Odours of Plasmodium falciparum-infected participants influence mosquito-host interactions

Malaria parasites are thought to infuence mosquito attraction to human hosts, a phenomenon that may enhance parasite transmission. This is likely mediated by alterations in host odour because of its importance in mosquito host-searching behaviour. Here, we report that the human skin odour profle is afected by malaria infection. We compared the chemical composition and attractiveness to Anopheles coluzzii mosquitoes of skin odours from participants that were infected by Controlled Human Malaria
Infection with Plasmodium falciparum. Skin odour composition difered between parasitologically negative and positive samples, with positive samples collected on average two days after parasites emerged from the liver into the blood, being associated with low densities of asexual parasites and the
absence of gametocytes. We found a signifcant reduction in mosquito attraction to skin odour during infection for one experiment, but not in a second experiment, possibly due to diferences in parasite strain. However, it does raise the possibility that infection can afect mosquito behaviour. Indeed, several volatile compounds were identifed that can infuence mosquito behaviour, including 2- and
3-methylbutanal, 3-hydroxy-2-butanone, and 6-methyl-5-hepten-2-one. To better understand the impact of our fndings on Plasmodium transmission, controlled studies are needed in participants with gametocytes and higher parasite densities.