Prevalence of kdr and ace-1 mutant genes and potential insecticide resistance among four field strains of Anopheles sinensis (Diptera: Culicidae) collected from high-malaria-risk areas in the Republic of Korea

The relationship between phenotypic resistance to organophosphate and pyrethroid insecticides and the frequencies of knockdown resistance ( kdr ) and acetylcholinesterase ( ace-1 ) target-site mutations was investigated in four field strains of Anopheles sinensis collected from high-malaria-risk areas in the Republic of Korea (ROK). Six kdr genotypes and six ace-1 genotypes were identified, and the overall frequencies of resistance-associated mutations ranged from 62.1% to 96.8% for kdr and from 84.5% to 100% for ace-1 . Among larvae that survived exposure to LC 50 concentrations of selected insecticides, resistance-associated genotypes, including Phe-Phe (TTT) in kdr and Gly (GGR)-Ser (YGC) in ace-1 , were predominantly detected. Although the mean frequency of ace-1 resistance-associated mutations was higher than that of kdr mutations, the difference was not statistically significant ( P = 0.42). In contrast, bioassay results showed that the mean resistance levels to pyrethroids were significantly higher than those to organophosphates ( P = 0.006). Correlation analyses revealed no statistically significant association between kdr mutation frequency and pyrethroid resistance or between ace-1 mutation frequency and organophosphate resistance. These findings suggest that resistance-associated target-site mutations are widespread in An. sinensis populations from high-malaria-risk areas near the DMZ, but their frequencies alone do not fully explain phenotypic resistance levels. Therefore, while molecular data are useful for monitoring the distribution of resistance-associated mutations, they should be interpreted alongside bioassay results when developing insecticide resistance management strategies.