Scientists bite back in battle with mosquitoes

The nightmare of being eaten alive by biting insects may become just a bad memory now that scientists have isolated the body chemicals that protect a small percentage of the human population from the attentions of mosquitoes.

The group, from Rothamsted Research and Aberdeen University, hopes that ultimately everyone may be able to shelter behind this chemical barrier.

They are investigating the possibility of commercially exploiting their discovery to create a new class of insect repellents.

Preliminary results of ongoing work on yellow fever mosquitoes and Scottish midges were presented at the annual meeting of the Society for Experimental Biology at Heriot-Watt University in Edinburgh this week.

It is known that blood-sucking insects are more attracted to some people than to others. But the body chemicals that determine whether an individual is more or less likely to be bitten have evaded detection.

The research team, led by John Pickett, head of biological chemistry at Rothamsted Research, and Jenny Mordue Luntz, professor of zoology at Aberdeen University, has carried out tests that show that a number of volatile compounds secreted by the skin of the fortunate few are highly effective in driving away biting insects.

While the work on mosquitoes is more advanced than on midges, the scientists expect similar results.

Professor Pickett said: "We have demonstrated unequivocally that human beings are differentially attractive to insects."

The chemicals work by interfering with the insects' ability to recognise and home in on a meal, by either masking the chemical signals that enable them to find a potential host or by simply repelling them.

The scientists collected up to 400 different volatile chemicals that emanate from human skin. A shortlist of those that could be detected by the insects were identified with electronic detectors, to which mosquito and midge antennae were attached.

Live insects were then exposed to these individual chemicals. Some were attractive, including the carbon dioxide that everyone exhales. Others had the opposite effect.

James Logan, a PhD student at Rothamsted Research, said that the people who produced the repellent chemicals reported they were rarely, if ever, bitten by insects. "This could be a potential product in the future," Mr Logan said.