Background
Arthropod assaults on humans can have many manifestations clinically, histologically, and immunologically. Hemiptera is an order of insect species of "true bugs" that has piercing-sucking mouthparts and includes the family Cimicidae (bedbugs), which are blood-sucking ectoparasites of mammals or birds.
All Cimex species organisms are reddish brown insects. Cimex lectularius is 5-7 mm in size, with the females slightly larger than the males. Cimex hemipterus organisms are approximately 25% longer than C lectularius organisms. Females deposit fertilized eggs in cracks or crevices, with newborns emerging in 4-5 days. Note the images below.
The bedbug is a flat, oval, reddish brown insect that turns violaceous after feeding. Courtesy of Colonel Dirk M. Elston, MD (from Elston, 2000). 
Bedbugs are parasitic arthropods from the family Cimicidae. They are typically less than 1 cm in length and reddish brown in color. Bedbugs can be found in furniture, floorboards, peeling paint, or other small spaces, most commonly in areas of clutter. These insects come out at night in search of prey upon which to feed, with peak feeding times just before dawn. Bedbugs are typically attracted to body heat, carbon dioxide, vibration, sweat, and odor. The image of a Cimex lectularius is shown courtesy of the US Centers for Disease Control and Prevention (CDC). Bedbug infestations seem to be increasing around the world at an alarming rate, possibly due to insecticide resistance.[1] Resistance to pyrethroid insecticides is already widespread in the United States. The bedbug occurs in aggregations when conditions are favorable, but the arthropods disperse when conditions are unfavorable.[2] Active female dispersal can potentially lead to treatment failures and should be taken into account when using control methods. New tactics may be needed for this escalating public health concern.
Go to Papular Urticaria and Acute Urticaria for complete information on these topics.
Pathophysiology
The mechanism of skin injury by arthropods depends on the structure of the mouthparts. These insects are categorized as vessel feeders if they insert the tip into a capillary or as pool feeders if they feed on the extravasated blood from damaged tissue. They often inject different pharmacologically active substances (eg, hyaluronidase, proteases, kinins), which may cause different skin reactions (eg, erythema, wheal, vesicle, hemorrhagic nodule). See the following image.
Bedbugs feeding on a human host. Courtesy of Colonel Dirk M. Elston, MD (from Elston, 2000). 
After bedbugs find a food source, they bite down with their mouths and inject anticoagulant and anesthetic compounds into the skin. Depending on the species, these parasites feed on the host blood via 1 of 2 mechanisms. Vessel feeders directly insert their mouthparts into superficial capillaries, whereas pool feeders damage the superficial tissue and feed on the accumulated blood. As bedbugs feed, their color may change as they swell with the host blood, as shown in this picture of a larval bedbug feeding on a volunteer host. Image courtesy of the US Centers for Disease Control and Prevention (CDC). Bite reactions
The type of reaction provoked depends on previous exposure; repeated bites may lead to an allergic reaction, which may lead to pronounced cutaneous manifestations. Some patients show a severe systemic hypersensitivity to arthropod allergens. The site of the bite can also become secondarily infected with bacteria infection and lead to ecthyma, cellulitis, and/or lymphangitis. See the image below.
Bedbug bites themselves are typically painless. However, the subsequent allergic reaction that may develop can cause intense pruritus. While feeding, bedbugs may inject one of several pharmacologically active substances, including hyaluronidase, proteases, and kinins. These compounds may induce different skin reactions, such as erythema, wheals, vesicles, or hemorrhagic nodules. Repeated bites may sensitize individuals, leading to more pronounced cutaneous manifestations or systemic hypersensitivity reactions. The local trauma from bedbug bites can lead to secondary bacterial infection, causing ecthyma, cellulitis, or lymphangitis. There is some evidence that bedbugs may also be a vector for hepatitis B and Chagas disease. Histologic findings from bite-site biopsy specimens typically show eosinophilic infiltrates, which are indicative of the allergic nature of the reaction. The image shown is papular urticaria, which may develop from bedbug bites. Insect bites, including those from the bedbug, have been proposed as a factor contributing to the formation of a cutaneous reaction termed papular urticaria. Patients with papular urticaria have been shown to demonstrate immunoglobulin (Ig) G antibodies to bedbug (C lectularius) antigens.[3] Thus, IgG against C lectularius, Cimex pipiens, and Pulex irritans in patients with papular urticaria may contribute the pathogenesis of this condition.
Host susceptibility
Susceptibility to arthropod bites depends on many external factors, such as occupation, conditions of employment, cohabitation with a variety of domestic animals, housing, climate, and clothing. An arthropod is usually attracted to its host by body heat, carbon dioxide in exhaled air, vibration, human sweat, and/or odor. The Cimex (bedbug) genus attacks both mammals and birds. C hemipterus (the tropical bedbug) bites mostly humans and is found in warm climates, whereas C lectularius (the common bedbug) also attacks bats and domestic animals, such as chickens.
Bedbug feeding
Bedbugs are 5-7 mm in length with reduced wings and modified mouthparts for piercing and sucking. These insects live between wooden floorboards, in furniture, in bed frames, in mattresses, or behind peeling paint. Bedbugs sneak out to grasp human skin with their forelegs, pierce the skin, and inject anticoagulant- and anesthetic-containing saliva.
Bedbugs normally feed at night, usually approximately 1 hour before dawn. However, if the conditions are favorable, they also feed during the day. Feeding takes 3-12 minutes. In proper conditions, adult bedbugs can survive without a meal for 1 year or longer. Each female lays approximately 300 eggs in her lifetime. The eggs hatch in 10 days. The nymph stage lasts 6 weeks, undergoing 5 molts.
Etiology
Bedbugs can be seen anywhere, but they tend to occur in environments in disarray. Old furniture makes an excellent home for bedbugs. These insects also like to hide in the seams and folds of mattresses and in bed frames and springs.
Passenger ships provide conditions suitable for the survival and growth of many pest populations. In a 2008 study, pest infestations were identified in 21 ferries: 18 with flies, 11 with cockroaches, and with 3 with bedbugs.[4]
Epidemiology
Bedbug infestations affect both sexes and people of all ages and races in the United States and globally, particularly in poor regions of the world.[5] The reported rate of bedbugs (Cimex hemipterus) was 37.5% in children's beds from a rural region of Gambia. Recently, bedbugs were allegedly reintroduced from abroad into Seoul, Korea, because there had been no reports on bedbugs in Seoul for more than 20 years.[6]
Prognosis
The prognosis for bedbug bites is excellent, although these bites can create considerable anxiety and localized and occasionally systemic reactions. Sometimes, if the bite reactions are intensely pruritic, scratching with excoriations may be complicated by impetigo.
In addition, bedbugs may be a vector for hepatitis B[7] and, in endemic areas, for American trypanosomiasis (Chagas disease).[8] Of note, reports have indicated the risk of insect transmission of human immunodeficiency virus (HIV), if any, is extremely low and likely nonexistent.[9, 10]
Anaphylactoid reactions are well described. One such case occurred in a 41-year-old businessman in a first-class urban hotel in the United States.
Patient Education
Educate the patient and family about bedbugs and their habits. Patients should avoid scratching the bite sites to reduce local irritation and prevent secondary infection. See also Prevention of Bedbug Bites.
For patient education information, see Allergies Center as well as Insect Bites and Severe Allergic Reaction (Anaphylactic Shock).
Romero A, Potter MF, Potter DA, Haynes KF. Insecticide resistance in the bed bug: a factor in the pest's sudden resurgence?. J Med Entomol. Mar 2007;44(2):175-8. [Medline].
Pfiester M, Koehler PG, Pereira RM. Effect of population structure and size on aggregation behavior of Cimex lectularius (Hemiptera: Cimicidae). J Med Entomol. Sep 2009;46(5):1015-20. [Medline].
Abdel-Naser MB, Lotfy RA, Al-Sherbiny MM, Sayed Ali NM. Patients with papular urticaria have IgG antibodies to bedbug (Cimex lectularius) antigens. Parasitol Res. May 2006;98(6):550-6. [Medline].
Mouchtouri VA, Anagnostopoulou R, Samanidou-Voyadjoglou A, Theodoridou K, Hatzoglou C, Kremastinou J, et al. Surveillance study of vector species on board passenger ships, risk factors related to infestations. BMC Public Health. Mar 27 2008;8:100. [Medline].
Gbakima AA, Terry BC, Kanja F, Kortequee S, Dukuley I, Sahr F. High prevalence of bedbugs Cimex hemipterus and Cimex lectularis in camps for internally displaced persons in Freetown, Sierra Leone: a pilot humanitarian investigation. West Afr J Med. Oct-Dec 2002;21(4):268-71. [Medline].
Lee IY, Ree HI, An SJ, Linton JA, Yong TS. Reemergence of the bedbug Cimex lectularius in Seoul, Korea. Korean J Parasitol. Dec 2008;46(4):269-71. [Medline].
Ogston CW, Wittenstein FS, London WT, Millman I. Persistence of hepatitis B surface antigen in the bedbug Cimex hemipterus (Fabr.). J Infect Dis. Sep 1979;140(3):411-4. [Medline].
Pipkin AC Sr. Transmission of Trypanosoma cruzi by arthropod vectors: anterior versus posterior route infection. Int Rev Trop Med. 1969;3:1-47. [Medline].
Iqbal MM. Can we get AIDS from mosquito bites?. J La State Med Soc. Aug 1999;151(8):429-33. [Medline].
Webb PA, Happ CM, Maupin GO, Johnson BJ, Ou CY, Monath TP. Potential for insect transmission of HIV: experimental exposure of Cimex hemipterus and Toxorhynchites amboinensis to human immunodeficiency virus. J Infect Dis. Dec 1989;160(6):970-7. [Medline].
KINNEAR J. Epidemic of bullous erythema on legs due to bed-bugs. Lancet. Jul 10 1948;2(6515):55. [Medline].
Reinhardt K, Kempke D, Naylor RA, Siva-Jothy MT. Sensitivity to bites by the bedbug, Cimex lectularius. Med Vet Entomol. Mar 9 2009;[Medline].
Crissey JT. Bedbugs: An old problem with a new dimension. Int J Dermatol. Jul-Aug 1981;20(6):411-4. [Medline].
Liebold K, Schliemann-Willers S, Wollina U. Disseminated bullous eruption with systemic reaction caused by Cimex lectularius. J Eur Acad Dermatol Venereol. Jul 2003;17(4):461-3. [Medline].
Masetti M, Bruschi F. Bedbug infestations recorded in Central Italy. Parasitol Int. Mar 2007;56(1):81-3. [Medline].
Scarupa MD, Economides A. Bedbug bites masquerading as urticaria. J Allergy Clin Immunol. Jun 2006;117(6):1508-9. [Medline].
Fletcher MG, Axtell RC. Susceptibility of the bedbug, Cimex lectularius, to selected insecticides and various treated surfaces. Med Vet Entomol. Jan 1993;7(1):69-72. [Medline].
Weeks EN, Logan JG, Gezan SA, et al. A bioassay for studying behavioural responses of the common bed bug, Cimex lectularius (Hemiptera: Cimicidae) to bed bug-derived volatiles. Bull Entomol Res. Jan 27 2010;1-8. [Medline].
Lindsay SW, Snow RW, Armstrong JR, Greenwood BM. Permethrin-impregnated bednets reduce nuisance arthropods in Gambian houses. Med Vet Entomol. Oct 1989;3(4):377-83. [Medline].
Pereira RM, Koehler PG, Pfiester M, Walker W. Lethal effects of heat and use of localized heat treatment for control of bed bug infestations. J Econ Entomol. Jun 2009;102(3):1182-8. [Medline].
Wang C, Gibb T, Bennett GW, McKnight S. Bed bug (Heteroptera: Cimicidae) attraction to pitfall traps baited with carbon dioxide, heat, and chemical lure. J Econ Entomol. Aug 2009;102(4):1580-5. [Medline].
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