Susceptibility and Resistance of Field Populations of Anopheles sinensis (Diptera: Culicidae) Collected from Paju to 13 Insecticides

OBJECTIVES: Over 20% of all malaria cases reported annually in the Republic of Korea (ROK) occur in Paju, Gyeonggi Province. Vector control for malaria management is essential, but the insecticide resistance of the vector, Anopheles mosquitoes, has been a major obstacle in implementing effective control. In this study, the insecticide resistance of the vector mosquitoes was evaluated and compared with that of vector mosquitoes collected from the same locality in 2001 and 2009. METHODS: The insecticide resistance of Anopheles sinensis s.s. collected from Paju, Gyeonggi Province in the ROK was evaluated under laboratory conditions with a micro-application method using 13 insecticides currently used by local public health centers and pest control operators in the ROK. RESULTS: Based on median lethal dose (LC(50)) values, An. sinensis s.s. were most susceptible to the insecticides bifenthrin, cyfluthrin, and etofenprox in that order, and least susceptible to permethrin. An. sinensis showed higher susceptibility to pyrethroids than organophosphates, except for fenthion and permethrin. In a comparative resistance test, the resistance ratios (RRs) of An. sinensis collected in 2012 (AS12) to the 13 insecticides were compared to the RRs of two strains of An. sinensis collected from the same locality in 2001 (AS01) and 2008 (AS08). With some exceptions, AS12 demonstrated higher resistance to all tested insecticides compared to AS01 and AS08, and less resistance to bifenthrin, cyfluthrin, and cypermethrin compared to AS01. CONCLUSION: These results indicate that careful selection and rotation of these insecticides may result in continued satisfactory control of field populations of An. sinensis s.s. for effective malaria management in Paju.