Insecticide resistance and underlying mechanisms in multiple-resistant tropical bed bugs, Cimex hemipterus (Hemiptera: Cimicidae)

The modern resurgence of common (Cimex lectularius) and tropical bed bugs (C. hemipterus) is primarily due to the development of insecticide resistance. While reports on insecticide resistance in C. lectularius are frequent, the information on insecticide resistance status and its underlying mechanisms in C. hemipterus were limited. In this study, we examined DDT, malathion, deltamethrin, permethrin, lambda-cyhalothrin resistance, and the underlying resistance mechanisms of several C. hemipterusstrains (Queensland, Kuala Lumpur, Tanjung Tokong, Christian, and Greenlane). We used surface contact method, synergism studies (piperonyl butoxide [PBO], S,S,S-tributyl phosphorotrithioate [DEF] and diethyl maleate [DEM]), and molecular detection of kdr mutations. Results showed that the C. hemipterus strains were highly resistant to DDT and the three pyrethroids, and moderately resistant to malathion. Synergism studies demonstrated that deltamethrin resistance was significantly (P < 0.05) inhibited by PBO. However, it was not affected in the presence of DEF and DEM, respectively. Malathion resistance was significantly (P < 0.05) reduced by DEF in all strains. Results of PBO and DEF synergism studies suggest the involvement ofmetabolic resistance (cytochrome P450, esterases). Molecular detection demonstrated the presence of one or multiple kdrmutations (M918I, D953G, and L1014F) in these strains. Closer investigation on Tanjung Tokong strain found individuals with three types of kdr mutation combination: D953G + L1014F, M918I + D953G + L1014F (heterozygous M918I), and M918I + D953G + L1014F (homozygous M918I). Individuals with M918I + D953G + L1014F (homozygous M918I) showed significantly (P < 0.05) slower deltamethrin knockdown than the other individuals.