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NEW YORK (Reuters Health) - In a study of U.S. military personnel, researchers noted a significant positive association between infection with Toxoplasma gondii and the risk of schizophrenia.
Toxoplasmosis is a parasitic infection that often causes no symptoms in individuals with healthy immune systems. However, it can be dangerous in pregnant women and immunocompromised patients. Carried by about 60 million in the U.S. it is the third leading cause of death from food-borne illness.
Dr. David W. Niebuhr of Walter Reed Army Institute of Research, Silver Spring, Maryland and colleagues analyzed stored blood samples for T. gondii, and other infectious agents, in 180 military personnel who had been hospitalized and discharged with schizophrenia and in 532 healthy recruits.
They found that 7.0 percent of the schizophrenics tested positive for T. gondii compared with 5.3 percent of the healthy recruits.
The association between T. gondii and schizophrenia was consistent for nearly all time periods analyzed, both before and after the schizophrenia diagnosis, Niebuhr and colleagues note in the American Journal of Psychiatry.
These findings are similar to those of previous studies indicating increased levels of antibodies to T. gondii, indicating infection with this parasite in individuals with schizophrenia, they point out.
However, in previous studies, T. gondii antibodies were measured after diagnosis, which, the researchers say, raises the possibility that the increased levels of antibodies were the result of disease-related environmental factors.
The current study "indicates that increased levels of Toxoplasma antibodies are there before the onset of symptoms and are therefore unlikely related to symptom-associated exposures alone, Niebuhr's group explains.
"Since treatments are available for Toxoplasma, early detection of T. gondii infection and initiation of therapy may play a role in schizophrenia prevention or disease modification," they conclude.
The researchers also noted a significant positive association between human herpes virus-6 and schizophrenia, but not with any of the other pathogens tested, including other herpes viruses, influenza A and B viruses, Epstein-Barr virus, and varicella zoster virus.
SOURCE: American Journal of Psychiatry, January 2008.
