Extensive Resistance of Anopheles sinensis to Insecticides in Malaria-Endemic Areas of Hainan Province, China

Anopheles sinensis is one of the major malaria vectors and among the dominant species in Hainan Province, China. The resistance of An. sinensis to insecticides is an important threat to malaria control. However, few reports on insecticide resistance of An. sinensis were reported in this area. Eight districts in Hainan Province were selected as the study areas. Insecticide susceptibility bioassays were tested on wild-caught female mosquitoes of An. sinensis to 4% dichlorodiphenyltrichloroethane (DDT), 0.05% deltamethrin, and 5% malathion by using the World Health Organization standard resistance tube assay procedure. All the tested An. sinensis mosquitoes demonstrated resistance to 4% DDT, with less than 72% mortality in the standard assay. The populations from Baisha and Qiongzhong demonstrated possible resistance to 0.05% deltamethrin, with 94–95% mortality, whereas the populations from other districts demonstrated resistance to 0.05% deltamethrin in the standard assay. The populations from Baisha, Qiongzhong, and Dongfang demonstrated susceptibility to 5% malathion, but the populations from other districts demonstrated resistance. These results facilitate the improvement of effective control strategies for malaria vector mosquitoes in Hainan.