(Beyond Pesticides, December 15, 2011) New research suggests that the recent re-emergence of bed bug infestations may originate from insecticide use in the tropics. According to the results, which were presented at the American Society of Tropical Medicine and Hygiene’s 60th annual meeting, exposure to treated bed nets and linens caused populations of bed-bugs to build resistance to those chemicals. The findings presented at the gathering showed that 90% of 66 populations sampled from 21 U.S. states were resistant to a group of insecticides, known as pyrethroids, commonly used to kill unwanted bugs and flies. Other research has already shown that an over-reliance on chemical controls over the years has helped bed bugs evolve to be resistant to these chemicals.
One of the co-authors, evolutionary biologist Warren Booth, Ph.D. from North Caroline State University in Raleigh, told the BBC news that the genetic evidence he and his colleagues had collected show that the bed-bugs infecting households in the U.S. and Canada in the last decade are not domestic bed bugs, but imports.
The team collected samples from across the eastern U.S. and discovered populations of bed-bugs that are genetically very diverse. “If bed-bugs emerged from local refugia, such as poultry farms, you would expect the bed-bugs to be genetically very similar to each other,” explained entomologist and co-author Coby Schal, Ph.D. also from North Carolina State University. “This isn’t what we found.” Dr. Schall explained to the BBC news that this suggests that the bugs originated from elsewhere, and relatively recently because the different populations had not had time to interbreed.
“The obvious answer is the tropics, where they have used treated bed nets [and] high levels of insecticides on clothing and bedding to protect the military,” Dr Booth told BBC News.
Bed bugs have slowly been developing resistance mechanisms and have become resistant to most, if not all, insecticides on the market. On average, insecticides labeled for bed bug control can take over 150 hours to kill a bed bug, compared to seconds or minutes in previous years. An Ohio State study, â€śTranscriptomics of the Bed Bug,â€ť published January 2011 in the journal PLoS One confirms bed bug resistance to pyrethroid insecticides and highlights the need to adopt non-chemical methods for controlling bed bugs and other insect pests.
Pyrethroids, some of the most common chemicals used in attempts to treat bed bug infestations, are a class of pesticides that are synthetic versions of pyrethrin, a natural insecticide found in certain species of chrysanthemum. They were initially introduced on the market as â€ťËśsaferâ€™ alternatives to the heavily regulated and highly toxic organophosphates such as chlorpyrifos and diazinon, which were banned for residential use in 2001 and 2004, respectively. Despite the fact that there are plenty of effective pest control methods that are not nearly as toxic, pyrethroids are now some of the most popular household pesticides. They are cause for concern to consumers because of their link to serious chronic health problems. Synthetic pyrethroids are suspected endocrine disruptors, and have been found lingering in the dust at daycare centers.
The bed bug resurgence in the U.S. in recent years has been met by increasingly widespread pesticide resistance, as people have tried to manage them with chemicals. This has led to public anxiety about the pests and drastic attempts to stem their spread through various means, often including the use of highly toxic and harmful chemicals. For example, the State of Ohio, dealing with infestation in several major cities in 2009, petitioned the U.S. Environmental Protection Agency (EPA) to approve the indoor use of the pesticide propoxur. The agency considers propoxur to be a probable carcinogen and, due to concerns posed to children, banned it for in-home use in 2007. About 25 other states supported Ohioâ€™s request for an emergency exemption. In comments to the agency objecting to the petition for propoxur, Beyond Pesticides and other environmental and public health advocates urged the agency to reject the request, citing numerous serious public health threats associated with the chemical, as well as the availability of alternatives. EPA rejected Ohioâ€™s petition in June.
The good news is that these pests can be effectively controlled with non-toxic approaches. An IPM approach, which includes methods such as vacuuming, steaming, and exposing the bugs to high heat, can control an infestation without the dangerous side effects. This approach, as well as taking steps such as sealing cracks and crevices, reducing clutter and encasing mattresses, can also help to prevent an infestation in the first place.
For more information on bed bugs and least-toxic control methods, see our factsheet, â€śGot Bed Bugs, Donâ€™t Panic,â€ť on our Bed Bug program page.
All unattributed positions and opinions in this piece are those of Beyond Pesticides.