January 20, 2011

Study Suggests Bedbugs May Be Pesticide-Resistant

The recent revival of bedbugs could be due to a genetic resistance to pesticides, claims a study published in the online journal PLoS One on Wednesday.

Entomologists at Ohio State University sequenced the genetic map of the bedbug (Cimex lectularius), which have started becoming prevalent again in recent years and made headlines due to an outbreak in late 2010. They discovered that these little, six-legged, bloodsucking pests possess "genes that appear to be pesticide-resistant," according to a January 19 report by AFP.

"While bedbugs are poised to become one of the major household pests across the United States in the coming years, we know very little about their genetic makeup and their mechanisms of resistance to insecticides," Omprakash Mittapalli, corresponding author of the study and an assistant professor of entomology at OSU's Ohio Agricultural Research and Development Center, said in a statement.

Mittapalli, who claims that this is the first study "to elucidate the genetic makeup of the insect and to obtain fundamental molecular knowledge regarding potential defense pathways and genes that may be involved in metabolic resistance to commonly used pesticides," and his colleagues used 454 sequencing technology and successfully identified 35,646 expressed sequence tags (ESTs). Previously, less than 2,000 bedbug ESTs had been discovered and identified.

"The common assumption today is that pesticide resistance in bedbugs results from point mutations in certain genes," the OSU professor said. "However, the role of detoxification and antioxidant enzymes in pesticide resistance of bedbugs is poorly understood. Enzymes such as Cytochrome P450s and glutathione S-transferases (GSTs) have been shown in other insects to act as detoxification agents, allowing the insects to get rid of toxic compounds such as insecticides and not be killed by them."

Those enzyme groups were a main focus of Mittapalli's research, he said.

"From the database we created, we profiled the transcript level for a cytochrome P450 (CYP9) and a GST (Delta-epsilon) in different developmental stages (early-stage nymphs, late-stage nymphs and adults) of pesticide-susceptible and pesticide-exposed bedbugs," Mittapalli explained. "We found higher transcript levels for CYP9 in all developmental stages in pesticide-exposed populations compared to pesticide-susceptible populations. We also found higher transcript levels of Delta-epsilon in the late-instar nymphs of pesticide-exposed bedbug populations."

While additional research is needed, the OSU professor said that their research shows that "the mode of resistance" in bedbugs "could be attributed to a combination of changes in the bug's genetic makeup (such as mutations) as well as transcriptomic adjustments leading to differential gene expression. Pinpointing such defense mechanisms and the associated genes could lead to the development of novel methods of control that are more effective."

Image Courtesy CDC/ Harvard University, Dr. Gary Alpert; Dr. Harold Harlan; Richard Pollack. Photo Credit: Piotr Naskrecki


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