Metabolic Resistance Mechanism And Synergistic Effect Of Culex Quinquefasciatus In Zhongshan,Guangdong Province

Mosquitoes are important vector insects in terms of public health importance,which transmit a number of diseases,such as malaria,yellow fever,dengue fever etc.Chemical insecticides are still commonly used for control of disease vectors and synthetic pyrethroids have become more popular and predominate for public health use in China,but repeated use of synthetic insecticides for mosquito control has disrupted natural biological control systems and led to resurgences in mosquito populations.It has also resulted in the development of resistance.In order to clarify the resistance of Culex quinquefasciatus to commonly used pyrethroids,dimefluthrin and meperfluthrin,in China,and associate with the present-day vector control strategies and ongoing resistance management strategies.In this paper,we monitored the resistance level of dimefluthrin and meperfluthrin to Culex quinquefasciatus at Guangdong Zhongshan,Jiangxi Dayu,Chongqing Bishan respectively,determined the synergistic effect of two enzyme inhibitors on dimefluthrin by capillary microdissection method,investigated the m RNA expression levels of 10 genes of wild Culex quinquefasciatus and sensitive Culex quinquefasciatus in vivo by quantitative real-time PCR,screened the repellent effects of 20 kinds of essential oils and two mosquito repellents on field and sensitive Culex quinquefasciatus by the triple cylinder method respectively,determined the synergistic effect of by 10 kinds of plant essential oils,insect repellent Icaridin and insect growth regulator Pyriproxyfen to dimefluthrin and meperfluthrin by capillary microdissection method.The results are as follows:1.The results showed that the populations of the wild Culex quinquefasciatus of Guangdong Zhongshan,Jiangxi Dayu,Chongqing Bishan was currently widespread resistance to dimefluthrin and meperfluthrin by capillary microdissection method.Among them,The resistance ratios of the first generation?fielded collection the larvae of Culex quinquefasciatus and cultured for adults indoor as the first generation?of the wild Culex quinquefasciatus,at Zhongshan Dongfeng,collected in the September,November and December,was 6.56,3.11,1.86 and 9.15,3.10,2.32 to dimefluthrin and meperfluthrin respectively;The strongest resistance ratios of Culex quinquefasciatus collected in the September,at Zhongshan Dongfeng.at Zhongshan Fuxi,collected in September,October November and December,was 3.33,3.98,1.82,2.97 and 3.96,4.63,2.30,2.38 respectively;at Jiangxi DaYu,collected in July,was 3.62 and 5.71 respectively;at Chongqing Bishan,collected in June,was 3.00 and 3.07 respectively.The resistance level of Culex quinquefasciatus after several generations of culture indoor was decreased at different time and regions and the biggest drop was Zhongshan Dongfeng.2.The synergistic effect of the enzyme inhibitors PBO?piperonyl butoxide?and S₂?octachlorodipropyl ether?to dimefluthrin and meperfluthrin was investigated by the method of treatment insecticide after the enzyme inhibitor and simultaneously treatment insecticide and the enzyme inhibitor.The results showed that PBO had the most significant synergistic effect on dimefluthrin and meperfluthrin,the synergistic ratio was 7.27 and 2.50respectively,by the method of treatment insecticide after the enzyme inhibitor;the synergistic ratio was 1.34 and 1.76 respectively,by the method of simultaneously treatment insecticide and the enzyme inhibitor;and the synergistic effect of PBO on the pyrethroid by the method of treatment insecticide after the enzyme inhibitor was better than that of simultaneously treatment insecticide and the enzyme inhibitor.The synergistic effect of S₂on dimefluthrin and meperfluthrin was not obvious by the both method.3.The expression levels of wild Culex quinquefasciatus at Zhongshan Dongfeng of cytochrome oxidized subunit I,chymotrypsin,cytochrome b,phosphorylase,glutathione S-transferase,sterol carrier protein 2,Hzc4 apoptotic protease and larval serum protein 1?chain 8 were significantly higher than that of susceptible Culex quinquefasciatus and their expression levels were 2.0,1.8,2.5,2.5,2.0,8.0,3.3 and 1.8 times than susceptible population respectively by quantitative real-time PCR.The expression levels of mitochondrial ribosomal large subunit and lipase 3 were lower than that of susceptible Culex quinquefasciatus and their expression levels were 0.8 and 0.6 respectively.4.As field Culex quinquefasciatus,the repellent rates of menthol,basil oil,cinnamic aldehyde,niaouli,citronellol,?-pinene,catnip,camphol and cajeput Oil were 100%,93.7%,96.5%,100%,98.8%,98.6%,92.4%,98.7%,90.6%respectively,in 90 min at a dose of 2.2?g/cm³;the repellent rates of menthol,basil oil,cinnamic aldehyde,niaouli,citronellol were100%,93.2%,93.9%,96.1%,94.6%respectively,in 120 min at a dose of 2.2?g/cm³.As field Culex quinquefasciatus,the repellent rates of aldehyde,menthol,peppermint oil and catnip were 96.7%,95.3%,90.9%and 94.7%.respectively,in 90 min at a dose of 0.22?g/cm³;the repellent rates of aldehyde,menthol,peppermint oil were 95.5%,92.6%,91.1%respectively,in 120 min at a dose of 0.22?g/cm³.As sensitive Culex quinquefasciatus,the repellent rates of catnip and menthol were 98.3%and 97.3%respectively,in 90 min at a dose of 0.22?g/cm³;the repellent rates of catnip and menthol were 93.5%and 91.2%respectively,in 120 min at a dose of 0.22?g/cm³.5.The synergism ratio of 10 kinds of plant essential oil,insect repellent Icaridin and insect growth regulator Pyriproxyfen mixed with dimefluthrin by 1:1 mass ratio respectively were determined by capillary microdissection method.the synergism ratio of menthol,cinnamon aldehyde,basil oil,alpha pinene,peppermint oil and insect growth regulator pyriproxyfen to dimefluthrin in the populations of wild Culex quinquefasciatus at Zhongshan Dongfeng was 4.63,2.81,14.68,1.31,1.93 and 1.16 respectively,by capillary microdissection method;the other essential oils are not synergistic effect.the synergism ratio of menthol was 2.18,in the populations of wild Culex quinquefasciatus at Zhongshan Fusha.Menthol has a certain synergistic effect.