Pyrethroid and organochlorine susceptibility in Aedes aegypti populations from eastern black sea region, Türkiye: traces in the kdr gene region of the species origin

Aedes aegypti (Linnaeus 1762) is a significant public health concern in both its native and invaded regions because of the transmission of arboviruses. Target-site mutations in the voltage-gated sodium channel (vgsc) gene, commonly referred to as knockdown resistance (kdr), represent the most extensively studied mechanism underlying pyrethroid resistance. Therefore, we aimed to assess possible pyrethroid and organochlorine resistance levels, knockdown resistance, and mutation types known to contribute to the resistance profile in the Black Sea region of Türkiye in 2020. Bioassay results showed that all field populations, as well as the Bora Bora laboratory strain, were susceptible and predominantly carried wild-type genotypes. For kdr, all samples were wild type for the V410L, L982W, S989P, I1011V/M, L1014F, V1016I/G, and T1520I mutations. The mutant allele was detected in only one specimen in the Pazar population, where it was found in a homozygous state at position F1534C from ten specimens. Novel mutations in the vgsc gene region, with unknown implications for resistance, were determined at positions A1498T, R1599C, P1611L, and P1615S in the studied populations. Two different intron types were detected in the kdr gene (in domain 2) between nucleotide positions 3111 and 3228 and within an intron region (coded as type-1 and type-2). These findings indicate that, Ae. aegypti populations in the Eastern Black Sea region remain susceptible to pyrethroid and organochlorine insecticides. Genetic analyses indicate that these populations likely originated from Asia, with evidence of two distinct lineages. Notably, this study represents the first molecular and phenotypic assessment of insecticide resistance in Ae. aegypti populations conducted in Türkiye.