- Author: Robert A Schwartz, MD, MPH; Chief Editor: Dirk M Elston, MD more...
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.
See When Bugs Feast: What's Causing that Itch?, a Critical Images slideshow, to help identify various skin reactions, recognize potential comorbidities, and select treatment options.
Bedbug infestations seem to be increasing around the world at an alarming rate, possibly due to insecticide resistance. 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. 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 in locations with high occupant turnover, such as hotels, hospitals, and nursing homes. Indeed, in the past decade bedbugs have become a worldwide urban pest, with the number of American households affected markedly increased. Recent genetic data suggest that C lectularius may be undergoing lineage divergence through host association.
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 images.
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.
Thus, although these insects usually cause mild cutaneous reactions, more severe responses, including anaphylaxis, may occur. Bullae may be noted. Skin responses at bite sites may evolve from immediate, pruritic, edematous macules into bullae within 24 hours. Histopathologically, an urticarial-like reaction can develop into a leukocytoclastic vasculitis, sometimes with a destructive, necrotizing, eosinophil-rich vasculitis with prominent infiltration of CD68+ histiocytes and collagen necrobiosis.
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. Thus, IgG against C lectularius, Cimex pipiens, and Pulex irritans in patients with papular urticaria may contribute the pathogenesis of this condition.
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.
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.
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.
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. 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.
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 and, in endemic areas, for American trypanosomiasis (Chagas disease).[12, 13] Of note, reports have indicated the risk of insect transmission of human immunodeficiency virus (HIV), if any, is extremely low and likely nonexistent.[14, 15]
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.
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.
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