Bedbugs are developing resistance to insecticides, study shows

A new study from Purdue University finds that bedbugs are developing resistance to insecticides, allowing them to reach epidemic proportions across North America and Europe.

After decades of being kept under control, infestations of bedbugs have once again become a serious problem over the past 10 to 15 years. All but eradicated from Canada, the US and the rest of the industrialized world by the 1950s, the pesky biters have returned to major nuisance status mostly due to developing resistance to DDT and other insecticides.

Bedbugs are developing resistance to insecticides such as commonly-used deltamethrin…

Now, research has shown that not only are bedbugs resistant to the commonly-used deltamethrin insecticide but they are beginning to develop resistance to the second-tier toxins bifenthrin and chlorfenapyr, as well.

“In the past, bed bugs have repeatedly shown the ability to develop resistance to products overly relied upon for their control,” says study co-author Ameya Gondhalekar of the Department of Entomology at Purdue University in Indiana, in a statement. “The findings of the current study also show similar trends in regard to chlorfenapyr and bifenthrin resistance development in bed bugs.”

The researchers looked at ten different bedbug populations across the United States and studied their susceptibility to both chlorfenapyr and bifenthrin insecticides, going by the rationale that if more than 25 per cent of the insects survived spraying, they were determined to have reduced susceptibility (i.e., to have developed a level of resistance). In these cases, the researchers found that three of the populations had reduced susceptibility to chlorfenapyr and five had reduced susceptibility to bifenthrin.

As well, the same populations had developed resistance to both insecticides, a surprising result, as the two chemicals work in completely different fashions, one being a nerve toxin while the other disrupts mitochondrial activity in the insect’s cells.

The study’s authors say that research into the initial stages of resistance development is crucial to informing health and pest management strategies. “Proactive insecticide susceptibility monitoring studies are essential for low-level resistance detection in target pest populations,” the study’s authors say, “which allows for implementation of resistance management strategies that delay or prevent the onset of resistance-associated control failures.”

Bedbugs, while they don’t spread diseases give painful bites which can cause adverse reactions in some people. About the size and shape of an apple seed, the Cimex lectularius hide in the seams of mattresses and only come out at night to feed on human blood, leaving an itchy bite mark similar to a mosquito bite. Bedbugs can travel from place to place on clothes and furniture and even electronics. Peak season for bedbugs is usually in the warmer months between June and October.

Once an infestation has occurred, getting rid of them is notoriously difficult. According to a survey of pest management professionals in the US, 68 per cent of respondents pointed to the bedbug as the most difficult pest to control. The bug’s thick exoskeleton gives the insect extra protection against insecticides — and that, too, has been improving. Research from the University of Sydney in Australia found that bedbugs have been developing thicker cuticles to shield them from the chemicals.

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