A new knockdown resistance (kdr) mutation, F1534L, in the voltage-gated sodium channel of Aedes aegypti, co-occurring with F1534C, S989P and V1016G

Background Aedes aegyptiis a primary vector of dengue, chikungunya and Zika infections in India. In the absence of specific drugs or safe and effective vaccines for these infections, their control relies mainly on vector control measures. The emergence of insecticide resistance in vectors, especially against pyrethroids, is a serious threat to the insecticide-based vector control programme. This study reports the presence of multiple knockdown resistance (kdr) mutations present in anAe. aegyptipopulation from Bengaluru (India), including a new mutation F1534L. Methods Aedes aegypticollected from Bengaluru were subjected to insecticide susceptibility tests with DDT, deltamethrin and permethrin. The DNA sequencing of partial domain II, III and IV of the voltage-gated sodium channel (VGSC) was performed to screenkdrmutations present in the population and PCR-based assays were developed for their detection. Genotyping ofkdrmutations was done using PCR-based assays, allelic frequencies were determined, and tests of genetic association ofkdrmutations with the insecticide resistance phenotype were performed. Results TheAe. aegyptipopulation was resistant to DDT, deltamethrin and permethrin. The DNA sequencing of the VGSC revealed the presence of fourkdrmutations, i.e. S989P and V1016G in domain II and two alternativekdrmutations F1534C and F1534L in domain III. Allele-specific PCR assays (ASPCR) were developed for the detection ofkdrmutations S989P and V1016G and an existing PCR-RFLP based strategy was modified for the genotyping of all three knownkdrmutations in domain III (F1534L, F1534C and T1520I). Genotyping ofAe. aegyptisamples revealed a moderate frequency of S989P/V1016G (18.27%) and F1534L (17.48%), a relatively high frequency of F1534C (50.61%) and absence of T1520I in the population. Mutations S989P and V1016G were in complete linkage disequilibrium in this population while they were in linkage equilibrium withkdrmutations F1534C and F1534L. The alleles F1534C and F1534L are genetically associated with permethrin resistance. Conclusions A newkdrmutation, F1534L, was found in anAe. aegyptipopulation from Bengaluru (India), co-occurring with the other three mutations S989P, V1016G and F1534C. The findings of a new mutation have implications for insecticide resistance management.