London: Researchers have found stronger evidence for a link between a parasite in cat faeces and undercooked meat and an increased risk of schizophrenia.

Research published today in Procedings of the Royal Society B, shows how the invasion or replication of the parasite Toxoplasma gondii in rats may be inhibited by using anti-psychotic or mood stabilising drugs.

The researchers tested anti-psychotic and mood stabilising medications used for the treatment of schizophrenia on rats infected with T. gondii and found they were as, or more, effective at preventing behaviourial alterations as anti-T. gondii drugs. This led them to believe that T. gondii may have a role in the development of some cases of schizophrenia.

Dr Joanne Webster from Imperial College London, and lead researcher
said: “Although we are certainly not saying that exposure to this parasite does definitely lead to the development of schizophrenia, this and previous studies do show there may be a link in a few individuals, providing new clues for how we treat toxoplasmosis and schizophrenia.”

Previous epidemiological and neuropathological studies have indicated some cases of schizophrenia may be associated with environmental factors, such as exposure to the parasite T. gondii. At the same time several of the medications used to treat schizophrenia have been shown to posess anti-parasitic and in particular anti-T.gondii properties.This led the authors to suspect that the anti-psychotic activity of these medications may be due in part to their inhibition of these parasites.

When the rats were given Haloperidol, an anti-psychotic, and Valporic acid, a mood stabiliser, the behavioural symptoms of T.gondii were reduced. They found the drugs were able to limit the ‘suicidal feline’attraction by which the rats became less aware of the dangers of cats.

Dr Joanne Webster added: “By showing that drugs used to treat schizophrenia affect the parasite T. gondii, this does provide further evidence for its role in the development of some cases schizophrenia. It may be that anti-psychotic drugs work partly by parasite inhibition, and this could lead to new medicine and treatment combinations.”

The researchers have already begun human clinical trials using anti-T. gondii treatments as adjunct therapies for schizophrenia with researchers at Johns Hopkins University.

Website: www.imperial.ac.uk