Researchers investigated the response of mosquitoes infected with P. falciparum malaria parasites and uninfected to human odor collected on fabric. Mosquitoes that were infected with the parasites landed and probed significantly more than uninfected mosquitoes in response to the odor. Previous research has already shown that the malarial parasite can alter mosquito behavior in ways that increase the rate of malaria transmission. For example, malaria-infected mosquitoes also consume larger, more frequent blood meals than their uninfected counterparts.
Studies of mosquito behavior in the context of malaria transmission usually use uninfected mosquito subjects. This study suggests that such behavioral studies may not always be representative of the behavior of infected mosquitoes. They conclude that understanding the olfactory changes underlying the behavior of these infected mosquitoes may help identify new compounds that could be used to develop mosquito traps for surveillance programs.
Malaria Infected Mosquitoes Express Enhanced Attraction to Human Odor. (2013) PLoS ONE 8(5): e63602. doi:10.1371/journal.pone.0063602
There is much evidence that some pathogens manipulate the behaviour of their mosquito hosts to enhance pathogen transmission. However, it is unknown whether this phenomenon exists in the interaction of Anopheles gambiae sensu stricto with the malaria parasite, Plasmodium falciparum – one of the most important interactions in the context of humanity, with malaria causing over 200 million human cases and over 770 thousand deaths each year. Here we demonstrate, for the first time, that infection with P. falciparum causes alterations in behavioural responses to host-derived olfactory stimuli in host- seeking female An. gambiae s.s. mosquitoes. In behavioural experiments we showed that P. falciparum-infected An. gambiae mosquitoes were significantly more attracted to human odors than uninfected mosquitoes. Both P. falciparum-infected and uninfected mosquitoes landed significantly more on a substrate emanating human skin odor compared to a clean substrate. However, significantly more infected mosquitoes landed and probed on a substrate emanating human skin odor than uninfected mosquitoes. This is the first demonstration of a change of An. gambiae behaviour in response to olfactory stimuli caused by infection with P. falciparum. The results of our study provide vital information that could be used to provide better predictions of how malaria is transmitted from human being to human being by An. gambiae s.s. females. Additionally, it highlights the urgent need to investigate this interaction further to determine the olfactory mechanisms that underlie the differential behavioural responses. In doing so, new attractive compounds could be identified which could be used to develop improved mosquito traps for surveillance or trapping programmes that may even specifically target P. falciparum-infected An. gambiae s.s. females.