Identification of Knockdown Resistance Mutations in the Cimex hemipterus (Hemiptera: Cimicidae) in Iran

The worldwide resurgence of tropical bed bug Cimex hemipterus beginning in the late 1990s has led to growing concern. Molecular data on pyrethroid resistance, which is essential for the control strategies, is unknown for C. hemipterus in Iran. The current study evaluated the deltamethrin resistance status of C. hemipterus by bioassay and molecular tests. Live bed bugs were collected from sleeping quarters (dormitories) in the city of Tehran and used for insecticide bioassay tests. For bioassay evaluation, mixed-sex pools of adult bugs were exposed to deltamethrin (0.025%)-treated paper. Polymerase chain reaction assay evaluated resistance-related mutations in the voltage-gated sodium channel gene (VGSC) gene of studied populations. On the basis of the bioassay test within the 48-h exposure to deltamethrin, C. hemipterus were determined to be resistant. Knockdown time ratios (KR50) in the studied populations of C. hemipterus was 5.5-fold compared with those of the C. lectularius Teh strain. DNA sequencing of the VGSC gene revealed the presence of mutations at M918I and L1014 in C. hemipterus. According to the bioassay and molecular results of current study, C. hemipterus showed a high degree of pyrethroid resistance. The application of multiple approaches including physical, biological, and chemical tests should be regarded in future bed bug control strategies.