Malaria may alter the way people smell to make them more alluring to
mosquitoes, according to a new finding that can help detect the deadly disease
non-invasively through body odour.
An infection with malaria pathogens changes the scent of infected mice,
making those infected more attractive to mosquitoes, researchers have found.
Malaria is and 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.
In order to complete its life-cycle, the plasmodium parasite must eventually
be acquired by another mosquito, which occurs when the insect bites an
infected person.
In a new study, researchers from ETH Zurich and Pennsylvania State
University show that 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.
However, the pathogens do not appear to trigger the expression of unique
scent components.
"There appears to be an overall elevation of several compounds that are
attractive to mosquitoes," said Consuelo De Moraes, from ETH Zurich.
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," said study leader Mark Mescher.
What 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.
Although the findings cannot be directly transferred to human malaria, they
suggest that similar effects might be involved in the attraction of mosquitoes
to infected people.
In addition to aiding efforts to disrupt malaria transmission by mosquitoes,
researchers hope that findings may also be used to develop new non-invasive
diagnostic procedures that would facilitate effective screening of human
populations for malaria infections, particularly in order to identify individuals
who don't otherwise have symptoms but remain capable of spreading the
disease.




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