Brett Smith for redOrbit.com – Your Universe Online
A new study published in the Proceedings of the National Academy of Sciences has found that the parasite responsible for Malaria alters the scent of its mammalian host – causing it to become more attractive to the mosquitoes that spread the disease from host to host.
The malaria parasite can be propagated only by mosquito. The flying insect ingests the parasite via infected blood, leading to the following generation developing within the mosquito’s gut. These burgeoning parasites then journey to the mosquito’s salivary glands and are transferred to the new host during the following ingestion of blood.
The new study showed mosquitoes are particularly attracted to mice infected with malaria, even when the mice didn’t show symptoms.
“Malaria-infected mice are more attractive to mosquitos than uninfected mice,” said study author Mark Mescher, associate professor of entomology at Penn State. “They are the most attractive to these mosquito vectors when the disease is most transmissible.”
In the study, researchers from Penn State and the Swiss Institute of Technology in Zurich (ETH Zurich) examined chemicals emitted by infected mice. They discovered that the chemicals mosquitoes like the most were predominantly released during the highly infectious phase of the disease – 13 to 20 days after infection.
“There appears to be an overall elevation of several compounds that are attractive to mosquitoes,” said Consuelo De Moraes, a professor of biocommunication and Entomology at ETH Zurich.
The international team was able to identify four specific chemical compounds that were highly attractive for the mosquitoes.
The study team mentioned although afflicted people smell more attractive, they generally do not develop a distinct body odor. They added that the malaria pathogen could also have negative effects on mosquitoes.
“Since mosquitoes probably don’t benefit from feeding on infected people, it may make sense for the pathogen to exaggerate existing odor cues that the insects are already using for host location,” Mescher said.
Surprisingly, the researchers also found that when afflicted mice no longer had symptoms, they still released the mosquito-attracting chemicals.
While the results of the mice-based study can’t be directly translated to humans, the researchers said they were interested in focusing future research on how to prevent the spread of malaria from asymptomatic individuals.
“We were most interested in individuals that are infected with the malaria parasite but are asymptomatic,” De Moraes said. “Asymptomatic people can still transmit the disease unless they are treated, so if we can identify them we may be able to better control the disease.”
“If this holds true in humans, we may be able to screen humans for the chemical scent profile using this biomarker to identify carriers,” Mescher added.
Another malaria study published in March found warming temperatures will allow mosquitoes spreading the disease to travel into higher altitudes. The study team said without improved monitoring and control efforts, malaria cases will increase significantly as the planet’s temperatures increase in the years ahead – spreading the disease to areas of Africa and South America that have traditionally faced a low risk of infection.