Leeds, England -- British scientists say toxoplasmosis parasite may trigger the development of schizophrenia and bipolar disorders.

The team from the University of Leeds shows the parasite may play a role in the development of the disorders by affecting the production of dopamine -- the chemical that relays messages in the brain controlling aspects of movement, cognition and behavior.

Toxoplasmosis, which is transmitted through cat feces -- and can be found on unwashed vegetables as well as raw or undercooked infected meat -- is relatively common, with 10 percent to 20 percent of the British population and 22 percent of the U.S. population estimated to carry the parasite as cysts. Most people with the parasite are healthy, but for those who are immune-suppressed -- and particularly for pregnant women -- there are significant health risks that can occasionally be fatal.

"Toxoplasmosis changes some of the chemical messages in the brain, and these changes can have an enormous effect on behavior," study leader Dr. Glenn McConkey said in a statement.

"Studies have shown there is a direct statistical link between incidences of schizophrenia and toxoplasmosis infection and our study is the first step in discovering why there is this link."