Correlation between pyrethroid knockdown resistance and mutation frequency of voltage-gated sodium channel and its application in Aedes aegypti management.

Aedes aegypti , the primary vector responsible for transmitting dengue fever in southern Taiwan, has developed a relatively high resistance to synthetic pyrethroids. It has evolved four amino acid substitutions in the voltage-gated sodium channel (VGSC), namely S996 P , V1023 G , F1565 C , and D1794 Y. To unveil the distribution and correlation of VGSC mutations and pyrethroid resistance among different field populations, Ae. aegypti collected from various districts in Kaohsiung and Tainan Cities underwent tests for resistance development against different pyrethroids and frequency of S996 P , V1023 G , F1565 C , and D1794 Y substitutions. The adult knockdown assay revealed a relatively high knockdown resistance in the Ae. aegypti populations from Kaohsiung and Tainan against permethrin, cypermethrin, and fenvalerate (averaging >50-fold). Conversely, less resistance was observed against α-cypermethrin, deltamethrin, λ-cyhalothrin, cyfluthrin, and etofenprox (averaging <35-fold). Using Polymerase Chain Reaction/restriction fragment length polymorphism analysis, four mutant haplotypes were identified in these field populations. Notably, the S IA VFD and S IB VFD wild haplotypes were absent. Analysis utilizing IBM SPSS Statistics 20.0 and Spearman's rank correlation coefficient indicated that Haplotype C (P IA G FD), especially P allele, frequency displayed a significant positive correlation with five Type II pyrethroid resistance, while 1023G and 1023G/G exhibited a significant association with permethrin and fevalerate resistance. Conversely, Haplotype E (S IB V C D) negatively correlated with pyrethroid resistance, particularly fenvalerate resistance (−0.776). Haplotype C and E were the most prevalent and widely distributed among the investigated field populations. This prevalence of haplotype C is likely tied to the extensive and excessive use of Type II pyrethroids for dengue control over the past three decades. Given the significant positive correlation, the best-fit lines and R2 values were established to facilitate the swift prediction of knockdown resistance levels to various pyrethroids based on VGSC mutation frequency. This predictive approach aims to guide insecticide usage and the management of pyrethroid resistance in the field populations of Ae. aegypti in Taiwan. [Display omitted] • Four VGSC mutations were detected in Aedes aegypti of southern Taiwan. • Only mutant haplotypes and diplotypes of these mutations were detected in the field populations. • Haplotype C (P IA G FD) had strong correlation with most Type II pyrethroid resistance. • 1023 G and 1023 G / G exhibited a significant correlation with permethrin and fevalerate resistance. • A molecular detection tool was developed to predict knockdown resistance levels in the field populations. [ABSTRACT FROM AUTHOR]