Stability of super-kdr mutations of voltage-sensitive sodium channel gene in the common bed bug, Cimex lectularius

The common bed bug, Cimex lectularius (Heteroptera: Cimicidae), is an increasing global health threat that can lead to both physical and mental disorders. According to recent investigations, a large proportion of bed bugs collected from residences are resistant to pyrethroid insecticides. A high level of pyrethroid resistance in bed bugs is primarily attributed to two mutations (V419L and L925I) in the voltage-sensitive sodium channel (vssc), collectively referred as the knockdown resistance (kdr) trait. The primary aim of this study was to assess the stability of the kdr allele in bed bug vssc. Remarkably, even when bed bugs were not exposed to pyrethroid insecticides, the resistance alleles remained persistent for over 20 generations. This stability was further confirmed by crossing bed bugs between pyrethroid-susceptible and -resistant strains for five generations. In this crossing experiment, the frequency of the kdr mutations gradually increased, indicating a fitness advantage. This finding further suggests that the most effective approach for addressing pyrethroid resistance in bed bugs is to institute control using alternative insecticides. To assess the efficacy of alternative insecticides for controlling pyrethroid-resistant bed bugs, laboratory bioassays using both pyrethroid-susceptible and -resistant strains were conducted. Based on their low LD50 values and lack of cross-resistance, our findings suggest imidacloprid as the most optimal substitute insecticide for effective control against pyrethroid-resistant bed bugs. Other neonicotinoids tested, except for dinotefuran, along with fipronil may provide effective control against pyrethroid-resistant bed bugs.