[Resistance of Anopheles sinensis to three common insecticides in Hainan Province]

Anopheles sinensis adults were collected by cow-baited trap in Haikou City, Sanya City, Lingshui County, Changjiang County and Qiongzhong County of Hainan Province during 2011-2013. The mosquitoes were exposed to insecticide impregnated papers with discriminating concentrations of DDT (4%), deltamethrin (0.05%), and malathion (5%) using WHO standard assays. Knockdown rate was recorded at 10, 15, 20, 30, 40, 50, and 60 min, and KT50 values were calculated. Mortality was recorded after 24 hours of exposure. The resistance level was graded as sensitive group (S) with a mortality rate of 98%-100%, preliminary resistance group (M) with mortality rate of 80%-97%, and resistance group (R) with mortality rate of lower than 80%. The results showed that the mortality rate of An. sinensis in Qiongzhong County in 24 h-post-exposure to 0.05% deltamethrin was 95.0% with a resistance degree of M. That to 0.05% deltamethrin in the other 4 sites was 17.0%-63.0%, all with a resistance degree of R. That to 4% DDT in Haikou, Sanya, Lingshui, Qiongzhong and Changjiang was 36.0%, 27.0%, 24.0%, 59.1%, and 82.0%, with a resistance level of R, R, R, R, and M, respectively. That to 5% malathion in Haikou, Sanya, and Lingshui was 16.0%-41.0%, all with a resistance degree of R, while that to malathion in Qiongzhong and Changjiang was 100% and 98.0%, respectively, with a resistance level of S.