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Bed Bugs Bite Back

written by: •edited by: Paul Arnold•updated: 7/5/2011

Bed bugs are big pests. It was assumed that their fire had gone out, and the threat diminished. But as their genomes have evolved, these blood sucking beasts are biting back... big time! Surprisingly, there have been relatively few genetic studies of them. However, all that is changing.

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    Where Do Bed Bugs Come From?

    The common bed bug (Cimex lectularius) is a nocturnal creature that has been making an unwelcome comeback. One of the most common questions asked of these critters is where do bed bugs come from? They can be found all over the world and travel surprisingly well. This is a by-product of plane travel in the modern age. Bed bugs are easily spread from country to country as more people than ever before are globetrotting. Approximately 4 mm in length they bury themselves in suitcases or hide in clothes, making transmission extraordinarily easy. And contrary to popular belief they don't just reside in flea-bitten motels, they can be found in clean home and hotel environments too.

    When bed bugs attack they crawl on your skin, pierce it, and suck your blood through two hollow tubes. It's been estimated that a bed bug can consume up to seven times its own body weight in one midnight feast. A bed bug bite causes an annoying itch. The redness around the bite area is an allergic reaction to a chemical in the bug's saliva. However, there is some good news. Despite being equipped with all the necessary tools, these human parasites do not spread disease.

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    Bed Bug Genetics

    Cimex lectularius - image of bed bug released into the public domain by US Federal Govt. There are probably several reasons why the bed bug genome has not been explored in any great detail. In the first instance we were perhaps a little complacent and underestimated the threat; bed bugs have not been a serious problem in urban environments for decades. And as they don't cause any diseases there has never really seemed to be a sense of urgency to get under their skin to find out how they work.

    That'll teach us! It seems now that they are an unpleasant itch that just won't go away, so science is starting to turn its firepower onto the little beasties.

    Since DDT was banned the weapon of choice has been pyrethroid insecticides which attack the bed bug nervous system, but increasingly the chemicals have been unable to contain some infestations.

    Researchers from the University of Massachusetts Amherst and Korea's Seoul National University have been probing the little critters to find out how they've been able to develop resistance against the insecticides designed to destroy them. What they found were that genetic mutations in nerve cells somehow neutralise the effect of the pyrethroid toxins. The mutations affect sodium channels in the neurons' outer membrane so that they no longer respond to the paralytic effect of the insecticide. It's not sure how widespread this resistance is.

    In other studies scientists from the University of Arkansas are looking at bed bug population genetics for insight into the genetic variation among populations that has lead to their dispersal, and resistance to insecticides.

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    The Battle with Human Parasites

    As with antibiotic resistant bacteria, it could be that we have entered into an evolutionary arms race with bed bugs. We develop weapons, they outsmart them, we then have to develop new improved versions, they outsmart them too, and so the cycle goes on. The trick of course to getting rid of bed bugs, is to stay permanently one step ahead of their greedy blood sucking game.