The infection toxoplasmosis is caused by the parasite Toxoplasma gondii and is widespread. It’s estimated that 30 to 50 percent of the global human population are carriers. Cats are the parasites’ main host, but the infection is also spread among other animals, including humans. A series of studies has previously shown that the parasite affects the brains of infected rats so that they lose fear of cats and even become attracted to cats’ scent, making them an easy prey. The parasite spreads by ensuring that the rat is eaten by a cat. Toxoplasmosis is life-threatening to people with impaired immune systems and to unborn foetuses, but causes only mild symptoms in healthy individuals. However, there are studies showing that mental illnesses such as schizophrenia, depression and anxiety disorder are more common in people who are carriers of Toxoplasma gondii. There are also studies indicating that the parasite may affect aggressive or risky behaviour.