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Abstract & Commentary
The Enigma of Bedbugs
By Alan D. Tice, MD, FACP, Infectious Disease Consultants, John A. Burns School of Medicine, University of Hawaii, Honolulu, is Associate Editor for Infectious Disease Alert.
Dr. Tice reports no financial relationship to this field of study.
Synopsis: Bedbugs have been a global problem for centuries, but recently have had a resurgence in prosperous countries, where they had been relatively dormant for years. Despite the nature of this pest, they have not been identified as a vector for any infections, though the potential risk cannot be completely ignored.
Source: Delaunay P, et al. Bedbugs and infectious diseases. Clin Infect Dis 2011;52:200-210.
A group of investigators in France undertook an exhaustive review of bedbugs and found evidence of them in the tombs of Egypt 3,500 years ago. They found them to be a common problem in developing countries throughout history, although there apparently was some decline with DDT. The dominant strains affecting humans are Cimex lectularius and Cimex hemipterus, although there are other strains that affect animals as well. The bans of DDT use in the United States in 1972 and globally in 2001 have been blamed for the recrudescence, but are probably not responsible for the resurgence of this hematophagous arthropod, as many are resistant to DDT and other pesticides, especially in countries with limited resources.
Bedbugs are unusual creatures that feed primarily on humans and reproduce by traumatic insemination, whereby the male penetrates the female through her cuticle instead of her reproductive tract, which is often fatal to the female. However, the survivors usually produce 200-500 eggs in a lifetime, which become larva within about a week and molt with each new blood meal until they become adults. They can live for a year without feeding and longer in colder climates.
These tiny insects are nocturnal and hide out in dark places such as beds, mattresses, clothes, and luggage. When a person or animal becomes available, they inflict a bite or blood collection with the help of an anesthetic and anticoagulants in their saliva. The wounds generally become apparent the next day, with itching and then a cluster of papules at the dinner table. These papules vary with the host; they may be small and itch a bit, but urticaria and bullae and even anaphylaxis have been reported.
With this history and the ability to crawl around, it seems only logical that they could spread a variety of infections. In fact, a large number of curious investigators have studied these bugs over the years and have been able to isolate as many as 45 different potential pathogens from them. Upon further investigation, however, the role of this worldly arthropod is questionable, especially when rigorous criteria are applied, such as vectorial competence (e.g., acquisition, maintenance, and transmission) and vectorial capacity (e.g., reasoning and detection in the wild). Many of the possible pathogens have been inoculated into bedbugs, but they do not even perpetuate themselves.
While a role in transmission on a limited level cannot be excluded, there have not been any outbreaks of human pathogens documented or even associated. Among the front-runners for apparent infections to consider are Coxiella burnetti, Wolbachia, Aspergillus species, Tripanosoma cruzi, hepatitis B, and HIV.
The resurgence of bedbugs is a curious phenomenon. They are an irritant to travelers, a headache to hoteliers, and have created a media frenzy, especially with eradication programs, which have briefly closed some very fashionable clothing stores.1 We are fortunate, however, that they are not vectors or carriers for what could be much more virulent organisms. Why this arthropod has not become a vector for disease over the years is unclear and a bit of a surprise given the role of so many other insects such as mosquitoes and fleas. Perhaps they are able to suppress the growth of intruders through immune or other mechanisms a defense for themselves as well as the hosts they feed on.
The question now becomes what to do about these annoying pests. The authors refer to a simple and prompt test that is being used to detect this parasite: A dog trained to recognize the obnoxious odor the bedbugs produce simply snifs around the infested room or luggage or clothing. Once bedbugs are detected, the next step is to clean up all materials that may harbor these bugs and vaccum the premises thoroughly. Clothing that may be infested should be put into sealed plastic bags until washed and then dried in a hot machine drier. They are often resistant to common pesticides. Fumigation is often not effective because of resistance and failure to penetrate their hiding places in beds, bedding, clothing, furniture, and luggage. Spray pesticides may help reach into the dark depths of their existence where fumigation usually cannot, but resistance is a problem there as well. Another route of elimination is to super-heat the infested rooms for a day or so, which apparently kills them off.2
So, beware of the potential for bedbugs wherever you travel and beware of their potential to cause disease, although secondary transmission may not be a problem, yet.