Human skin triglycerides prevent bed bug (Cimex lectularius L.) arrestment

Bed bugs (Cimex lectularius) have proliferated globally and have become one of the most challenging pests to control indoors. They are nocturnal and use multiple sensory cues to detect and orient towards their human hosts. After feeding, usually on a sleeping human, they return to a shelter on or around the sleeping surface, but not directly on the host. We hypothesized that although human skin odors attract hungry bed bugs, human skin compounds may also prevent arrestment on hosts. We used arrestment assays to test human skin swabs, extracts from human skin swabs, and pure compounds identified from human skin swabs. When given a choice, bed bugs preferred to arrest on substrates not previously conditioned by humans. These responses were consistent among laboratory-reared and apartment-collected bed bugs. The compounds responsible for this behavior were found to be extractable in hexane, and bed bugs responded to such extracts in a dose-dependent manner. Bioassay-guided fractionation paired with thin-layer chromatography, GC–MS, and LC–MS analyses suggested that triglycerides (TAGs), common compounds found on human skin, were preventing arrestment on shelters. Bed bugs universally avoided sheltering in TAG-treated shelters, which was independent of the number of carbons or the number of double bonds in the TAG. These results provide strong evidence that the complex of human skin compounds serve as multifunctional semiochemicals for bed bugs, with some odorants attracting host-seeking stages, and others (TAGs and possibly other compounds) preventing bed bug arrestment. Host chemistry, environmental conditions and the physiological state of bed bugs likely influence the dual nature behavioral responses of bed bugs to human skin compounds.

Decade Long Upsurge In Target Site Pyrethroid Resistance In Bed Bug Populations In The United States

Over the past three decades, the bed bug Cimex lectularius has resurged as a prominent indoor pest on a global scale. Knockdown-associated insecticide resistance (kdr) involving the voltage-gated sodium channel, targeted by organochlorine and pyrethroid insecticides, was first reported in C. lectularius within a few years of the widespread use of Dichlorodiphenyltrichloroethane (DDT) and has been implicated as a significant factor contributing to the species recent resurgence. Since then, selection with pyrethroid insecticides has intensified, yet little is known regarding its short-term impacts on the frequency of kdr-associated mutations. Here, we report temporal changes in the frequencies of three kdr-associated mutations in C. lectularius populations collected across the United States from two time periods, sampled approximately a decade apart. Results reveal a significant increase in the frequencies of kdr-associated mutations over this period, and absence of the insecticide-susceptible genotype in recent collections. Furthermore, a significant transition towards infestations possessing multiple kdr-associated mutations was observed. These results suggest that the persistent use of pyrethroid insecticides over the past decade continues to impose strong selection pressure on C. lectularius populations, driving the proliferation of kdr-associated mutations. They demonstrate that, if unabated, strong anthropogenic selection can drive the rapid evolution of adaptive traits.

Estranged companions: Bed bugs, biologies, and affective histories

In recent decades, bed bugs have swept across wealthy industrialized nations. After near extirpation in North America and Northern Europe, the return of these insects has led to a significant level of public anxiety and cultural notoriety. Here, we undertake an analysis of human-bed bug relations in order to both better understand this contemporary resurgence and critically examine the concept of “companion species.” We argue for conceiving of bed bugs as “estranged companions,” and foreground the need to understand contemporary encounters between humans and the insects through distinct histories that have been shaped by the opening and closing of spaces between classed and racialized bodies and that have been dependent upon the development and deployment of particular technologies such as Dichlorodiphenyltrichloroethane (DDT). Further, we argue that “estrangement” has wider conceptual purchase and contributes to a body of research that has countered a strain of scientism in theory that decenters “the human” by interrogating the relations between companion species, (bio)political interventions, and colonial histories. Estrangement contributes to this task by, first, foregrounding that relationships with all companion species are imbricated in situated histories and biopolitical regimes and, second, drawing attention to the differential ethico-political implications of these regimes.

De bedwants: a bad bug?

The bed bug: a bad bug? The common bed bug, Cimex lectularius, is a bloodsucking ectoparasite which attacks mammals and is on the rise since the beginning of the early 21st century. They are brown and flat. Skin lesions appear after the painless bite, often during the predawn hours. Small, purpuric macules develop into erythematous, indurated papules on exposed areas of skin of the face, neck and extremities, and resolve over the course of 2 weeks. Often, a linear or cluster configuration of 3 to 4 lesions (‘breakfast, lunch and dinner’) appears. Pruritic wheal reactions represent a type 1 hypersensitivity reaction elicited by the parasite’s saliva antigens. The clinical differential diagnosis is broad and may include other insect and arthropod bites and stings, scabies infestation, dermatitis herpetiformis, ecthyma, etc. There is no evidence that bed bugs are vectors and transmit human pathogens. They are responsible for considerable physical irritation and significant psychological distress. Very rarely, the patient could develop anemia or anaphylaxis. Control involves treating both the patient’s symptoms and the cause by the eradication of the infestation, a challenge that may require a professional exterminator for an integrated pest management strategy. “Good night, sleep tight, don’t let the bed bugs bite!”

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

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

Pesticides Misused for Bed Bug Control: Comparing Professional and Nonprofessional Applications Reported to the National Pesticide Information Center, 2013–2017

Objectives. To compare outcomes when pesticides are used to control bed bugs by professionals and nonprofessionals. Methods. All US National Pesticide Information Center inquiries from 2013 to 2017 were assessed to identify scenarios involving bed bugs and pesticide applications. Cases were evaluated with respect to types of applicators, misapplications, and human pesticide exposures. Results. Misapplications were more than twice as likely to be reported in cases involving nonprofessional applications (14%) as in cases involving professional applications (5%). Human exposures to pesticides were reported more often when pesticides were misapplied (70%) than when there were no apparent misapplications (31%). Conclusions. Both professionals and nonprofessionals may misuse pesticides to control bed bugs, which may increase the risks of exposure and adverse outcomes. Policy interventions may reduce pesticide incidents related to bed bug control by promoting professional involvement and adherence to product label instructions. (Am J Public Health. Published online ahead of print June 29, 2021: e1–e3. https://doi.org/10.2105/AJPH.2021.306307 )