F1534S kdr mutation drives the geographical heterogeneity of pyrethroid resistance in Aedes albopictus from Hangzhou, China

Introduction The rapid evolution of insecticide resistance in mosquitoes has substantially compromised control efficacy against Aedes albopictus . This study aimed to evaluate the resistance levels to commonly used insecticides in field populations of Ae. albopictus from Hangzhou, China, and characterize knockdown resistance ( kdr ) mutations in the voltage-gated sodium channel ( VGSC ) gene, thereby providing a scientific basis for developing localized insecticide resistance management strategies. Methods Field populations of Ae. albopictus were collected from 14 districts in Hangzhou from May to September 2025. Resistance to 0.2% fenitrothion, 0.2% bendiocarb, 1.4% alpha-cypermethrin, 0.4% permethrin, and 0.7% beta-cyfluthrin was evaluated using the adult mosquito contact tube bioassays. Mutations in multiple kdr loci within VGSC domains and the G119 site of the ace-1 gene were detected by PCR amplification followed by Sanger sequencing. Results Bioassays revealed that all field populations were resistant to permethrin (mortality: 2.67%–88.00%), and 86.7% of populations exhibited resistance or possible resistance to beta-cyfluthrin. However, all populations were susceptible to bendiocarb, and no confirmed resistance to fenitrothion was detected. Molecular analyses identified a high-frequency mutation exclusively at the F1534 locus of the VGSC gene (mutant TCC allele frequency: 89.23%). Significant variations in genotypic frequency distribution were observed among the districts (p < 0.001). Core urban districts (e.g., Gongshu and Yuhang) exhibited significantly higher kdr allele frequencies (>98%) and resistance levels compared with counties such as Fuyang and Lin’an. Conclusion Ae. albopictus populations in Hangzhou exhibit widespread resistance to pyrethroid insecticides, which is spatially associated with a high frequency of the F1534S kdr mutation in the VGSC gene. The potential contribution of metabolic resistance, which may vary geographically, was not evaluated in this study. These findings suggest that resistance management strategies, including insecticide rotation and area-specific interventions, may be needed and should be informed by further investigation of local resistance mechanisms.