Bedbugs Foil Pesticides With Special Adaptations In Their Armor

Bedbugs have resurged in cities across the world, and a few scientists think they’ve found the little bug’s wily secret: special genes active in its outer shell that produce an anti-insecticide arsenal.

Some scientists think that DDT use in the 20th century and its subsequent ban wiped out all but the hardiest of the little bloodsuckers. The bedbugs we have now seem to be the fittest of the fit, the most resistant to whatever we throw at them; scientific testing shows pesticide bombs don’t work, and neither do sonic devices. But, if we can unravel the bedbug’s strategy for combating poisons, perhaps we can create poisons that can penetrate their frustratingly thick shells.

Fang Zhu, a Washington State University scientist, described some of the genetic traits that contribute to the bedbug’s pesticide resistance in a talk on Monday at the national meeting of the American Chemical Society in Indianapolis. Zhu and colleagues from the University of Kentucky took a close look at the bedbug’s genome to try and pinpoint the origin of its ability to dodge insecticides. In March, they published a paper on the topic in the journal Scientific Reports, detailing how they identified 14 genes in the bedbug’s poison resistance toolkit.

"The surprise discovery we never expected is that most of the genes responsible for pesticide resistance in the bedbug are active in its outer skin-like shell or cuticle,” Zhu said in a statement. “This is [a] unique adaption that has not been discovered in cockroaches, termites, ants or other insects."

Thanks to its genetic utility belt, a bedbug’s cuticle has an array of methods for dealing with insecticides. It can secrete substances that partially digest poisons and make them harmless; it’s outfitted with biological pumps that can shunt invading poisons back out. There might be a way to exploit this knowledge, though, by engineering pesticides specifically targeting these defenses.

But we may not be able to just count on better killing through chemistry. Other research shows that bedbugs can quickly adapt to new insecticides. According to Zhu, other researchers have found that bombarding laboratory colonies of bedbugs with lethal doses of pyrethroid pesticides becomes ineffective within a year or so: the insects can develop resistance within a few generations.

"It reminds us how quickly a new insecticide can become ineffective," Zhu says. "In the future, efficient bedbug management should not rely on any single insecticide. We need to combine as many chemical and non-chemical approaches as we have to get rid of the infestation."

There are nonchemical preventative measures that can help you stave off or beat back an infestation: removing clutter from the bedroom, frequently vacuuming, sealing cracks and crevices, encasing mattresses and pillowcases, and giving that free mattress sitting on the curb a very wide berth.

In April, another group of scientists found that one Eastern European folk remedy for bedbugs proved surprisingly effective: kidney bean leaves. The leaves have spiky little hairs that are positioned just right to impale bedbugs in their most vulnerable spots. Sometimes, in the face of chemical and genetic trickery, brute force turns out to work best.

SOURCE: Zhu et al. “Bed bugs evolved unique adaptive strategy to resist pyrethroid insecticides.” Scientific Reports 3, 1456, March 2013.