Mosquitos like the smell of malaria infected children

Researchers have found children infected with malaria give off a distinctive smell through their skin which makes them even more attractive to mosquitoes.

In research published today a team including scientists from Cardiff University, who reported on the study, have been able to identify this unique chemical fingerprint for the very first time, opening up the possibility of developing a system to lure mosquitoes away from human populations.

In their study, the team collected odour samples from fifty six children in western Kenya aged between five and twelve by placing a special plastic bag around their foot. The foot odour collected on a filter was analysed by Dr Ailie Robinson, of the London School of Hygiene and Tropical Medicine, who also studied whether the “nose” of the mosquito responded differently to the collected odours of children with and without malaria.

The team identified a “fruity and grassy” smell emitted through the skin of children infected with the malaria parasite, plasmodium. Using the nylon socks worn by the children for one night, it was shown that the body odour of children with malaria was indeed more attractive to mosquitoes than the odours of malaria-free children. Analysing the precise nature and concentration of the smell revealed that a group of compounds known as aldehydes, specifically heptanal, octanal and nonanal, were responsible for the unique odour.

The results showed that the proportion of aldehydes increased from about 15% of the total odour in non-infected children to almost 23% in infected children, with a higher amount of aldehydes emitted in line with a higher the density of parasites in the blood.

The findings are published in Proceedings of the National Academy of Sciences.

Co-author of the study Professor John Pickett, from Cardiff University’s School of Chemistry, was the first to identify mosquito pheromones in the eighties and believes the new findings could help develop a system to trap malaria carrying mosquitoes. He said “In this study we’ve identified the underlying chemical fingerprint, comprising specific volatile aldehydes, which is given off as an odour when humans become infected by malaria parasites.

Lead author of the study Dr Jetske de Boer, from Wageningen University, said “These are fairly common smells, which are described as fruity or grassy. But for malaria mosquitoes they are very attractive. Now that we have identified and quantified the aldehydes associated with malaria infection, we understand more of the parasite’s infection route. That also creates opportunities to intervene in that chain. We can improve our odour-baited traps for mosquitoes by adding a considerable amount of these attractants. Moreover, these compounds can serve as biomarkers with which diagnostic tools can be developed, without the physician having to draw blood. This would be faster and a lot more child-friendly.”

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