Download Panel 2 - One parasite One mosquito One man ( PDF , 496 Ko)

One parasite
One mosquito
One man
One parasite, one mosquito, one man: there are three main
characters in the transmission of malaria. A mosquito, infected by
a human with the parasite, contaminates in turn another human,
and so on. There is thus no direct human-to-human transmission,
except in cases of blood transfusions or, occasionally, mother-to-child
during pregnancy or childbirth.
Red blood cells colonised
by the malaria parasite.
A life more complicated!
The parasites have a life cycle that runs in several successive phases. In man, the parasites multiply quickly,
by means of asexual reproduction, first in the liver cells and then in the blood cells they colonise. After several
reproductive cycles, a small number become male and female. Once ingested by mosquitoes, fertilisation between
these males and females can then take place in the insect’s stomach. This sexual reproduction makes possible
a form of gene intermingling, which ensures that there is wide variety in the new parasites, thus increasing
their ability to adapt to the organisms they will go on to infect.
The malaria parasites come from the Plasmodium genus, which has more than 200 species. Only 5 are pathogenic for man. These parasites are characterised
by their remarkable ability to adapt in man and mosquitoes. How can Plasmodium permanently acclimatise to these different milieus? To answer this key question,
scientists have been studying the cell and molecular mechanisms that allow the parasites to invade and then adapt to the host cells in both mosquitoes and man.
Larva of an anophele mosquito. Only the female
of this mosquito can transmit malaria.
Serial killers
Only the female mosquitoes from the Anopheles genus can transmit malaria; they are vectors of the disease.
They are attracted by the heat, scents and gases emitted by man and they feed of human blood. These meals, which
are essential for the development of their eggs, only occur at night. It is therefore at nighttime that it is essential
for there to be protection, particularly given the fact that anophele mosquitoes are silent when they fly and their bites
are painless! The longer the mosquito lives (from 2 to 4 weeks in a tropical milieu), the greater its ability
to become infected and infect new hosts.
Around thirty species of Anopheles are the major vectors for malaria. Researchers are interested in the characteristics specific to each one: egg-laying areas,
environmental conditions that encourage their activities, frequency of the blood meals, life expectancy, and so on. This makes it possible to better combat
them and to find means of reducing their ability to infect.
Blood meal for an Anophele gambiae, one of the most effective vectors for malaria.
Analysing a water sample containing
anophele larvae (Mali).