Fixation of knockdown resistance mutations in Cimex hemipterus (Hemiptera: Cimicidae) from east Iran

The tropical bed bug, Cimex hemipterus (F.), is an obligate blood-feeding ectoparasite and a well-established pest in urban settings, particularly in tropical and subtropical regions. Insecticide resistance is one of the main challenges in bed bug management worldwide, with pyrethroid resistance being especially widespread. Iran's diverse geography and climate support the presence of both Cimex lectularius L. and C. hemipterus, with the latter being commonly found in the warmer, arid eastern provinces. In this study, we investigated the target site mutations that underlie pyrethroid resistance in C. hemipterus populations from eastern Iran-an area previously lacking genetic data on resistance mechanisms. Bed bug samples collected from residential infestations across three eastern provinces were analyzed through PCR amplification and sequencing of a fragment of the voltage-gated sodium channel (VGSC) gene. All study strains (n = 80) exhibited homozygous double mutations at positions M918I and L1014F associated with super knockdown resistance (kdr) genotype. The uniform presence of this double-mutation haplotype across all populations can be attributed to either prolonged selection pressure from pyrethroid use or founder effect, which requires further investigations. No other resistance-associated mutations previously reported in the VGSC in C. hemipterus were detected. By documenting these fixed mutations in eastern Iran, this study contributes additional insight that helps generate an understanding of resistance profiles of C. hemipterus from a previously uncharacterized region of Iran and reinforces the need for routine resistance monitoring and integrated pest management (IPM) strategies to preserve the efficacy of available control tools.