Scientists have long observed that about 20 percent of people are particularly attractive to mosquitoes.
Just what makes those people mosquito magnets has been a puzzle, however. Diet has been a leading contender, but research findings linking various types of foods to mosquito attractiveness are inconsistent — with one possible exception. A 2010 study found that people who drink beer appear to be more likely to get bitten than those who abstain.
As for certain foods being “natural” mosquito repellants, well, there’s no good evidence for that, either. One old wives’ tale — that eating garlic cuts down on being bitten — didn’t hold up under scientific scrutiny. And taking vitamin B has been shown to be ineffective as well.
Body odor, however, has been linked to mosquito attractiveness, and it’s known that a person’s particular body odor is controlled, at least in part, by genetic factors. So the authors of the current study, which was published online last week in the journal PLOS ONE, decided to investigate whether those two factors combined could mean that genetics underlies our attractiveness — or unattractiveness — to mosquitoes.
Study design
For this pilot study, researchers at London School of Hygiene and Tropical Medicine conducted a series of experiments involving 18 identical and 19 non-identical (fraternal) twins.Identical and fraternal twins are used to test heritability factors because the genetic code from identical twins is nearly the same while that from fraternal twins is not. (Fraternal twin share the same amount of genetic material as any pair of siblings.)
During one of the experiments, each woman from a twin pair was asked to place a hand on a branch of a Y-shaped tube. Dengue mosquitoes (Aedes aegypti) were then released into the third branch of the tube to see which twin they would fly to (and how quickly) — in other words, to see which twin they were most attracted to. Other forms of the experiments were also conducted. In one, for example, each woman was tested against a tube of “clean air.”
This study explores whether or not mosquitoes are attracted equally to twins.
An analysis of all the data revealed that the mosquitoes were equally attracted to identical twins, but not to fraternal ones.
In fact, the level of heritability involved in being attractive (or not) to mosquitoes observed in this study turned out to be very similar to the heredity levels for height and IQ.
Caveats and implications
Of course, this was a small, pilot study. When studies involve this few participants (only 74), the results can’t be considered conclusive.But if the findings do hold up after further research, they may have important — indeed, lifesaving — implications, say the study’s authors.
“Now that we know that your level of attractiveness to mosquitoes is controlled genetically, the next stage is to identify the genes that are involved,” explains James Logan, a co-author of the study and a professor of medical entomology at the London School of Hygiene and Tropical Medicine, in a video released by his institution. “That might allow us to determine how much at risk a certain population is in a developing country, and that would have implications for controlling diseases like malaria or dengue.”
Malaria, dengue and yellow fever — just three of the many diseases transmitted by mosquitoes — kill several million people globally each year, according to the World Health Organization.
“The other thing we might be able to do,” added Logan, is to “develop a drug — a pill that you might take when you go on holiday — that would cause your body to produce natural repellants and would minimize the need to actually put repellants on your skin.”
Those Brits have to go on holiday to encounter mosquitoes?
You can read the study in full on the PLOS ONE website. The video in which Logan explains his study (and in which two twins demostrate the experiment) is also available online.
