Environmental contaminants drive insecticide resistance in Anopheles mosquitoes in Ghana.

Insecticide-based interventions such as IRS and LLINs have significantly reduced malaria transmission globally. However, their sustainability is increasingly threatened by insecticide resistance. While insecticide and pesticide use are known resistance drivers, the role of environmental contaminants remains underexplored. This study investigated the impact of environmental contaminants on insecticide resistance by sampling Anopheles larvae from six sites in Ghana, including petroleum spill sites, mining areas and industrial zones. WHO bioassays revealed resistance to clothianidin (Mortality rate (MR) = 54% – 80%) and chlorfenapyr (MR = 80% − 84%) in all site categories. Interestingly, high-intensity resistance to pirimiphos methyl (MR = 10x = 1.7%) was detected in vectors from Obuasi. High-intensity pyrethroid resistance [deltamethrin (MR = 10x = 79–92%); permethrin (MR = 10x = 74–95%)] was observed across all sites, with varying frequencies of kdr mutations (L995F, V402L, I1527T, P1874L; 0.12–0.98) were observed across all sites. High allele frequency of Ace-1 (0.62) was observed in Obuasi. Chemical analyses of water from breeding habitats revealed significant associations between heavy metals and insecticide resistance (P = 0.04). Anopheles coluzzii (81.7%) was the dominant species across all sites. These findings provide evidence that environmental contaminants may contribute to insecticide resistance. There is an urgent need for enhanced surveillance and resistance management strategies for effective malaria vector control.