Parasite "Brainwashes" Rats Into Craving Cat Urine, Study FindsBen Harder
for National Geographic News

April 3, 2007
The parasite Toxoplasma gondii uses a remarkable trick to spread from rodents to cats: It alters the brains of infected rats and mice so that they become attracted to—rather than repelled by—the scent of their predators.

A new study reveals that rodents infected with the parasitic protozoa are drawn to the smell of cat urine, apparently having lost their otherwise natural aversion to the scent.

The parasite can only sexually reproduce in the feline gut, so it's advantageous for it to get from a rodent into a cat—if necessary, by helping the latter eat the former.

In rodents, "brain circuits for many behaviors overlap with the brain circuits responsible for fear," said Ajai Vyas of Stanford University, who led the new study.

"One would thus assume that if something messes up fear of cat pee, it will also mess up a variety of related behaviors."

Bu