Parasite Makes Mice Fearless of Cats In an adaptation that probably doesn't end well for the rodents By Arden Dier, Newser Staff Posted Sep 19, 2013 1:52 PM CDT 15 comments Comments You talkin' to me? (Shutterstock) (Newser) – Good news for cats: Mice are no longer afraid of them—at least mice that have been infected with a parasite common in mammals. Not only does Toxoplasma gondii leave mice less afraid and thus more likely to venture into striking distance, the effects last after the parasite has cleared, reports a PLoS One study. "Long after we lose the ability to see it in the brain, we still see its behavioral effect," says a Berkeley researcher. In fact, that effect might be permanent, reports Nature.com. How do scientists explain the weird phenomenon? It could be the parasite being very, very sneaky, explains Science News. It can only reproduce inside a cat's gut, and an easy way for it to get there is by way of a delicious, fearless mouse. The parasite achieves the trick by eliminating the mouse's fear of cat urine, reports NBC News. Once infected, the mouse is actually attracted to the scent.