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Everyone who has ever been camping or walking in the wild with friends cant have failed to notice

how insects seem to prefer some peoples flesh to others. Some unlucky souls are totally covered in

itchy red blotches and others are miraculously spared. Sometimes only some family members are

affected. My mother has never been bitten by a mosquito (though fleas like her) while my brother and

I are often the targets.

Previous observations have shown a higher mosquito preferencefor larger people(who produce

more CO2),beer drinkersandpregnant women, and although diet was often suspected as a factor,

nothing in what we eat (even garlic) stood up to scrutiny.

The authors of a new study in PLOS Oneclaim to have found the answer.They studied the

differences in attraction of skin odours to mosquitoes, specificallyAedes aegypti, in a group of brave

volunteers drawn from a group of female identical and non-identical twins part of the large

nationalTwinsUK cohortthat I set up 21 years ago. The reason for using both kinds of twin was to

separate the effects of nature and nurture (or genes and environment). In humans this is the onlyway to get a good estimate of the contribution of genetics to the differences between people.

Aedes aegypti during blood mealJames Gathany/USDHHS

http://www.mosquito.org/fun-factshttp://www.mosquito.org/fun-factshttp://www.washingtontimes.com/news/2013/jul/16/bad-buzz-mosquitoes-love-beer-drinkers-study/http://www.washingtontimes.com/news/2013/jul/16/bad-buzz-mosquitoes-love-beer-drinkers-study/http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1127358/http://www.plos.org/wp-content/uploads/2013/05/pone-10-4-Fernandez-Grandon.pdfhttp://www.plos.org/wp-content/uploads/2013/05/pone-10-4-Fernandez-Grandon.pdfhttp://www.twinsuk.ac.uk/http://commons.wikimedia.org/wiki/File:Aedes_aegypti_during_blood_meal.jpghttp://commons.wikimedia.org/wiki/File:Aedes_aegypti_during_blood_meal.jpghttp://www.washingtontimes.com/news/2013/jul/16/bad-buzz-mosquitoes-love-beer-drinkers-study/http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1127358/http://www.plos.org/wp-content/uploads/2013/05/pone-10-4-Fernandez-Grandon.pdfhttp://www.twinsuk.ac.uk/http://commons.wikimedia.org/wiki/File:Aedes_aegypti_during_blood_meal.jpghttp://www.mosquito.org/fun-facts

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Our valiant twins put their hands into a specially constructed plexiglass sealed dome where the

odours either attract or repel 20 female mosquitoes without being allowed to bite. Each subject was

given an attractiveness score compared to the other hand at the other end of the dome. Sure enough

the identical twins, who share all their genes, had consistently more similar scores compared to

fraternal twins showing a clear genetic component. This comparison estimated that 67% of the

differences between people (called heritability) was down to their genes.

Repel With Smell

Why might this be? Many years ago in another twin studywe showedthat underarm body odour as

perceived by human sniffers had a genetic basis with huge variability in how strong smells were

perceived. This showed that we have gene variations controlling both the odours we perceive and

the chemical odours we produce. In this way we are similar to mosquitoes because they also have

big differences in which odours and chemicals attract and repel them.

http://chemse.oxfordjournals.org/content/30/8/651.fullhttp://chemse.oxfordjournals.org/content/30/8/651.fullhttp://chemse.oxfordjournals.org/content/30/8/651.full