Toxoplasmosis is a very strange disease. For ordinary mortals, it remains a mild infection, often even invisible, which, at worst, causes a slight fever and a few pimples. Benign and very widespread since it is considered that it affects 30% of humanity. But if your immune system proves to be seriously deficient, the pathogen can become fatal. The ravages wrought among AIDS patients are a reminder of this. The fetus, whose immunity is still faltering, is the other weak point of our species. If it infects the mother, the parasite can seriously affect the proper development of the future baby.
Pregnant women all know it: the domestic cat is a prime carrier of the parasite. Above all, do not change the litter if you are not already immunized by a previous infection, hammer the gynecologists. In fact, the link between the Toxoplasma gondii – the full name of the pathogen, discovered in 1908 in a small Tunisian rodent, the gondi – and the cat goes far beyond the risk it poses to us humans. In an article published in NatureCommunicationsa team from the University of Limoges, which houses the National Reference Center for strains of the parasite, reveals that its evolution and spread across the five continents are intimately associated with the domestication of the feline.
This observation is not entirely a surprise as the Felidae hold a special place in the Toxoplasma cycle. If this unicellular protozoan can infect almost all warm-blooded animal species (mammals, birds, etc.) and survive on plants, all this little world is only a stepping stone towards the final target of the parasite: the felids. In all the so-called intermediate hosts, the Toxoplasma must content itself with asexual multiplication. But in the body of the cat and its forty cousins, it operates a sexual reproduction.
No one knows if the protozoan finds personal satisfaction in it. But the species derives a real benefit from it. “It is in felines that diversification can take place, the meeting of different strains, their recombination”, explains Aurélien Mercier, lecturer at the Faculty of Pharmacy of Limoges and coordinator of the study. To achieve this supreme happiness, Toxoplasma goes so far as to manipulate its intermediate hosts: infected mice stop fleeing cats, monkeys fall in love with leopards, hyenas with lions… with the result that one can imagine.
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