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. 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. 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.