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Mosquitoes attack some people more than others… But why?

Credits: Wikimedia Commons

Whenever we are in a hot climate, we all take the same precautions, and do our best to protect ourselves from mosquito bites. It is true that these insects target certain people more, while they appear less (or not at all) interested in others. A teacher of genetics has shed some light on this phenomenon. 

Most of us have surely noticed that we are either more or less affected than others by mosquito bites. Without knowing the real reason, we assume that mosquitoes prefer certain blood types to others, which comes out in our body odour. Certain previous observations have shown that people who drink beer, pregnant women and people who are overweight (and who produce more CO2) are more likely to appeal to mosquitoes. Our diets, often suspected of playing a role in our attractiveness to mosquitoes, has never been properly scientifically studied.

A study led in 2015 by Dr. G. Mandela Fernandez-Grandon of Greenwich University (UK) could well have found the answer. Published in the journal PLOS One, this study helped us understand more about the diverse ways in which mosquitoes can be attracted by the odours emitted by people’s bodies. It should be noted that the mosquitoes studied were of the Aedes aegypt variety, and that the human volunteers in the experiment were all female twins (monozygotic and dizygotic).

Using different kinds of twins in this study allowed researchers to differentiate between what is genetic as opposed to what comes from the environment – in other words, what is down to nature and what is down to nurture. Twin studies are the only way to evaluate the influence of genetics vs the influence of the environment in humans.

The human guinea pigs were asked to dip their hands into a type of plexiglass dome, and the odours on their hands either attracted or repelled mosquitoes. Each of the volunteers was thus given a score in terms of their attractiveness to mosquitoes. The monozygotic twins (identical twins who share 95% of their genetic makeup), obtained more similar scores, in comparison to the dizygotic twins (non-identical twins who have only the same genetic overlap as any other siblings). The study noted that 67% of the individual differences were genetic, or heritable.

But that is not all, as the researchers had previously wrongly dismissed a bacterial influence on these odours, as it had long been established that bacteria could not be affected by genetics. However, the bacteria that cause these chemical odours (which either attracted or didn’t attract the mosquitoes), which are found for example in our mouths, our intestines or on our skin, choose us depending on our genetic profiles. Incredible, right? Therefore, we can only hope that we don’t have a genetic profile that attracts certain microbes that cause chemical odours that are very popular with mosquitoes!

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