Pyrethroid resistance and associated mutations in Aedes albopictus in urban area of Zhongshan,Guangdong Province,China
Objective To investigate the pyrethroid resistance and the knockdown resistance mutations in the voltage-gated sodium channel gene(VGSC)of field populations of Aedes albopictus in the central urban areas of Zhongshan,Guangdong Province,China in 2020,so as to provide a reference for effective vector control.Methods Aedes adults and larvae were collected from five different habitats in urban area of Zhongshan from July to October,2020.After laboratory rearing,female adult mosquitoes of Ae.albopictus were selected for pyrethroid resistance testing using the World Health Organization tube bioassay.The VGSC gene fragments of Ae.albopictus in Zhongshan were amplified for sequencing using polymerase chain reaction.SPSS 25.0 software was used for statistical analysis.The Chi-square R×C contingency table test or Fisher's exact test was used for multi-group comparison,and the Bonferroni test was used for pairwise comparison.Results The 24 h mortality of field populations of Ae.albopictus was 9.48％-50.82％for 0.03％deltamethrin,6.89％-40.69％for 0.08％alpha-cypermethrin,2.61％-38.13％for 0.07％lambda-cyhalothrin,0.88％-50.00％for 0.4％permethrin,and 17.95％-94.00％for 0.4％beta-cypermethrin.All the populations of Ae.albopictus showed resistance to the five pyrethroid insecticides,except for the Jinzishan population with suspected resistance to 0.4％cypermethrin.A total of 318 Ae.albopictus mosquitoes were tested for VGSC gene variants,detecting mutations at locus 1534 and no mutation at locus 1532.There were four mutant alleles at locus 1534,including TTG/L(most frequent,57.23％),TCC/S,TCG/S,and TGC/C.There were nine genotypes at locus 1534:wild-type homozygous TTC/TTC(F/F);wild/mutant-type heterozygous TTC/TCC(F/S),TTC/TCG(F/S),TTC/TTG(F/L),and TTC/TGC(F/C);mutant homozygous TTG/TTG(L/L),TCC/TCG(S/S),and TCC/TCC(S/S);and mutant heterozygous TTG/TCC(L/S).The mutant homozygote L/L accounted for the highest proportion of 41.82％.Conclusions Field Ae.albopictus populations in central urban area of Zhongshan have developed high resistance to pyrethroids.In order to reduce the risk of mosquito-borne diseases,it is necessary to continue to monitor insecticide resistance,and take targeted control measures according to resistance status.
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