Thursday, May 12, 2011

Do bed bugs carry disease?

A study just published in the CDC journal, Emerging Infectious Diseases, looks at the question of whether bed bugs might be vectors (carriers) of antibiotic-resistant bacteria.  In scientific parlance this is a great example of a Q&D study (quick and dirty).  The Vancouver, BC researchers had three hospitalized patients come in with bed bugs on their persons.  They thought, "wouldn't it be interesting to test these bed bugs to see if they have any antibiotic-resistant pathogens?"  So they took the bed bugs, crushed them up, and tried to isolate bacteria from them.

It turned out that two of the patients had one bed bug each that tested positive for vancomycin-resistant Enterococcus faecium (VRE).  The third patient had three bed bugs that tested positive for methocillin-resistant Staphylococcus aureus (MRSA).  The authors speculated that the bed bugs may have picked up these bacteria from the low-income community where the patients were from (infections from the two bacteria are prevalent there).  They also hypothesized that bed bugs in this community could be acting as a hidden environmental reservoir for MRSA, and could be contributing to the spread and amplification of MRSA infections in these impoverished and overcrowded communities. 

Such speculations and hypotheses are useful for researchers who love to make guesses and then test their hypotheses through further observations and experiments.  But it is important for those of us in the pest management field to not confuse speculation and hypothesis with facts.  Vector biologists can cite many examples of pests that have been shown to harbor a pathogen, but are not considered to be infectious to humans.  The standard of proof is pretty high for stating that a given insect or animal is capable of spreading infection.  This test does not meet that burden of proof by a mile.  And the authors would be the first to admit it.

So have bed bugs been shown to carry human disease?  Not yet.  In a clinical review published in the Journal of the American Medical Association, entomologist Jerome Goddard and medical doctor Richard deShazo combed the medical literature and could find no strong evidence showing bed bugs to be disease carriers. Based on collections from bed bugs, the hepatitis B virus (HBV) may be the best candidate for human disease transmission by bed bugs; however in an African study, a two-year eradication program that achieved 100% control of bed bugs had no effect on HBV infection rates. The authors concluded that "Although transmission of more than 40 human diseases has been attributed to bed bugs, there is little evidence that they are vectors of communicable disease." 

This is not to say that bed bugs lack health implications for humans.  Goddard and deShazo describe the most common reaction to bed bug bites as "2- to 5-mm pruritic maculopapular, erythematous lesions", medical terminology for "red itchy spots".  These spots usually itch and, "if not abraded, resolve within a week."  Some people, however, have more complex reactions to the bites including rashes and secondary infections.  Also, some people develop severe allergic reactions after multiple exposures to the bites (interestingly, in a 1985 experimental study cited in this review, only 30% of a volunteer cohort showed any reaction to bed bug bites).

In a joint statement issued last year, the Centers for Disease Control and the U.S. Environmental Protection Agency pointed out the emerging health implications of our growing bed bug problem.  In it they addressed the impact that bed bugs can have on mental health, saying, "Bed bugs may also affect the mental health of people living in infested homes. Reported effects include anxiety, insomnia and systemic reactions."  This aspect of the bed bug problem needs more study, and seems to be poorly appreciated by many in the hospitality and pest control industries.

When addressing the medical importance of bed bugs to your customers, it's important to look at the whole picture.  Bed bugs are a public health issue, even though they are not known at present to carry any disease pathogens. It would be unethical to imply that bed bugs are carriers of disease at this time; but at the same time bed bug elimination is important work.  Effective control of bed bugs alleviates anxiety, insomnia and discomfort for your clientele, and maintains a sanitary environment in which to live.  Isn't that what the pest control profession is all about?

3 comments:

Mike Merchant, PhD said...

According to one colleague, nearly 500 articles appeared in press on Friday about this bed bug research. Remember it's important to read beyond the headlines and ask yourself if something has really been proven, or it's just speculation.

Anonymous said...

I read the article and why am I bumping into a "well they MIGHT carry diease but we don't know" I am interested in this topic because the community I am in recently has been immersed in bedbugs and the speculation is that it has been brought in by overseas workers but I suspect they have always been here but are attracted by sweat and dead skin cells (call it an educated hunch. I live with a drinker who sweats a lot) Is there any study that actually shows that bedbugs carry lymes diease or is there any historical information on this? (Like a news clipping from NYC or Chicago from 1900-1950 for example) The reason why I ask that is I would think that ticks and bed bugs might be in a similar genus or family and logically you could conclude that they would carry the same dieases. Just wondering.

Mike Merchant, PhD said...

You might want to re-read the article, and especially check out the link to the clinical review in the JAMA. There is no evidence that bed bugs transmit any diseases--and it's not for lack of looking for a connection.