Of Mice and Men

Robert Sapolsky's new book, Monkeyluv, contains this curious fact, cited in a review in today's NY Times Book Review, namely that there is "a parasite that infects the brains of rats without any effect on their behavior except that they lose their instinctual aversion to the smell of cats and, instead, are drawn to it. Needless to say, such absurdly obliging prey is quickly gobbled up: bad for the rat but great for the parasite, since it can only reproduce inside a cat host. The next generation hitches a ride out on the cat's feces, which are ingested by rats to start the cycle over again."

A quick google search (keywords: parasite rat brain cat feces) netted several articles on the topic, one of which began with the following statement : "Toxoplasma gondii is a heteroxenic coccidian parasite of felids with an unusually wide range of intermediate and paratenic hosts, including humans." Confused but intrigued, I read on: "...infected rats have higher activity levels, lower neophobia, reduced learning capacity and lowered level of avoidance of cat odour." In other words, they become hyperactive and thrill-seeking while demonstrating a fatal combination of stupidity and arrogance.

Naturally one wonders whether other paratenic hosts exhibit the same symptoms...