The first complete genetic study of bedbugs has uncovered genes associated with pesticide resistance.
The genes encode for enzymes that help them detoxify – and ultimately allow them to adapt to repeated insecticide use. Ruh-roh.
These blood-feeders are poised to replace cockroaches as the biggest household pest in the US. In the past decade, their numbers have increased as much as 500%, costing homeowners and infested businesses billions of dollars a year.
Despite this, “we know very little about their genetic makeup and their mechanisms of resistance to insecticides," says study author Omprakash Mittapalli of Ohio State University.
To find a genetic explanation for what makes them so hard to kill, Mittapalli and OSU colleagues analyzed laboratory-reared bedbugs known as the Harlan strain, which are still susceptible to insecticides.
Harlan’s colony has been kept completely isolated with “absolutely no exposure to insecticides," says coauthor Susan Jones." When you expose it to insecticides, the bugs just keel over."
The team compared those with bedbugs collected from an apartment in Columbus who have survived repeated exposure to insecticides. "We're dealing with a different bug than what we were decades ago," Jones says. One that's up to 1,000 times harder to exterminate.
The team focused on enzymes shown in other insects to detoxify and help them survive insecticides.
They found that these enzymes are indeed higher in the pesticide-exposed populations compared to Harlan’s susceptible population.
Scientists had thought that a DNA mutation made bedbugs resistant, but these findings suggest many genes have helped the insects adapt to them.
Exposure to pesticides actually may trigger genes to react in defense. Wall Street Journal explains: Repeated applications of the same insecticides act as a form of natural selection for bedbugs. Any surviving insects pass on traits to their offspring and to succeeding generations. Resistance to chemicals designed to kill the bugs can become a permanent part of their genetic inheritance.
“Pinpointing such defense mechanisms and the associated genes could lead to the development of novel methods of control that are more effective," Mittapalli says.
Our association with these bugs dates back to 1350 B.C. Well-preserved bedbug remains were recovered from the Workmen's Village at el-Amarna, Egypt. They were introduced to North America by early colonists in the 17th century. They were extremely common pests before World War II, but the arrival of DDT and other long-lasting insecticides axed their numbers.
Their recent comeback is largely due to a boom in international travel, increased exchange of used furniture, a shift away from the potent but dangerous DDT and their development of resistance to currently used pesticides.
This Cimex lectularius study was published in PLoS ONE this week.
The Harlan strain is named after bedbug expert Harold Harlan of the Armed Forces Pest Management Board. My only bedbug experience ever came from meeting Dr. Harlan last spring outside of DC. He was carrying a little box of over a dozen famished bedbugs, and I let them feed off my left forearm… as you do.
Image: Armed Forces Pest Management Board via Flickr