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A Deadly Attraction

September 19, 2011

Rats are supposed to be afraid of cats, but a tiny pathogen has turned the relationship around for its own benefit.



An unnatural attraction to danger…I’m Bob Hirshon and this is Science Update.

A tiny pathogen called toxoplasma gondii reproduces inside the digestive tract of cats. In order to get there, the felines have to eat vermin. But since rodents are naturally afraid of cats, the parasite has evolved a way to override their fear response. To find out what causes this unnatural attaction, Stanford School of Medicine neuroscientist Patrick House and his colleagues exposed toxoplasma-infected male rats to the smell of cat urine and measured activity in a region of their brain called the amygdala.

PATRICK HOUSE (Stanford School of Medicine):

You actually get activity that’s very similar to when you take a normal animal and expose it to a female in heat. And so, this parasite seems to be able to get inside the brain and alter a very strong hard-wired rodent repsonse to a predator and flip that around for its own benefit.


He says toxoplasma may also be related to human mental health conditions such as schizophrenia. I’m Bob Hirshon, for AAAS, the science society.