Diagnosis: Bed Bug Bites
A 20-year-old woman presented with a 2-week history of pruritic skin lesions on her hands, arms, feet, legs, abdomen, and face. These multiple, 4-mm to 8-mm red papules would appear in the morning and persist for several days. Prior to the occurrence of the lesions, she had moved into an old and malodorous furnished apartment.
The bed bug can be found worldwide. Cimex lectularius (C. lectularius, also referred to as the “common bed bug”) and Cimex hemipterus (C. hemipterus, which are found in warmer climates and referred to as the “tropical bed bug”) are the species that most frequently affect humans. However, they also parasitize bats, birds and other mammals. Global bed bug infestations, which are generally reported from apartments, cruise ships, homes and hotels, are becoming an increasingly prevalent problem. Insecticide resistance, less effective pesticides and changes in pest control practices resulting from the suppression of bed bugs’ natural predators, such as cockroaches, red ants and certain species of spider are postulated as causes for the resurgence of bed bugs.1-8 Bed bugs are nocturnal bloodsucking arthropods. They usually feed just before dawn. While their bites are painless, bed bug bite reactions are typically observed in the morning on the host’s exposed skin. Management of skin lesions often involves measures that provide symptomatic relief and more rapid resolution of the reactive inflammation. Elimination of bed bugs from the sleeping quarters is necessary to prevent future bites.3,5,9,10
The Bed Bug Physiology
Bed bugs belong to the order Hemiptera, which includes insects. Their family is Cimicidae (‘true bugs’) and their genus is Cimex. Although most sources describe bed bugs to be wingless (which is partially valid since the hind wings are entirely absent), forewings are present, albeit reduced, and appear as shoulder (hemelytral) pads.3,9,10,11 Female bugs lay between 200 to more than 300 eggs in their lifetime. The eggs hatch in 10 days. During a course of 6 weeks, the bugs develop into adults through four nymphal stages and five molts, each of which is preceded by a full blood meal.3,4,10,11,12,13 Bed bugs are small, oval, brown to red-orange, flattened insects, which appear violaceous after feeding. The adult bug is approximately 5 mm in length, ranging in length from 3 mm to 7 mm. Male bugs are slightly shorter than female bugs and C. lenticularius is about 25% shorter than C. hemipterus.2,3,4,9,10,12 Similar to other insects, the bed bug has three body parts: a pyramid-shaped head with prominent compound eyes, a thorax from which the legs are attached, and an abdomen with 11 segments. Bed bugs also have six legs, and two slender antennae, which each have four segments, including a short segment attached to the head and three long, thin segments.
Feeding is accomplished by the use of two sets of paired stylets. The first set of stylets from the maxilla pierce the host’s skin. The second set of stylets, consisting of a set of tubes, permits bug saliva to be injected into the wound and then allows for consumption of a combination of host blood and bug saliva in a retrograde manner.2,9,10,11,12 The bed bug bite is painless. The injected material, which enables feeding to occur, contains three components: an anticoagulant (an inhibitor of the conversion of factor X to factor Xa), a proteolytic enzyme (apyrase), and a vasodilator (nitric oxide). A complete feeding requires between 12 to 30 minutes.4,7,11,14
Where They Live
Bed bugs are most frequently located on the mattress of the person being bitten. Clues to their discovery include visual or olfactory evidence of their presence. Inspection of the linen on the bed may reveal either dark fecal spots or red blood spots. Also, the bugs may occasionally be found “hiding” on the underside of the bedding or within the seams of the mattress. In addition, since the bugs have special glands that secrete an oily malodorous secretion, a distinctive pungent odor in the room may be noticed when large numbers of bed bugs are present.3,4,5,12,13,15 Bed bugs are not restricted to only the mattress of the bed. They can be in the cracks and crevices of the bed frame or behind the headboard. In addition, they can take up residence in the furniture, behind loose wallpaper or hung pictures, inside luggage or unused stoves, under carpets, or within the floor cracks and space along the baseboards of the room.3,5,16 Bed bugs are very adaptable to adverse environments. An adult bug can live up to a year or longer without a meal. Also, they can survive after exposure to a wide range of ambient temperatures. For example, bed bugs (infesting an individual item) will succumb to high temperatures if the item is wrapped in plastic and placed in a location a where the minimum temperature is greater than 120 degrees Fahrenheit for several days. Cold temperatures — below freezing — can also result in bed bug death; however, the duration of chilling must be at least 2 weeks.2,13,14,17,18
When and Where They Bite
Bed bugs only emerge at night and usually feed in the early morning hours before dawn. They are attracted to the human body temperature and carbon dioxide production. Bed bug bites predominantly occur on exposed body areas that are not covered by clothing. These often include the distal extremities and the face.4,9,10
Cutaneous reactions occur at the sites of bites. A linear array of three papules is very suggestive of bed bug bites; this has been referred to as the “breakfast, lunch, and dinner” pattern. The bug biting the hand of the patient described in this report added an additional ‘snack’ between two of its meals.2,4,10,16,19 Bite reactions from bed bugs frequently appear as urticarial papules. A hemorrhagic puncta at the site of the bite may also be present. Other clinical presentations of skin lesions resulting from bed bug bites include purpuric macules, pruritic and ecchymotic wheals, and vesicles or bullae.2,16,19 The diagnosis of bed bug bite reaction is usually based on the morphology and distribution of the skin lesions and associated history. Examination of the causative bug is optimum for confirming the diagnosis. However, the offending insect is usually not available. Even patients who suspect that their skin lesions are the result of an arthropod assault have not entertained the possibility that their problem is the result of a reaction to bed bug bites — as they otherwise would have more closely examined their mattress and bed rooms and perhaps discovered the causative culprit.2,19
Diagnosis and Related Issues
The clinical differential diagnosis of a cutaneous reaction to bed bug bites includes other conditions that present with persistent red, pruritic, urticarial papules (papular urticaria). In addition to bites and stings from other insects, similar-appearing skin lesions can be noted in patients with allergic contact dermatitis, atopic dermatitis, dermatitis herpetiformis, drug reactions, echthyma, Gianotti-Crosti syndrome, pityriasis lichenoides et varioliformis acuta, scabies infestation and transient acantholytic dermatosis (Grover’s disease).4,12 When the possibility of a cutaneous reaction to bed bug bites is either not suspected or the history and morphology of the skin lesions promotes concern for alternative diagnoses, a skin biopsy may be performed for pathologic evaluation. Dermal edema and a superficial and deep perivascular infiltrate of predominantly lymphocytes, with frequent eosinophils, is often observed. The presence of neutrophils is not a prominent finding. With the exception of bite reactions caused by ticks, bed bug bite-related skin lesions show an inflammatory infiltrate that is denser and deeper than those observed following bites from other common insects or arthropods.3,4,12,19 Bed bugs are capable of in vivo incubation of the infectious organisms of several human diseases, including American trypanosomiasis, brucellosis, leishmaniasis, leprosy, pasturella, plaque, Q fever, relapsing fever, rickettsia, tularemia and yersinia. Yet, substantial evidence of transmission of these organisms from feeding bed bugs to humans has not been recorded. Hepatitis B virus and human immunodeficiency virus have also been detected in bed bugs following exposure to infected human sera. However, the potential for viral transmission from the beg bugs to humans is considered to be highly unlikely since the bed bugs lack not only the specific proteins necessary for hepatitis B virus replication, but also the T4 antigen on their cell surface that is required for human immunodeficiency virus replication.2,4,15,16,20
TREATMENT: Eliminate the Source
To eliminate bed bugs, the entire room, not just the mattress, must be treated. Some sources suggest that the mattress can be encased in a bed bug tight cover so that the bugs trapped inside will be unable to feed and will eventually die. However, this treatment may not be successful since an adult bed bug can survive up to a year without a blood meal. In general, insecticides should not be used on mattresses (or infested bedding and garments), since these can be toxic to the human hosts. Hence, often the mattress needs to be discarded; when doing so, it is considerate to mark the infested mattress (and possibly furniture) “infested with bed bugs” so that these items are not inadvertently collected and redistributed.5,15,17,18,21,22 The bed should be moved away from shelving and the wall. The legs of the bed can be coated with a 2-inch wide band of Vaseline or mineral oil. Use of a vacuum can be helpful in removing bed bugs and their eggs from mattresses, carpet, walls and other surfaces. The contents of the vacuum should be discarded in a sealed trash bag.1,14,17,18,21 Cracks in the floor and walls should be caulked. Loosened wallpaper should be glued down. Steam cleaning of carpets may also be effective in killing bed bugs and eggs that persist after vacuuming. Double-sided carpet tape can be used to trap beg bugs so that they do not approach the sleeping area of a room.4,17,21 A professional exterminator is frequently necessary to treat the bed bug infestation. Insecticidal formulations consist of the following: insect growth regulators (which affect the development and reproduction of the bugs), contact insecticides (such as pyrethroids, which kill the bugs after they come in direct contact with the product or its residue), and insecticidal dusts (such as silica gel dust, which abrade the bug’s outer waxy coat and cause them to dry out quickly). The dry dusts are less toxic; some also include a small amount of another kind of pesticide.4,15,17,23,24 In the United States, additional information regarding bed bug pesticides may be obtained from the National Pesticide Information Center which can be reached by telephone (800-858-7378) or via the Web (npic.orst.edu).2,21
Treatment for Cutaneous Reactions
The cutaneous reactions to bed bug bites often will eventually resolve spontaneously. The important aspect to underline to the patient is that even though the condition is a form of insect infestation, the infestation is not on the skin but on the fomites; therefore, the skin condition is just a reaction pattern and is not communicable. Treatment may be initiated to provide symptomatic relief of the associated pruritus and, perhaps, to hasten the resolution of the bite reaction. An oral non-sedating antihistamine (loratadine, desloratadine or fexofenadine) may be taken each morning and a sedating antihistamine (diphenhydramine, hydroxyzine or chlorpheniramine) may be added in the evening, if needed. Depending on the location of the bites, a mid- to upper-strength topical corticosteroid (ranging from triamcinolone acetonide 0.1% to clobetasol propionate 0.05%) in either a lotion, cream, ointment, gel or foam vehicle may also be used. In addition, a menthol 0.5%/camphor 0.5%-containing topical lotion or a low-potency topical anesthetic- (pramoxine 1.0%) containing preparation may provide temporary relief of the lesion-associated itching. Topical antibiotics or systemic antibiotics or both may be necessary for impetiginized lesions or secondarily infected bite sites.3,16,19
The pruritus associated with our patient’s cutaneous bed bug bite reactions was treated systemically and topically. She received loratidine 10 mg each morning and diphenhydramine elixir (12.5 mg to 50.0 mg, as needed) each evening. She also applied a lotion containing menthol 0.5% and camphor 0.5% (Sarna) several times each day; the lotion was refrigerated to provide additional symptomatic relief of her itching. Our patient returned to her apartment and found numerous bed bugs in the seams of her mattress. Red and black spots were observed on the mattress, representing her blood and bug feces, respectively. She contacted the building manager; her mattress was replaced, and the apartment was treated by a bug exterminator. Within the next few days, the pungent odor in the apartment cleared and her skin lesions, along with their associated pruritus, resolved.
Dr. Cohen is affiliated with The University of Houston Health Center, the Department of Dermatology, The University of Texas M.D. Anderson Cancer Center, and the Department of Dermatology, University of Texas-Houston Medical School, all in Houston, TX. Dr. Tschen is affiliated with the Department of Dermatology, University of Texas-Houston Medical School, Houston, Texas, St. Joseph Dermpath, Bellaire, Texas, and the Department of Dermatology, Baylor College of Medicine, Houston, Texas. Mr. Robinson is a medical student at University of Houston Health Center, University of Houston, Houston, Texas. Dr. Gray is affiliated with University of Houston Health Center, University of Houston, Houston, Texas. Dr. Khachemoune, the Section Editor of Derm Dx, is with Department of Dermatology, State University of New York, Brooklyn, NY.