High levels of pyrethroid resistance and super-kdr mutations in the populations of tropical bed bug, Cimex hemipterus, in Iran

Abstract

Background The tropical bed bug, Cimex hemipterus, is an important ectoparasite causing various health problems. This species is mainly confined to tropical regions; however, insecticide resistance, global warming, and globalization have changed its distribution map. Molecular information on pyrethroid resistance, which is essential for the development of control programs, is unknown for C. hemipterus in expanded areas. The present study was designed to determine the permethrin resistance status, characterize the pyrethroid receptor sites in voltage-gated sodium channel (vgsc) gene, and identify the resistance-related mutations in the populations of tropical bed bug in Iran. Methods Live bed bugs were collected, and adults of C. hemipterus were selected for bioassay and molecular surveys. Bioassay was performed by tarsal contact with permethrin 0.75% in mixed-sex of samples. Conventional and quantitative TaqMan and SYBR Green real-time PCR assays were conducted to characterize the vgsc gene and genotypes of studied populations. Results In the bioassay tests, the mortality rates were in the range of 30.7–38.7% and 56.2–77.4% in 24 and 48 h, respectively. The knockdown rates of studied populations were in the range of 32.2–46.6% and 61.5–83.8% in the first and second days, respectively. The KT50 and KT90 values in the Cimex lectularius Kh1 strain were presented as 5.39 and 15.55 h, respectively. These values in the selected populations of C. hemipterus varied from 27.9 to 29.5 and from 82.8 to 104.4 h, respectively. Knockdown time ratios (KR50 and KR90) in these populations varied from 5.17 to 6.17-fold compared with those of the C. lectularius Kh1 strain. Fragments of vgsc gene with 355 bp and 812 bp were amplified. Analysis of sequences revealed the A468T substitution, kdr-associated D953G, and super-kdr M918I and L1014F mutations in all populations. Conclusions The specific/sensitive, safe, and rapid diagnostic assays developed in this study are recommended for detection of kdr/super-kdr mutations and frequency of mutant alleles. The presence of super-kdr mutations and high resistance to permethrin in all the populations necessitate the reconsideration of control approaches against C. hemipterus. Graphical Abstract

Morphometric Characteristics and Species Identification of Bed Bugs (Hemiptera: Cimicidae) in Eastern Iran

“…Cimex hemipterus was reported from northwestern and the west of Iran based on unmentioned morphological criteria and molecular studies (11). Some reports from other regions of the country indicate the presence of C. hemipterus (12,18). Cimex lectularius was reported from Mashhad in 2019 (19), and in the present study, we could not find this species in the study area, including Mashhad city.…”

“…The identification of bed bugs at the species level is usually based on morphological characteristics such as pronotum, hind tibial, paragenital sinus, and paramer (12). The pronotum width-to-length ratio is the most influential factor for differentiating C. hemipterus and C. lectularius.…”

“…Following the initial report of the presence of C. hemipterus in Iran (4), subsequent researches have also confirmed the existence of tropical bed bugs in the western and central regions of the country (11,12). Bahrami et al (13) studied the phylogenetic and ultrastructure characterization of bed bugs in southwestern Iran and showed that C. hemipterus was the predominant species in that region.…”

Testing the Sensitivity of the Tropical Bed Bug Cimex hemipterus (Hemiptera: Cimicidae) to Deltamethrin, Phoxim and Propetamphos in Eastern Iran

“…These effects were significantly higher compared to either deltamethrin or propetamphos agents . Cimex lectularius used to be widespread in Iran, but now it has been replaced by C. hemipterus as the predominant species ( 11 ). In our previous study, we showed that diazinon, λ-cyhalothrin, and malathion were not effective against C. lectularius populations in northeastern Iran ( 12 ), however, this study demonstrated that bed bugs are susceptible to phoxim.…”

The first recent case ofCimex hemipterus(Hemiptera: Cimicidae) withsuper-kdrmutations in the Republic of Korea

“…In C. lectularius , 3 kdr mutations (V419L, L925I, and I936F) have been reported (Yoon et al 2008, Zhu et al 2010, Dang et al 2015a), whereas 9 kdr mutations (L899V, M918I, D953G, L1014F, Y/L995H, V1010L, I1011F, V1016E, and L1017F/S) have been reported in C. hemipterus (Dang et al 2015b, Punchihewa et al 2019). In particular, the double mutation of M918I and L1014F is known as a super-knockdown resistance ( super-kdr ) mutation (Ghavami et al 2021). In addition, the F348Y mutation associated with resistance to organophosphates and carbamates in the paralogous acetylcholinesterase gene ( p-Ace ) was recently identified in both bed bug species (Komagata et al 2021).…”