Common Parasite Associated with an Increased Risk of Schizophrenia

There is increasing evidence that infection with Toxoplasma gondii, a common parasite of people, cats and rodents is associated with an increased risk of a schizophrenia diagnosis.

Toxoplasma gondii is a single-celled parasite that causes toxoplasmosis. According to the Center for Disease Control and Prevention, the parasite is transmissible through the womb, possibly explaining some (all?) heritability. According to the CDC, “While the parasite is found throughout the world, more than 60 million people in the United States may be infected with the Toxoplasma parasite. Pregnant women and individuals who have compromised immune systems should be cautious; for them, a Toxoplasma infection could cause serious health problems.”

21.4% (13.7% to 30.6%) of schizophrenia is a preventable parasitic infection. This is not a new idea, just one that is threatening to the factors that make Abilify@ the world’s number one money making pharmaceutical.

How do people get toxoplasmosis? A Toxoplasma infection occurs by:

  • Eating undercooked, contaminated meat (especially pork, lamb, and venison).
  • Accidental ingestion of undercooked, contaminated meat after handling it and not washing hands thoroughly (Toxoplasma cannot be absorbed through intact skin).
  • Eating food that was contaminated by knives, utensils, cutting boards and other foods that have had contact with raw, contaminated meat.
  • Drinking water contaminated with Toxoplasma gondii.
  • Accidentally swallowing the parasite through contact with cat feces that contain Toxoplasma. This might happen by cleaning a cat’s litter box when the cat has shed Toxoplasma in its feces, touching or ingesting anything that has come into contact with cat feces that contain Toxoplasma.
  • Accidentally ingesting contaminated soil (e.g., not washing hands after gardening or eating unwashed fruits or vegetables from a garden).
  • Mother-to-child (congenital) transmission.
  • Receiving an infected organ transplant or infected blood via transfusion, though this is rare.

Most people who become infected with Toxoplasma gondii are not aware of it. Most infants who are infected while still in the womb have no symptoms at birth, but they may develop symptoms later in life.

How does the Medical Psychologist rule out T. gondii vs schizophrenia? It is difficult to identify a long-standing T. gondii infection.

In animals, infection with Toxoplasma gondii can alter behavior and neurotransmitter function. In humans, acute infection with T. gondii can produce psychotic symptoms similar to those displayed by persons with schizophrenia. Since 1953, a total of 19 studies of T. gondii antibodies in persons with schizophrenia and other severe psychiatric disorders and in controls have been reported; 18 reported a higher percentage of antibodies in the affected persons; in 11 studies the difference was statistically significant. Two other studies found that exposure to cats in childhood was a risk factor for the development of schizophrenia.

Multiple studies demonstrate that the brains of individuals with schizophrenia show structural and functional changes and that these exist even in patients who have never been treated with antipsychotic medications. Schizophrenia, like multiple sclerosis and Parkinson disease is a chronic disease of the central nervous system. As with other such diseases, infectious agents should be considered as possible etiologic agents, perhaps in persons who also have an increased genetic susceptibility.

Some medications used to treat schizophrenia inhibit the replication of T. gondii in cell culture. Establishing the role of T. gondii in the cause and development of schizophrenia might lead to new medications for its prevention and treatment.