Bedbugs were thought to be a thing of the past thanks to the use of dichlorodiphenyltrichloroethane, or DDT, which was developed during the 1940s.
But the bugs made a resurgence during the 1990s and early 2000s, and the longtime theory was that international travelers, who were able to fly more due to less expensive airfares, were responsible for the bugs hitching a ride out of Europe and to the United States.
Turns out, that theory is not supported by research findings.
“What we found was that there was no real evidence that there was a lot of genetic exchange occurring between Europe and the U.S. and Canada, or vice versa,” Warren Booth, professor of urban entomology at Virginia Tech, said.
Using whole genome sequencing and insecticide resistance-associated genes, “we found out there was a clear pattern of differentiation that Europe was on its own, the U.S. was very much on its own, and Canada fell somewhere in between, more associated with Europe than with the U.S., which is kind of really interesting considering we share a border,” Booth said.
Not only does the research debunk the idea that the 1990s bedbug resurgence was due to international travel, “what the data actually did tell us was that it looks like populations never went away in the U.S.,” he said.
“They likely remained probably, unfortunately, in low-income housing or in rural areas where pest control wasn’t common and wasn’t easily obtained,” he said. “And as a result, over time they simply resurged … probably because they have evolved resistance to most of the major insecticide active ingredients that are out there,” he added.
The U.S. banned the use of DDT in the early 1970s, but there has been a constant development of chemicals to keep pests such as bedbugs under control.
“If we look at when active ingredients were introduced following DDT, we had a time series where you had new active ingredients coming out. And within four to five years, we see evidence of resistance occurring in most insect species that have been subjected to them, and bedbugs are no different. We find that they’re resistant to the majority of the active ingredients present,” Booth said.
Long story short, the right set of circumstances aligned in the wrong ways allowed the bugs an avenue of return.
“I think the reason we saw them suddenly appearing in the early 2000s was it was just the right time,” Booth said. “They were resistant to all of the major active ingredients, and there was nothing kind of reducing populations.”
Bedbugs in the U.S. are a genetically diverse bunch, but when it comes to at-home infestations, they lack diversity, according to Booth. That’s because bedbug infestations “can start from a single pair of individuals or a single female that’s pregnant, and they will interbreed and inbreed for generations and generations.”
Booth said his lab has colonies that have been in culture and inbreeding for over 50 years where only one female needs to be pregnant and then it will “cause a nightmare in your home.”
“It’s a very unusual system, but many invasive insects can use this and overcome what would normally be detrimental for most species,” he said. “They seem to be able to override that and form very large populations through inbreeding.”
And it doesn’t take long for them to reproduce and wreak havoc.
“From one, you can end up within a month with several hundred, and when they all start breeding, within six months, you could end up with over 30,000,” Booth said.
Infestations can spread really rapidly, he points out.
“We studied a population in North Carolina in an assisted living facility that we traced back to probably one introduced female that was pregnant, and that spread through nine stories and 81 apartments within two years. So, they’re a pretty horrifying species if you, unfortunately, get to interact with them,” Booth said.
If you find bedbugs in your home, it’s best to let pest control experts take care of them.
“With the common insecticides that are pyrethroid-based, for example, we’ve shown that they’re about 16,000-fold resistant to that, so it’s going to do nothing for them. They can do the backstroke in there, and they’re going to come out happy, so it’s best to go with a reputable firm that’s going to be effective,” he recommends.
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