Spatial distribution of insecticide resistance in Aedes aegypti (Diptera: Culicidae) across Burkina Faso highlights strengthened resistance management strategies

Responses to recurrent dengue outbreaks rely on insecticide-based tools, effective use of which require understanding of insecticide resistance patterns. A nationwide study across all 13 regions of Burkina Faso was performed to assess countrywide resistance profiles of Aedes aegypti to major insecticide classes for informing decision-makers. WHO tube bioassays were performed under controlled conditions in a centralised location on Ae. aegypti adult females raised from eggs collected in each region. Mosquitoes were exposed to pyrethroids, carbamates, and organophosphates and mortality assessed 24-hours post-exposure. Fifty unexposed mosquitoes per region were genotyped for the F1534C, V1016I, and V410L kdr mutations, which confer resistance to pyrethroids, using melting curve qPCR analysis. Ae. aegypti populations from all 13 regions showed ubiquitous, and often strong resistance to deltamethrin. The F1534C mutation was the most prevalent with overall frequency of 0.89. The V1016I (0.25 - 0.58) and V410L (0.23 - 0.54) mutations were found at moderate and similar frequencies. Populations from seven regions showed resistance to bendiocarb. The resistance to pirimiphos-methyl and especially malathion was generally lower and less than half of the populations classified as resistant in each case. Across the four insecticides all 13 regions showed confirmed or suspected resistance to at least two insecticides and only eight of 13 showed any susceptibility, usually to an organophosphate. Thus, organophosphates, particularly malathion, appear the best overall option for control, and pyrethroid products are likely to show reduced efficacy. However, widespread multiple resistance across these three widely-used insecticide classes presents a challenge to resistance management, and newer alternative classes should be considered and testing built into monitoring programmes.