datasets. Significant spatial and temporal variations in kdr-L995F frequency were detected in both field and laboratory populations of An. coluzzii . Allele frequencies ranged from 0.27 in Ziniaré to 0.50 in Banfora. In Vallée du Kou, the frequency declined from 0.51 in 2021 to 0.31 in 2025, while in the laboratory colony it decreased from 0.74 (generation F5) to 0.21 (generation F27). Despite persistent pyrethroid resistance, the marked decline in kdr-L995F frequency in both field and laboratory populations of An. coluzzii suggests the involvement of additional resistance mechanisms. These findings underscore the need for integrated phenotypic and molecular surveillance to support insecticide resistance management.

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