How did bed bugs get here? Did they never leave? Recent research on genetics and inbreeding

by nobugsonme on December 16, 2011 · 1 comment

in bed bug epidemic, bed bug research, bed bug treatment, bed bugs, bed bugs and travel, history, spread of bed bugs

A new article by Katherine Harmon in Scientific American explores genetic research into bed bugs, which may be used to explain how they spread and thrive.

North Carolina State Entomologist Dr. Coby Schal and other researchers (including Drs. Warren Booth and Ed Vargo of NCSU and Changlu Wang of Rutgers) have been collecting samples from around the US and from within individual buildings, to learn more about how they were introduced and about their genetic diversity.

Harmon writes,

A genetic survey across the U.S. found that among towns, bedbugs have great genetic variation. That diversity suggests that, rather than having been brought into the country only a few times, the parasites crossed the borders many times—and are likely continuing to do so. These founder bugs go on to create larger populations. Even in well-connected and highly populated cities on the Interstate 95 corridor along the east coast, bedbug populations remained relatively distinct from one another.

Within each domestic population, however, the genetic distribution is a much different story. In a single home or apartment building, for example, the bugs show “an extremely high rate of inbreeding,” Schal said. His team found that an entire population within an apartment building—such as were the cases in infested Jersey City, N.J., and Raleigh, N.C. buildings—was so genetically similar that it might have been founded by a single fertilized female. Bugs in the next generation then would have mated with one another, and so on, in a seemingly indefinite incestuous line.

Not only does bed bug inbreeding not appear to have the same negative effects that it can have in human and many other animal populations, but evidence found by the team in one building even suggested that, given other options, bed bugs may “prefer” it.

(Nasty little buggers!)

We first heard about this study when the researchers received a grant for it back in 2008 (this information forms a footnote to this interview with Dr. James Austin about bed bugs, chickens and DNA).   It is good to hear some of the results.

Another interesting soundbite from the article?  Dr. Kenneth Haynes of the University of Kentucky is cited as saying that bed bugs can move 2.5 meters in five minutes.

Nasty and fast.

A winning combination, unfortunately.

Haynes and Schal were among the speakers at the American Society of Tropical Medicine and Hygiene meeting on December 6th, and additional articles shed more light on their research projects and findings.

Science News, Nature, and offer additional details on the work of Schal’s team, as well as on Ken Haynes’ work on genetics and pyrethroid resistance.

Science provides the abstracts for Schal’s teams’ two unpublished studies (which are under review) here (PDF) and here (PDF).

Interestingly, the BBC explores Schal’s hypothesis that bed bugs were reintroduced recently into the US from tropical countries where bed bugs persisted (and had developed resistance to heavily-used pesticides) after they had been virtually eradicated in the US.

When I say virtually, however, I note that there is evidence which suggests that bed bugs were never entirely eliminated in the US.  See the references former Bedbugger hopelessnomo provides in her comment on her Bedbugger article from 2008, in particular her comment dated 1/13/2008 at 10:35 pm — which affirm the presence of bed bugs in the US in the period from 1986-1999.

And that’s not counting the ones who lived with chickens.

The BBC cites Dr. Clive Boase,who reminds us once again that bed bugs were present in smaller numbers in the UK throughout the 1970s and 1980s, after DDT stopped being used, and notes that

“We don’t have to invoke stories of disease control programmes in Africa; all the evidence here in the UK is that our problem is home-grown.”

Dr Boase wondered that if the US had similar long-term records whether the researchers would have reached a different conclusion.

The BBC story also cites the University of Sheffield’s Dr. Richard Naylor (well known to Bedbugger forum users), who also questioned the team’s hypothesis:

“It doesn’t seem that difficult to develop resistance or lose it; in lab cultures, if you stop exposing [bed-bugs] to pyrethroids it drops out of lab populations very quickly,” he said.

Mr Naylor asked that if the US bed bugs had been exposed to the chemicals elsewhere in the past, “why would they still be resistant?”

The Science article suggests Schal is working on testing this hypothesis by collecting samples from abroad.

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Thanks to Bait for drawing our attention to the Scientific American article.  See more Bedbugger articles about Dr. Coby Schal.

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1 chuck007 December 17, 2011 at 7:32 am

Now this is a nice article . these are the questions that were on my mind .

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