Bedbugs: An Update on Recognition and Management

Robyn S. Fallen, BHSc and Melinda Gooderham MD, MSc, FRCPC^1
1Skin Centre for Dermatology and Skin Laser Clinic, Peterborough, ON, Canada

ABSTRACT

The common bedbug (Cimex lectularius) is increasingly prevalent and a source of concern and questions for patients. In addition to a range of cutaneous presentations and potential for serious sequelae, bedbug bites cause significant psychological distress and create an economic burden associated with infestation control. Recognition of characteristic entomology, clinical presentation, diagnostic features and differential diagnosis can support expedient identification of patients exposed to infestations and support their appropriate management.

Key Words: bedbugs, Cimex lectularius, infestation, pest control

Introduction

The common bedbug, Cimex lectularius (C. lectularius), is a hematophagus arthropod. A pest to mankind for centuries, bedbug populations in industrial nations declined steadily with the advent of novel pesticides, improved sanitation practices, and economic conditions.¹ In contrast, infestations in developing countries have persisted.² However, pest control companies in Canada and the United States are reporting overwhelming increases in the number of new bedbug encounters compared with 10 years ago.³ This recent bedbug resurgence has been attributed to evolving pesticide resistance coupled with increased rates of international trade and travel, as travellers can bring the insects home in their clothing and luggage.^4,5 Bedbugs have since established more widespread infestation of environments serving transient populations such as hotels, dormitories, hospitals, cruise ships, and homeless shelters.^6-9 In addition to this increased prevalence, bedbugs are also widely discussed in popular media and may be presented as a concern by patients.¹⁰ Awareness of the entomology, diagnosis, and management of bedbugs can assist physicians in detecting affected individuals and providing concerned patients with education on this topic.

Epidemiology

Bedbugs can be introduced to an environment from either local or distant sites. Local transmission occurs by "active dispersal" as the insects walk short distances to find a source for feeding. This is the predominant means of infestation in multi-unit dwellings as the bedbugs travel through ductwork, crevices in drywall, or electrical outlets. Infestation from distant sites occurs via "passive dispersal" when bedbugs travel on clothing, luggage, or shipped furniture.¹¹ As such, poorly maintained living conditions, overcrowding and transitory populations can confer increased risk of bedbugs.¹² Local public health departments often have limited resources to combat this problem, and municipal regulatory bodies struggle to assign responsibility of high eradication costs to landlords or transient tenant populations. ¹³

Entomology

Bedbugs are broad, oval-shaped, flat, wingless insects.¹⁴ Adults are red-brown in color and typically measure 4-7 mm; they are often likened to apple seeds in their appearance.¹¹ Patients may describe a distinctive, characteristic 'sweet' odor associated with the insects. While they may be difficult to detect early in the course of infestation, the bedbug life cycle can result in an exponential increase in numbers during the first month. The typical lifespan in temperate climates averages from 6 to 24 months, and an adult female could lay 200-500 eggs during this time.¹⁵ Nymphs hatch after 4 to 10 days and are pale and translucent. To reach full maturity they must molt four times, which can only occur with a blood meal. If a host is available they will feed every 3 to 7 days.¹⁵ However, adding to their resilience, bedbugs can survive 12 months without feeding, and even more than 2 years in cooler environments.¹¹

Hosts are typically bitten at night on exposed skin and an insect will feed for 10 to 20 minutes until completely engorged.¹⁵ The proboscis, an elongated feeding organ, is composed of two tubules. The first tubule secretes several substances, including an anesthetizing compound (producing a painless bite that may be undetectable for hours), proteolytic enzymes, anticoagulants (such as factor-X inhibitor), and vasodilatory substances (such as nitric oxide).¹⁶ This collection of substances can contribute to the subsequent local hypersensitivity reactions.¹¹ The second tubule simultaneously extracts the blood meal.

Bedbugs do not stay on the body of the host after feeding. Unable to fly or jump, they have six legs with which they are able to travel into crevices and evade detection at ambient temperatures.¹⁷ While they are most active in temperate environments, bedbugs exhibit incredible tolerance for temperature extremes and have been demonstrated to require 1 hour of exposure to temperatures lower than -16°C or greater than 48°C in order to be killed.^18,19

Psychological Consequences

The social and psychological impact of bedbugs can be devastating for affected individuals. Infestation can be stigmatizing due to the misconception that bedbugs are related to poor housekeeping or inadequate hygiene. In reality, bedbugs are attracted to carbon dioxide and body heat and they are nourished by blood, not excrement or waste.⁶ Minimizing clutter can thus reduce hiding places where insects may remain undetected, but patients can be reassured that they are not to blame. In addition to the stresses of identifying and controlling bedbugs in the home or workplace, some patients suffer anxiety due to fears of reinfestation even after the insects have been eliminated.²⁰ Extreme cases can result in delusions of parasitosis and in these situations a referral to psychiatry can be helpful.²¹

Cutaneous Manifestation

The bites of bedbugs can closely resemble those of other arthropods; however, they tend to be clustered on skin that is freely exposed when sleeping, such as the face and distal extremities. Bites may follow a linear path, or characteristically, appear in a group of three to five (colloquially known as 'breakfast, lunch, and supper').^22,23 In non-sensitized individuals, pruritic, erythematous macules may be the only cutaneous evidence of bedbug bites.²⁴ Bite sites typically appear as pruritic papules and wheals, which form in response to components of the saliva injected by the bedbug. The lesions often have a hemorrhagic punctum in the centre. Exaggerated local reactions, such as wheals, vesicles and bullae, may occur in patients whom have previously been bitten or have been sensitized to other insects.^25-27 Papular eruptions that mimic urticaria have been associated with IgG antibodies to C. lectularius proteins.^28,29 However, compared with other causes, urticaria from bedbugs has been found to last longer and blanches less easily.²⁹ In contrast, it is IgE that mediates the occasionally-manifested bullous allergic hypersensitivity.²² Although rare, cases of asthma exacerbations, type I hypersensitivity allergic cutaneous reactions, and severe anemia secondary to bedbug bites have been reported.^25,30

Diagnostic Considerations

Differential Diagnosis

Insect bite reactions are often non-specific and, as such, are susceptible to misdiagnosis. In the absence of typical presentation or evidence of infestation, bedbug bites can be challenging to differentiate from those of other arthropods. Further, in addition to the common bedbug C. lectularius, the tropical bedbug Cimex hemipterus and bat bug Cimex pipistrelli cause similar clinical symptoms.³¹ Bites from bedbugs have been incorrectly diagnosed and documented as:⁴

• Mosquito bites
• Spider bites
• Scabies
• Drug eruption
• Food allergy
• Staphylococcus infection
• Varicella

Histology

In the event of biopsy, bedbug reactions are similar histologically to other arthropod bite reactions. Tissue demonstrates dense eosinophil-predominant perivascular infiltrate of both superficial and deep dermis with minimal spongiosis. Subepidermal vesiculation and edema of the papillary dermis may also be seen.^14,29,32

Disease Transmission

In addition to cutaneous and possible allergic reactions to bedbugs, the risk of disease transmission via bites has also been raised as a concern.³³ There is both historical and experimental laboratory data supporting the Hepatitis B virus as a candidate for bedbug transmission.³⁴ Further, a recent case report details the isolation of both vancomycin-resistant Enterococcus faecium (VRE) and methicillin-resistant Staphylococcus aureus (MRSA) bacterial colonies from bedbugs.³⁵ However, although the question of the hematogphagus bedbug vectorial capacity is compatible with logic and these parasitic insects have been found to carry > 40 different microorganisms, they have not been identified as transmitting human disease.^11,26

Management

Uncomplicated bedbug bites usually resolve within 1-2 weeks and are self-limited. Although the evidence base is weak, management is otherwise symptomatic. Topical or oral antipruritic agents combined with an intermediate corticosteroid can bring some relief. For some patients, having prescription topicals compounded with menthol and camphor can be soothing. Superinfection can occur, especially in cases with significant excoriation, and can be treated with topical or oral antibiotics.¹⁶

Systemic reactions to bedbug bites are treated with intramuscular epinephrine, antihistamines, and oral corticosteroids, as in insect-induced anaphylaxis.¹⁶

In tandem with the control of symptoms, eliminating the infestation must be aggressively pursued to prevent further bites. Goddard et al. (2009) have outlined several steps that are useful in successful eradication of bedbugs:¹⁶

1. Proper identification of the bedbugs species
2. Education of the patient, other dwelling occupants, and landlord, as applicable
3. Thorough inspection of both infested and other nearby areas
4. Implementation of pesticide and non-chemical control measures
5. Follow-up to ensure control of the infestation

Conclusion

Bedbug infestation is increasingly prevalent and generates much anxiety in patients, which is fuelled by media coverage of this issue. As such, bedbug bites are a prudent component of a differential diagnoses if arthropod bites are suspected or history is suspicious for infestation. Confirmation of infestation may be necessary to establish the diagnosis in light of the often equivocal constellation of clinical symptoms. In addition to the cutaneous discomfort of bites and potentially serious sequelae, such as anaphylaxis, bedbug bites can cause significant psychological distress. Controlling symptoms through corticosteroids and anti-pruritics is helpful for patient comfort. However, ultimately, eradication of the offending insect and the prevention of further bites is the goal of therapy for these patients.

References

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In this issue:

1. Combination Therapy of Biologics with Traditional Agents in Psoriasis
2. Bedbugs: An Update on Recognition and Management
3. Update on Drugs and Drug News - June 2011