Investigation of knockdown resistance genes and pyrethroid resistance in Aedes albopictus mosquitoes in Zhuhai city
Objective To understand the distribution of knockdown resistance(kdr)genes in Aedes albopictus mosquitoes in Zhuhai city,Guangdong province,and assess their resistance levels to pyrethroid insecticides,and provide scientific basis for mosquito control in the region.Methods In August and September 2023,wild larvae of Aedes albopictus mosquitoes were collected from five administrative districts in Zhuhai city.These larvae were brought back to the laboratory and feeded until they developed into adult mosquitoes.After morphological identification,genomic DNA was extracted from individual adult mosquitoes.A segment of the voltage-gated sodium channel(VGSC)gene was amplified and sequenced,and SnapGene software was used to analyze the mutations in the kdr gene.The World Health Organization-recommended larval immersion method was employed to determine the resistance levels of Aedes albopictus to pyrethroid insecticides.Additionally,the probit analysis and SPSS 20.26 software were utilized to calculate the toxicity regression equation and the lethal concentration for 50%(LC50)of the larvae.Results kdr gene mutations were detected at the V1016 and F1534 loci in wild populations of Aedes albopictus in Zhuhai city.Among 154 mosquitoes collected from the five administrative districts,the 1016 locus exhibited two genotypes:wild-type homozygous V/V(94.81%)and mutant homozygous G/G(5.19%).The 1534 locus revealed eight genotypes,including wild-type homozygous F/F(45.45%),wild/mutant heterozygous F/C(1.30%),F/S(18.18%)and F/L(0.65%),mutant homozygous C/C(13.64%),S/S(10.39%),L/L(9.74%),and mutant heterozygous S/L(0.65%).The resistance ratio of Aedes albopictus larvae to deltamethrin ranged from 12.00 to 26.00 in the five administrative districts,with Xiangzhou district,Gaoxin district,and Jinwan district showed high resistance levels,while the other districts showed moderate resistance.The resistance ratio to high-efficiency cypermethrin was 10.33-17.33,and all five administrative regions showed moderate resistance levels.The resistance ratio to permethrin was 4.10-7.40,and all five administrative regions showed low resistance levels.Conclusions The wild population of Aedes albopictus mosquitoes in Zhuhai city had developed varying degrees of resistance to three types of pyrethroid insecticides,and a higher frequency of kdr gene mutations had been observed.Continuous monitoring of mosquito resistance levels could provide a scientific foundation for the rational use of insecticides and the delay of resistance development.
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