Parasite deludes rats into liking cats

A protozoan that infects rats dims their wariness around cats and can even lead to what Oxford researchers call a fatal attraction.

That’s too bad for the rat, but it works for the parasite, explains Manuel Berdoy in England.

The protozoan, Toxoplasma gondii, needs to jump from rat to feline to complete its life cycle. The rat’s getting caught by a cat fits the parasite’s agenda, Berdoy and his colleagues argue in the Aug. 7 Proceedings of the Royal Society of London: Biological Sciences.

The researchers monitored rats exposed to cat odors. Normal rats avoid such smells. Yet infected rats seemed to lose their wariness and sometimes even prefer cat fragrance. This rat personality change marks the clearest example yet of a parasite manipulating its victimized mammal, claims Berdoy.

The parasite can infect many types of mammals but reproduces only in a few. In people, a latent infection can flair up and cause mental decline. Now, the researchers speculate that low-grade infections may result in more subtle effects, such as odd behavior and IQ dips. They estimate that the parasite infects 22 percent of UK residents and 88 percent of the French.

Susan Milius is the life sciences writer, covering organismal biology and evolution, and has a special passion for plants, fungi and invertebrates. She studied biology and English literature.