A new study shows for the first time that infection with the malaria parasite causes mosquitoes to change smell-stimulated behavior so they are more strongly attracted to the smell of humans than uninfected mosquitoes.
The burden of malaria around the world is huge: the parasite infects over 200 million people a year and kills an estimated 770,000, note the researchers.
The infection, which causes fever and headache, and in severe cases can result in coma or death, spreads through human populations because malaria-inducing Plasmodium parasites living in the guts of female Anopheles mosquitoes pass into people’s bloodstreams through mosquito bites.
There are different strains of malaria-inducing Plasmodium parasites, and different strains of host Anopheles mosquitoes. One of the deadliest parasites is Plasmodium falciparum, which is predominantly carried by Anopheles gambiae mosquitoes.
Writing in a 15 May online issue of PLOS ONE, researchers from the London School of Hygiene & Tropical Medicine in the UK describe how they showed significantly more A. gambiae mosquitoes infected with P. falciparum “landed and probed” on a fabric matrix emanating human skin odor than uninfected mosquitoes.
Previous studies have already shown that the malaria parasite changes host behavior to help it spread. For example, malaria-infected mosquitoes tend to consume larger, more frequent blood meals than uninfected mosquitoes.
However, this is the first study to show that the parasite changes odor-related behavior in its mosquito host.
(An intriguing example of altering host behavior featured recently in a study published in the journal mBio that describes how the luminous bacterium Vibrio fischeri regulates the daily rhythm of its host, the Hawaiian bobtail squid, by interacting with its clock genes.)
The researchers say their results offer a useful starting point for improving malaria control and eradication. It could help us find out more about how A. gambiae mosquitoes infect humans.
And, by understanding the olfactory changes that underly the altered smell-seeking behavior of the mosquitoes, it may be possible to find compounds to make traps for monitoring or capturing parasite-carrying A. gambiae mosquitoes, they conclude.
In another study published recently in the journal Science, researchers in the US show how they used a bacterium to stop the malaria parasite developing in the mosquito and created a stable population where immunity to the parasite was passed onto new generations.
Written by Catharine Paddock PhD