Bedbugs suck — blood mostly, but they are also a costly problem, says Rajeev Vaidyanathan of SRI International in Menlo Park, California, who led a series of talks on the creepy parasites at the American Society for Tropical Medicine and Hygiene in Philadelphia today.
New York City has reported a cost of US$10 million-40 million to control them, says Vaidyanathan, and in 2010 some 95% of pest-control agencies reported bedbugs as a number-one concern. They’ve been a huge worry for the hotel and hospitality industry in the United States, and after a few speakers presented their data (with stomach-wrenching pictures), several members of the audience were asking for ways to keep the parasites from hitchhiking home on their luggage.
A driving question for the past few years has been why, in just the past decade or so, have bedbugs come to thrive in the United States? Colby Schal of North Carolina State University in Raleigh has been looking to answer this question through bedbug genetics, as we reported earlier this year.
Samples from up and down the East Coast of the United States and from other sources show a very low genetic diversity (to a point indicating inbreeding) in individual populations, such as in an apartment or building that has been newly infested. But there is much wider diversity among populations in different cities, and even within the same city. For Schal, this suggests that multiple introductions have taken place over time.
Resistance to insecticides may have been a major factor in their re-emergence as well, says Ken Haynes, an entomologist at the University of Kentucky in Lexington. He notes that DDT “had a profound effect on bedbug populations”, suppressing them to the point that most folks had forgotten about them, even long after DDT use stopped. Nevertheless, DDT resistance was noted as early as 1948, says Haynes. Bedbugs were one of the first insects to develop such resistance, and their ability to tolerate currently used insecticides now seems quite widespread.
Both Haynes and Schal have demonstrated that upwards of 90% of bedbugs sampled in US cities have one or two common mutations associated with resistance to modern pyrethroid insecticides. In trying to find a lethal dose of insecticide for one strain of bedbug from Cincinnati, Haynes says, his team had them “wading around in a snowdrift of technical grade deltamethrin” a common pyrethroid. Alarmingly, some of the populations of bedbugs that he tested in a lab became resistant to combinations of pyrethroid and neonicotinoid insecticides after just one generation. These insecticides are on the top-10 list for pest-control companies in 2011, says Haynes. For many people dealing with an infestation, when insecticides fail, furniture and bedding may end up on the curb. When taken by others, the insecticide-resistant bugs can spread.
Still, a session on bedbugs is not what you’d normally expect at a meeting for a meeting on tropical diseases. Although bedbugs certainly exist in tropical climes, they are not a vector for any known disease. Many researchers don’t even consider budbugs a health concern.
But a more organized strategy may be necessary to stop their blood-sucking march. Mark Feldlaufer, a researcher at the US Department of Agriculture in Beltsville, Maryland, says that the common perception of bedbugs—as ‘equal-opportunity’ parasites that affect the wealthy just as often as the poor—is going away. While it’s true that anyone can be infected, he says, the options for remediation can be costly making bedbugs a bigger problem for those on the lower end of the socioeconomic spectrum. Heating a room to more than 120 degrees Fahrenheit for several hours seems to be one of the most comprehensive control techniques, but it can cost thousands of dollars.
And all of the speakers stressed that although bedbugs aren’t known to spread infectious diseases, they often bring about quite a bit of psychological distress. Some city health departments have begun to take an active role in stopping their spread, but budgets are tight. Still, something has to be done, says Haynes. “I think the idea that it’s not a public health concern is off the mark.”
Credit: Piotr Naskrecki