Bedbugs Becoming Immune

The first comprehensive genetic study of bedbugs, the irritating pests that have enjoyed a world-wide resurgence in recent years, indicates they are quickly evolving to withstand the pesticides used to combat them.

The new findings from entomologists at Ohio State University, reported Wednesday online in PLoS One, show that bedbugs may have boosted their natural defenses by generating higher levels of enzymes that can cleanse them of poisons.

In New York City, bedbugs now are 250 times more resistant to the standard pesticide than bedbugs in Florida, due to changes in a gene controlling the resilience of the nerve cells targeted by the insecticide, researchers at the University of Massachusetts in Amherst recently reported.

Recent studies show that bedbugs around the world have developed a resistance to the chemicals used to control them. Scientists are now studying the molecular biology of these pests to develop more lasting control measures.

New findings from entomologists at Ohio State University, reported Wednesday online in PLoS One, show that bedbugs may have boosted their natural defenses by generating higher levels of enzymes that can cleanse themselves of common pyrethroid-based pesticides.

The findings add to a growing body of evidence from molecular-biology studies that bedbugs have recently evolved at leastthree improved biochemical defenses against common pesticides. Bedbugs today appear to have nerve cells better able to withstand the chemical effects, higher levels of enzymes that detoxify the lethal substances, and thicker shells that can block insecticides.

"These bugs have several back doors open to escape," said evolutionary entomologist Klaus Reinhardt at the University of Tuebingen in Germany, who was familiar with the new research butn't involved in the projects. "Simple spraying around of some pesticides may not [be enough] now or in the future."

In an era of antibiotic-resistant infections and herbicide-resistant weeds, the ability of bedbugs to survive once-lethal doses of insecticides is the newest evidence that efforts to eradicate pests that plague humankind may make some of them stronger. It is a key reason for the spread of bedbugs in the past decade, several researchers who study them said.

Well-adapted to homes, hotels and dormitories, these tiny blood-sucking parasites usually hide in mattresses, bed frames and furniture upholstery. Bedbugs feed every five to 10 days, leaving painful welts on the skin and sometimes triggering allergic reactions.

Laboratory tests in the U.S., Europe and Africa show today's bedbugs can survive pesticide levels a thousand times greater than the lethal dose of a decade or so ago. "There is a phenomenal level of resistance," said bedbug entomologist Michael Siva-Jothy at the University of Sheffield in the U.K. "It has evolved very recently."

Since the pesticide DDT was banned starting about 40 years ago, people usually have treated bedbug infestations with pesticides based on a family of compounds called pyrethroids, usually deltamethrin or lambda-cyhalothrin, synthetic versions of chemicals found in chrysanthemum blossoms.

There are few chemical alternatives, because the residential market for insecticides is relatively small, and the cost of development, safety tests and regulatory approval is relatively high, several researchers said. Since the bugs don't transmit any serious infectious diseases, there also is little medical funding to research new control measures.