Toxo is smarter than you
Interesting article in Scientific American Mind this month.
T. gondii, the cause of toxoplasmosis and the bane of pregnant women and the men who have to change the cat litter, is a pretty amazingly designed bug. It’s a pathogen that sexually reproduces only in the intestines of cats, but can maintain itself indefinitely in pretty much any warm blooded animal. As you likely recall from those exciting ID months in med school, infected cats shed millions of the toxo oocysts in their local litter boxes. From there, they are taken up by all kinds of animal, including humans, and they infect muscle and brain tissue, hiding out and escaping the host’s immune system. But in order to reproduce, they must get back into cats belly’s. But how? How can a simple bug dictate its own course of inter intestinal travel?
Recent research has the answer and its pretty mind blowing (no pun intended).
Toxoplasmosis has been most thoroughly studied in rats and mice. Both species have deep seated, innate fear of cats for obvious reasons. Spray a bit of cat urine into a corner, and the rodent will avoid this location. In contrast, an infected animal loses it innate fear of cats. By some measures, it even appears to be mildly attracted to the smell of felines. This is an unfortunate turn of events for the rodent, because it is now more likely to be successfully hunted by a cat. On the other hand, this is a great deal for T. gondii. When the cat devours the sick critter and its contaminated brain, T. gondii moves into its final host., where it reproduces, completing its life cycle.
And this subtle change in behavior is all that is different with Mr. Rat. For all other intents and purposes, the rat still acts like a rat, unlike in rabies where the rat starts acting like, well a nutjob. But what’s awesome about this, is that since T. gondii can only reproduce in felines, it wants the rat to be attracted to not just any old pee, but specifically cat pee, and only cat pee. Amazing that a little bug can cause this sublte and specific change in behavior in order to promote its own reproduction.
Now what’s also interesting is that schizophrenic patients are two to three times more likely to carry antibodies to T. gondii than controls. Could this bug also cause some of this abhorrent behavior in these patients? Coincidence? Perhaps, as I don’t think the voices are telling them to seek out feline urine samples, but they could be contributing to behavior on some level. The exact link between T. gondii and psychiatric disorders is still unclear.