Insecticide resistance in larval populations of Aedes aegypti and Aedes albopictus from Panama.

INTRODUCTION: The control of Ae. aegypti and Ae. albopictus is the most effective strategy for preventing the transmission of the arboviruses DENV, ZIKV, and CHIKV. However, insecticide resistance threatens the sustainability of vector control programs. Monitoring insecticide resistance enables the identification of potential associated factors, its intensity and distribution, and contributes to the development of more effective strategies for its management. The aim of this study was to evaluate insecticide resistance in larvae of Ae. aegypti and Ae. albopictus from Panama. MATERIALS AND METHODS: Standardized WHO methodologies were used to generate dose-response curves and to estimate resistance ratios (RR₅₀ and RR₉₀) for the insecticides tested in larvae of Ae. aegypti and Ae. albopictus. Differences in RR₅₀ values were analyzed using analysis of variance (ANOVA) followed by Tukey's test. RESULTS: Aedes aegypti populations from 24 de Diciembre, Puerto Armuelles, and San Isidro showed moderate resistance to temephos (RR₅₀ = 6.5-7.3). Additionally, populations from El Coco, Aguadulce, David, and Puerto Armuelles exhibited moderate resistance to deltamethrin (RR₅₀ = 7.3-8.5) and lambda-cyhalothrin (RR₅₀ = 5.8-7.8). In Ae. albopictus, the population from Canto del Llano showed moderate resistance to deltamethrin (RR₅₀ = 9.7) and temephos (RR₅₀ = 7.3). Significant differences in resistance levels between Ae. aegypti and Ae. albopictus were observed based on RR₅₀ values (F = 20.82, df = 1, p < 0.001). CONCLUSION: The variable resistance patterns observed for the insecticides evaluated may limit the effectiveness of operational interventions aimed at controlling Ae. aegypti and Ae. albopictus. Considering the results of this study, it can be indicated that the evaluated insecticides could still be used, provided that the PNCA implements and maintains a systematic resistance monitoring program to prevent its evolution and establishment or to eliminate selection pressure over time, allowing mosquito populations to recover susceptibility. Furthermore, it is essential to evaluate and implement alternative nonchemical strategies to preserve and extend the useful life of currently available insecticides for public health vector control in Panama.