Study On Resistance And Mechanism Of Aedes Albopictus To Pyrethroid Insecticides In Zhongshan

Zhongshan City is located in the central and southern part of Guangdong Province,in the center of the Guangdong-Hong Kong-Macao Greater Bay Area,which has a high risk of transmission of imported mosquito-borne diseases.Zhongshan has a warm climate all year round,with an average temperature of 21.8℃ and an average relative humidity of 83%.It is suitable for Aedes albopictus and other disease vectors to breed in Zhongshan,and Aedes albopictus is one of the dominant mosquito species in the city.There have been several outbreaks of dengue fever in Zhongshan City in recent years,both in the form of imported cases and local cases.The prevention and control of dengue fever and other insect-borne diseases mainly rely on spraying insecticides to reduce the density of mosquitoes.However,with the emergence of mosquito resistance,the prevention and control effect is seriously affected and the risk of dengue transmission is increased.This study from 2019 to 2020,the peak time of mosquito activity in selected six collect mosquito samples in different habitats,zhongshan city,through the bioassay method about mosquito method for the strain of insecticide resistance levels,and biochemical assay to determine its resistance related metabolic enzyme activity,and the level of molecular biology to explore its resistance mechanism,to provide reasonable suggestions for the prevention and control measures of local mosquito-borne diseases.The main research results are as follows:1.Bioassay results showed that the field population of Aedes albopictus in Zhongshan City developed a high level of resistance to pyrethroids.The 1h knockdown rates of 0.03% deltamethrin,0.4% beta-cypermethrin,0.4%permethrin,0.07% beta-cyhalothrin and 0.08% cis-pyrethroid of Zhongshan population were 19.09% to 89.82%,and the 24 h mortality was 17.69% to56.61%.Five habitats of Ae.albopictus(JZ,GY,HG,FJ and SX)were detected,and the five populations showed different degrees of resistance to the above five insecticides.Mortality rates ranged from 21.43% to 94.00%,from 21.37% to 55.83%,from 6.60% to 54.78%,from 4.04% to 66.67%,and from 2.61% to 40.98%,respectively.Only the resistance level of JZ population to 0.4% beta-cypermethrin was the potential resistant population M,and the rest was the resistant population S.2.The results showed that the enzyme activities of JZ population,GY population,HG population,FJ population and SX population were detected in five habitats.For GST,the enzyme activities of field population varied widely(14.33～77.47 nmol/min mg pr),and the enzyme activity level of FJ population was higher than that of sensitive strain.The enzyme activities of JZ and HG populations were lower than those of sensitive strains.For MFO,the range of enzyme activities in field population was small(0.91～1.90 nmol Cyt C /mg pr).The enzyme activities in JZ population,Gy population and SX population were higher than those in sensitive strain,and those in FJ population were lower than those in sensitive strain.For NSE,the enzyme activity of field population varied widely(63.27～155.53 nmol a-naphthol/min mg pr),and JZ population,GY population,HG population and FJ population were significantly lower than those of sensitive strain.3.The results of genetic testing showed that there were high frequency mutations at 1534 site of kdr gene,but no mutations at 1532 site in six habitats of Aedes albopictus,including JZ population,GY population,HG population,FJ population,SX population and DJ population.There is only one allele at locus 1532,wild-type ATC/I,and one genotype,wild-type homozygous ATC/ATC(I/I).There were 5 alleles at site 1534,including wild-type TTC/F,mutant TTG/L,TCC/S,TCG/S and TGC/C.10 genotypes were wild-type homozygous TTC/TTC(F/F),wild-type heterozygous TTC/TCC(F/S),TTC/TCG(F/S),TTC/TTG(F/L),TTC/TGC(F/C),respectively.Mutant homozygous TTG/TTG(L/L),TCC/TCG(S/S),mutant heterozygous TCC/TCC(S/S),TTG/TCC(L/S),TCC/TGC(S/C).4.The results of gene testing showed that both resistant and sensitive kdr gene locus 1534 were mutated,and the sensitive strain group were all wild type.Chi-square test showed that the mutation frequency of resistant and sensitive kdr gene locus 1534 had no significant difference(P<0.05).The adult mosquitoes of Ae.albopictus in the wild population of Zhongshan City developed different degrees of resistance to pyrethroids,and the alternate use of different insecticides could slow down the development of resistance to pyrethroids,so as to improve the elimination effect.The metabolic enzyme activity of mosquitoes in Zhongshan population increased,and the mutation of kdr gene appeared at a higher frequency,which indicated that the metabolic resistance and knockdown resistance were the main reasons for the resistance formation of mosquitoes in Zhongshan population.It is of great significance for the prevention and control of arbo-borne diseases to monitor the long-term resistance of Aedes albopictus in Zhongshan and to explore the causes of resistance formation.