A New A1022T Knockdown Resistance (kdr) Mutation in Pyrethroid Resistant Aedes aegypti Populations From Southern West Bengal, India

Abstract

Aedes aegypti (Ae. aegypti)-mediated transmission of arboviral diseases is posing a great concern globally. The challenge to traditional vector control methods is heightened by the increasing resistance of mosquitoes to chemical pesticides. In the present study, adulticide susceptibility tests against the pyrethroid insecticides—Permethrin and Deltamethrin were conducted using standard protocols, subsequently characterizing the partial segments of the voltage-gated sodium channel (VGSC) gene for Ae. aegypti populations sampled across ten districts of West Bengal, India. The mean mortalities for Permethrin and Deltamethrin were found to be 86.87 ± 2.36 and 92.03 ± 1.54, respectively, with significant differences between the regional populations. The knockdown time, KDT90 (min.), ranges between 61.85–314.68 and 74.49–298.92, respectively. Analysis of segment 6 from the partial domains II, III, and IV of the VGSC gene indicated amino acid substitutions at specific positions: S to P at 989, V to G at 1016, A to T at 1022, T to I at 1520, and F to C at 1534. The F1534C is the most frequent mutation (0.41) observed amongst the resistant population. Analysis of Molecular Variance (AMOVA) revealed significant genetic variation within and among the regional populations (F = 0.453 p < 0.001). Though the allele frequencies lied within the 95% confidence interval of the Hardy–Weinberg parabola, slight deviation of the allele frequencies from the equilibrium is indicative of operational selection pressure favouring the kdr mutants. Haplotype map shows the phylogeographical pattern with two distinct haplogroups diverging by 32 mutational steps. Thus, the study identified the resistance profile of Ae. aegypti mosquitoes across districts, aiding the selection of region-specific pesticides.