Bedbug Genome Reveals Pesticide Resistance

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Scientists have found some new genetic hints that could help explain why bedbugs are so hard to kill.

Some bedbugs appear to have evolved a mechanism that helps them break down toxins, including the ones in many pesticides, a team from The Ohio State University reports in the journal PLoS ONE.

The finding comes after earlier research found genetic changes in bedbugs that help protect nerve cells from specific pesticides.

Together, the findings suggest that current efforts to curb bedbug infestations will be more difficult than in the past, says Susan Jones, an urban entomologist at Ohio State University in Columbus.

"We're dealing with a different bug than what we were decades ago," Jones says, one that's harder to exterminate.

The latest genetic explanation for bedbugs' ability to resist pesticides comes from a study comparing genes from modern bedbugs with those from a colony started decades ago by a military bug expert named Harold Harlan.

We're dealing with a different bug than what we were decades ago.

Harlan's colony has been kept completely isolated, Jones says. "So it has had absolutely no exposure to insecticides," she says." When you expose it to insecticides, the bugs just keel over."

Breaking Down Pesticides

Bugs from Harlan's colony were compared with bugs from an apartment complex in Columbus that had been treated repeatedly with insecticide, Jones says.

Researchers focused on genes known to be involved in breaking down toxins and removing them from the body, says Omprakash Mittapalli, an entomologist from The Ohio State University in Wooster.

Mittapalli suspected modern bedbugs had genes that encouraged their bodies to produce more of the enzymes that break down pesticides. And, he says, that's just what the team found.

"These enzymes are indeed higher in the pesticide-exposed populations compared to the pesticide-susceptible population," Mittapalli says.

Bedbugs' ability to eliminate toxins and protect nerve cells has become quite common, says Ken Haynes, an entomologist at the University of Kentucky who has studied many populations of modern bedbugs.

He says nearly all of the populations he's studied have some resistance to common pesticides known as pyrethroids. And many "have a level of resistance that's quite extraordinary," he says, meaning they can withstand up to 1,000 times the dose that would usually be lethal.

A New Approach To Killing Bedbugs

All the new information about resistance suggests it may be time to try a different approach to killing bedbugs, Haynes says.

"Instead of relying on the same insecticide generation after generation of the bedbugs," Haynes says, "you'd rotate to a different class of pyrethroid or a different class of insecticide altogether with a different mode of action."

Bedbug control also should include nonchemical approaches like heat to kill the bugs and vacuuming to remove them from a room, says Louis Sorkin, an entomologist at the American Museum of Natural History in New York.

"It's not just one chemical approach and that's the end of it," Sorkin says.