Current susceptibility status and resistance mechanisms to pyrethroids and organophosphates in Aedes aegypti (Diptera, Culicidae) from Atlantico, Colombia

Abstract

Insecticide resistance in Aedes aegypti is a growing concern for vector control programs in Colombia. Monitoring resistance and associated mechanisms is essential to guide timely and effective chemical control strategies. The susceptibility of Ae. aegypti populations from Soledad, Puerto Colombia, and Juan de Acosta in the Atlantico Department was evaluated against organophosphates (temephos, malathion, and pirimiphos-methyl) and pyrethroids (lambda-cyhalothrin, permethrin, and deltamethrin), using standardized WHO and CDC methodologies. The activity of detoxifying enzymes and the frequency and distribution of the kdr mutations V1016I, F1534C, and V410L in the voltage-gated sodium channel (VGSC) gene were also analyzed. All populations were susceptible to malathion and pirimiphos-methyl. The population from Juan de Acosta exhibited moderate resistance to temephos. In contrast, all populations were resistant to the three pyrethroids tested. Biochemical assays revealed altered α-esterase activity in all populations and altered β-esterase activity in the Soledad population. Kdr mutations were detected in all populations, occurring at variable frequencies. The co-occurrence of V410L, V1016I, and F1534C was confirmed, and eight trilocus haplotypes were detected. The most frequent were VL/VI/CC, VV/VV/CC, and LL/II/CC. These results indicate that resistance to pyrethroids in Ae. aegypti from Atlantico is widespread and likely mediated by both metabolic mechanisms, particularly altered α-esterases, and target-site resistance conferred by kdr mutations. The continued susceptibility to organophosphates suggests these compounds remain viable alternatives. Our findings highlight the importance of ongoing monitoring to inform evidence-based vector control strategies in the region.