Two related questions: As a cat owner, I’ve been a little concerned recently about rumors that cat poop can cause schizophrenic behavior in people who are overexposed to the waste. How much truth is in this–and if there is any truth to it, what amount can possibly count as overexposure? I’m also bothered by the supposed risk to pregnant women that changing the litter box can cause–not so much to them as to the fetus, through bacteria and whatnot. If that’s really true, then with a third of all Americans owning cats, why don’t we see higher rates of these dreadful birth defects? Certainly some of these women must get pregnant sometime, and I doubt they all know the dangers posed to them by cleaning up what Puss left behind. What gives? –Onnie in Baltimore
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While you’re surely right that not everyone has gotten the word, the medical profession and hopefully most women of childbearing age know that if you’re pregnant you don’t want to get near cat feces. The problem is the protozoan Toxoplasma gondii, for which cats are the principal host. The microscopic parasites reproduce in the cat’s gut, the eggs are excreted, and by a process I’m not about to describe the critters wind up in your brain and muscles, where they create tiny cysts, leading to a condition known as toxoplasmosis. Unpromising as this sounds, the symptoms of toxoplasmosis are generally mild to nonexistent in adults, which is good, because roughly a third of all humans are infected, with the rate in some tropical countries approaching 100 percent.
Here’s where things get strange. While the link between toxoplasmosis and birth defects has long been recognized, scientists now suspect that T. gondii may cause schizophrenia too. That in itself represents a major change in thinking–till recently the prevailing assumption, based on twin studies and the like, has been that schizophrenia is transmitted genetically. No way, scoffers say: schizophrenia is so profoundly disabling that sufferers tend not to reproduce. Germs are a likelier candidate. Studies typically have found T. gondii antibodies occurring in schizophrenics at twice the rate seen in control groups.
