Parasite turns rats into cat lovers

RATS infected by a brain-warping parasite develop a fatal attraction for cats, researchers have found.

To get into a cat and complete its life cycle, the organism changes the behavior of the rat so that it is more likely to be caught and eaten. Affected rats lose their fear of cats and are even drawn to feline smells, scientists say. They believe the one-cell parasite, Toxoplasma gondii, could also alter the personalities of humans it infects. About 22 per cent of the UK population carry the organism, which is transmitted through eating uncooked meat or contact with cat faeces. In France, it is carried by up to 87 per cent of residents. "We believe that these results may explain the reports of altered personality and IQ levels in some humans," said University of Oxford researcher Dr Manuel Berdoy, who conducted experiments to find the effect on cats. Research in Brazil has linked Toxoplasma gondii with hyperactivity in children.

The organism's main home is the gut of cats. Rats act as intermediary hosts, carrying the parasite in the form of dormant cysts which become lodged in the brain. Rats are super-cautious animals. They are highly neophobic , which means they have a fear of anything new and are terrified of cats. Co-researcher Dr Joanne Webster said: "The behavior of rats infected with this parasite is altered so that they are more likely to be predated." Dr Webster said it was not known how the parasite affected the brain, but it appeared to reduce anxiety in a similar way to valium. Toxoplasma gondii cysts sit in the brains of humans. Evidence suggests the cysts can affect human personalities, especially in people taking immuno-suppressant drugs. "Neurologists should really be looking at what this parasite is doing and where it's going in humans," she said.