Artificial infection of the bed bug with Rickettsia parkeri

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.

Cimicids of Medical and Veterinary Importance

Members of the Cimicidae family are significant pests for mammals and birds, and they have attracted medical and veterinary interest. A number of recent studies have investigated bed bugs, due to their dramatic resurgence all over the world. Indeed, bed bugs are of significant public health and socioeconomic importance since they lead to financial burdens and dermatological complications and may have mental and psychological consequences. It is important to note that certain cimicids with a preference for specific hosts (birds and bats) use humans as an alternative host, and some cimicids have been reported to willingly feed on human blood. In addition, members of the Cimicidae family can lead to economic burdens and certain species are the vectors for pathogens responsible for diseases. Therefore, in this review, we aim to provide an update on the species within the Cimicidae family that have varying medical and veterinary impacts, including their distribution and their associated microorganisms. Various microbes have been documented in bed bugs and certain important pathogens have been experimentally documented to be passively transmitted by bed bugs, although no conclusive evidence has yet associated them with epidemiological outbreaks. Additionally, among the studied cimicids (bat bugs, chicken bugs, and swallow bugs), only the American swallow bug has been considered to be a vector of several arboviruses, although there is no proven evidence of transmission to humans or animals. Further studies are needed to elucidate the reason that certain species in the Cimicidae family cannot be biologically involved in transmission to humans or animals. Additional investigations are also required to better understand the roles of Cimicidae family members in the transmission of human pathogens in the field.

Experimental infection of bed bugs (Cimex lectularius L.) with Burkholderia multivorans

The bacterium Burkholderia multivorans is an opportunistic nosocomial pathogen of humans. A previous study reported molecular detection of this bacterium in several specimens of the common bed bug (Cimex lectularius L.) collected from an elderly care facility in the U.S.A., raising questions about the possibility of vector-borne transmission. However, the ability of B. multivorans to colonize bed bugs and the ability of bed bugs to transmit the bacteria both remained untested. To resolve this knowledge gap, here we performed a set of experiments to examine the persistence and shedding of B. multivorans following ingestion by bed bugs in a blood meal. We isolated viable B. multivorans from the bodies of bed bugs for up to 13 days post-ingestion, but bacterial load substantially diminished over time. By 16 days post-ingestion, the bacteria could not be isolated. Further, B. multivorans was not shed in the saliva of infected bugs during feeding nor was it transmitted vertically from infected insects to their progeny. Based on these results, significant biological or mechanical transmission of B. multivorans to humans by bed bugs appears unlikely. Nonetheless, some viable bacteria were passively shed into the environment through defecation, a process which could potentially contribute to transmission through indirect contamination under rare circumstances.

Knowledge, Experience, and Concerns Regarding Bed Bugs Among Emergency Medical Service Providers

Introduction

Bed bugs are commonly encountered by emergency medical service (EMS) providers. The objective of this study was to determine the frequency with which EMS providers encountered bed bugs, assess their knowledge about bed bugs, and analyze the actions they take after finding bed bugs.

Methods

We anonymously surveyed 407 EMS providers from 180 EMS agencies in northeast Ohio between September 1, 2018, through March 31, 2019.

Results

Among the providers surveyed, 21% (n = 84) of the EMS providers reported seeing bed bugs at least monthly, and 6% (n = 24) reported seeing bed bugs at least weekly. Being younger, male, and working in an urban environment (vs. rural) were associated with EMS providers reporting more frequent bed bug encounters (p: ≤.05). The mean level of concern for encountering bed bugs among EMS providers was 3.54 (SD: 1.15; scale: 1 = no concern, 5 = very concerned). Among the EMS providers who reported seeing bed bugs at least monthly, 30% took the affected EMS stretcher out of service when they encounter a bed bug, 43% took the EMS rig out of service, 83% cleaned the EMS stretcher with a disinfectant, and 88% notified the ED that their patient has bed bugs. EMS providers scored poorly (mean: 69% correct responses) in a seven-question assessment of basic bed bug biology and public health.

Conclusion

Based on our findings, we concluded that EMS knowledge and behavior related to bed bugs are suboptimal.

Case not Closed: Arguments for New Studies of the Interactions between Bed Bugs and Human Pathogens

Bed bugs (Cimex spp.) are common ectoparasites of humans. Their ubiquity across diverse human environments combined with their blood-feeding behavior creates an ideal interface for the transmission of pathogenic microbes. Despite this potential, the current dogma is that bed bugs are not vectors of any known infectious agents. However, this conclusion is based largely on the results of studies conducted before the advent of modern molecular biology and the resurgence of bed bugs on a global scale. More importantly, a small but compelling body of modern research suggesting that bed bugs can potentially vector some human pathogens exists but is often overlooked. This article critically examines the current classification of the bed bug as an insect that does not transmit disease agents. In doing so, it highlights key knowledge gaps that still exist in understanding the potential of bed bugs as pathogen vectors and outlines several arguments for why new research on the topic is necessary.

Molecular detection of Rickettsia infection in field-collected bed bugs

Bed bugs are now one of the most prevalent human-associated, blood-feeding pests in the urban world, but few studies of their association with human pathogens have been conducted since their resurgence. Here, we used PCR to screen samples of field-collected bed bugs (Cimex spp.) for the presence of Rickettsia bacteria and we describe the first detection of an uncharacterized Rickettsia in Cimex lectularius in nature. Rickettsia was detected in 5/39 (12.8%) of the bed bug samples tested. In particular, three pools from the USA and two individual insects from the UK were positive for Rickettsia DNA. Sequencing and analysis of a fragment of the citrate synthase gene (gltA) from positive samples from each country revealed that the Rickettsia detected in both were identical and were closely related to a Rickettsia previously detected in the rat flea Nosopsyllus laeviceps. Additional experiments indicated that the Rickettsia localizes to multiple tissues in the bed bug and reaches high titres. Attempts were made to infect mammalian cells in culture but these efforts were inconclusive. Our findings suggest that Rickettsia are secondary endosymbionts of bed bugs and have potential implications for both bed bug control and public health. However, further investigation is required to determine the pathogenicity of this Rickettsia, its transmission mechanisms, and its contributions to bed bug physiology.

The Benefit of a Single Oral Dose of Ivermectin in Humans: The Adverse Effects on Cimex lectularius L. Populations and Fecundity

Objective

To measure the population size and fecundity of the common bed bug Cimex lectularius L. (C. lectularius) after feeding it with the blood obtained from human subjects who have consumed a single dose of ivermectin.

Methods 

Serial blood samples were obtained from two human subjects at hour 0 (control) and 4-96 hours after they received a single 0.2 mg/kg dose of ivermectin. The blood samples were then fed to 2,273 bed bugs. Bed bug incapacitation rates, fecundity, and population sizes were recorded over a 54-day period. Whole blood ivermectin levels were measured in the human subjects and the insects.

Results 

The fold change in the size of the control group population over the course of the experiment was found to be 2.16. This was significantly greater (p: <.001) than for all the post-ivermectin feeding groups (range: -11.04-1.43). Two weeks after the experiment, the number of eggs laid per live adult female bed bug per day was 10.74 for controls, which was significantly different (p: <0.001) compared to all the post-ivermectin feeding groups (range: 0-4.28).

Conclusions 

There were significant reductions in C. lectularius population size and fecundity in insects that fed on blood obtained from human study subjects up to 96 hours after they have consumed a single oral dose of ivermectin.

Bed bugs and possible transmission of human pathogens: a systematic review

The global population of bed bugs (Cimex lectularius and Cimex hemipterus, family Cimicidae) has undergone a significant resurgence since the late 1990s. This is likely due to an increase in global travel, trade, and the number of insecticide-resistant bed bugs. The global bed bug population is estimated to be increasing by 100-500 % annually. The worldwide spread of bed bugs is concerning, because they are a significant socioeconomic burden and a major concern to public health. According to the United States Environmental Protection Agency, bed bugs are "a pest of significant health importance." Additionally, 68 % of U.S. pest professionals reported that bed bugs are the most challenging pest to treat. Upwards of 45 disease pathogens have been reported in bed bugs. Recent studies report that bed bugs may be competent vectors for pathogens, such as Bartonella quintana and Trypanosoma cruzi. However, public health reports have thus far failed to produce evidence that major infectious disease outbreaks have been associated with bed bugs. Since many disease pathogens have previously been reported in bed bugs and the worldwide bed bug population is now drastically increasing, it stands to reason to wonder if bed bugs might transmit human pathogens. This review includes a literature search on recently published clinical and laboratory studies (1990-2016) investigating bed bugs as potential vectors of infectious disease, and reports the significant findings and limitations of the reviewed studies. To date, no published study has demonstrated a causal relationship between bed bugs and infectious disease transmission in humans. Also, we present and propose to expand on previous hypotheses as to why bed bugs do not transmit human pathogens. Bed bugs may contain "neutralizing factors" that attenuate pathogen virulence and, thereby, decrease the ability of bed bugs to transmit infectious disease.

Competence of Cimex lectularius Bed Bugs for the Transmission of Bartonella quintana, the Agent of Trench Fever

Background

Bartonella quintana, the etiologic agent of trench fever and other human diseases, is transmitted by the feces of body lice. Recently, this bacterium has been detected in other arthropod families such as bed bugs, which begs the question of their involvement in B. quintana transmission. Although several infectious pathogens have been reported and are suggested to be transmitted by bed bugs, the evidence regarding their competence as vectors is unclear.

Methodology/Principal Findings

Bed bugs at the adult and instar developmental stages were fed three successive human blood meals inoculated with B. quintana bacterium from day one (D1) to D5; subsequently they were fed with pathogen-free human blood until the end of the experiment. Bed bugs and feces were collected in time series, to evaluate their capacities to acquire, multiply and expel viable B. quintana using molecular biology, immunohistochemistry and cultures assays. B. quintana was detected molecularly in 100% of randomly selected experimentally infected bed bug specimens (D3). The monitoring of B. quintana in bed bug feces showed that the bacterium was detectable starting on the 3^rd day post-infection (pi) and persisted until day 18±1 pi. Although immunohistochemistry assays localized the bacteria to the gastrointestinal bed bug gut, the detection of B. quintana in the first and second instar larva stages suggested a vertical non-transovarial transmission of the bacterium.

Conclusion

The present work demonstrated for the first time that bed bugs can acquire, maintain for more than 2 weeks and release viable B. quintana organisms following a stercorarial shedding. We also observed the vertical transmission of the bacterium to their progeny. Although the biological role of bed bugs in the transmission of B. quintana under natural conditions has yet to be confirmed, the present work highlights the need to reconsider monitoring of these arthropods for the transmission of human pathogens.

Bartonella quintana, the etiologic agent of trench fever and other human diseases, is known to be transmitted by the feces of body lice. Recently, the DNA of this bacterium has been detected in bed bugs. Several pathogens have been associated and suggested to be transmitted by bed bugs, despite the insufficient evidence to support this vector role. The aim of the present study was to assess the competence of bed bugs in the transmission of B. quintana using an experimental artificial model of infection. To this end, bed bugs were fed with human infected blood meals. On the 3^rd day post-infection (dpi) B. quintana was detected molecularly in 100% of experimentally infected bed bug. The bacterium was also detectable in bed bug feces starting on the 3^rd dpi and persisted until 18±1 dpi. Although immunohistochemistry assays localized the bacteria to the gastrointestinal bed bug gut, B. quintana was also detected in the first and second instars larva. The present work highlights the need to reconsider monitoring of bed bugs for the transmission of pathogens.

A High-Performance Vacuum Cleaner for Bed Bug Sampling: A Useful Tool for Medical Entomology

Arthropods can be captured by two modes: a passive mode using traps or an active mode mainly based on the use of mouth or powered aspirators. These apparatuses are useful tools for collecting large numbers of crawling, flying, resting, or jumping arthropod specimens, particularly small specimens, such as mosquitoes or sandflies, for laboratory experiments or breeding. Different aspirator models are used to collect various arthropod specimens. However, to our knowledge, no specific system is currently available for the reliable sampling of live bed bugs in the field. Thus, we described a new system based on a classic autonomous house aspirator that requires few modifications for the collecting bed bugs. The low weight and size of this apparatus is advantageous, and it provides for rapid and secure bed bug sampling for medical entomology purposes.

Survey of Bartonella spp. in U.S. bed bugs detects Burkholderia multivorans but not Bartonella

Bed bugs (Cimex lectularius L.) have resurged in the United States and globally. Bed bugs are hematophagous ectoparasites of humans and other animals, including domestic pets, chickens, and bats, and their blood feeding habits contribute to their potential as disease vectors. Several species of Bartonella are re-emergent bacterial pathogens that also affect humans, domestic pets, bats and a number of other wildlife species. Because reports of both bed bugs and Bartonella have been increasing in the U.S., and because their host ranges can overlap, we investigated whether the resurgences of these medically important pathogens and their potential vector might be linked, by screening for Bartonella spp. in bed bugs collected from geographic areas where these pathogens are prevalent and from bed bugs that have been in culture in the laboratory for several years. We screened a total of 331 bed bugs: 316 bed bugs from 36 unique collections in 29 geographic locations in 13 states, 10 bed bugs from two colonies maintained in the laboratory for 3 yr, and 5 bed bugs from a colony that has been in culture since before the recent resurgence of bed bugs. Bartonella spp. DNA was screened using a polymerase chain reaction assay targeting the 16S–23S rRNA intergenic transcribed spacer region. Bartonella DNA was not amplified from any bed bug, but five bed bugs from four different apartments of an elderly housing building in North Carolina contained DNA sequences that corresponded to Burkholderia multivorans, an important pathogen in nosocomial infections that was not previously linked to an arthropod vector.

Bed bug detection: current technologies and future directions

Technologies to detect bed bugs have not kept pace with their global resurgence. Early detection is critical to prevent infestations from spreading. Detection based exclusively on bites is inadequate, because reactions to insect bites are non-specific and often misdiagnosed. Visual inspections are commonly used and depend on identifying live bugs, exuviae, or fecal droplets. Visual inspections are inexpensive, but they are time-consuming and unreliable when only a few bugs are present. Use of a dog to detect bed bugs is gaining in popularity, but it can be expensive, may unintentionally advertise a bed bug problem, and is not foolproof. Passive monitors mimic natural harborages; they are discreet and typically use an adhesive to trap bugs. Active monitors generate carbon dioxide, heat, a pheromone, or a combination to attract bed bugs to a trap. New technologies using DNA analysis, mass spectrometry, and electronic noses are innovative but impractical and expensive for widespread use.