SSS 2011-08-17

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When a healthy rat smells a cat, it flees. But rats infected with the Toxoplasma brain parasite¹ actually follow cat odors, often presumably to their doom², red in tooth and claw. Now researchers have found out exactly what's going on in the rat's infected brain—it's in love. The study is in the journal Public Library of Science ONE. 

 

That Toxo-infected rats approach cats has long been a well-known example of a parasite manipulating the behavior of its mammalian host. The protozoan needs to be in a cat's intestine³ to reproduce. It then gets pooped out and has to find its way into another cat to continue its fabulously⁴ glamorous⁵ lifestyle. Rats that touch the poop and then get eaten by a cat can complete the circuit. 

 

The new research reveals that when a Toxo-infected rat smells cat urine, it has increased activity in brain regions associated with sexual attraction. Which the researchers say is "compelling evidence that Toxoplasma overwhelms the innate⁶ fear response by causing, in its stead, a type of sexual attraction to the normally aversive cat odor." That's right, the rat is turned on. Before it's permanently⁷ turned off.

 

Thanks for the minute. For Scientific American's 60-Second Science, I'm Steve Mirsky.

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