Insecticide resistance and kdr mutation profiling in Culex mosquitoes across different climatic regions in Sri Lanka

Vector-borne diseases make up over 17% of global infectious cases, with Culex mosquitoes playing a key role in transmission. This study evaluated insecticide resistance in Culex quinquefasciatus from various Sri Lankan regions, comparing them with Culex nigropunctatus and Culex sitiens from the same sites. Bioassays revealed high resistance to Malathion (66.7%), propoxur, pyrethroids, and DDT (100%). Elevated detoxifying enzymes and acetylcholinesterase (AChE) insensitivity were major resistance mechanisms. Molecular analyses detected kdr mutations, including the first reports of L1017S, F1020A, K1557R, and Y995L. Cx. Sitiens from forested habitats had low enzyme activity, while Cx. nigropunctatus showed moderate levels. In contrast, Cx. quinquefasciatus exhibited significantly higher enzyme activity, correlating with broad resistance. These findings emphasize the need for continuous surveillance of Culex resistance to guide effective vector control strategies.