Molecular surveillance of insecticide resistance: High frequency of kdr mutations in permethrin-exposed Aedes mosquitoes from Kuala Lumpur and Selangor, Malaysia

Despite ongoing vector control programs, dengue incidence in Malaysia continues to rise. A significant contributing factor is the emergence of insecticide resistance in Aedes mosquitoes, particularly against pyrethroids such as permethrin. This study aimed to evaluate permethrin resistance in Aedes aegypti and Aedes albopictus from Kuala Lumpur and Selangor and to investigate the prevalence of knockdown resistance (kdr) mutations in the voltage-gated sodium channel (Vgsc) gene. Due to limited sample quantity and quality, molecular assessment of kdr mutations was performed only for Ae. aegypti. Ovitraps were deployed in three dengue hotspot areas to collect Aedes eggs. Eggs were reared to adulthood under controlled laboratory conditions. Adult female mosquitoes were subjected to the WHO tube bioassay using permethrin to assess phenotypic resistance. Genomic DNA was extracted from individual Ae. aegypti, and polymerase chain reaction (PCR) was conducted to amplify target regions of the Vgsc gene using published kdr-associated primers. Direct sequencing of PCR products was performed to identify point mutations associated with pyrethroid resistance. Both Ae. aegypti and Ae. albopictus populations showed high levels of permethrin resistance, with mortality rates of <5% and <50%, respectively, indicating confirmed resistance. Sequencing of Ae. aegypti revealed the presence of pyrethroid resistance-associated kdr mutations, including S989P, A1007G, V1016G, and F1534C. These findings suggest strong selective pressure on local Ae. aegypti populations, reflecting ongoing adaptation to insecticidal interventions. The identification of these mutations emphasizes the challenges faced by current vector control strategies relying predominantly on chemical control.The detection of both phenotypic permethrin resistance and kdr mutations in Ae. aegypti populations from Kuala Lumpur and Selangor highlights the urgent need to revise and diversify vector control strategies. Improved sampling and molecular surveillance of Ae. albopictus are recommended to provide a more comprehensive understanding of insecticide resistance dynamics in Malaysian dengue vectors.