Insecticides resistance of Anopheles sinensis in China-Myanmar border areas
Objective To investigate the current status of insecticide resistance of Anopheles sinensis in China-Myanmar border areas,so as to provide scientific basis for vector control in this region after malaria elimination in China.Methods From July 4 to 26,2023,in Tengchong City,Cangyuan Wa Autonomous County(Cangyuan),and Yingjiang County along the China-Myanmar border,one natural villages each suitable for An.sinensis breeding were selected as investigation points.At each survey point,no less than 800 female blood-sucking An.sinensis mosquitoes were collected and brought back to the laboratory,and on the following day,mosquito resistance to nine insecticides was measured using the WHO tube test.Blank control were set up,and three replicates were conducted for each dose of insecticides.The contact time of the insecticide,the first mosquito strike time,the 60 min mosquito strike count,and the number of mosquito deaths at 24 h were recorded.The mean first knockdown time,knockdown rate at 60 min,median knockdown time(KT50),and 24 h corrected mortality were caculated.The Chi-square test was used to compare the 24 h corrected mortality of test insects for each insecticide at the three survey sites.The reference insecticides and the WHO-recommended tubes were both provided by the department of vector biology and control,national institute for communicable disease control and prevention,Chinese center for disease control and prevention.Results The resistance of a total of 2 224 An.sinensis mosquitoes were measured at three surveillance counties to nine insecticides including 0.05％deltamethrin,0.15％lambda-cyhalothrin,0.15％beta-cyfluthrin,5％malathion,0.5％permethrin,1％fenitrothion,0.1％bendiocarb,0.1％propoxur,and 0.06％fipronil.At Cangyuan survey point,the 24 h average corrected mortality rates of An.sinensis adults were 25.68％,26.58％,46.67％,100％,39.19％,86.75％,55.29％,35.96％,and 25.40％for the nine insecticides,respectively;at Tengchong survey point,the 24 h average corrected mortality rates were 40.40％,44.58％,34.74％,96.05％,5.00％,97.00％,44.19％,27.96％,and 63.41％,respectively;at Yingjiang survey point,the 24 h average corrected mortality rates were 39.73％,49.41％,53.95％,100％,26.47％,100％,91.67％,100％,and 43.37％,respectively.There were significant differences in the 24 h average corrected mortality rate between the three surveillance points for seven insecticides,including 0.15％lambda-cyhalothrin,0.15％beta-cyfluthrin,0.5％permethrin,1％fenitrothion,0.1％bendiocarb,0.1％propoxur,and 0.06％fipronil(all P＜0.05).Conclusions In the surveyed areas along the China-Myanmar border,An.sinensis has developed resistance to multiple insecticides,and the use of insecticides should be adjusted according to surveillance results to delay the occurence and development of insecticide resistance while effectively controlling the malaria vectors.
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