Many of us live with a living pet –so to speak — that we’ve never even met. Humans, meet Toxoplasma gondii, a parasite that can only reproduce when it is inside a cat’s digestive tract. So, when it is outside of a cat, these protozoa have just one goal: To have whatever creature it is in get eaten by a cat. Its method for achieving this goal? Well, when it’s in a non-feline creature –like, say, a mouse–it affects said creature brain by lessening any inherent fear of cats and making the creature suddenly feel inexplicably attracted to the smell of cat urine.
Apparently, it does roughly the same thing to humans, because, as any a single-person cat-owner has likely considered, a human who has a lot of cats might eventually end up dead and eaten by her cats. When the Toxoplasma gondii gets inside human brains, we become crazy cat ladies. But you don’t have to eat mice or lick cat urine in order to get it. It can live in the water you drink, on the steak you broil, in the cat litter you vacuum out of the bathroom corners. According to this diagram I found, one should also be wary of making friends with miniature buffalo.
What does Toxo do to humans? There’s some interesting stuff there that’s reminiscent of what’s going on in rodents. Some literature is coming out now reporting neuropsychological testing on men who are Toxo-infected, showing that they get a little bit impulsive. And then the truly astonishing thing: two different groups independently have reported that people who are Toxo-infected have three to four times the likelihood of being killed in car accidents involving reckless speeding. In other words, you take a Toxo-infected rat and it does some dumb-ass thing that it should be innately skittish about, like going right up to cat smells. Maybe you take a Toxo-infected human and they start having a proclivity towards doing dumb-ass things that we should be innately averse to, like having your body hurdle through space at high G-forces. Maybe this is the same neurobiology.
In this weekend’s New York Times, Choire Sicha has a great little piece of satire: A cat’s manifesto written in reaction to the Atlantic’s piece, “How Your Cat is Making You Crazy.” Writes Sicha, channeling his inner Garfield:
We have trained, by means of this gentle biological warfare, your women to let us into your homes, and your men to stay home and scratch us in our difficult places. You need not wake up facedown in a litter box after a rough “girls’ night out” to acquire our little friend. Toxoplasma lurks all about. We can, however, promise that as long as no humans become hysterical about their guaranteed eventual infection, and continue to do our bidding, we shall live in peace, as we have for so long. So do not panic. Take in more strays and no one gets scratched. The victory was decisive. Our will be done. Meowver and out.
I prefer the dogs’ strategy to gaming humans into doing their evolutionary bidding: they’re just really cute.