Mosquitoes: Who the beasts fly at

Christiane Fux studied journalism and psychology in Hamburg. The experienced medical editor has been writing magazine articles, news and factual texts on all conceivable health topics since 2001. In addition to her work for, Christiane Fux is also active in prose. Her first crime novel was published in 2012, and she also writes, designs and publishes her own crime plays.

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MunichSome people are particularly attractive to mosquitoes - others, on the other hand, ignore the bloodsuckers. But why? Is it the body scent? Is it because of the things you eat? Or is it actually the much-quoted “sweet blood” that attracts the winged attackers? Researchers have now found a surprising answer.

Earlier studies have already provided some initial indications. Large people are more attractive to mosquitoes than thin people - probably because of their higher CO2 emissions. Likewise pregnant women - and interestingly, beer drinkers too. There was no evidence of any influence on other foods - including garlic, which had no deterrent effect on the little vampires. But so far no one has really solved the riddle of insects' preferences.

Twins in the mosquito test

Now researchers headed by Mandeala Fernández-Granon from the London School of Hygiene and Tropical Medicine have put twins to the test - both monozygotic and dizygoti. In this way they wanted to find out how great the genetic influence is on the popularity of the buzzing pests. Lo and behold: it is considerable.

For the experiment, the researchers constructed a plexiglass tube that branched out in a y-shape. This allows a direct comparison of two test subjects. Because each of the two twins put a hand in the end pieces, which were protected from mosquito bites by a grille. 20 female mosquitoes of the species Aedes aegypti were placed in the entrance of the pipe system per round. Only the females are keen on blood - because they need it for egg production. A fan also created a slight headwind for the insects, which on the one hand blew the individual human smell in their direction, and on the other hand required a certain amount of effort to get to the source of the tempting smell.

Hereditary conditional mosquito protection

The researchers assessed how attractive each smell was based on two factors: How many of the animals had flown into the respective branch of the tube. And how far they had penetrated into it. If both twins each put one hand into the construction, the relationship with the identical twins was much more balanced than with dizygotic twins, whose attraction to the mosquitoes evidently varied more strongly. This is clear evidence that the attractiveness is strongly genetic and therefore hereditary.

What exactly is responsible for the different attraction to mosquitoes is still open. They could also be components of sweat, as well as breakdown products of microbes that settle on human skin. These differ from person to person - and they are also influenced, among other things, by the genetic makeup of their “host”.

The researchers suspect that not some people smell particularly tempting for mosquitoes, but that others simply appear particularly unattractive. In a sense, they spread a natural anti-mosquito haze.

Help against mosquitoes

The scientists hope that more effective anti-mosquito agents can be developed on the basis of further research. Because while the bites in our latitudes usually only cause annoying, itchy wheals, mosquitoes in more southern regions are carriers of potentially fatal diseases such as malaria and dengue.

There are already sprays that have a deterrent effect on mosquitoes - especially those with the active ingredient DEET, which is particularly recommended in the tropics. However, it has the disadvantage of dissolving plastic, for example in clothing, and can irritate the skin. Icaridin, which is also effective, is usually sufficient in northern latitudes.

In the open air, so-called "mosquito coils" also have a good effect: slowly burning incense that also keeps mosquitoes away.

In addition, long sleeves and trouser legs do not offer 100 percent protection - they still keep some hungry mosquitos at bay. (cf)

Source: G. Mandela Fernández-Grandon et al .: Heritability of Attractiveness to Mosquitoes; PLOS one, April 22, 2015

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