Bizarre study builds a “human smell buffet” for mosquitoes

Couples and travel groups can sing a song about it: mosquitoes seem to prefer certain people.

Research has long been concerned with the question of whether this is actually true and, above all, with the criteria by which mosquitoes choose their victims – with insufficient results, as Conor McMeniman from the Johns Hopkins Bloomberg School of Public Health’s Malaria Research Institute finds. So he set up a curious experiment with his own team in Zambia.

In a cage of around 1,000 cubic meters, the mosquitoes were served a kind of buffet of human smells – or, as McMeniman put it in John Hopkins Health press materials himself calls, a multiple-choice questionnaire.

Volunteers took turns sleeping in six tents around the cage, shielded from the mosquitoes in the construction. Their smell was able to get into the cage via hose systems, where it was presented to the mosquitoes on cushions that were warm to the body.

McMeniman explains that these conditions were more realistic than any other study, not only because of the number and freshness of the odor samples and the sheer size of the test area. In the laboratory, studies on half a cubic meter would usually only compare two smells at a time instead of six on an area that is 2,000 times larger, as the microbiologist explains to the institute.

In addition, the experiment offered the opportunity to test with sleeping people at night – the time when mosquitoes are most active.

In this way, the study was able to confirm what others had already found before it – namely that mosquitoes actually prefer the smell of certain people. But while previous research has only been able to offer vague theories about a person’s diet, blood type or even preferred soap, McMeniman wanted to find out exactly which chemical compounds actually attract or deter mosquitoes.

Like the results in the journal Current Biology published show that humans are most attractive to mosquitoes that exhale carboxylic acids such as butyric acid or isovaleric acid. The so-called acetoin, which is probably produced by bacteria on human skin, also seems to be particularly appetizing for mosquitoes.

On the other hand, the animals found the least attractive people who exhale so-called eucalyptol – a chemical compound that can not only be ingested through food but is also found in cosmetic products. Such findings could be enormously important for malaria protection.

But the team intends to continue researching in order to obtain better-founded results. “We plan to use this design to test 100 to 120 people at a time in Zambia in the coming years,” explains McMeniman.

An experiment in the USA is also planned. At the same time, research is being carried out on genetically modified mosquitoes. All of this information would be used, according to McMeniman, “to find novel ways to get a grip on malaria.”