Plan B Forum

Finally, there's the weird, unsettling connection between cats, a parasite called Toxoplasma gondii, and litter boxes.

This parasite can infect pretty much any sort of animal — including humans — but it can only sexually reproduce when inside the intestines of cats. In order to get there, it's been found to alter the behavior of infected rodents, making them less fearful of predators. In other words, when T. gondii gets picked up by a mouse, it increases the chance that the mouse will get eaten by a cat, so the parasite can reproduce once again.

This may seem bizarre enough, but over the past few years, some scientists have begun to suspect that the parasites alter human behavior in a similar way. Humans often pick up T. gondii from handling cats' litter boxes (because the parasites can be found in their feces), and there's an increasing amount of evidence that the resulting long-term, latent infection can subtly change a person's personality over time.

"When parasites found in cat litter infect humans, they seem to subtly change personality over time"

Of course, we're not rodents, so the parasites aren't successful in getting us eaten by cats. But the actual consequences are just as troubling. People who have been infected have greater rates of neuroticism and schizophrenia, and have slower reflex times in lab experiments. As a result, it seems, they get into traffic accidents more often. There's evidence that they have higher rates of suicide. All this, it seems, are unintended results of the parasite's ability to alter a mouse's brain to increase the chance of predation.

Of all God's creatures there is only one that cannot be made the slave of the lash. That one is the cat. If man could be crossed with the cat it would improve man, but it would deteriorate the cat.
- Notebook, 1894