Scientists have found that an infection with malaria pathogens changes the scent of infected mice,
making those infected more attractive to mosquitoes.
Malaria remains a formidable disease
that is transmitted to humans by the anopheles mosquito. The pathogen is a protozoan
of the genus Plasmodium. If left untreated, malaria can be deadly.
However, the
plasmodium parasite has a problem. To complete its lifecycle, it must
eventually be acquired by another mosquito, which occurs when the insect bites
an infected person. Pathogen elicits the strongest odour during
reproduction phase.
In a new study published in PNAS,
researchers showed that whether mosquitoes find the right victim to bite is not
left to chance by the pathogen.
Instead, the plasmodium parasite appears to
manipulate its host by changing the characteristics of the infected
individual’s body odour, which makes the carrier more attractive to hungry
mosquitoes.
Mosquitoes were most attracted to
infected mice with a high concentration of gametocytes, the plasmodium
parasite’s reproductive cells, in their blood.
When the mosquito consumes these
cells along with the blood, a new development cycle starts in the mosquito’s
gut.
No unique cocktail of scent
components.
However, the pathogens do not appear to trigger the expression of unique scent components. The researchers were unable to find any components that existed only in infected persons.
Instead the malaria pathogens alter the levels of
compounds already present in the scent of uninfected individuals.
The researchers believe it is
logical that infected people smell more attractive but do not form highly
specific body odours, especially given that the malaria pathogen can also have
adverse effects on mosquitoes.
“Since mosquitoes probably don’t benefit from
feeding on infected people, it may make sense for the pathogen to exaggerate
existing odour cues that the insects are already using for host location,” says
study leader Mark Mescher.
What the researchers found most
surprising is the fact that the malaria infection leaves its mark on body odour
for life. Even when infected mice no longer had symptoms, their body odour
showed that they were carriers of the pathogen.
However, not all stages of the
disease smelled the same: the scent profile of the acutely ill differs from the
profile found in individuals exhibiting later stages of malaria infection.
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