Bed bugs, those blood-sucking assassins of tranquility, have most often been seen throughout history as pests with a small “p.” Their itchy bites can be profound nuisances, and the thought of them infesting mattresses and crawling across us during sleep can provoke shudders, and the turmoil they cause can turn a household upside-down. But we have at least had the consolation that unlike, say, mosquitoes with malaria or dengue and sand flies with leishmaniasis, bed bugs do not kill or cause disease. That is certainly the commonplace wisdom, as mentioned by Amy Maxmen in her good new review, “Bedbug 2011: What You Need to Know.”
Yet disturbingly, that reassuring fact might not hold true in the future. As Maryn McKenna reports on her Superbug blog, Canadian researchers Christopher F. Lowe and Marc G. Romney announce in the June issue of Emerging Infectious Diseases that three hospitalized patients from Downtown Eastside, a very poor neighborhood in Vancouver, were infested with bed bugs that proved to carry drug-resistant bacteria. Specifically, the bacteria were vancomycin-resistant Enterococcus faecium (VRE), which often causes serious hospital-acquired infections, and methicillin-resistant Staphylococcus aureus (MRSA), staph organisms that can trigger lethal infections in people with weakened immune systems. The spread of such antibiotic-resistant germs is one of today’s most urgent infectious disease threats.
As Maryn writes:
[Lowe and Romney] point out that several research groups have tried in the past to link bedbugs and disease transmission (of hepatitis, for instance) and have failed. They certainly have not proven transmission in this case. But they also say that there is a density of these two organisms in the area where the men live that make it more likely that bedbugs could be involved in diseases pingponging through the neighborhood. First, there’s the high density of bedbug presence, in 31 percent of Downtown Eastside residents. Second, there’s the high prevalence of MRSA, in 58 percent of the skin infections in the St. Paul’s ER. And third, there’s the previously recorded and persistent presence of VRE in in-patients at St. Paul’s.
The US CDC believes that crowding, poor hygiene and skin disruption increase the likelihood of MRSA infection; crowding and poor hygiene are common in homelessness and shelter living, and bedbugs by definition disrupt the skin’s barrier by their bites. Meanwhile, in the ill and hospitalized, VRE frequently causes infections in disrupted skin, such as a surgical incision or a diabetic ulcer.
In short, the pathological potential of the bacteria, the habits of the bed bugs and the crowded, unhygienic living conditions in which many of the poor would be forced to live could combine to spread these infections. The involvement of the bed bugs in the transmission of the bacteria is somewhat passive: they probably wouldn’t be injecting the germs into their hosts. Rather, they would leave trails of the bacteria on the skin in their droppings; people later scratching at the itchy bites would break the skin and introduce the bacteria to their tissues.
Just to be clear and prevent panic: there is as yet no evidence of bed bugs transmitting these infections to people. Lowe and Romney are only pointing out a seemingly plausible way in which the bugs could become involved in the spread of these germs throughout the community—particularly poor communities. For now, it’s a danger that health authorities need to monitor.
Meanwhile, no one should overreact to a perceived threat—because such overreactions can themselves be highly dangerous. As Amy Maxmen writes, the pesticides commonly sold over the counter to combat bed bugs aren’t effective and carry risks:
Worse yet, misuse of these sprays may lead to digestive problems, skin irritation, and may worsen asthma and allergies (1). “People think if you can buy a pesticide at a supermarket it can’t be dangerous, so they use them like mad when in fact almost none of these chemicals have been tested on humans,” says Stephanie Chalupka, an environmental and occupational health expert in Massachusetts at Worcester State College and Harvard School of Public Health in Boston. “I think the public health community could do a better job of getting out information on what is useful and safe, and what may put kids at risk.” Chalupka says she’s particularly concerned for pregnant women and their developing babies. “All sorts of compounds can get to the developing fetus, which is at a very vulnerable state as its organs and systems are forming.”
And it now seems that a misguided, reckless attempt to exterminate bed bugs might have killed at least one person: 23-year-old Sarah Carter of New Zealand, who died last February while touring in Thailand. As reported by the Dominion-Post at Stuff.co.nz:
Ms Carter died and her friends Emma Langlands and Amanda Eliason became gravely ill while on holiday in Chiang Mai, Thailand.
Traces of chlorpyrifos, which is used to kill bedbugs but has been banned in other countries, have been found in samples that current affairs television show 60 Minutes had independently tested.
United Nations scientist Ron McDowall said there was a strong likelihood Ms Carter died from excessive exposure to the substance, which causes identical symptoms to those suffered by the trio as well as several other tourists who died after staying at the hotel.
The fact traces of chlorpyrifos were found three months after Ms Carter’s death and after the room was cleaned suggested there was a high concentration when she was staying there.
“I think she has been killed by an overzealous sprayer who’s been acting on the instructions of the hotel owner to deal with bed bugs,” Mr McDowall said.
Even a slight mistake in the dosage of chlorpyrifos, which has been banned for indoor use in many countries, could be lethal, he said.
Tragic and needless. Bed bugs are bad, but poison is can sometimes be still worse. [Modified in response to Richard Pollack's comment below.]
Update (5/12): Dan Diekema at Controversies in Hospital Infection Prevention helps to put the fact of bed bugs carrying MRSA in context by pointing out that four million people in the U.S. already carry MRSA in their noses. So potential sources of infection are not in short supply already. I’m not sure that the prevalence of those infections in people negates the potential significance of these bacteria in the bugs. If anything, it’s troubling to learn that MRSA-carrying bed bugs represent yet another potential source of infection. Still, the important word in all this discussion is potential. Much more information is needed before we even know whether the concentrations of MRSA left on the skin by bed bugs would be at all efficient in practice at causing inflammations, for example. For now, I think I’ll stand by my concern that overreactions to bed bug infestations—including imprudent use of pesticides and surrendering to panic—represent greater threats to public health than do the bugs themselves.
Delaunay P, Blanc V, Del Giudice P, Levy-Bencheton A, Chosidow O, Marty P, and Brouqui P. Bedbugs and Infectious Diseases. Clin Infect Dis. (2011) 52 (2): 200-210. doi: 10.1093/cid/ciq102
My previous bed bug posts:
Hazards of Bed Bugs—and of Getting Rid of Them by PLOS Blogs Network, unless otherwise expressly stated, is licensed under a Creative Commons Attribution 4.0 International License.