A team of scientists has potentially solved the puzzle of why mosquitoes specifically target people who are already carrying the malaria parasite. The parasites produce a scent, only detectable by mosquitoes, that lures them to the person carrying malaria. The findings may help researchers develop better forms of mosquito control, including traps that could lure and then kill the insects. The details are in a paper that was just published in the journal Science.
Malaria is caused by different species of Plasmodium parasites, microorganisms that can be carried by mosquitoes. The mosquitoes act as vectors for the disease; they are not personally affected by the parasite but can transmit it to humans. If a mosquito bites someone who’s been infected, they can then spread it by biting another person. Malaria can be a very serious illness and the World Health Organization estimated that 438,000 people died from malaria in 2015. Children are especially vulnerable and make up the majority of deaths caused by malaria. Although a vaccine was recently developed, it doesn’t work on everyone and its use is not yet widespread. Recent research has showed that mosquitoes are more attracted to people who are already infected with the malaria parasite but the reasons were unknown.
Malaria specialists collaborated to better study the factors that draw mosquitoes to humans who have already been infected with malaria. The team released mosquitoes in a controlled environment, giving them two food options. One vial contained healthy human blood while the other vial contained human blood mixed with malarial substances. In every trial, the mosquitoes flocked to the vial with malaria—and they consumed larger amounts of this blood. The research team determined that a chemical called (E)-4-hydroxy-3-methyl-but-2-enyl pyrophosphate (HMBPP) was a possible contributor to this extreme feeding response. HMBPP is produced by malaria parasites and triggers red blood cells to rapidly release extra carbon dioxide, aldehydes, and monoterpenes. This combination of chemicals smells good to the mosquitoes, luring them to the infected human.
The team’s findings show that mosquitoes may be attracted to humans already infected with malaria because of chemical scents released by blood cells. The smell is extremely attractive to mosquitoes, encouraging them to spread the parasite throughout the human population. The researchers hope that this new information can lead to better forms of mosquito control.
Emami et al. A key malaria metabolite modulates vector blood seeking, feeding, and susceptibility to infection. Science (2017).