The cat and mouse chase is over

By Casey Frye, CCNN Writer

mouse on cat
Hey, why is my dinner hanging out on my head?

We all know how the story goes: cat sees mouse and wants to have a tasty dinner, so mouse runs away to save its own life. Well… that’s how it happens most of the time. However, rodents infected with a parasite called Toxoplasma gondii lose their fears of felines, and instead of running away from one, they just wait to be eaten! Wendy Ingram – a graduate student from the University of California, Berkeley – wanted to know what caused the strange behavior when she made an astonishing discovery: the parasite’s effects last long after it leaves a mouse’s body!

Wait, why does the infection change a rodent’s behavior in the first place? It’s actually a really interesting story. A cat’s stomach is the only place where the microorganisms can grow, and so T. gondii  is very fond of helping the mewling hunters catch mice. The parasites aren’t doing it to be nice though, because once the cat devours the poor critter, they can reproduce inside the belly as the host kitty purrs with satisfaction. It’s a good deal for everyone! Except for the mice, of course.

Even if the mouse manages to scurry away, they aren’t left totally unscathed. Ingram isn’t exactly sure how it happens, but once the tiny cheese-scarfing furballs are infected, their brains are changed permanently, so felines don’t appear scary anymore. She suspects that T. gondii alters the brain area responsible for smelling cats, which usually strikes fear in the tiny hearts of mice. “The idea that this parasite knows more about our brains than we do, and has the ability to exert desired change in complicated rodent behavior, is absolutely fascinating,” said Ingram. “Toxoplasma has done a phenomenal job of figuring out mammalian brains in order to enhance its transmission through a complicated life cycle.”

Well, this is great news for the researchers who get an interesting study, the parasites that get a home with free food, and the cats that get an easy meal. However, I think we can all agree that mice got the short end of the stick on this one!

Featured image courtesy of cloud_nine on Flickr. Image of mouse on cat’s head courtesy of UC Berkeley and Wendy Ingram. Video courtesy of GeoBeats News.