Bed bugs are the original human pest. They’ve been chomping down on people since ancient times. A new study out of Virginia Tech in the U.S. reveals they may also be getting harder to kill.
In April, associate professor Warren Booth and graduate student Camille Block discovered a gene mutation in certain bed bugs that made them resistant to an array of insecticides. It was proof that bed bugs are adapting.
In the early 20th century, particularly around the two world wars, people battled bed bugs with hot water and lye soap. But in the 1950s, scientists created the pesticide dichloro-diphenyl-trichloroethane, commonly known as DDT. It was an effective tool in the fight against bed bugs, with outbreaks plummeting. Unfortunately, DDT had negative effects on the environment and people’s long-term health, causing breast cancer and cardiovascular disease.
Most countries banned DDT by the 1990s. Canada began phasing it out in the mid-1970s, with DDT sales illegal after December 31, 1990. However, since then, bed bugs seem to be making a resurgence, including during the 2023 Paris outbreak.
Up to this point, researchers had observed that certain types of bed bugs had become resistant to certain insecticides, but it was unclear how. Booth theorized that some bed bugs may have developed a mutated gene in their nerve cells that made them resistant. A similar gene, known as the Rdl gene, had been discovered in German cockroaches and white flies.
Bugs suck! Here are some bugs we love to hate
To find out, Booth tasked Block with analyzing one bed bug from each of the 134 unique bed bug populations. She used samples provided by pest control companies across North America, who’d collected the bed bugs between 2008 and 2022. By using a sequencing machine, Block was able to study the genome of each sample.
Throughout the sequencing, she found two bed bugs from two separate populations that had the Rdl gene. “It was literally my last 24 samples,” said Block, in a statement.
According to the researchers, extensive inbreeding amongst bed bugs causes them to have a genetic uniformity, meaning one sample generally represents that entire population of bed bugs. But Booth wanted to make sure they’d discovered the mutation, so they tested every specimen they had in the two populations.
“When we went back and screened multiple individuals from the two populations, every one of them had the mutations,” said Booth, in a statement. “So, they were fixed for these mutations, and it’s the same mutation that we find in German cockroaches.”
The Rdl gene makes the bed bugs resistant to insecticides such as dieldrin and fipronil. Both insecticides have proven effective in killing bed bugs in lab tests. Dieldrin, however, was developed as an alternative to DDT and is now banned in most countries. Whereas fipronil is still used to treat cats and dogs for fleas.
Cottage Q&A: What attacked me in the lake?
Booth has a hunch that fipronil may have contributed to developing the gene mutation in bed bugs. Since many people let their cats and dogs sleep with them, it could expose the bedding to fipronil residue. Any bed bugs in the bedding would be exposed to the fipronil and then select for that mutation in the population.
“We don’t know if that mutation is novel,” said Booth, “or whether it was occurring in populations 100 years ago.”
Moving forward, the team will look for the Rdl gene in bed bugs in different regions of the world, particularly Europe. They will also look for it in different time periods by analyzing museum specimens.
So far, the team has already discovered that bed bug populations mirror human expansion, booming in urban centres. In fact, it’s likely bed bugs have been tied to humans for 60,000 years, first hitching a ride on a Neanderthal moving out of a cave.
Related Story Living with pests, big and small: A how-to guide for coexisting with common cottage invaders
Related Story How bad will the mosquitoes be in Ontario’s cottage country this summer?
Related Story 5 fascinating facts about beetles