Findings from what is believed to be the largest comparison of blood samples collected from healthy individuals and people with schizophrenia suggest that infection with the common Toxoplasma gondii parasite, carried by cats and farm animals, may increase the risk of schizophrenia.

For more information; http://www.hopkinschildrens.org/toxoplasma-infection-increases-risk-of-schizophrenia.aspx