Insecticide resistance levels, spatial distribution, and kdr mutations in the dengue vector Aedes albopictus of Hong Kong.

Aedes albopictus (Skuse), a primary dengue vector in Hong Kong, poses significant challenges to public health due to escalating insecticide resistance in Asia. To address this concern, we evaluated resistance profiles of five field-derived Ae. albopictus populations across Hong Kong using WHO insecticide susceptibility bioassays. Metabolic detoxification using synergists test with piperonyl butoxide (PBO) and target-site mutations referred to as knockdown resistance (kdr) in the voltage-gated sodium channel (VGSC) gene were characterized to elucidate resistance mechanisms. The results show that Ae albopictus populations in Hong Kong exhibited high resistance to commonly used pyrethroids (permethrin, deltamethrin) and the organochlorine dichlorodiphenyltrichloroethane (DDT), as well as emerging resistance to the organophosphate malathion. Resistance to three larvicides, temephos, spinosad, and pyriproxyfen, is likely to be developing, whereas Bacillus thuringiensis israelensis (Bti) still retains efficacy. Sequencing revealed the F1534S/L mutation in VGSC Domain III (29.0% mutation frequency), strongly correlated with pyrethroid survivorship. A minor dual mutation (S406T + L424H) in Domain I was recorded but showing limited phenotypic association. Synergist assays demonstrated partial or full restoration of pyrethroid susceptibility with PBO, implicating cytochrome P450-mediated metabolic resistance as a co-factor. These findings confirm that Ae. albopictus in Hong Kong has evolved multifaceted resistance mechanisms, driven by both target-site mutations and metabolic detoxification. This study provides critical evidence to optimize local vector control strategies and contributes resistance profiles to the Asia-Pacific region, aiding regional efforts to mitigate dengue transmission risks.