Insecticide resistance and resistance mechanisms in bed bugs, Cimex spp. (Hemiptera: Cimicidae)

Review on the impacts of indoor vector control on domiciliary pests: good intentions challenged by harsh realities

Arthropod vectored diseases have been a major impediment to societal advancements globally. Strategies to mitigate transmission of these diseases include preventative care (e.g. vaccination), primary treatment and most notably, the suppression of vectors in both indoor and outdoor spaces. The outcomes of indoor vector control (IVC) strategies, such as long-lasting insecticide-treated nets (LLINs) and indoor residual sprays (IRSs), are heavily influenced by individual and community-level perceptions and acceptance. These perceptions, and therefore product acceptance, are largely influenced by the successful suppression of non-target nuisance pests such as bed bugs and cockroaches. Adoption and consistent use of LLINs and IRS is responsible for immense reductions in the prevalence and incidence of malaria. However, recent observations suggest that failed control of indoor pests, leading to product distrust and abandonment, may threaten vector control programme success and further derail already slowed progress towards malaria elimination. We review the evidence of the relationship between IVC and nuisance pests and discuss the dearth of research on this relationship. We make the case that the ancillary control of indoor nuisance and public health pests needs to be considered in the development and implementation of new technologies for malaria elimination.

Bed bug control with various dusts: Efficacy comparison between silicon dioxide, diatomaceous earth, and Sommières earth

Bed bugs are considered a major public health problem in industrialized countries. Usually, bed bug infestations are managed using a combination of physical and chemical methods. In recent years, new strategies for bed bug control have emerged, particularly the use of dusts like diatomaceous earth and silicon dioxide. However, in Europe, the use of silicon dioxide is restricted to professional, while diatomaceous earth can be harmful to the lungs. This study aimed to assess bed bug mortality rates associated with Sommières earth, green clay, talc, and sodium bicarbonate compared to silicon dioxide and diatomaceous earth from a pest management company, diatomaceous earth for litter conditioner, and diatomaceous earth from a supermarket. We tested permanent exposure, short exposure, horizontal transfer and repellent effect on two bed bug colonies. Sommières earth demonstrated efficacy ranging from 75% to 100% in permanent and short exposures, similar to the efficacy of diatomaceous earth from the pest management company. On the contrary, diatomaceous earth for litter conditioner and diatomaceous earth from a supermarket, green clay, talc, and sodium bicarbonate were found to be ineffective. This study demonstrates, for the first time, the efficacy of Sommières earth against bed bugs, but also highlights the variability in efficacy of diatomaceous earths on bed bugs depending on their quality.

Trends in poisoning associated with the use of insecticides for bed bug infestations: a 20-year retrospective study in France

Bed bugs are pervasive global pests that have reemerged in the last 20 years as a significant public health concern, especially in densely populated urban areas. Beyond financial losses, expenses, inconvenience, and psychological distress, bed bug infestations often necessitate chemical management, posing poisoning risks to those with an infestation. The French Poison Control Centers recorded 1056 cases of exposure to bed bug insecticide products between 1999 and 2021. This study followed cases over 2007-2021, with a notable surge in reports of adverse reactions from 2016 onwards. Data revealed an increased recurrent misuse of insecticides, including substances banned or not approved for this use. Our findings underscore the growing public reliance on chemical insecticides for home bed bug management. With this is the concern of increased poisoning risks, and potential long-term health consequences from non-professional efforts by the public to manage bed bugs in their homes. This escalating trend emphasizes the need for safer and more sustainable pest management strategies in urban environments.

Repellency of N,N-diethyl-3-methylbenzamide (DEET) during host-seeking behavior of bed bugs (Hemiptera: Cimicidae) in binary choice olfactometer assays

The bed bug (Cimex lectularius L.) is one of the most prolific and burdensome indoor pests, and suppression of bed bug populations is a global priority. Understanding bed bug behavior is important to the development of new tactics for their control. Major gaps exist in our understanding of how host cues, insecticide resistance, and exposure modality impact the repellency of formulated products to bed bugs. Here, we validate the use of a binary choice olfactometer for assessing bed bug repellency behaviors using N,N-diethyl-3-methylbenzamide (DEET) in a dose-dependent manner, while considering the role of host-associated stimuli (with vs. without CO2), exposure modality (olfactory vs. olfactory and contact), and resistance status (susceptible vs. resistant) on repellency. We observed that host-seeking insecticide-susceptible bed bugs were repelled only when olfactorily exposed to high concentrations of DEET. However, exposure to DEET by contact repelled insecticide-susceptible bed bugs at 100-fold lower dose of DEET. Further, we demonstrate for the first time that insecticide-resistant bed bugs were significantly more responsive to DEET than susceptible bed bugs. We conclude that the 2-choice olfactometer is an effective tool for assessing the behavioral responses of bed bugs to spatial and contact repellents.

Development, feeding, and sex shape the relative quantity of the nutritional obligatory symbiont Wolbachia in bed bugs

The common bed bug, Cimex lectularius, is a hemipteran insect that feeds only on blood, and whose bites cause public health issues. Due to globalization and resistance to insecticides, this pest has undergone a significant and global resurgence in recent decades. Blood is an unbalanced diet, lacking notably sufficient B vitamins. Like all strict hematophagous arthropods, bed bugs host a nutritional symbiont supplying B vitamins. In C. lectularius, this nutritional symbiont is the intracellular bacterium Wolbachia (wCle). It is located in specific symbiotic organs, the bacteriomes, as well as in ovaries. Experimental depletion of wCle has been shown to result in longer nymphal development and lower fecundity. These phenotypes were rescued by B vitamin supplementation. Understanding the interaction between wCle and the bed bug may help to develop new pest control methods targeting the disruption of this symbiotic interaction. The objective of this work was thus to quantify accurately the density of wCle over the life cycle of the host and to describe potential associated morphological changes in the bacteriome. We also sought to determine the impact of sex, feeding status, and aging on the bacterial population dynamics. We showed that the relative quantity of wCle continuously increases during bed bug development, while the relative size of the bacteriome remains stable. We also showed that adult females harbor more wCle than males and that wCle relative quantity decreases slightly in adults with age, except in weekly-fed males. These results are discussed in the context of bed bug ecology and will help to define critical points of the symbiotic interaction during the bed bug life cycle.

Species identification and pyrethroid resistance genotyping of recently resurgent Cimex lectularius and Cimex hemipterus in Korea

The global resurgence of bed bug infestations, exacerbated by increasing international travel, trade, and insecticide resistance, has significantly impacted Korea. This study identified the bed bug species and performed pyrethroid resistance genotyping of recently resurgent bed bugs in Korea. Thirty-one regional bed bug samples were collected from 5 administrative regions: Gyeonggi-do (n=14), Seoul (n=13), Busan (n=2), Jeonllanam-do (n=1), and Chungcheongbuk-do (n=1). The samples underwent morphological and molecular identification. Twenty-four regional samples (77.4%) were identified as the tropical bed bug, Cimex hemipterus, and the remaining 7 regional samples (22.6%) were identified as the common bed bug, Cimex lectularius. The C. hemipterus regional samples carried at least three mutations associated with knockdown resistance (kdr), including 2 super-kdr mutations. The 7 C. lectularius regional samples possessed at least one of the 3 kdr-related mutations associated with pyrethroid resistance. This study confirms that the prevalent bed bug species recently in Korea is C. hemipterus, replacing the previously endemic C. lectularius. Additionally, the rise in bed bug populations with pyrethroid resistance underscores the necessity of introducing alternative insecticides.

Optimization and establishment of laboratory rearing conditions for Cimex lectularius L. against variable temperature and relative humidity

Emerging infestations of bed bugs are affecting normal human lifestyle globally. This study has been designed to optimize the rearing conditions for Cimex lectularius L. (Hemiptera), to support the scientific research on them. Bed bugs have been projected onto three different temperature (20 °C, 25 °C, and 30 °C) and relative humidity (50%, 70%, and 90%) conditions to check their overall growth and survival rate. Adult mortality, weight loss, egg laying, percentage hatching, hatching initiation and completion, nymph mortality, and molting have been evaluated to optimize the best conditions. The temperature at 25 °C with 90% RH showed minimum mortality for adults (female 13.33 ± 3.33% and male 6.67 ± 3.33%) and nymphs (13.33 ± 3.33%), while maximum egg laying (40.33 ± 1.86), with highest percentage hatching (98.23 ± 0.58%). At 30 °C with 90% RH, hatching initiation and completion (5.19 ± 0.12 days and 7.23 ± 0.16 days) as well as molting initiation and completion (3.73 ± 0.12 days and 7.00 ± 0.24 days) were found to be fastest. Thus, it can be concluded that 25 °C with 90% RH is ideal for rearing of adults and 30 °C with 90% RH is appropriate for rapid growth of nymphs.

Strong resistance to β-cyfluthrin in a strain of the beetle Alphitobius diaperinus: a de novo transcriptome analysis

The lesser mealworm, Alphitobius diaperinus, is an invasive tenebrionid beetle and a vector of pathogens. Due to the emergence of insecticide resistance and consequent outbreaks that generate significant phytosanitary and energy costs for poultry farmers, it has become a major insect pest worldwide. To better understand the molecular mechanisms behind this resistance, we studied a strain of A. diaperinus from a poultry house in Brittany that was found to be highly resistant to the β-cyfluthrin. The strain survived β-cyfluthrin exposures corresponding to more than 100 times the recommended dose. We used a comparative de novo RNA-Seq approach to explore genes expression in resistant versus sensitive strains. Our de novo transcriptomic analyses showed that responses to β-cyfluthrin likely involved a whole set of resistance mechanisms. Genes related to detoxification, metabolic resistance, cuticular hydrocarbon biosynthesis and proteolysis were found to be constitutively overexpressed in the resistant compared to the sensitive strain. Follow-up enzymatic assays confirmed that the resistant strain exhibited high basal activities for detoxification enzymes such as cytochrome P450 monooxygenase and glutathione-S-transferase. The in-depth analysis of differentially expressed genes suggests the involvement of complex regulation of signaling pathways. Detailed knowledge of these resistance mechanisms is essential for the establishment of effective pest control.

Population genetics as a tool to understand invasion dynamics and insecticide resistance in indoor urban pest insects

Many indoor urban pest insects now show a near-global distribution. The reasons for this may be linked to their cryptic behaviors, which make unintentional transport likely, tied to their reliance on human-mediated dispersal that can result in spread over potentially long-distances. Additionally, numerous species exhibit an array of mechanisms that confer insecticide resistance. Using population genetics, it is possible to elucidate the genetic characteristics that define globally successful indoor urban pest insect species. Furthermore, this approach may be used to determine the frequency and distribution of insecticide resistance. Here, I review the recent literature that utilizes population genetic analyses in an effort to identify the characteristics that help explain the success of indoor urban pests.

Key Contributions of the Overexpressed Plutella xylostella Sigma Glutathione S-Transferase 1 Gene (PxGSTs1) in the Resistance Evolution to Multiple Insecticides

The overexpression of insect detoxification enzymes is a typical adaptive evolutionary strategy for insects to cope with insecticide pressure. In this study, we identified a glutathione S-transferase (GST) gene, PxGSTs1, that exhibited pronounced expression in the field-resistant population of Plutella xylostella. By using RNAi (RNA interference), the transgenic fly models, and quantitative real-time polymerase chain reaction (RT-qPCR) methods, we confirmed that the augmented expression of PxGSTs1 mediates the resistance of P. xylostella to various types of insecticides, including chlorantraniliprole, novaluron, λ-cyhalothrin, and abamectin. PxGSTs1 was found to bolster insecticide resistance in two ways: direct detoxification and enhancing antioxidative defenses. In addition, our findings demonstrated that pxy-miR-8528a exerts a pivotal influence on forming insecticide resistance in P. xylostella by downregulating PxGSTs1 expression. In summary, we elucidated the multifaceted molecular and biochemical underpinnings of PxGSTs1-driven insecticide resistance in P. xylostella. Our results provide a new perspective for understanding the insecticide resistance mechanism of P. xylostella.

Effectiveness of heat treatment in rapid control of bed bugs in environmental conditions resembling their natural habitats

We evaluated lethal temperatures and times for killing bed bugs in diverse covered and uncovered conditions simulating their natural habitats. A total of 5400 adult bed bugs were collected alive from 17 infested locations in Paris. They were morphologically identified in laboratory as Cimex lectularius. They were then distributed in multiple sets of 30 specimens to examine in covered (tissue, furniture, mattress or blanket) and uncovered (direct exposure) conditions and in diverse step-function temperatures (50, 55 and 60°C) and times (15, 30, 60 and 120 minutes), replicated three times. Effective mortality was observed in 1080 specimens exposed directly to 50°C for 60 minutes. In specimens covered by tissue (1080 specimens), furniture (1080) or mattress (1080), all were dead at 60°C within 60 minutes. The specimens covered by blanket (1080) at the same temperature were dead after 120 minutes. A 60-minutes delay in reaching to lethal temperature within blanket compared to uncovered thermometer was observed.

The Emergence and Sustainability of Urban Entomology

Urban entomology is the study of arthropod and other pests of the urban environment. It has gained worldwide recognition as a distinct discipline. Its origin is associated with Walter Ebeling's publication Urban Entomology in 1975. Urbanization, invasive pests, increased demand for pest management services, and changes in legislation collided in the 1970s to create a need for research and extension activities worldwide. This resulted in urban entomology as a discipline and, within two decades, its national and international recognition. In this review, we present the factors that led to the development of urban entomology and how they have shaped its current meaning. As urbanization intensifies and the global economy increases, the demands for urban pest management will continue to grow. We discuss how these future challenges may shape and alter the discipline.

A cuticular protein, BgCPLCP1, contributes to insecticide resistance by thickening the cockroach endocuticle

Overuse of insecticides has led to severe environmental problems. Insect cuticle, which consists mainly of chitin, proteins and a thin outer lipid layer, serves multiple functions. Its prominent role is as a physical barrier that impedes the penetration of xenobiotics, including insecticides. Blattella germanica (L.) is a major worldwide indoor pest that causes allergic disease and asthma. Extensive use of pyrethroid insecticides, including β-cypermethrin, has selected for the rapid and independent evolution of resistance in cockroach populations on a global scale. We demonstrated that BgCPLCP1, the first CPLCP (cuticular proteins of low complexity with a highly repetitive proline-rich region) family cuticular protein in order Blattodea, contributes to insecticide penetration resistance. Silencing BgCPLCP1 resulted in 85.0 %-85.7 % and 81.0 %-82.0 % thinner cuticle (and especially thinner endocuticle) in the insecticide-susceptible (S) and β-cypermethrin-resistant (R) strains, respectively. The thinner and more permeable cuticles resulted in 14.4 % and 20.0 % lower survival of β-cypermethrin-treated S- and R-strain cockroaches, respectively. This study advances our understanding of cuticular penetration resistance in insects and opens opportunities for the development of new efficiently and environmentally friendly insecticides targeting the CPLCP family of cuticular proteins.

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.

The common bed bug Cimex lectularius synthesizes hemozoin as an essential defense against the toxic effects of heme

The common bed bug Cimex lectularius (Linnaeus 1758) is an ectoparasite that feeds preferably on human blood, being considered an important public health issue. Blood-feeding is a challenging process for hematophagous organisms, and one of the inherent risks with this kind of diet is the liberation of high doses of free heme after the digestion of hemoglobin. In order to deal with this potent cytotoxic agent, such organisms have acquired different defense mechanisms. Here, we use UV-visible spectrophotometry and infrared spectroscopy to show that C. lectularius crystalizes free heme to form the much less dangerous compound, hemozoin. According to our results, the peak of formation of hemozoin in the intestinal contents occurred 4-5 days after the blood meal, primarily in the posterior midgut. The quantification of the rate of conversion of heme to hemozoin revealed that at the end of digestion all the heme was in the form of hemozoin. Inhibition of the synthesis of hemozoin using the anti-malarial drug quinine led to an increase in both catalase activity in the intestinal epithelium and the mortality of the bed bugs, indicating that the insects were unable to cope with the oxidative stress generated by the overload of free heme. The data presented here show for the first time how C. lectularius deals with free heme, and how the process of formation of hemozoin is essential for the survival of these insects. Since resistance to insecticides is a common feature among field populations of bed bugs, there is an urgent need to develop alternative control methods. Thus, targeting the synthesis of hemozoin emerges as a possible novel strategy to fight bed bugs.

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

Background

Bedbugs are nocturnal ectoparasites that have made a comeback after 20 years and have become one of the main challenges for pest control methods worldwide. Monitoring chemical pesticide resistance is crucial for identifying the best bed bugs management strategies to effectively manage arthropods. This study aims to assess the susceptibility of Cimex hemipterus (Hemiptera: Cimicidae) collected from different parts of Khorasan-Razavi Province, (northeast of Iran) to deltamethrin (pyrethroid), phoxim (organothiophosphate) and propetamphos (phosphoramidate).

Methods

This study was conducted from Dec 2020 to May 2021. The efficacy of three insecticides (deltamethrin, phoxim, and propetamphos) on adult C.hemipterus was assessed using a bioassay method recommended by the World Health Organization (WHO),. Concentrations of deltamethrin used were 10, 20, 40, 80, 160, 320, 640, 1280, and 2560 ppm, while concentrations of phoxim and propetamphos were 10, 40, 160, and 320 ppm. The bed bugs were continuously exposed to the insecticide for 24 hours, and mortality was assessed at regular intervals during the observation period. The concentration-response data were subjected to POLO-PC software and data were analyzed by the one-way and two-way ANOVA procedures.

Results

The lethal concentration fifty values of deltamethrin, phoxim and propetamphos on the examined bed bugs were 0.551, 0.148 and 0.237 ppm, respectively. Insecticide effects of phoxim were significantly higher (P≤ 0.05) compared to each of either deltamethrin and propetamphos agents.

Conclusion

The insecticide effects of phoxim against bed bugs were significantly higher compared to each of either deltamethrin or propetamphosinsecticides.

Are the issues involving acephate already resolved? A scientometric review

Acephate is a pesticide classified as moderately toxic, and its metabolite methamidophos is highly toxic for mammals and birds; even so, it is one of the most used insecticides in pest control for agricultural and domestic use. Acephate toxicity affects both target and non-target organisms and causes serious damage to the environment. There are several studies on different perspectives of acephate, such as monitoring, toxicity, and modeling. In this sense, this research aims to identify the structure of intellectual production on acephate and analyze the gaps and trends of scientific production on acephate through a scientometric analysis. The data was obtained from the Web of Science database, and after the refinement, 1.085 documents were used. A temporal pattern of the main research objectives is displayed. Most selected studies evaluated acephate efficiency, followed by toxicity and residue detection methods. The USA, China, India, Brazil, and Japan had the highest number of publications on acephate. The keywords most utilized were pesticides, toxicity, insecticide resistance, and residue. Research involving acephate requires greater attention from areas such as ecotoxicology, biochemistry, genetics, and biotechnology. There needed to be more discussions on chronic toxicity, genotoxicity, and cytotoxicity. Moreover, few studies about metabolic and biochemical pathways and genes related to acephate action and biodegradation were scarce.

Overexpression of the Chemosensory Protein CSP7 Gene Contributed to Lambda-Cyhalothrin Resistance in the Bird Cherry-Oat Aphid Rhopalosiphum padi

Lambda-cyhalothrin is one of the most important pyrethroids used for controlling wheat aphids. Extensive spraying of lambda-cyhalothrin has led to the development of high resistance to this pyrethroid inRhopalosiphum padi. The mechanisms of resistance are complex and not fully understood. In this study, we found that a laboratory-selected strain of R. padi showed extremely high resistance to lambda-cyhalothrin and cross-resistance to bifenthrin and deltamethrin. The expression level of RpCSP7 was significantly elevated in the resistant strain compared to that in the susceptible strain. Knockdown of RpCSP7 increased the susceptibility of R. padi to lambda-cyhalothrin, whereas the susceptibility to bifenthrin and deltamethrin was not significantly changed. The recombinant RpCSP7 displayed a high affinity for lambda-cyhalothrin but no affinities to bifenthrin and deltamethrin. These findings suggest that the overexpression of RpCSP7 contributes to the resistance of R. padi to lambda-cyhalothrin. This study provides valuable insights into CSP-mediated insecticide resistance in insects.

Geographical survey of the mycobiome and microbiome of Southern California glassy-winged sharpshooters

The glassy-winged sharpshooter, Homalodisca vitripennis Germar, is an invasive xylem-feeding leafhopper with a devastating economic impact on California agriculture through transmission of the plant pathogen, Xylella fastidiosa. While studies have focused on X. fastidiosa or known symbionts of H. vitripennis, little work has been done at the scale of the microbiome (the bacterial community) or mycobiome (the fungal community). Here, we characterize the mycobiome and the microbiome of H. vitripennis across Southern California and explore correlations with captivity and host insecticide resistance status. Using high-throughput sequencing of the ribosomal internal transcribed spacer 1 region and the 16S rRNA gene to profile the mycobiome and microbiome, respectively, we found that while the H. vitripennis mycobiome significantly varied across Southern California, the microbiome did not. We also observed a significant difference in both the mycobiome and microbiome between captive and wild H. vitripennis. Finally, we found that the mycobiome, but not the microbiome, was correlated with insecticide resistance status in wild H. vitripennis. This study serves as a foundational look at the H. vitripennis mycobiome and microbiome across Southern California. Future work should explore the putative link between microbes and insecticide resistance status and investigate whether microbial communities should be considered in H. vitripennis management practices. IMPORTANCE The glassy-winged sharpshooter is an invasive leafhopper that feeds on the xylem of plants and transmits the devastating pathogen, Xylella fastidiosa, resulting in significant economic damage to California's agricultural system. While studies have focused on this pathogen or obligate symbionts of the glassy-winged sharpshooter, there is limited knowledge of the bacterial and fungal communities that make up its microbiome and mycobiome. To address this knowledge gap, we explored the composition of the mycobiome and the microbiome of the glassy-winged sharpshooter across Southern California and identified differences associated with geography, captivity, and host insecticide resistance status. Understanding sources of variation in the microbial communities associated with the glassy-winged sharpshooter is an important consideration for developing management strategies to control this invasive insect. This study is a first step toward understanding the role microbes may play in the glassy-winged sharpshooter's resistance to insecticides.

Laboratory Insecticide Efficacy Trials of Lethal Harborages for Control of the Common Bed Bug, Cimex lectularius (Hemiptera: Cimicidae)

Over the past two decades, there has been a worldwide resurgence in the bed bugs Cimex lectularius L. and Cimex hemipterus (F.). This is primarily due to insecticide resistance, making bed bug management and eradication challenging and expensive. To address the need for more affordable control solutions, "lethal harborages" were explored. Cardboard squares were treated using insecticidal dusts at different dosage levels, including silica dioxide, diatomaceous earth, deltamethrin, permethrin, and fipronil. Two strains of C. lectularius, one susceptible and one resistant, were allowed to enter the treated harborages, and mortality rates were recorded daily. The silica dioxide products proved to be the most efficacious, consistently achieving 100% mortality between 14-17 d at the highest dose. An artificial environment trial using the "new ChinChex®" formulation of silica dioxide resulted in the complete elimination of bed bugs in the treated harborages within 21 d. These findings suggest that lethal harborages, especially those impregnated with silica dioxide, offer a cost-effective solution that could be incorporated into broader integrated bed bug management strategies. This approach may help alleviate the burden of bed bug infestations in economically disadvantaged communities.

Characterization of the common bed bug's eggshell and egg glue proteins

An insect egg is one of the most vulnerable stages of insect life, and the evolutionary success of a species depends on the eggshell protecting the embryo and the egg glue securing the attachment. The common bed bug (Cimex lectularius), notorious for its painful and itchy bites, infests human dwellings to feed on blood. They are easier to find these days as they adapt to develop resistance against commonly used insecticides. In this study, we identify and characterize the eggshell protein and the probable egg glue protein (i.e. keratin associated protein 5-10 like protein) of the bed bug by using mass spectrometry and bioinformatics analysis. Furthermore, by using transcription profiling and in vivo RNA interference, we show evidences that the keratin associated protein 5-10 like protein functions as the glue protein. Finally, structural characterizations on the two proteins are performed using recombinant proteins. Amino acid sequences of various insect eggshell and egg glue proteins support their independent evolution among different insect groups. Hence, inhibiting the function of these proteins related to the earliest stage of life can achieve species-specific population control. In this respect, our results would be a starting point in developing new ways to control bed bug population.

Survey of bed bug infestations in homeless shelters in southern France

Bed bug has become a major public health pest worldwide. Infestation may result in numerous negative health effects. Homeless shelters are one of the most habitats that can be infested with bed bugs, a few studies have focused on bed bug infestations in these settings. We conducted a survey of infestations of bed bugs in a homeless shelter in southern France, using an innovative seven-level scale (0-6) to assess the degree of infestation, MALDI TOF-MS to identify bed bugs, and a biomolecular tool to detect bacteria. Bed bug infestations were documented in 13% (9/68) of investigated rooms. A total of 184 bed bugs were collected and morphologically identified as Cimex lectularius. MALDI TOF-MS analysis allowed us to obtain high-quality MS spectra for all 184 specimens, to correctly identify all specimens, and included 178/184 (97%) Log Score Values higher than 1.8. Among the bacteria tested, Wolbachia sp. DNA was found in 149/184 (81%) of the bed bugs, and one sample was positive for Coxiella burnetii, the agent of Q fever. Our study is the first of its kind that offers new perspectives for increasing public awareness of the conditions in homeless shelters.

Identification of cuticular protein genes and analysis of their roles in phosphine resistance of the rusty grain beetle Cryptolestes ferrugineus

The rusty grain beetle, Cryptolestes ferrugineus (Stephens) is one of the most economically important stored grain pests, and it has evolved the high resistance to phosphine. Cuticular proteins (CPs) are the major structural components of insect cuticle, and previous studies have confirmed that CPs were involved in insecticide resistance. However, the CPs of C. ferrugineus are still poorly characterized, and thus we conducted transcriptome-wide identification of CP genes and analyze their possible relationships with phosphine resistance in this pest. In this study, a total of 122 putative CPs were annotated in the C. ferrugineus transcriptome data by blasting with the known CPs of Tribolium castaneum. The analysis of conserved motifs revealed these CPs of C. ferrugineus belonging to 9 different families, including 87 CPR, 13 CPAP1, 7 CPAP3, 3 Tweedle, 1 CPLCA, 1 CPLCG, 5 CPLCP, 2 CPCFC, and 3 CPFL proteins. The further phylogenetic analysis showed the different evolutionary patterns of CPs. Namely, we found some CPs (CPR family) formed species-specific protein clusters, indicating these CPs might occur independently among insect taxa, and while some other CPs (CPAP1 and CPAP3 family) shared a closer correlation based on the architecture of protein domains. Subsequently, the previous RNA-seq data were applied to establish the expression profiles of CPs in a phosphine susceptible and resistant populations of C. ferrugineus, and a large amount of CP genes were found to be over-expressed in resistant insects. Lastly, an up-regulated CP gene (CPR family) was selected for the further functional analysis, and after this gene was silenced via RNA interference (RNAi), the sensitivity to phosphine was significantly enhanced in C. ferrugineus. In conclusion, the present results provided us an overview of C. ferrugineus CPs, and which suggested that the CPs might play the critical roles in phosphine resistance.

Perception, attitudes, and knowledge on infestation and management of bed bugs in major cities of Indonesia: A cross-sectional online survey

The resurgence of bed bugs is a global phenomenon, but until now reports on bed bug infestations in Indonesia are rare. The success of bed bug control is affected by people's knowledge and awareness. Stigma against bed bugs in Indonesia discourages the public from reporting infestations and therefore knowledge of their impact on public health is scarce. Herein, this study investigates the public's perception, attitudes, and knowledge on bed bug-related issues in several major cities in Indonesia through an online survey. Despite low case reports, three in five respondents (n = 600) have encountered bed bugs at least once; mostly in their homes (74.1%). Approximately half of the respondents correctly identified bed bugs, whereas mites were often misidentified for bed bugs (26.3%). Bite marks were not a useful indicator for detecting bed bugs. We found age, gender, and level of education affects the public's perception toward various bed bug-related issues. Regarding bed bug treatment, above 50% respondents are unaware of the availability of bed bug-specific insecticidal products and are unwilling to pay pest management professionals to control infestation. This study provides the first overview of the public's awareness and perception of bed bug infestations in some major cities of Indonesia, which can be useful for designing public health policies for bed bug management. The reported data represents the perspectives of online users, most likely from metropolitan regions. A bigger monitoring program encompassing pest professionals and hospitality businesses would give a more thorough overview of the bed bug impact in Indonesia.

The first recent case of Cimex hemipterus (Hemiptera: Cimicidae) with super-kdr mutations in the Republic of Korea

With the increase in international travel and trade, in conjunction with the development of insecticide resistance, infestations of Cimex lectularius (L.) and Cimex hemipterus (F.) (Hemiptera: Cimicidae) have resurged globally in the last 2 decades. Recently, it was reported that C. hemipterus was also found in temperate regions, indicating the possibility of its expansion outside tropical regions. Cimex hemipterus has not been officially recorded in Korea since its initial description in 1934. Here, we report the first recent case of C. hemipterus in Korea based on morphological and molecular identification. Partial sequencing of the voltage-sensitive sodium channel gene revealed super-kdr mutations (M918I and L1014F) that are associated with pyrethroid resistance. This case report serves as a warning to intensify the bed bug surveillance system in Korea regarding the presence of C. hemipterus and to prepare effective alternative insecticides for pyrethroids.

Bed Bugs (Hemiptera, Cimicidae): A Global Challenge for Public Health and Control Management

Bed bugs, Cimex lectularius, and C. hemipterus are among the most common ectoparasites in human life worldwide. They feed on humans of all ages and sexes across all socioeconomic levels. Bed bugs' blood feeding is responsible for a wide range of clinical manifestations varying from minor reactions to bullous eruptions or severe allergies. In addition, they are responsible for considerable psychological distress. Therefore, diagnosis of bed bug bites and their consequence manifestations is beneficial in adapting remedies and treatment protocols advised by clinicians. So far, there is regrettably no definitive way to control these ectoparasites despite extensive efforts of public health authorities to manage them. An overview of the literature and medical documents gathered from bed bug-infested patients referred to the Parasitology and Dermatology departments of Avicenne Hospital (Bobigny, France) allowed us to document and illustrate a range of clinical disorders and psychological concerns caused by bed bugs' bites and their clinical diagnosis. We also review the available tools currently used to control the bed bugs and present potential candidate methods for their successful eradication.

Expression and purification of snustorr snarlik protein from Plutella xylostella

Snustorr snarlik (Snsl) is a type of extracellular protein essential for insect cuticle formation and insect survival, but is absent in mammals, making it a potential selective target for pest control. Here, we successfully expressed and purified the Snsl protein of Plutella xylostella in Escherichia coli. Two truncated forms of Snsl protein, Snsl 16-119 and Snsl 16-159, were expressed as a maltose-binding protein (MBP) fusion protein and purified to a purity above 90% after a five-step purification protocol. Snsl 16-119, forming stable monomer in solution, was crystallized, and the crystal was diffracted to a resolution of ∼10 Å. Snsl 16-159, forming an equilibrium between monomer and octamer in solution, was shown to form rod-shaped particles on negative staining electron-microscopy images. Our results lay a foundation for the determination of the structure of Snsl, which would improve our understanding of the molecular mechanism of cuticle formation and related pesticide resistance and provide a template for structure-based insecticide design.

Status of Acaricide Resistance and Detecting the Knockdown Resistance Mutation T2134A in the Cattle Tick Rhipicephalus microplus (Acari: Ixodidae) from Northeastern Mexico

Rhipicephalus microplus is the most important tick in veterinary medicine, given its repercussions on animal production. The principal strategy to avoid adverse effects associated with R. microplus is the chemical control of tick populations through organosynthetic acaricides. Therefore, monitoring susceptibility to acaricides is paramount in any control program. This study aimed to analyze the resistance status of 2 populations of R. microplus from northeastern Mexico to the organochlorine (OC) lindane, organophosphates (OP) coumaphos, chlorfenvinphos, diazinon, and chlorpyrifos, and the synthetic pyrethroids (SPs) flumethrin, deltamethrin, and cypermethrin. Discriminating doses (DD) of each acaricide were used in the larval packet bioassay (LPT). Additionally, the presence of the knockdown resistance (kdr) mutation T2134A associated with pyrethroid resistance was evaluated using allele-specific polymerase chain reaction (PCR). The populations of R. microplus showed a high frequency of resistance to SP, with mortality rates of less than 5%; they also showed resistance to the OPs (diazinon and chlorpyrifos) with mortality rates ranging from 1.29% to 34.62%; meanwhile, they were susceptible to coumaphos and chlorfenvinphos. Mortality rates higher than 66% were observed for lindane, indicating susceptibility. The mutant allele of the kdr mutation T2134A was detected in 75% and 100% of the pools analyzed. The populations studied presented a highly resistant profile to pyrethroids, with the presence of the kdr mutant allele A2134. The susceptibility to the organophosphates such as coumaphos and chlorfenvinphos of R. microplus from northeastern Mexico should be noted.

Development of an efficient insecticide substrate and inhibitor screening system of insect P450s using fission yeast

Metabolic resistance is one of the most frequent mechanisms of insecticide resistance, characterized by an increased expression of several important enzymes and transporters, especially cytochrome P450s (CYPs). Due to the large number of P450s in pests, determining the precise relationship between these enzymes and the insecticide substrates is a challenge. Herein, we developed a luminescence-based screening system for efficient identification of insecticide substrates and insect P450 inhibitors. We recombinantly expressed Bemisia tabaci CYP6CM1vQ (Bt CYP6CM1vQ) in the fission yeast Schizosaccharomyces pombe and subsequently permeabilized the yeast cells to convert them into "enzyme bags". We exploited these enzyme bags to screen the activity of twelve luciferin substrates and identified Luciferin-FEE as the optimal competing probe that was further used to characterize the metabolism of eight candidate commercial insecticides. Among them, Bt CYP6CM1vQ exhibited notable activity against pymetrozine and imidacloprid. Their binding modes were predicted by homology modeling and molecular docking, revealing the mechanisms of the metabolism. We also tested the inhibitory effect of eight known P450 inhibitors using our system and identified letrozole and 1-benzylimidazole as showing significant activity against Bt CYP6CM1vQ, with IC₅₀ values of 23.74 μM and 1.30 μM, respectively. Their potential to be developed as an insecticide synergist was further proven by an in vitro toxicity assay using imidacloprid-resistant Bemisia tabaci. Overall, our luciferin-based enzyme bag method is capable of providing a robust and efficient screening of insect P450 substrates and, more importantly, inhibitors to overcome the resistance.

A major 6 Mb superlocus is involved in pyrethroid resistance in the common bed bug Cimex lectularius

In the last few years, the bed bug Cimex lectularius has been an increasing problem worldwide, mainly due to the development of insecticide resistance to pyrethroids. The characterization of resistance alleles is a prerequisite to improve surveillance and resistance management. To identify genomic variants associated with pyrethroid resistance in Cimex lectularius, we compared the genetic composition of two recent and resistant populations with that of two ancient-susceptible strains using a genome-wide pool-seq design. We identified a large 6 Mb "superlocus" showing particularly high genetic differentiation and association with the resistance phenotype. This superlocus contained several clustered resistance genes and was also characterized by a high density of structural variants (inversions, duplications). The possibility that this superlocus constitutes a resistance "supergene" that evolved after the clustering of alleles adapted to insecticide and after reduction in recombination is discussed.

Insecticidal and Synergistic Potential of Three Monoterpenoids against the Yellow Fever Mosquito, Aedes aegypti (Diptera: Culicidae), and the House Fly, Musca domestica (Diptera: Muscidae)

As resistance to the limited number of insecticides available for medical and veterinary pests becomes more widespread, there is an urgent need for new insecticides and synergists on the market. To address this need, we conducted a study to assess the toxicity of three monoterpenoids—carvone, menthone, and fenchone—in comparison to permethrin and methomyl against adults of two common pests: the yellow fever mosquito (Aedes aegypti) and the house fly (Musca domestica). We also examined the potential for these monoterpenoids to enhance the effectiveness of permethrin and methomyl when used together. Finally, we evaluated the ability of each monoterpenoid to inhibit acetylcholinesterase, comparing them to methomyl. While all three monoterpenoids performed relatively poorly as topical insecticides (LD50 > 4000 ng/mg on M. domestica; >6000 ng/mg on Ae. aegypti), they synergized both permethrin and methomyl as well as or better than piperonyl butoxide (PBO). Carvone and menthone yielded synergistic co-toxicity factors (23 and 29, respectively), which were each higher than PBO at 24 h. Currently, the mechanism of action is unknown. During preliminary testing, symptoms of acetylcholinesterase inhibition were identified, prompting further testing. Acetylcholinesterase inhibition did not appear to explain the toxic or synergistic effects of the three monoterpenoids, with IC50 values greater than 1 mM for all, compared to the 2.5 and 1.7 µM for methomyl on Aedes aegypti and Musca domestica, respectively. This study provides valuable monoterpenoid toxicity and synergism data on two pestiferous insects and highlights the potential for these chemistries in future pest control formulations.

Development and biological evaluation of nanoencapsulated-based pyrethroids with synergists for resistance management of two soybean pests: insights for new insecticide formulations

BACKGROUND

Chemical control is commonly used against Euschistus heros (F.) and Chrysodeixis includens (Walker) in soybean fields in South America. However, previous studies reported that these pests have reduced susceptibility to pyrethroids in Brazil. On this basis, we developed and evaluated nanoencapsulated-based bifenthrin (BFT) and λ-cyhalothrin (LAM) with the synergists piperonyl butoxide (PBO) and diethyl maleate (DEM) for insect resistance management (IRM).

RESULTS

Nanoformulations of BFT and LAM with PBO and DEM presented good physical-chemical characteristics and were stable. The spherical morphology of all systems and the encapsulation efficiency in nanostructured lipid carriers did not change when synergists were added. Nanoencapsulated BFT with DEM applied topically increased the susceptibility of E. heros to BFT by 3.50-fold. Similarly, nanoencapsulated BFT and LAM with PBO in diet-overlay bioassays increased the susceptibility of C. includens to both chemicals by up to 2.16-fold. Nanoencapsulated BFT and LAM with synergists also improve control efficacy of both species, causing higher mortality than commercial products containing these chemistries.

CONCLUSIONS

It is possible to develop nanoencapsulated-based formulations of BFT and LAM with PBO or DEM, and these nanoformulations have the potential to improve control of E. heros and C. includens with recognized low susceptibility to pyrethroids. This study provides updates for designing new insecticide formulations for IRM. © 2022 Society of Chemical Industry.

Metabolic resistance to deltamethrin is mediated by P450 and esterases in common bed bugs Cimex lectularius L. (Heteroptera: Cimicidae)

The infestations of Cimex lectularius L. (Heteroptera: Cimicidae) registered in the last decades have been influenced by several human activities, including international tourism and commerce. Moreover, the development of insecticide resistance and careless pest control strategies contributed to the dispersal of bed bugs. Given the complexity of the topic, distinguishing physiological and molecular mechanisms involved in resistance can help design proper control tools and limit the resistance spread. Here we determined the susceptibility to deltamethrin and imidacloprid in bed bugs collected in Italy. Also, we assessed the role of esterases and P450 monooxygenases by direct enzymatic activity measurement and inhibition by synergism bioassays. Our results showed that the field-collected colony exhibited high resistance ratios to imidacloprid and deltamethrin (757 and >60,000 times, respectively) compared to the susceptible colony. Moreover, resistant bed bugs showed increased activity of esterases and P450 monooxygenases. The synergistic effect of piperonyl butoxide (PBO) suggests the significant contribution of both enzymatic groups as detoxification pathways implicated in pyrethroid-resistant bed bugs. Further investigations are needed to unravel the biochemical and molecular basis involved in the resistant phenotype for developing novel strategies for pest control.

Performance of Pyrethroid-Neonicotinoid Mixture Formulations Against Field-Collected Strains of the Tropical Bed Bug (Hemiptera: Cimicidae) on Different Substrates

The residual performance of two pyrethroid-neonicotinoid mixture formulations: Temprid SC (10.5% beta-cyfluthrin and 21% imidacloprid) and Tandem (3.5% lambda-cyhalothrin and 11.6% thiamethoxam) on two substrates (glass and filter paper) against eight pyrethroid-resistant strains (BM-MY, BP-MY, CH-MY, GL-MY, KL-MY, SAJ-MY, TT-MY, and QLD-AU) of the tropical bed bug, Cimex hemipterus (F.) (Hemiptera: Cimicidae) collected from Malaysia, and Australia were evaluated. The aging effect of treatment residues on glass was also investigated. A susceptible C. lectularius L. strain (Monheim) was used for comparison. Temprid SC showed varying levels of performance against all C. hemipterus strains: TT-MY (PR50 = 6.5-fold, high performance), BM-MY, GL-MY, SAJ-MY, and QLD-AU (12.8-21.6-fold, moderate performance), BP-MY, and KL-MY (48.2-49-fold, poor performance), CH-MY (128.2-fold, very poor performance). On the other hand, Tandem displayed high performance against all C. hemipterus strains (1.8-8.3-fold). Tandem caused faster mortality than Temprid SC for all strains. Temprid SC and Tandem residues killed C. hemipterus significantly faster on glass than filter paper. Compared with fresh residues, the efficacy of Temprid SC residues significantly declined after one week of aging, while the effectiveness of Tandem residues declined after two weeks of aging. Further investigations using the topical assay method with a diagnostic dose of imidacloprid found two strains (CH-MY and GL-MY) resistant to imidacloprid. The six other strains (BM-MY, BP-MY, KL-MY, SAJ-MY, TT-MY, and QLD-AU) were susceptible.

The Efficacy of a Pyrethroid-impregnated Mattress Liner on Multiple International Strains of Cimex lectularius (Hemiptera: Cimicidae) and Cimex hemipterus (Hemiptera: Cimicidae)

Modern bed bugs are resistant to multiple insecticide classes, particularly the pyrethroids. The efficacy of pyrethroid-impregnated mattress liners marketed for bed bug management has been variable. This study evaluated the efficacy of a permethrin-impregnated mattress liner, ActiveGuard, against 24 bed bug strains, consisting of both Cimex hemipterus (F.) and Cimex lectularius L. A 'mat assay', employing an allethrin-impregnated mat, was used to establish the pyrethroid resistance profile of all strains. Three experiments were conducted to evaluate the effect of ActiveGuard exposure on bed bug knockdown: 1) exposing the bed bugs continuously on the liner for up to 24 d, 2) holding the bed bugs on the liner for either 4 or 6 h, and 3) placing a noninsecticide treated fabric above the liner with the bed bugs held continuously on top. Our results indicated that all modern strains (collected within the last 15 years during the current resurgence) were pyrethroid-resistant, although the magnitude of resistance was highly variable between strains. In the continuous exposure study, an incomplete knockdown was recorded for most modern bed bug strains, with some having no knockdown even up to 7 d of constant exposure. In the 4 or 6 h exposure study, the level of knockdown was reduced even further, and very few bed bugs were knocked down in the double fabric study. The results of this study indicate that pyrethroid-impregnated mattress liners are not likely to be effective in the management of most modern bed bug infestations involving either C. hemipterus or C. lectularius.

Perspective on Biology and Management of Bed Bugs: Introduction

Bed bugs are an important group of medical and urban insect pests. They are obligate blood-feeders. Their bites may cause skin irritation and allergic reactions and, under some circumstances, may lead to mental and other health issues. Despite numerous discoveries on the biology of these obnoxious pests and progress in control strategies over the last two decades, bed bugs continue to preferentially plague those from low socioeconomic communities because the poor generally could not afford effective control options. As a result, such infestations in poorer communities serve as a reservoir for wider society. This Special Collection of the Perspective on Biology and Management of Bed Bugs presents nine original research papers on bed bug detection, insecticide performance and resistance, nonchemical treatment, fungal biopesticides, and pest management procurement and contracts. We hope that these investigative findings will spur research on safer, more affordable, and effective control options in the future.

A Case Study on Tropical Bed Bug, Cimex hemipterus (Hemiptera: Cimicidae) Infestation and Management in Dormitories

Numerous bed bug research papers have been published in the past 20 yr as a result of bed bug (Cimex spp.) (Hemiptera: Cimicidae) resurgence in the world. Yet, few of them focused on the management of the tropical bed bug, C. hemipterus (F.). Here, we describe a case of tropical bed bug infestation in two dormitory buildings and effectiveness of a tropical bed bug treatment program. The study site consisted of 125 dormitories in two buildings. An initial building-wide monitoring with ClimbUp interceptors revealed 25 infestations. The spatial distribution of bed bug infested rooms showed a significant aggregated distribution pattern with same infestation status for neighboring units sharing walls. All infested rooms were monitored every 2 wk and treated using a combination of steam and diatomaceous earth (DE) dust application if bed bugs were still found. For the 25 initially identified infested rooms, after 14 wk treatment, 44% of them no longer had bed bugs, and the mean number of bed bugs captured per room decreased by 94.1%. A combination of steam and DE dust treatment is an effective strategy for suppressing tropical bed bug infestations in dormitory environment.

A comprehensive survey of permethrin resistance in human head louse populations from northwest Iran: ex vivo and molecular monitoring of knockdown resistance alleles

BACKGROUND

Head louse infestation is an important public health problem, and expanding resistance to permethrin is a major challenge to its control. The mapping and detection of pyrethroid resistance are essential to the development of appropriate treatments and ensure the effectiveness of current measures. The aim of this study was to present the phenotypic and genotypic basis of permethrin resistance and identify knockdown resistance (kdr) mutations in head louse populations in northwestern Iran.

METHODS

Adult head lice were collected from 1059 infested girls in Ardebil, East Azerbaijan, West Azerbaijan and Zanjan Provinces, northwestern Iran. The toxicity of permethrin and the possible synergistic effect of piperonyl butoxide (PBO) on this toxicity were assessed using bioassays. Fragments of voltage-sensitive sodium channels (vssc) and cytochrome b (cytb) genes were amplified and analyzed for the detection of knockdown resistance (kdr) mutations and mitochondrial groups. Moreover, genotypes of the two hot spot regions of the vssc gene were determined by melting curve analysis of amplicons.

RESULTS

A total of 1450 adult head lice were collected during 2016-2021. Live lice were exposed to a dose of 1% permethrin for 12 h, and the median lethal time (LT₅₀) and time to achieve 90% mortality (LT₉₀) were determined to be 6 and 14.8 h, respectively. Topical application of 2 and 16 ng permethrin per louse resulted in 25% and 42.11% mortality, respectively. Pre-exposure of samples to 3% piperonyl butoxide had no synergistic effect on the effects of permethrin. Analysis of the 774-bp vssc gene fragment showed the presence of the M815I, T917I and L920F mutations, wild-type and T917I mutation, in 91.6%, 4.2% and 4.2% of samples, respectively. Investigation of the mitochondrial cytb gene demonstrated the predominance of clade B. The frequency of domain II segment 4 (S4)-S5 kdr genotypes in mitochondrial groups was identical, and heterozygotes were present in 93.5% of samples. A significant difference was detected in the frequency of domain IIS1-S3 kdr genotypes, and the frequency of resistant alleles and heterozygotes was higher in clade B than in clade A.

CONCLUSIONS

The presence of kdr mutations in the vssc gene and the non-synergist effect of PBO indicate that pyrethroid target site insensitivity is the main resistance mechanism. This phenomenon and the high frequency of resistant alleles necessitate that new pediculosis management programs be developed. Further studies need to be conducted to identify all factors contributing this resistance and to develop alternative pediculicides.

Insecticide Resistance of Cimex lectularius L. Populations and the Performance of Selected Neonicotinoid-Pyrethroid Mixture Sprays and an Inorganic Dust

Insecticide resistance is one of the factors contributing to the resurgence of the common bed bug, Cimex lectularius L. This study aimed to profile the resistance levels of field-collected C. lectularius populations to two neonicotinoids and one pyrethroid insecticide and the performance of selected insecticide sprays and an inorganic dust. The susceptibility of 13 field-collected C. lectularius populations from the United States to acetamiprid, imidacloprid, and deltamethrin was assessed by topical application using a discriminating dose (10 × LD₉₀ of the respective chemical against a laboratory strain). The RR₅₀ based on KT₅₀ values for acetamiprid and imidacloprid ranged from 1.0-4.7 except for the Linden 2019 population which had RR₅₀ of ≥ 76.9. Seven populations had RR₅₀ values of > 160 for deltamethrin. The performance of three insecticide mixture sprays and an inorganic dust were evaluated against three C. lectularius field populations. The performance ratio of Transport GHP (acetamiprid + bifenthrin), Temprid SC (imidacloprid + β-cyfluthrin), and Tandem (thiamethoxam + λ-cyhalothrin) based on LC₉₀ were 900-2017, 55-129, and 100-196, respectively. Five minute exposure to CimeXa (92.1% amorphous silica) caused > 95% mortality to all populations at 72 h post-treatment.

Historical and Contemporary Control Options Against Bed Bugs, Cimex spp

Bed bugs (Hemiptera: Cimicidae) are an important group of obligate hematophagous urban insect pests. The global resurgence of bed bugs, involving the common bed bug, Cimex lectularius L., and the tropical bed bug, Cimex hemipterus (F.), over the past two decades is believed to be primarily due to the development of insecticide resistance, along with global travel and poor pest management, which have contributed to their spread. This review examines and synthesizes the literature on bed bug origins and their global spread and the literature on historical and contemporary control options. This includes bed bug prevention, detection and monitoring, nonchemical and chemical control methodologies (and their limitations), and potential future control options. Future research needs are highlighted, especially the factors behind the modern resurgence, the necessity of identifying differences between the two bed bug species relevant to control, and the need to improve insecticide test protocols and management strategies.

Chitosan–silver nanocomposites as a promising tool for controlling the bed bug: Cimex lectularius (Heteroptera: Cimicidae)

This study evaluates the use of chitosan–silver nanocomposites (CSN) as an insecticide against the bed bug ( Cimex lectularius). Adult bed bugs were collected from infested residential areas and identified using light microscopy and scanning electron microscopy. CSN were prepared and photographed for characterization using transmission electron microscopy, dynamic light scattering, and zeta potential. The insecticidal effect of different concentrations of CSN (400–1000 ppm) was compared to that of 0.1% cypermethrin as a positive control and normal saline as a negative control. The bugs ( n = 25) were immersed for 20 min in the corresponding medium, dried with filter papers, and then incubated at 27–28°C and 70% RH with a 12:12 h light–dark photoperiod. The mortality rates were recorded at different time intervals (2, 4, 6, 12, and 24 h post-incubation (hPI)), and the entire experiment was repeated five times. Image analysis showed round- to spherical-shaped CSN ranging in size from 34 to 72 nm. The mortality rates were positively associated with increasing concentrations of CSN. The mortality rate first reached 100% for concentrations of 800 ppm at 24 hPI and 1000 ppm at 12 hPI. The calculated LC50 was found at a concentration of 1165 ppm at 2 hPI, and the LC99 was found at a concentration of 1914 ppm at 2 hPI. The positive control, cypermethrin, induced 100% mortality among the bugs at 2 hPI, while the negative control caused no mortality. These results clearly show the potential of CSN as an insecticide against C. lectularius. Future studies on best practices for implementing these particles in clinical settings are recommended.

Behavioral interactions of bed bugs with long-lasting pyrethroid-treated bed nets: challenges for vector control

BACKGROUND

Widespread vector control has been essential in reducing the global incidence and prevalence of malaria, despite now stalled progress. Long-lasting insecticide-treated nets (LLINs) have historically been, and remain, one of the most commonly used vector control tools in the campaign against malaria. LLINs are effective only with proper use, adherence, retention and community adoption, which historically have relied on the successful control of secondary pests, including bed bugs. The emergence of pyrethroid-resistant bed bugs in malaria-endemic communities and failure to control infestations have been suggested to interfere with the effective use of LLINs. Therefore, the behavioral interactions of bed bugs with commonly used bed nets should be better understood.

METHODS

To investigate the interactions between bed bugs (Cimex lectularius L.) and LLINs, insecticide-susceptible and pyrethroid-resistant bed bugs were challenged to pass through two commonly used LLINs in two behavioral assays, namely host (blood meal)-seeking and aggregation-seeking assays. The proportions blood-fed and aggregated bed bugs, aggregation time and mortality were quantified and analyzed in different bed bug life stages.

RESULTS

Overall, both the insecticide-susceptible bed bugs and highly resistant bed bugs showed a varying ability to pass through LLINs based on treatment status and net design. Deltamethrin-treated nets significantly impeded both feeding and aggregation by the susceptible bed bugs. While none of the tested LLINs significantly impeded feeding (passage of unfed bed bugs through the nets) of the pyrethroid-resistant bed bugs, the untreated bed net, which has small mesh holes, impeded passage of fed bed bugs. Mortality was only seen in the susceptible bed bugs, with significantly higher mortality on deltamethrin-treated nets (63.5 ± 10.7%) than on permethrin-treated nets (2.0 ± 0.9%).

CONCLUSIONS

Commonly used new LLINs failed to prevent the passage of susceptible and pyrethroid-resistant bed bugs in host- and aggregation-seeking bioassays. The overall low and variable mortality observed in susceptible bed bugs during both assays highlighted the potential of LLINs to impose strong selection pressure for the evolution of pyrethroid resistance. Already, the failure to control bed bug infestations has been implicated as a contributing factor to the abandonment or misuse of LLINs. For the first time to our knowledge, we have shown the potential of LLINs in selecting for resistant secondary pest populations and so their potential role in stalling malaria control programs should be further investigated. The emergence of pyrethroid-resistant bed bugs in malaria-endemic communities may interfere with the effective use of pyrethroid-impregnated bed nets. We assessed the interactions of two bed bug strains with commonly used bed nets using two behavioral assays, namely host (blood meal)-seeking by unfed bed bugs and aggregation-seeking by freshly fed bed bugs. These assays assessed the passage of bed bugs through various bed nets in response to host cues and aggregation stimuli, respectively. Conditioned paper is a section of file folder paper that has been exposed to bed bugs and has been impregnated with feces and aggregation pheromone; it is attractive to aggregation-seeking fed bed bugs. An unconditioned ramp is a similar section of file folder paper that allows bed bugs to traverse the bed net and gain access to a blood-meal source.

Evolutionary trade-offs associated with copy number variations in resistance alleles in Culex pipiens mosquitoes

Organophosphate and carbamate insecticides have largely been used worldwide to control mosquito populations. As a response, the same amino acid substitution in the ace-1 gene (G119S), conferring resistance to both insecticides, has been selected independently in many mosquito species. In Anopheles gambiae, it has recently been shown that the G119S mutation is actually part of homogeneous duplications that associate multiple resistance copies of the ace-1 gene. In this study, we showed that duplications of resistance copies of the ace-1 gene also exist in the Culex pipiens species complex. The number of copies is variable, and different numbers of copies are associated with different phenotypic trade-offs: we used a combination of bioassays and competition in population cages to show that having more resistance copies conferred higher resistance levels, but was also associated with higher selective disadvantage (or cost) in the absence of insecticide. These results further show the versatility of the genetic architecture of resistance to organophosphate and carbamate insecticides around the ace-1 locus and its role in fine-tuned adaptation to insecticide treatment variations.

Efficacy of a topical product combining esafoxolaner, eprinomectin and praziquantel against bedbug (Cimex lectularius) experimental infestations in cats

Bedbugs (Cimex lectularius) are a persistent nuisance pest for humans and their home environment, and may also opportunistically feed on other mammals, including household pets like dogs and cats. NexGard® Combo is a topical endectoparasiticide product for cats combining esafoxolaner, an isoxazoline compound with insecticidal and acaricidal properties, the nematocide eprinomectin and the cestocide praziquantel. The insecticidal efficacy of this product was evaluated in cats experimentally infested with C. lectularius in a blinded, negative controlled and randomized study. Two groups of 7 cats were formed: an untreated control group, and a NexGard® Combo group treated once on Day 0 at the label dose. Cats were then challenged weekly, each with twenty unfed adult C. lectularius, on Days 1, 7, 14, 21 and 28. After close contact with the cat's skin for 15 min, live fed C. lectularius were collected and incubated for 96 h. The weekly efficacy evaluations were based on a comparison of the number of surviving bedbugs in the control and the treated group after 48, 72 and 96 h of incubation. The model was demonstrated to be robust as in the control group the average feeding rate after the 15-minute challenge was 94%, and as 96% of incubated bed bugs were alive after 96 hours of incubation. Significant live bedbug reductions were demonstrated in the Nexgard® Combo treated group: after 96 h of incubation, the reductions ranged from 80.6 to 88.0% during the Day 1 to Day 21 period, and dropped to 58% at Day 28.

Varroa destructor resistance to tau-fluvalinate: relationship between in vitro phenotypic test and VGSC L925V mutation

BACKGROUND

Varroa destructor is a parasitic mite of the honey bee, Apis mellifera. Its presence in colonies can lead to a collapse within a few years. The use of acaricides has become essential to manage the hive infestation. However, the repeated and possibly incorrect use of acaricide treatments, as tau-fluvalinate, has led to the development of resistance. The in vitro phenotypic test allows the proportion of susceptible or resistant individuals to be known following an exposure to an active substance. In Varroa mites, resistance to tau-fluvalinate is associated with the presence of mutations at the position 925 of the voltage-gated sodium channel (VGSC).

RESULTS

Here, we compared the results obtained with an in vitro phenotypic test against tau-fluvalinate and those obtained with an allelic discrimination assay on 13 treated and untreated Varroa populations in France. The correlation between the phenotype and the genetic profile rate is found to be 0.89 Varroa mites having resistant phenotypic profile have a probability of 63% to present the L925V mutation (resistance detection reliability). However, 97% of the Varroa mites having the susceptible phenotype do not present the L925V mutation (susceptible detection reliability).

CONCLUSION

The L925V mutation explains most of the resistance to tau-fluvalinate in V. destructor in the populations tested. However, other mutations or types of resistance may also be involved to explain the survival of Varroa mites in the phenotypic test. © 2022 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Household perception and infestation dynamics of bedbugs among residential communities and its potential distribution in Africa

Bedbugs have experienced an extraordinary upsurge in the recent past across the world. This cross-sectional study aimed to explore the community perception of the pest outbreaks, the population dynamics, and dispersal patterns under different habitat systems. A survey was conducted within communities in nine counties in Kenya, where geographical coordinates of the sites of bedbug presence were recorded and maximum entropy distribution modelling (MaxEnt) was used to map and predict the potentially suitable habitat, while system thinking and system dynamics approach with Vensim PLE 8.0.9 software was applied to implement bedbug infestation dynamics. Our results indicated that majority of the respondents had ample knowledge on bedbugs and were concerned about the physico-psychologic and socio-economic health effects. Spatial distribution analysis showed regions in Kenya with optimal to suitable for bedbug occurrence in the whole country, and similar results were found at continental level across Africa. Furthermore, infestation dynamics results showed a rapid mobility of bedbug from one house to another. In terms of management strategies, the models showed that the combination of chemical with other control methods was considerably much more effective compared to the use of chemical approach only, appointing integrated pest management strategy as a better intervention approach in controlling the pest.

Epidemiological and therapeutic studies on sheep lice in Sayint district, South Wollo Zone, Northeast Ethiopia

An epidemiological (cross-sectional) and therapeutic (randomized controlled field trial) study was conducted on sheep lice in Sayint district, South Wollo, Northeast Ethiopia. The aim of the study was to (i) quantify the magnitude of sheep lice burden and the prevailing lice species, (ii) identify and quantify risk factors affecting lice infestation in sheep, and (iii) evaluate the efficacy of commonly used acaricides (diazinon and ivermectin) against sheep lice infestation. A total of 232 randomly selected sheep, 15 naturally infested sheep, and 80 viable Bovicola ovis lice were used for epidemiological, in vivo, and in vitro based therapeutic studies, respectively. Three naturally infested treatment groups each with five sheep (Group I—treated with diazinon, Group II—treated with ivermectin, and Group III—untreated/control) were used for in vivo therapeutic study. Lice count for the corresponding treatment groups was conducted on weekly basis using clinical and parasitological examinations. We used logistic regression to quantify the association between different putative risk factors and lice infestation, and the independent t-test and one-way ANOVA to compare the within and between treatment group mean lice count variations. The overall prevalence of sheep lice in the study area was 48.3%, where Bovicola ovis (83%) was the dominant lice species. Hair length, body condition, agroecology, and season were significantly (P < 0.05) associated with sheep lice infestation. Analysis of variance revealed that mean lice count significantly (P < 0.05) varies between treatment groups. A significant (P < 0.05) low mean lice cunt was recorded in diazinon- and ivermectin-treated groups when compared to untreated group. The in vivo efficacy of ivermectin (81%) was lower than diazinon (99%) when compared to the efficacy standard limit (98–100%). However, no significant mean lice count variation was recorded between the two groups. In vivo (99%) and in vitro (95%) assay evidence revealed that diazinon was highly effective for the treatment of sheep lice. According to this study, it can be concluded that the magnitude of sheep lice burden in Sayint district was found to be high and this could have a potential negative impact on sheep productivity and health performances. Thus, applying an appropriate intervention measure including the right choice of effective acaricides could help to control sheep lice in the study area.

Transcriptome and population structure of glassy-winged sharpshooters (Homalodisca vitripennis) with varying insecticide resistance in southern California

Background

Homalodisca vitripennis Germar, the glassy-winged sharpshooter, is an invasive insect in California and a critical threat to agriculture through its transmission of the plant pathogen, Xylella fastidiosa. Quarantine, broad-spectrum insecticides, and biological control have been used for population management of H. vitripennis since its invasion and subsequent proliferation throughout California. Recently wide-spread neonicotinoid resistance has been detected in populations of H. vitripennis in the southern portions of California’s Central Valley. In order to better understand potential mechanisms of H. vitripennis neonicotinoid resistance, we performed RNA sequencing on wild-caught insecticide-resistant and relatively susceptible sharpshooters to profile their transcriptome and population structure.

Results

We identified 81 differentially expressed genes with higher expression in resistant individuals. The significant largest differentially expressed candidate gene linked to resistance status was a cytochrome P450 gene with similarity to CYP6A9. Furthermore, we observed an over-enrichment of GO terms representing functions supportive of roles in resistance mechanisms (cytochrome P450s, M13 peptidases, and cuticle structural proteins). Finally, we saw no evidence of broad-scale population structure, perhaps due to H. vitripennis' relatively recent introduction to California or due to the relatively small geographic scale investigated here.

Conclusions

In this work, we characterized the transcriptome of insecticide-resistant and susceptible H. vitripennis and identified candidate genes that may be involved in resistance mechanisms for this species. Future work should seek to build on the transcriptome profiling performed here to confirm the role of the identified genes, particularly the cytochrome P450, in resistance in H. vitripennis. We hope this work helps aid future population management strategies for this and other species with growing insecticide resistance.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12864-022-08939-1.

Comparative Insecticide Uptake Characteristics of Chlorfenapyr Suggests an Additional Reason Why Bed Bugs (Hemiptera: Cimicidae) are so Difficult to Control

Insecticides interact with biochemical sites, disrupting homeostasis, leading to moribundity and death. Considering this process of intoxication, investigating insecticide uptake ensures an understanding of exposure profile. This study evaluated insecticide uptake by bed bugs, Cimex lectularius L., as affected by time and formulation, and a comparative uptake by German cockroaches, Blattella germanica (L.). Insects exposed to chlorfenapyr residues from two Phantom insecticide formulations (i.e., Aerosol and Suspended Concentrate (SC)) were solvent extracted and analyzed by GC-ECD. Chlorfenapyr uptake by bed bugs significantly increased with time, but the rate of external chlorfenapyr adsorption between the two formulations was not significantly different. However, initial exposure and uptake to the aerosol-treated versus SC-treated surfaces were significantly greater by 2.7x. Absorption-rates of chlorfenapyr residues inside the insect, associated with internal insect tissues or exoskeleton-bound, were significantly lower compared with external adsorption, with aerosol and SC formulations accumulating at 4.8x and 14.4x less, respectively. An unexpected formulation effect occurred with aerosol-treated papers and aging of residues. A reformulation of the aerosol provided a greater adsorption of chlorfenapyr at 19.1x that of the original formula after 2 hr. External versus internal uptake of chlorfenapyr by cockroaches was inverse to that seen in bed bugs, with greater chlorfenapyr absorption. Obstructing cockroach mouthparts prevented an internal uptake of chlorfenapyr and provided a similar exposure profile to bed bugs. This work demonstrates a need to evaluate insecticide uptake with formulation and insect morphology to maximize dose, especially in such a morphologically and environmentally isolated insect as the bed bug.