Novel regional specific voltage-gated sodium channel ( vgsc ) mutations underlying pyrethroid resistance in Aedes albopictus (Skuse) from Northern Peninsular Malaysia
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Background
Controlling Aedes mosquitoes remains as a primary means through the application of synthetic insecticides in Malaysia, but its efficacy is undermined by the evolution of resistance. Aedes albopictus as one of the dominant and competent arboviral vectors has an elusive insecticide resistance status in different geographical regions of Northern Peninsular Malaysia. This underscores the importance of assessing the diverse types of insecticides used and their association with target-site resistance mechanism in this species, which forms the basis of the present study.
Methods
WHO-bioassays were performed on Ae. albopictus larvae and adults from four localities (Penang and Perlis), towards 0.034 ppm temephos, 0.25% permethrin, 0.03% deltamethrin, 0.25% primiphos methyl and 0.1% propoxur. The partial voltage-gated sodium channel ( vgsc ) gene domain (DIIS6, DIIIS6, and DIVS6) of pyrethroid-exposed samples were subsequently genotyped through direct sequencing for any diagnostic single-nucleotide mutations, together with genetic variations and haplotype networks analysis. The predicted protein structures for the mutated regions and their binding affinities to pyrethroids were also evaluated using in-silico docking.
Results and discussions
Varying degrees of resistance were observed in all Penang and Perlis strains to all tested insecticides. Moreover, the detection of the F1534L mutation and newly discovered non-synonymous mutations (A1022S/P, E1041K, P1585R, and F1695L) suggest the progression of resistance alleles dissemination in other strains. The analysis of genetic variations, resistance allele distribution patterns, and haplotype networks showed evidence for multiple origins of these mutations. Data also revealed the discovered mutations affect the affinity of vgsc-binding proteins to pyrethroids.
Conclusion
This study highlights the genotype-phenotype associations in Ae. albopictus and their genetic links to pyrethroid resistance, offering insights to strengthen vector control strategies in Malaysia.
Author summary
In Malaysia, as in many other countries, dengue epidemic control primarily relies on managing the main vector, Ae. albopictus through commercially available insecticide applications. Vector control strategies have been extensively implemented by local health authorities, often without comprehensive information on insecticide resistance mechanisms in vector populations that could pose a major drawback of insecticide used. In an effort to assess the susceptibility status of Ae. albopictus populations, and determine the most effective insecticide for reducing Malaysian vector populations from different geographical settings, we conducted bioassays towards pyrethroid, organophosphate, and carbamate insecticide classes. Altogether, molecular-based assays were incorporated with phenotypic assay to elucidate the mechanisms modulating insecticide resistance and to unravel their genetic dynamics. Such screening offers detailed insights into specific mechanisms involved in conferring resistance for distinct adopted insecticides. This evidence aims to guide local health authorities in developing vector control strategies and exploring alternative solutions.
