Published on 16/03/2015 by admin
Filed under Dermatology
Last modified 22/04/2025
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Whitney A. High and Glen R. Needham
Evidence Levels: A Double-blind study B Clinical trial ≥ 20 subjects C Clinical trial < 20 subjects D Series ≥ 5 subjects E Anecdotal case reports
Human bed bugs (Cimex lectularis) are insects that have afflicted mankind for at least 3000 years. There is evidence that human bed bugs were derived from bat bugs, which adapted from bats to humans when our ancestors inhabited caves. Bed bugs require a blood meal to complete their lifecycle, and this requisite blood meal is acquired by biting sleeping humans. While not all persons react to bed bug bites, the bite can elicit an allergic reaction, creating pruritic, erythematous papules that are often excoriated, and even secondarily infected.
Bed bug infestations were once ubiquitous. In the late 1940s and early 1950s widespread use of the insecticide dichlorodiphenyltrichloroethane (DDT) brought bed bug infestations to a nadir in the developed world. Following a worldwide ban on DDT, and with emerging resistance to this and other insecticides, bed bug infestations have resurged into prominence.
Most bed bugs bite during the early morning hours, just before dawn, and most bed bugs lie in close proximity to the sleeping quarters. Adult bed bugs are typically 5–7 mm in length (just less than 0.25 inch), with females being slightly larger than males.
While bite of the bed bug is painless, an allergic reaction may occur in some individuals, yielding a pruritic, erythematous papule. Bed bug bites tends to occur on exposed surfaces, such as the extremities or head/neck. The insect will not typically venture beneath bedding or bed clothes. A linear orientation to the bites is common.
Because the insect does not reside or lay eggs upon humans, ultimate treatment focuses upon detection and eradication of the household infestation.
Once an infestation has been confirmed, an extermination program should be commenced. Insecticides, growth regulating agents, and destructive modalities may be employed to kill adults, progeny, and eggs. Many authorities believe that safe and successful eradication of infestations requires professional assistance, although many purveyors of such materials may contest this assertion.
The use of insecticides in the US is regulated by the Environmental Protection Agency. DDT was once a premier insecticide for use against bed bugs, but the extended residual effect of the insecticide resulted in environmental damage; ultimately its use was banned. Resistance among bed bugs, first to DDT, but also later to malathion, may be an issue with its re-emergence as a scourge as well.
Most recently, the pyrethroid class of insecticides (e.g., deltamethrin) have emerged as a widely used substance for controlling bed bug infestations, but resistance problems are mounting for these agents as well.
There is great interest in the use of temperature extremes to eradicate bed bug infestations. For example, steam may be utilized to sterilize a mattress or other materials for which insecticides are inappropriate, but the target temperature of 160–180°F must be reached over the entirety of the surface.
Commercial whole room (or whole home) heating systems utilizing propane heaters and fans to develop convective cycles have been developed. Most of these systems are based on a target temperature of around 113°F, to be held for 15–60 minutes. This temperature is less than the laboratory-based thermal death point of 118°F, yet these treatments have proven successful, apparently due to the powerful convection currents created within the heated room that desiccate the insects.
Comparatively more simplistic measures, such as the use of impermeable mattress casings to isolate the bed bugs within the mattress from those on the surface, are widely advocated.
On the horizon, entomologists and other experts are seeking new ways to gain control over the epidemic of bed bugs. In this regard, the manipulation of insect pheromones is gaining interest. Bed bugs use pheromones to aggregate, thereby raising the likelihood of both successful mating, and also increasing local humidity to avoid desiccation. In this regard, the blocking of effective signaling may have disastrous effects upon a colony.
As all human-based treatments presently available for bed bugs are based on the symptomatic care of bite reactions, the successful detection of infestations is vital to employment of external eradications measures.
Skin reactions to bed bug bites are due to an allergic reaction to the saliva leaked during feeding. Sensitization is not universal, and sometimes an individual will not react to bed bug bites at all, meaning a query for others affected in a household may or may not be of significance.
Bed bug bites typically manifest as an erythematous wheal, followed by a firm, reddish papule, sometimes with a small central hemorrhagic punctum. Papulonecrotic forms have been described as well. The bites are often both inflammatory and pruritic, and are often present on exposed areas of the body, such as the head, neck, arms, legs, and shoulders. Bed bug bites rarely occur in the axillae or popliteal fossae, in stark contrast to the bites of many other medically relevant insects. Linear configurations are often observed.
The bites themselves are treated in the same way that most arthropod bites are treated: symptomatic relief with potent topical steroids such as betamethasone dipropionate and antihistamines such as hydroxyzine.
Regarding the potential for bed bugs to act as a vector for transmitting disease, the official position of the US Centers for Disease Control and Prevention (CDC), and the vast bulk of authorities for that matter, is that there is no evidence of successful transmission of any blood-borne pathogen via the bite of the bed bug. Therefore, additional laboratory testing, beyond bacterial culture of superinfected bite sites, is not, at present, justified. Despite this, however, it is frequently worried that the bite of bed bugs might transmit blood-borne pathogens, such as a hepatitis, HIV, or American trypanosomiasis.
It is widely asserted that one contributor to the recent ‘epidemic’ of bed bugs is travel. Indeed, many hotels and other shared lodging facilities, regardless of cleanliness or economic standing, may be infested with bed bugs and it is possible to bring an infestation home simply from staying in infested lodgings.
To this end, inspection of a hotel, in a manner akin to that described for visual inspection of one’s home, is important, but other steps must be followed. Luggage should be kept closed, except for brief periods of use, or even sealed in plastic bags to then be left at the destination upon departing. Use of dressers and bureaus at the hotel is strongly discouraged. As bed bugs do not like to climb upon metal, a metal luggage stand is superior to that of wood.
Romero A, Potter MF, Potter DA, Haynes KF. J Med Entomol 2007; 44: 175–8.
The authors describe high resistance to two pyrethroid insecticides, deltamethrin and λ-cyhalothrin, in bed bug populations collected from human dwellings in Kentucky and Ohio. Crossed offspring from these colonies manifested intermediate susceptibility to the same insecticides. The authors related that bed bug populations from across the US may already manifest significant resistance to pyrethroid insecticides.
With growing resistance to pyrethroids, bed bug infestations may prove difficult to eradicate with pesticides alone, and pesticides are not without untoward side effects to humans.
Centers for Disease Control and Prevention (CDC), MMWR 2011; 60: 1269–74.
While subject to concerns of over- or under-reporting, the CDC recently detailed 111 illnesses, over the span of 2003–2010, including one fatality, that were attributed to excessive and/or inappropriate use of insecticides directed at bed bugs. The authors hypothesize that increases in bed bug populations that are resistant to commonly available insecticides might result in increased misuse of pesticides, and they encourage persons with such infestation seek the services of a certified applicator, and that all persons applying insecticides adhere to product instructions for safe and appropriate use.
The use of consumer-grade, indoor ‘foggers’ or ‘bombs’ to treat bed bugs is discouraged by experts. These agents are ineffective and often serve only to scatter bed bugs over a larger area. Silica gel or diatomaceous earth may also be used as a less toxic (but less effective) alternative that kills via dehydration.
Siljander E, Gries R, Khaskin G, Gries G. J Chem Ecol 2008; 34: 708–18.
Experimental evidence exists that adult males, virgin adult females, and juvenile C. lectularius insects respond to an airborne aggregation pheromone. The authors suggest that purposeful manipulation of this aggregation pheromone might be useful for control devices, such as traps.
Similarly, bed bugs reproduce via traumatic insemination, and females have developed structural adaptations to deal with this insult, whereas males have no such adaptations. Instead young males secrete pheromones to discourage other adult males from destructive same-sex copulation, and this represents another avenue of potential susceptibility.
Lastly, some groups have discovered symbiotic bacterial infections within bed bugs that are similar to the symbiotic Wolbachia infections in other parasites, such as head lice.
Hosokawa T, Koga R, Kikuchi Y, Meng XY, Fukatsu T. Proc Natl Acad Sci USA 2010; 107: 769–74.
Wolbachia are bacterial symbionts that provide essential nutrients in many organisms. These authors discovered that in the bed bug Wolbachia species reside in a bacteriome and appears to be an obligate nutritional mutualist. Elimination of the Wolbachia symbiont resulted in retarded growth and sterility of the host insect.
It is hoped by some that the sporadic delivery of either antibiotics, or perhaps, in the alternative, sporadic delivery of other anti-parasitic medications, such as ivermectin, through the bite of purposefully medicated humans, may prove effective. In truth, too little is known at this stage regarding these emergent therapies to comment further, but additional investigation is warranted.
At present there is no effective ‘repellant’ for bed bugs, and bed bugs do not respond to the repellants employed for other insects, such as chiggers and mosquitoes.
Lowe CF, Romney MG. Emerg Infect Dis 2011; [serial on the Internet]. Available at: http://dx.doi.org/10.3201/eid1706.101978 Last accessed: 8/12/2012.
A recent report from Canada demonstrated that bed bugs may be capable of transmitting methicillin-resistant Staphylococcus aureus within an impoverished community.
Kolb A, Needham GR, Neyman KM, High WA. Dermatol Ther 2009; 22: 347–52.
In this review article the authors instruct that, upon returning home, immediate inspection of luggage and other belongings aids in the discovery of bed bugs or eggs in the midst of transport. Unpacking in the garage, and/or vacuuming the exterior, or even the interior, of bags, with immediate disposal of the vacuum bag itself in a sealed plastic bag, may be of benefit in preventing undesired translocation.
Visualization of the bed bug
Skin biopsy
Bed bugs are not microscopic. Even the eggs and nymphal stages of the organism may be visualized with the human eye. Therefore, when bed bug bites are suspected clinically, an appropriate starting point in investigation is simply careful inspection of sleeping quarters. Other advanced techniques to detect infestation includes simple taping of bed legs with sticky tape, placing bed posts in isolating devices (either home-made or purchased), bed bug detecting dogs, or use of specially designed bed bug traps (again either home-made or purchased).
Admittedly, on rare occasion, bed bug infestations may involve areas beyond sleeping quarters, including a hospital waiting room in North Carolina. Ideally most visual inspections should begin around the bed area. Adult bed bugs are 5–7 mm in length and vary in color from light brown to dark brown or even violaceous if they have recently fed. Nymphs are smaller and are often more clear in appearance, again unless having fed. Eggs are about 1 mm long, ovoid with an operculum, and they are sticky, adhering to surfaces in small aggregates.
In addition to simply detecting the organism, there should be a search for fecal smears or flecks of blood upon the bed linens, upon the edges of the mattress and box springs. Bed bugs, even adults, may fit within extraordinarily narrow cracks and crevices in furniture and walls, behind peeling wallpaper, and even behind switch plates. There is an old adage that, if a credit card can be inserted into a crevice, then it may also host bed bugs.
Lastly, when populations of bed bugs are particularly dense, a pungent but sweet odor, likened to coriander or cut cilantro, may permeate an infested room or even an entire house.
Dogs have been successfully trained to detect the odor of bed bugs. The training protocol of the commercial kennels is proprietary and the exact odor the dogs are detecting is unknown.
It is thought that bed bugs are attracted to humans via a combination of heat, carbon dioxide exhalation, and perhaps other detectable scents, such as human body volatiles, such as aldehydes and sulcatone.
Using this information, two commercial bed bug trapping devices have been marketed, and plans to build a home-made trap (using a cat-feeding bowl, dry ice, and a thermos vessel) have been widely published.
The principle in all these devices is an attractant, or combination of attractants, coupled with either a ‘pitfall area,’ into which the bed bugs fall and cannot escape, or sticky material that entraps the organisms.
Similar to the principle of the pit fall traps, other devices or maneuvers may serve monitoring functions for bed bugs. For example, there has been recent marketing of a device (Climbup Interceptor™) consisting essentially of two nested plastic bowls, one inside the other, into which the feet of the bed may be placed, thereby entrapping bed bugs migrating either into the bed or away from the bed. Along these same lines, inverted duct tape, or other tape, may be placed, sticky side out, upon the legs of the bed to entrap bed bugs as they migrate across it.
The histology of bed bug bites is non-specific and similar to that of many other insect and arthropod assault reactions, and includes a perivascular infiltrate of lymphocytes, histiocytes, eosinophils, and mast cells within the upper dermis, perhaps with dermal edema and/or extravasated erythrocytes.
Pfiester M, Koehler PG, Pereira RM. J Econ Entomol 2008; 101: 1389–96.
The authors examined canines trained to locate bed bugs based upon olfaction. Canines were trained to detect the bed bug (as few as one adult male or female) and viable bed bug eggs (five, collected 5 to 6 days after feeding) by using a modified food and verbal reward system. Under test conditions canines were able to discriminate bed bugs from other insects with a 97.5% positive indication rate (correct indication of bed bugs when present) and with zero false positives (incorrect indication of bed bugs when not present). Canines also were able to discriminate live bed bugs and viable bed bug eggs from dead bed bugs, cast skins, and feces, with a 95% positive indication rate and a 3% false positive rate on bed bug feces. In experimentally contrived ‘hotel rooms,’ canines were 98% accurate in locating live bed bugs.
Wang C, Tsai WT, Cooper R, White J. J Econ Entomol 2011; 104: 274–8.
A comparison was made of several bed bug monitoring devices including the CDC3000™, NightWatch™, and a home-made dry ice trap, while a passive monitor (the Climbup Interceptor™), without attractants, was used for estimating the bed bug numbers before and after placing active monitors. In occupied apartments, the relative effectiveness of the active monitors was: dry ice trap > CDC3000™ > NightWatch™. In lightly infested apartments, the Interceptor (operated for 7 days) trapped a similar number of bed bugs as the dry ice trap (operated for 1 day) and trapped more bed bugs than CDC3000™ and NightWatch™ (operated for one day). The authors concluded that all the monitors were effective tools in detecting early bed bug infestations and evaluating the results of bed bug control programs.
deShazo RD, Feldlaufer MF, Mihm MC Jr, Goddard J. Am J Med 2012; 125: 688–94.
The authors examined ‘severe’ cutaneous reactions, termed bullous or complex reactions, to bed bug bites, and concluded the phenomenon is not rare. Of 357 photographs of bed bug bites posted on the Internet, 6% were bullous. Histopathologic evaluation of bullous reactions showed a polymorphous picture with histologic evidence of an urticarial-like reaction early on that rapidly developed into a hybrid leukocytoclastic vasculitis, similar to the dermal vasculitis in patients with Churg–Strauss disease. However, even in these severe reactions, the authors advocated only efforts to prevent further bites and topical treatment with high-potency corticosteroids.
Treatment of Skin Disease Comprehensive Therapeutic Strategies 4e
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Identify and eradicate the infestation
Control symptoms associated with the bites using antihistamines, topical steroids, and in rare cases oral steroids
