Professors discuss bed bug resistance to insecticides
A resurgence of bed bugs has led to their highest recorded population in the past several centuries. They have an added advantage now — resistance to insecticide.
Kenneth Haynes, a professor of entomology from the University of Kentucky, spoke at the Department of Entomology March 15 about the urgent danger of the bed bug adaptation against insecticides.
Haynes, Changlu Wang and Richard Cooper are researchers attempting to help control the bed bug population growth that may be caused by growing resistance to insecticides — such as dichloro-diphenyl-trichloroethane, commonly known as DDT.
“A renewed resurgence of bed bugs is appearing not only in the U.S. but the whole world,” Haynes said.
From about 15-60 years ago, Haynes said bed bugs began coming back at a level that has not be seen for centuries.
“A big change came about 60 years ago when insecticides, like DDT, began to be used around the end of World War II. DDT went from very specialized use, from the military, to the home of the everyday consumer,” he said.
Pest control industry data from 2010 and 2011 show bed bugs are becoming the prominent household pests in several parts of the world, he said. They are currently listed as the pests most difficult to control.
Populations can build up so that one person can be feeding 10,000 bugs with their own blood each night, he said.
Bed bug growth typically depends on their ability to hide in crevices and sustain off very little, he said.
“Until recently, it had been very uncommon for a pest control professional to actually encounter bed bugs in their working lives,” he said.
He said insecticide resistance seems to be the main explanation to the current abundance of bed bug populations.
“Naturally, insects have multiple mechanisms to detoxify the harmful chemicals of insecticides,” said Wang, a University researcher in the Department of Entomology.
Bed bugs benefit mainly from mechanisms that prevent the insecticide from entering the body and processes that break down the harmful chemicals if they enter, he said.
“We tested the injection of chemicals via a temporary open body cavity for mating. One of the main genes we targeted was the P450 genes — which are responsible for insecticide detoxification,” Haynes said.
Most of this detoxification naturally occurs in the epidermis, the outer skin layer, because the nerve cells do not risk exposure to the insecticide toxins, he said. Injecting into the epidermis proved to reduce resistance.
“The insecticides were very effective for generations, but once you have the seeds of the resistance of one population — it just expands,” he said.
DDT resistance has been around for a while, but that leads to resistance to other insecticide chemicals such as pyrethroids, another type of insecticide chemical, Haynes said.
“Products with more pyrethroid dependency have been seeing less popularity recently. Some new products that have been used are combinations of pyrethroids and neonicotinoids, another class of insecticides,” he said.
He said it would be interesting to see how long exterminators will be able to use combination products — since one type of insecticide may mean the ability to develop a faster resistance to another type.
“Combination products are short-term solutions. Understanding population movement and improving our ability to detect bed bugs are some of the long-term, sustainable approaches,” said Richard Cooper, a graduate assistant in the Department of Entomology.
Understanding behavioral ecology and focusing largely on low-level populations is Cooper’s specialization, he said. Insecticides suffice as a temporary solution until they understand bed bug behavior.
“In better understanding, some of the bed bug ecology, biology and life history, you’re better prepared to manage the pest without relying so intensively on insecticides,” he said.
Despite their size, bed bugs move surprisingly quickly, Haynes said. Bed bugs were tracked to move 13 feet over the course of five minutes.
“One of my colleagues set down his camera bag for a second and found a bed bug on his bag,” he said.
Wang said there were many low-cost methods to control bed bugs beside chemicals, such as frequent inspection of belongings and reduction of hiding places.
He said inspections have to be done regularly — in hiding places such as bed linens, shoes and furniture.
Population growth may also be due to human-aided movement, Cooper said.
“You may see this nice couch on the road, and you may get an unexpected bonus from this bargain of a couch — the resistant bed bugs,” Haynes said.
Seeing a couch on the side of the road may be a sign of a failed attempt to control bed bug infestation — leading to a population with an amplified resistance, he said.
“Infestations may also go undetected for a period of time because not everyone develops reactions right away,” Cooper said.
They may go unnoticed for a few months or more, he said. Bed bug bites are difficult to identify — it is common to confuse bed bug bites for reactions to poison ivy, mosquito bites or chickenpox.
“Once the infestations get well-established, [they] become difficult to control. Bugs could be getting into belongings or travelling outside with people into school classrooms or libraries or the gym,” he said.
Fear of the presence of bed bugs may lead to sleeping and mental disorders — as well as economic problems for hotels and other businesses, Haynes said.
People don’t report when they have bed bug infestations because they don not want it to interfere with their personal lives, such as friends coming over, he said.
“It causes a lot of stress and anxiety. As far as I know, no one voluntarily lives with bed bugs,” he said.