Behavioral Response of the Tropical Bed Bug, Cimex hemipterus (Hemiptera: Cimicidae) to Carbon Dioxide

Genome-wide analysis of gustatory receptor genes and identification of the fructose gustatory receptor in Arma chinensis

Gustatory receptors (GRs) allow insects to sense tastes in their external environment. Gustatory perception is crucial for distinguishing between beneficial and harmful or toxic compounds, affecting survival. This study is the first to identify and classify the GR genes and investigate their expression in the predatory Arma chinensis. Thirteen GR genes (ArmaGr1-ArmaGr13) were identified and classified into four families via phylogenetic analysis. In the predacious developmental stages, ArmaGr7 expression gradually increased from the 2nd to 5th instar stages and then to adults. However, ArmaGr7 was also highly expressed in the non-predation 1st instar nymph and egg stages. ArmaGr7 expression was localized in the antennae, scalpella, forelegs, wings, head, and midgut of male and female adults, with wings displaying the highest expression. Furthermore, ArmaGr7 expression was positively correlated with fructose solution intake; molecular docking results showed that fructose could effectively dock withArmaGr7. A protein structure comparison revealed that the ArmaGr7 structure was different from that of other GR43a-like proteins, which may be related to the gene splicing of the A. chinensis GR gene. These results elucidate the crucial role of ArmaGr7 in fructose recognition by A. chinensis and provide a foundation for further studies on gustatory perception.

Repellent effect of two anthranilates against the tropical bed bug Cimex hemipterus (Hemiptera: Cimicidae) demonstrated in laboratory assays

BACKGROUND

The bites and blood sucking of bed bugs (Cimex spp.) (Hemiptera: Cimicidae) pose a serious threat to human physical and mental health. Application of an effective repellent can prevent or reduce bed bug bites. Previous studies on repellent screening mainly focused on Cimex lectularius L. In this study, we investigated the repellent effect of two safe food additives, ethyl anthranilate (EA) and butyl anthranilate (BA), against Cimex hemipterus (F.), and also explored the role of antennae and mouthparts on C. hemipterus perception of repellents.

RESULTS

Both EA and BA had a strong repellent effect against tropical bed bugs and their repellency was similar or lower than that of N,N-diethyl-3-methyl benzoyl amide, depending on whether or not a CO2 source was present. EA had higher repellency than BA and exhibited repellency to C. hemipterus for 3 days when a CO2 source was present. C. hemipterus avoided resting on 20% EA- and BA-treated harborages. Applying 20% EA and BA on rabbit skin significantly reduced the blood intake of C. hemipterus within 2 h. C. hemipterus could perceive EA and BA after their antennae or mouthparts or both antennae and mouthparts were removed.

CONCLUSION

Both EA and BA had strong repellency against C. hemipterus, with EA being more repellent. Ablation of antennae and mouthparts did not affect the perception of EA and BA by C. hemipterus. © 2023 Society of Chemical Industry.

Bed Bug Infestation: An Updated Review

In the past decade, there has been a global resurgence of bed bug infestations, especially in developed countries. Proper awareness and identification of bed bug infestations are essential to guide treatment and eradication. The purpose of this article is to familiarize physicians with bed bug bites so that they can effectively diagnose, treat, and address questions about bed bug bites and infestations. Bed bug bites are often painless. Typical reactions include pruritic, erythematous maculopapules occurring in clusters or in a linear or curvilinear distribution in exposed areas of the body. A small red punctum may be visualized at the center of the bite mark. Lesions that appear three in a row and papules on the upper eyelid associated with erythema and edema are highly suggestive of bites from bed bugs. Exaggerated local reactions such as vesicles, urticarial wheals, urticarial perilesional plaques, diffuse urticaria, bullae, and nodules may occur in previously sensitized individuals. Reactions to bed bug bites are self-limited. As such, treatment is mainly symptomatic. Topical pramoxine and oral antihistamines can be used to alleviate pruritus. Topical corticosteroids can be used for significant eruptions to control inflammation and pruritus, and to hasten resolution of the lesions. Integrated pest management, an approach for the eradication of bed bugs, includes monitoring devices (active monitors include the use of heat or carbon dioxide attractants and passive monitors include the use of sticky pads for trapping), and judicious use of nonchemical and chemical treatments known to be effective. Nonchemical interventions include keeping affected areas clean and free of clutter, vacuuming, washing linens with hot water, caulking wall holes and cracks where bugs can hide, proper disposal of highly infested items, and placement of bed bug traps/interceptors at the base of beds and furniture. Chemical interventions involve the use of insecticides such as synthetic pyrethroids, silicates, insect growth disruptors, carbamates, organophosphates, neonicotinoids, diethyl-meta-toluamide, chlorfenapyr, fipronil and plant essential oils. Insecticides should be used with caution to prevent over-exposure and toxicity (in particular, cardiovascular and neurologic toxicity), especially if there are young children around. It is important to note that multiple mechanisms of insecticide resistance exist and as such, chemical treatment should only be undertaken by trained professionals who understand the current literature on resistance. Both nonchemical and chemical technologies should be combined for optimal results. Bed bug infestations may cause diverse dermal reactions, stigmatization, poor self-esteem, emotional stress, anxiety, significant adverse effect on quality of life, and substantial socioeconomic burden to society. As such, their rapid detection and eradication are of paramount importance. Consultation with a professional exterminator is recommended to fully eradicate an infestation.

Identification and Validation of Reference Genes for Expression Analysis Using qRT-PCR in Cimex hemipterus (Hemiptera: Cimicidae)

The tropical bed bug, Cimex hemipterus (F.) (Hemiptera: Cimicidae) is an important public-health pest that feeds on the blood of humans and some other animals. To explore the function of the target genes of C. hemipterus, it is essential to select suitable reference genes for the accurate quantification of gene expression. Here, we selected 10 frequently used reference genes in insects and evaluated their stability in C. hemipterus under various biotic (developmental stage, sex, and tissue) and abiotic (gas stimulation and temperature) conditions through RefFinder (which integrates four computational programs: geNorm, NormFinder, BestKeeper, and ∆Ct). Results indicate that the optimal combination of reference genes for each experimental condition was as follows: RPL8 and EF1α for the developmental stage (eggs, early instar nymphs, late instar nymphs, and adults), RPL8 and RPS16 for adult sex, RPL8 and RPL11 for adult tissue (head, thorax, abdomen, and legs), RPL8 and β-tubulin for gas stimulation (air and carbon dioxide), and RPL8 and NADH for temperature (0, 5, 17, 30, and 37 °C). Finally, the expression pattern of the HSP70 and GR21 genes were analyzed, and the results highlight the importance of appropriate reference-gene selection. Our results provide a comprehensive list of optimal reference genes from C. hemipterus for the first time, which will contribute to accurately analyzing the expression of target genes.