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Mozzie magnetism is 'all in the genes'

Natural repellent The puzzle of why some people attract mosquitoes and others don't get bitten at all has nothing to do with diet and everything to do with genes, a new study has found.

A UK twin study has revealed that that certain people are genetically blessed with the ability to repel mosquitoes.

The study, published today in PLOS ONE , found that while identical twins were highly likely to show the same attractiveness to mosquitoes, non-identical twin pairs were not, suggesting a genetic basis for mosquito appeal.

In contrast, studies into whether garlic, vitamin B or beer repel mosquitoes have so far failed to find any effect of diet on mosquito attractiveness.

Co-author Dr James Logan, senior lecturer in entomology at the London School of Hygiene and Tropical Health, says the genetic link is strong.

"We're looking at the level of heritability that might be associated with things like human height or IQ; these traits that we know … are hereditary, and that we can pass on," says Logan.

"When you speak to people anecdotally, people will quite often say that my son or daughter is the same as me, they always get bitten or they seem to never get bitten."

These anecdotal reports, as well as Logan's frustration at his own apparent attractiveness to mosquitoes, prompted researchers to look into the question of what was behind this phenomenon.

The study used Y-shaped tubes to offer female Aedes aegypti mosquitoes the choice of one of two hands belonging to either identical or non-identical twin pairs.

This revealed that there was little difference between identical twins in how likely the mosquito was to pick one or the other twin, but significant differences when it came to non-identical twins.

Logan says previous studies comparing mosquito-attractive and non-attractive individuals suggests that people who don't attract mosquitoes produce extra chemicals in their skin that make them repellent.

"It's almost like body has natural defence system against mosquitoes and it seems to be genetically controlled, so if you put the two bits of the puzzle together, it suggests that the genes are controlling natural repellents produced by the body," Logan says.

While researchers are yet to examine whether people from malaria-prone areas might be more likely to have these natural repellent genes, Logan says the finding could help explain why some people are less likely to contract malaria than others.

"What we do know is that in Africa sometimes you get populations where 80 per cent of the population are not as at risk of getting malaria," he says.

"You can become immune to malaria, so that probably plays a role, and also things like access to bed nets, but this could also be playing a role."

While the study was only a pilot project, it could pave the way for research into these mosquito-repellent genes and the chemicals that they produce, with a view to developing drugs that might boost these chemicals.

"Imagine taking a pill when you go on holiday or during mosquito season, and it causes your body to start producing more of these repellent chemicals which would mean you wouldn't have to put so much of the sticky repellent on your skin," Logan says.

Related: Are some people more attractive to mosquitoes?

Photos: Mosquitoes in extreme close-up