Randomized detection of kdr allele frequencies in wild populations of Aedes aegypti (Diptera, Culicidae) in Colombo District, Sri Lanka

Sri Lanka is one of the most affected countries in South Asia by dengue fever, with the number of dengue cases increasing over the last five years. The main strategy for managing disease outbreaks is to reduce infected vector populations with pyrethroid insecticides. However, extensive pyrethroid exposure has resulted in an increase in the selection of knockdown resistance mutations in Aedes aegypti (Linnaeus) (Diptera, Culicidae) voltage-gated sodium channel (vgsc) gene that confer pyrethroid resistance. Colombo district records the highest dengue incidence across the country each year, thus a failed vector control program will be a major threat to public health. Multiplexed Allele-specific PCR was used to genotype kdr alleles in wild Ae. aegypti mosquitoes obtained via random sampling from Wellawatte, Borella, and Battaramulla areas in the Colombo district. This study presents the co-occurrence of F1534C and V1016G kdr mutations from a randomized population in the Colombo district. 1534C mutant allele was predominant (with a 56.7% frequency) and 1016G was prevalent in 32.5 per cent of the population. The heterozygous mutant 1016VG genotype showed the highest distribution (with a 65% frequency) and the incidence of 1534FC was 56.7 per cent. Interestingly, 1016GG was completely absent and the FC/VG mutation combination had the highest incidence with 46.7 per cent. Furthermore, 82.36 per cent of individuals with the 1534FC genotype also had the 1016VG genotype, indicating a high prevalence of pyrethroid resistance in the studied population.