Toxoplasma Infection Increases Schizophrenia Risk, Study Says

The parasite can be transmitted to humans through such things as contaminated soil, undercooked meat or cat feces.

Posted: February 12 2008 2 a.m. EDT

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Toxoplasma Infection Increases Schizophrenia Risk, Study Says
Toxoplasma can be transmitted to cats from infected rodents or birds.
A new study suggests that those infected with Toxoplasma have an increased risk of developing schizophrenia, according to researchers from the Walter Reed Army Institute of Research and Johns Hopkins Children’s Center.

Researchers compared military personnel — 180 who were diagnosed with schizophrenia and 532 who were healthy — and found those who had been exposed to the Toxoplasma parasite had a 24 percent higher risk of developing schizophrenia.

Toxoplasma is caused by the parasite Toxoplasmosis gondii, and is transmitted to humans through handling contaminated soil, exposure to cat feces or by eating undercooked meat. Cats contract the parasite by eating infected birds or rodents, and therefore outdoor cats are more likely to be carriers. Humans who come into contact with cat feces — through cleaning the litterbox or working in contaminated soil — and accidentally ingest the waste may become infected.

“Our findings reveal the strongest association we’ve seen yet between infection with this very common parasite and the subsequent development of schizophrenia,” said Dr. Robert Yolken, a neurovirologist at Hopkins Children’s.

The military routinely tests its soldiers for infectious agents — including Toxoplasma — and stores the blood samples, which allowed researchers to determine the timeline of Toxoplasma infection and the onset of schizophrenia, researchers said.

“Until now, the only thing we could say is that some people with schizophrenia also had been infected with Toxoplasma at some point, but we couldn’t tease out which came first,” Yolken said. “With our current study, we were able to show that infection came first.”

Researchers added that most people who become infected with Toxoplasma never develop schizophrenia, but the parasite may trigger the onset of the disease to those who are genetically predisposed to it. The study was published in the January issue of the American Journal of Psychiatry.

To help prevent Toxoplasma in cats, the American Veterinary Medical Association (AVMA) recommends that cats be kept indoors and that they only be fed cooked meat or processed food from commercial sources. Cats rarely show symptoms, and no vaccine currently exists, according to the AVMA.

Toxoplasma infections passed from cats to humans can be significantly reduced by taking a few precautions, according to the AVMA, such as changing litter daily, covering sand boxes to discourage cats from using them and washing hands thoroughly after handling soil. Symptoms resemble the cold or the flu, and include swollen lymph nodes and muscle aches. At-risk populations include pregnant women and those with suppressed immune symptoms. However, the risks for contracting the parasite are nonexistent if people wash their hands after cleaning the litterbox or prior to eating, and pregnant women and immune-compromised people can own cats if they take these simple precautions.

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Reader Comments

Robert    Syracuse, NY

2/17/2008 6:11:51 PM

A very good article and a bit scary. I have three cats (indoor) but I never considered the disease. Besides, I clean my cat's litter boxes daily, but I don't often wash my hands after doing so. I will from now on, after reading this article.

Ellen    Attleboro, MA

2/13/2008 12:55:46 AM

Good to know

Meghan    Glendora, CA

2/12/2008 9:15:24 PM

I love this article because it informs you of the recent news. I am glad you post things like this.

Sandra    Corydon, IN

2/12/2008 8:17:34 PM

Now I don't want my cat to ever go out!

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