A scientist has claimed that parasites passed from cats could be causing schizophrenia in their owners, the British Daily Mail newspaper reported on Feb. 10.

Jaroslav Flegr says he has come to the conclusion because he himself believes he is a living example, the report said. He says he has been infected by the parasite and it has altered his behavior over a period of time.

The parasite, which is excreted by cats in their feces, is called Toxoplasma gondii and is the microbe that causes toxoplasmosis ― the reason pregnant women are told to avoid cats’ litter boxes. Since the 1920s, doctors have recognized that a woman who becomes infected during pregnancy can transmit the disease to the foetus, resulting in severe brain damage in the baby ― or even death.

In adults the disease causes flu-like symptoms ― and those with a suppressed immune system can become seriously ill with complications such as encephalitis ― but many carrying the latent disease appear to have no symptoms.

However, once inside an animal or human host, the parasite then needs to get back into the cat, as that is the only place where it can sexually reproduce.

And this, Flegr believes, is why the infection is making subtle changes to the human brain to manipulate the host's behavior.

But from his own experience the Czech scientist, 63, claims that over the past two decades his personality has changed, leading him to behave in strange, often self-destructive ways.

His claims come after a study at Leeds University showed the parasite affects the production of dopamine, thus triggering schizophrenia and other bipolar disorders.

The parasite infects the brain by forming a cyst within its cells and produces an enzyme called tyrosine hydroxylase, which is needed to make dopamine, according to the Daily Mail.