Anyone who has ever dealt with a bed bug infestation knows the horrors of the biting mites and the difficulties of exterminating them.

Now, to make things worse, new research shows colonies of bed bugs are developing resistance to the most widely used class of insecticides.

Dr. Alvaro Romero, an assistant professor of urban entomology at New Mexico State University, said bed bugs, in areas previously treated with commonly used neonicotinoids, also called neonics, are showing the most resistance.

insecticide resistant bedbugs

While his study with Dr. Troy Anderson from Virginia Tech, published today in the Journal of Medical Entomology shows some populations now have immunity to these pesticides, further studies are needed to see if the effects extend elsewhere.

“We don’t know how widespread it is in the United States,” Romero told Healthline. “We need to know the scope of this.”

The use of neonics are cited as the possible reason for the declining bee populations in the U.S. According to the Xerces Society for Invertebrate Conservation, levels of neonic residues found in pollen and nectar can reach lethal levels for bees.

While the jury is still out on the extent of their impact on the bee population, neonics appear to be losing their grip on the bed bug extermination process overall.

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Colonies of Bed Bugs

Dr. Harold Harlan, a retired military entomologist, is the go-to guy in the world of bed bug research.

Since 1973, he’s been keeping his own population of bed bugs away from pesticides for research purposes. Every day, Harlan presses jars filled with the bugs and covered in fine mesh against his skin so they can feed off his blood.

Romero and Anderson used some of these bugs in their recent study to see how effective four neonics — acetamiprid, dinotefuran, imidacloprid, and thiamethoxam—were at killing them.

As expected, Harlan’s bugs died with only a little exposure to neonics.

Another set of bugs, gathered from Jersey City in 2008 before the widespread use of neonics, showed moderate resistance to acetamiprid and dinotefuran but not to imidacloprid or thiamethoxam.

When bed bugs are exposed to insecticides, they produce “detoxifying enzymes” to defend against them. Researchers found higher levels of these in the Jersey City bed bugs compared to Harlan’s.

Lastly, researchers found the highest resistance levels in beg bugs from Michigan and Cincinnati that existed in the wild while common insecticides were introduced to the U.S. market.

Researchers say half of Harlan’s bugs were killed with 0.3 nanograms of acetamiprid, while it took 10,000 nanograms to kill the same amount of the Michigan and Cincinnati bed bugs.

Comparatively, the Michigan bed bugs were between 198 to 33,333 times more resistant to different neonics.

These findings, Romero said, suggest pest control companies should be on the lookout for signs that the insecticides they use aren’t as effective. One sign is bed bugs living on previously treated surfaces.

“In these cases, laboratory confirmation of resistance is advised, and if resistance is detected, products with different modes of action need to be considered, along with the use of non-chemical methods,” Romero said.

One way to kill bed bugs without chemicals is to steam them at temperatures above 113 degrees Fahrenheit.

Read More: Indoor Pesticide Use Linked to Childhood Cancers »

The Basics of Bed Bugs

Bed bugs, or Cimex lectularius, feed on human blood. That process can cause itchy, red spots.

Some people may not feel the bites while others can have an allergic reaction. However, they’re not known to transmit diseases like other blood-sucking bugs.

As their nickname implies, they live on beds, furniture, and other places where they can feed off humans. Bed bugs are good hitchhikers and can quickly establish new colonies, most commonly in apartment buildings, single-family homes, and hotels.

Officials at the pest control company Orkin said they saw an 18 percent increase in bed bug calls in 2015. Cities with the highest infestation rates include Chicago, Detroit, Los Angeles, and Cleveland and Columbus, Ohio.

The increased prevalence of bed bugs, according to the U.S. Environmental Protection Agency, can be attributed to more people traveling, lack of knowledge about preventing infestations, ineffective pest control practices, and the increase in pesticide resistance.

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