J'avais déjà mentionné l'an dernier ma crainte du parasite de la toxoplasmose mais (via Etienne) The Atlantic a un article encore plus effrayant, où la toxoplasmose serait non pas un facteur parmi d'autres mais le principal propagateur de la schizophrénie dans le genre humain :
After an infected cat defecates, Flegr learned, the parasite is typically picked up from the soil by scavenging or grazing animals—notably rodents, pigs, and cattle—all of which then harbor it in their brain and other body tissues. Humans, on the other hand, are exposed not only by coming into contact with litter boxes, but also, he found, by drinking water contaminated with cat feces, eating unwashed vegetables, or, especially in Europe, by consuming raw or undercooked meat. Hence the French, according to Flegr, with their love of steak prepared saignant—literally, “bleeding”—can have infection rates as high as 55 percent. (Americans will be happy to hear that the parasite resides in far fewer of them, though a still substantial portion: 10 to 20 percent.) Once inside an animal or human host, the parasite then needs to get back into the cat, the only place where it can sexually reproduce—and this is when, Flegr believed, behavioral manipulation might come into play.
In fact, he says, schizophrenia did not rise in prevalence until the latter half of the 18th century, when for the first time people in Paris and London started keeping cats as pets. The so-called cat craze began among “poets and left-wing avant-garde Greenwich Village types,” says Torrey, but the trend spread rapidly—and coinciding with that development, the incidence of schizophrenia soared.
Epstein-Barr virus, mumps, rubella, and other infectious agents, they point out, have also been linked to schizophrenia—and there are probably more as yet unidentified triggers, including many that have nothing to do with pathogens. But for now, they say, Toxo remains the strongest environmental factor implicated in the disorder. “If I had to guess,” says Torrey, “I’d say 75 percent of cases of schizophrenia are associated with infectious agents, and Toxo would be involved in a significant subset of those.”
Just as worrisome, says Torrey, the parasite may also increase the risk of suicide. In a 2011 study of 20 European countries, the national suicide rate among women increased in direct proportion to the prevalence of the latent Toxo infection in each nation’s female population.