Apparently Toxoplasma is well known to pregnant women. It's some sort of parasite, found in cat feces, that if given the chance at a fetus will wreak havoc with the nervous system. So pregnant women are supposed to avoid cats and their feces in particular. First I've ever heard of it. Although I guess now certain people have legitimate reasons for requiring me to keep cats out of my household...
Anyway, toxo normally functions in a life cycle between cats and rats. Toxo can only reproduce in cat stomachs, so they hitch on to rats and make the rats lose their aversion to the smell of cat urine, which causes rats to head on over to cat smells and become dinner in no time at all. Providing, of course, a route for the parasite into the cat stomach for all the reproduction that could be imagined.
Amazingly, Dr. Robert Sapolsky of - guess where - has found that in toxo-infected rats, everything else functions normally. They still maintain their other normal fears of open space; they basically function absolutely normally except for suddenly being attracted to cat urine. So the parasite targets precisely this one function - and scientists would love to have the targeting precision.
Turns out that toxo migrates to the rat brain and goes latent, but in the amygdala, which controls fear and anxiety, it causes neurons to atrophy and disconnects fear circuits. It blunts the stress related to cat odor. It actually switches the response to cat urine from fear to sexual arousal, increasing testosterone in male cats. Female cats actually prefer toxo-infected males, presumably because of the elevated testosterone.
What does toxo do to humans? Well aside from fetuses, it was assumed that it doesn't do much because it goes latent. However, one study showed that males show a slight disinhibition related to neuropsychological tasks of impulse control. And two indpendent studies found that toxo-infected humans are two to four times more likely to die in car accidents related to speeding. Apparently, the disinhibition leads to more reckless behavior. However, those 3 studies are the only ones in existence related to toxo's effect in humans.
What is the take away? Apparently, according to Sapolsky, who incidentally got lost on the Caltrain on the way to speak this morning even though he is actually a Stanford professor and the meeting was at Stanford, parasites are really cool. And, even if thousands of neuroscientists study processes such as this, a parasite will still know more than they do. Makes you wanna go hmmm.
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