WHO figures show that malaria currently affects between 300 and 600 million people in various parts of the world. Several malaria-hit regions are experiencing an advance of the disease owing to the parasites increasing resistance to most antimalarial drugs. Any increase in efficacy of medical treatments, with optimal limitation of resistance, requires that scientists unravel the evolutionary strategies of the enemy they are fighting. One of the research leads involves prior determination of the population genetic structure of Plasmodium falciparum.
This work was recently accomplished by a joint team of researchers from the IRD and the CNRS (2). Dissections were conducted on over 10 000 mosquitoes of the species Anopheles gambiae and Anopheles funestus, two of the principal malaria vectors in Sub-Saharan Africa. The work was done simultaneously on two sites in Cameroon and one Kenyan site, all three strongly infected by malaria. This large-scale investigation resulted in the isolation of 746 Plasmodium falciparum oocysts from the gut of 183 infected mosquitoes.
Two years previously, a preliminary study carried out in Kenya by the same team solely on A. gambiae, had yielded 600 oocysts from 145 infected mosquitoes caught in 11 different localities. The oocyst of the parasite provided the researchers with a means of access to the diploid phase of the microorganism, containing all its genetic information. Up to then, nearly all studies aiming to determine the genetic structure of Plasmodium populations were elaborated with parasite samples taken from humans. However, that kind of genetic analysis results in several points of bias. With samples collected from humans, scientists can work only on the haploid phase of the parasite cycle during which only one example of each chromosome is present. Therefore they cannot measure the rate of association and organization between genes within populations.
Moreover, in the zones where malaria is endemic, inf
|Contact: Gregory Flechet|
Institut de Recherche Pour le Dveloppement