A study released by entomologists at Ohio State University shows why bedbugs are making a comeback. The study, published in the Public Library of Science journal PLoS ONE, shows that bedbugs are rapidly evolving, which allows them to develop resistance to the pesticides that have, in the past, been used to kill them.
Bedbugs (Cimex lectularius) are nocturnal, blood-feeding parasites that prefer to feed on humans. They have become a growing problem not only in the United States, but also worldwide. They are a public health issue affecting all socioeconomic levels.
Among the many reasons that bedbugs are now spreading so easily are that people are traveling more than in the past, including internationally, and people are more frequently acquiring used furniture. The problem isn’t limited to homes, however. A lot of hotels, in particular, are having problems with bedbugs, and even some libraries and other buildings, including stores, have become infested with these insects.
The authors of the study state, “During the past decade or so, the resurgence of C. lectularius has been recorded across the globe including North America, Europe, Australia, and Eastern Asia with an estimated 100–500% annual increase in bed bug populations.”
But why can’t we eliminate these pests?
In previous decades, such long-lasting residual insecticides as dichloro-diphenyl-trichloroethane (DDT) were effective in greatly reducing the number of bedbugs. However, because of the detrimental effects of DDT on the environment, DDT was banned in the United States in 1972. Therefore, people began to use pyrethroids—synthetic chemical compounds similar to the natural chemical pyrethrins produced by the flowers of pyrethrums (Chrysanthemum cinerariaefolium and C. coccineum), which are supposed to be safer than DDT, to fight bedbugs. Quite obviously, though, the pyrethroids are not as successful in eradicating these pests as manufacturers of the insecticides had hoped.
Why aren’t they? Because the bedbugs are gaining a resistance to the pyrethroids.
Very little is known about bedbugs at the molecular level. However, this study is changing that. The study is allowing us to learn more about the genetic makeup of the bedbugs, and it shows that bedbugs have increased their natural defenses against pesticides/insecticides. This new study adds to the evidence that bedbugs have evolved in a manner that gives them improved defenses against common pesticides; these improved defenses include nerve cells that are better able to withstand the effects of the chemicals, higher levels of enzymes for detoxification of the chemicals, and thicker shells that more effectively protect them from the pesticides.
We already know that bacteria can become resistant to antibiotics, viruses can become resistant to antiviral drugs, and weeds can become resistant to herbicides. Now, this latest study showing that bedbugs can evolve to resist pesticides/insecticides is further evidence that efforts to eliminate pests actually make some of them stronger.