[Resistance assay of malaria vectors to four kinds of common insecticides in some endemic areas of Hainan Province].

Objective: To determine the resistance of malaria vectors to four kinds of common insecticides in some endemic areas of Hainan Province.

Methods: Anopheline mosquitoes were collected between 2008 and 2010 from malaria endemic areas where insecticides were used for years. Anopheles dirus were collected from human-baited trap in Wangxia Town of Changjiang County. An. minimus and An. sinensis were collected by cow-baited trap in Jiangbian Town of Dongfang City. F0 generation female An. sinensis, F1 generation of female An. dirus and An. minimus were selected and exposed to insecticide impregnated papers with discriminating concentrations of DDT (4%), deltamethrin (0.05%), cyfluthrin (0.15%), and malathion (5%) using WHO standard assays. Knockdown rate was recorded at 10, 15, 20, 30, 40, 50, and 60 min, and KTm values were calculated. Mortality was recorded after 24 hours of exposure.

Results: Mortality in An. dirus was 100% to DDT, deltamethrin and malathion. Knockdown rate of An. dirus exposed to DDT and deltamethrin was 82.0% and 100%, with a KT50 value of 46.9 and 18.4 min, respectively. Mortality of An. minimus to DDT, deltamethrin, cyfluthrin and malathion was 98.1%, 99.0%, 100%, and 100%, respectively. The knockdown rate of An. minimus to DDT, deltamethrin, and cyfluthrin was 96.3%, 99.0%, and 100%, respectively, and the KTs value was 31.3, 16.8, and 7.4 min, respectively. Mortality of An. sinensis to DDT, deltamethrin, and malathion was 19.8%, 22.9%, and 43.8%, respectively. Knockdown rate of An. sinensis to DDT and deltamethrin was 2.0%, the KT50 can not be calculated.

Conclusion: An. dirus and An. minimus, the main malaria vectors in the survey sites of Hainan Province, are susceptible to the four insecticides, while secondary malaria vector An. sinensis showed resistance to DDT, deltamethrin, and malathion.