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Friday, August 11th 2006

Something Else At The Wheel

This is nothing new. I heard the same story in my microbiology class last year. Still, it is pretty wierd.

When [Toxoplasma gondii] infects the brains of rats and mice, it alters their behavior, making them more reckless than normal–reckless enough that they don’t avoid cats the way good sense would dictate. As a result, they’re devoured, at which point the micro-organisms are able to reproduce–something they can only do in felines. Then their eggs are excreted, and any mammal that eats something contaminated with the cat feces takes up the toxoplasma eggs. A rat, for example, who then begins to act reckless…and so on.

Humans eat toxoplasma too, in such things as unwashed vegetables; the worst affected are pregnant women, whose embryos can suffer from birth defects, and the immunocompromised–AIDS patients, for example, or those on chemotherapy. The rest of us might experience nothing more than mild, flu-like symptoms, no more.

But while we don’t go running out to find a mountain lion or other big cat to play with, it could well be that humans experience subtler behavioral changes than a rat would–a mild increase in the tendency to be adventurous, say. And because toxoplasma infection is actually quite common in humans, and varies from one region to another–about a third of Americans show antibodies to the parasite, but in Brazil the number rises to nearly 70%, while in South Korea it’s under 5%. And those differences, suggests the study’s author, could explain, at least in part, why people from different nationalities have developed differently along cultural lines. Lafferty acknowledges there are all sorts of factors that contribute to such traits, but argues that this tiny parasite could be one of them. And, he says, it’s not necessarily a bad thing since, as he notes in the release, it adds to cultural diversity.

The parasite is also tied to schizophrenia and as the Time Blog mentions it is tied to birth defects when the mother contracts an acute infection during pregnancy.

H/T Reddit

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