Overlooked factors in vector control: Addressing biological compromises in pyrethroid-resistant Aedes aegypti

Aedes aegypti mosquitoes account for the highest number of infections among vector-borne diseases and continue to present a formidable global health challenge. Due to the nonavailability of direct treatment of dengue, vector control relies on the use of insecticides currently dominated by pyrethroids. Recurring applications of these insecticides lead to transgenerational impacts on their fitness and resistance dynamics. This study investigates the threat to vector control techniques by altered biological fitness, metabolic and molecular properties after selection with permethrin exposure. Populations of Ae. aegypti were treated with a sublethal dose of permethrin (LC₅₀) in each generation, and their resistance status, together with its effect on biological fitness and transgenerational features, were analysed. To understand the different mechanisms of resistance development, detoxifying enzyme activity, the presence of kdr mutation and cuticular thickness were also analysed. Throughout the study, a prolonged larval and pupal stage was noted with reduced fecundity and hatchability. Moreover, biochemical assays revealed a major role of cytochrome P450 monooxygenases behind permethrin resistance, which was supported by a piperonyl butoxide assay. Major kdr mutations F1534C and V1016G were also found. Overall, reduction in life traits of resistant populations may seem in favour of vector management but this may be the manipulative strategy of Ae. aegypti to divert the essential fuels away from these features and invest it towards the maintenance of insecticide resistance. Therefore, to effectively combat resistance, insecticides must be used judiciously as part of a comprehensive strategy that includes non-insecticide methods and regular surveillance.