Insecticide resistance in Anopheles gambiae in villages around the Soum agropolis in the Center-West Region of Burkina Faso.

Background: Vector control for malaria prevention, primarily based on insecticide-treated materials, is increasingly threatened by the emergence and spread of insecticide resistance in key malaria vectors. Understanding the mechanisms of this resistance is essential for effective control strategies. In response to climate-related food insecurity, artificial dams and large agropoles have been set up in Burkina Faso. Considering the intensive use of insecticides in such areas, this study assessed the level of insecticide resistance in Anopheles gambiae sensu lato (s.l.) populations in villages located at varying distances from the Soum agropolis in the Centre-West Region of Burkina Faso.

Methods: Endophilic gravid mosquitoes were manually collected (using an aspirator) from three villages (Seguedin, Nazoanga and Soum) at the beginning (July 2023) and at the end (October 2023) of the rainy season. Mosquitoes were identified morphologically, and female An. gambiae s.l. were reared in the laboratory. First-generation mosquitoes (3-5 days old) were tested for susceptibility to deltamethrin, bendiocarb, pirimiphos-methyl and PBO + deltamethrin using WHO protocols. PCR was used for species identification and detection of kdr West and kdr East mutations.

Results: Out of 720 mosquitoes analysed, 96.3% (693/720) were identified. Anopheles coluzzii was predominant, representing 100% in Soum and Seguedin at both time points. In Nazoanga, Anopheles arabiensis accounted for 8.5% at the beginning and 5.4% at the end of the season. Anopheles gambiae s.l. populations were resistant to deltamethrin, with mortality ranging from 2% in Soum to 24.8% in Seguedin. Pre-exposure to PBO increased mortality in Soum from 2% to 88.2%, suggesting partial restoration of susceptibility. Resistance to bendiocarb increased by the end of the season in Nazoanga (mortality: 99% to 87%). All mosquito populations remained fully susceptible to pirimiphos-methyl (100% mortality), except in Nazoanga (99%). The kdr West mutation was detected in all villages, with the highest rate reported in Seguedin (0.60). The kdr East mutation was detected only in Nazoanga (0.03).

Conclusion: This study highlights a high level of pyrethroid resistance in An. gambiae s.l. in the study villages and confirms their susceptibility to organophosphates. These findings could contribute to guide resistance management strategies in agropole settings in Burkina Faso.