Detection of Pyrethroid Resistance Mutations in Aedes aegypti and Aedes albopictus from Ho Chi Minh City, Vietnam

Abstract

Vietnam is one of the Southeast Asian countries most heavily affected by dengue, where Aedes aegypti (L.) and Aedes albopictus (Skuse) serve as the primary vectors. The increasing prevalence of pyrethroid resistance in these two mosquito species, particularly in Ho Chi Minh City, poses a significant challenge to vector control efforts. This study aimed to evaluate resistance to 0.75% permethrin and to investigate knockdown resistance (kdr) mutations in IIS6 and IIIS6 domains of the voltage-gated sodium channel (VGSC) gene among resistant Ae. aegypti and Ae. albopictus individuals that survived bioassay exposure. The results showed that moderate levels of permethrin resistance were detected in both mosquito populations, Ae. aegypti and Ae. albopictus, with mortality rates ranging from 80.43% to 86.96% in Ae. aegypti and from 84.45% to 88.89% in Ae. albopictus. The Ser989Pro, Ile1011Met, and Val1016Gly mutations were not detected. In contrast, the Phe1534Cys mutation was observed at high frequencies, occurring in 80% (20/25) of Ae. aegypti and 92% (23/25) of Ae. albopictus specimens analyzed. The 1534C allele frequency was 0.62 in Ae. aegypti and 0.68 in Ae. albopictus, indicating comparable levels of the mutant allele in both species. Allele frequencies were calculated within the resistant group, and no statistically significant differences were detected between the two species. This study focused on resistant phenotypes without assessing haplotype structure or comprehensive genotype-phenotype associations. Nevertheless, its findings provide updated data on VGSC mutations linked to permethrin resistance in Ho Chi Minh City, thereby contributing to ongoing insecticide resistance surveillance and management within vector control programs.