Toxoplasma infection increases risk of schizophrenia, study suggests

January 16, 2008

Findings from what is believed to be the largest comparison of blood samples collected from healthy individuals and people with schizophrenia suggest that infection with the common Toxoplasma gondii parasite, carried by cats and farm animals, may increase the risk of schizophrenia.

A report on the study, conducted among U.S. military personnel by researchers from Walter Reed Army Institute of Research and Johns Hopkins Children’s Center appears in the January issue of the American Journal of Psychiatry.

Researchers found that of the 180 study subjects diagnosed with schizophrenia, 7 percent had been infected with toxoplasma prior to their diagnosis, compared to 5 percent among the 532 healthy recruits. Thus, people exposed to toxoplasma had a 24 percent higher risk of developing schizophrenia. The difference, while seemingly small, is important, researchers say, because the ability to explain even a small portion of the 2 million cases of schizophrenia in the United States may offer clues to the disease and some possible treatments.

For example, the investigators say they plan to study whether aggressive treatment of toxoplasma infection with antiparasitic drugs in patients with schizophrenia could halt the progression of the mental disorder, characterized by paranoia, delusions and hallucinations.

Most infections with toxoplasma occur early in life following exposure to the parasite in cat feces or undercooked beef or pork. Infections rarely cause symptoms, but the parasite remains in the body and can reactivate after lying dormant for years.

“Our findings reveal the strongest association we’ve seen yet between infection with this very common parasite and the subsequent development of schizophrenia,” says Robert Yolken, M. D., a neurovirologist at Hopkins Children’s who was among those conducting the analysis.

Previous studies have reported on the link between schizophrenia and the presence of toxoplasma antibodies, which are evidence of past infection, but this is the first study to show that infection with the parasite can precede the initial onset of symptoms and subsequent diagnosis with schizophrenia, Yolken says.

Because the U.S. military routinely tests its active personnel for toxoplasma, among other infectious agents, and stores blood samples in a central repository, researchers were able to determine the time line between infection and a diagnosis of schizophrenia.

“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 says. “With our current study, we were able to show that infection came first.”

While most people infected with toxoplasma never develop schizophrenia, the parasite may be a trigger in those genetically predisposed to the disorder, a classic example of how genes and environment come together in the development of disease, Yolken says.

Source: Johns Hopkins Medical Institutions

Explore further: The concept of schizophrenia is coming to an end – here's why

Related Stories

The concept of schizophrenia is coming to an end – here's why

August 24, 2017
The concept of schizophrenia is dying. Harried for decades by psychology, it now appears to have been fatally wounded by psychiatry, the very profession that once sustained it. It's passing will not be mourned.

Penn vet professor investigates parasite-schizophrenia connection

October 29, 2014
Many factors, both genetic and environmental, have been blamed for increasing the risk of a diagnosis of schizophrenia. Some, such as a family history of schizophrenia, are widely accepted. Others, such as infection with ...

Scientists unpack how Toxoplasma infection is linked to neurodegenerative disease

June 9, 2016
Toxoplasma gondii, a protozoan parasite about five microns long, infects a third of the world's population. Ingested via undercooked meat or unwashed vegetables, the parasite infects 15-30 percent of the US population. In ...

Toxoplasma-infected mice remain unafraid of cats even after parasite clearance

September 18, 2013
Chronic infection with the parasite Toxoplasma gondii can make mice lose their innate, hard-wired fear of cats. This loss of their innate fear may persist after the parasite is no longer detectable in their brains, suggesting ...

New study finds plant proteins control chronic disease in Toxoplasma infections

April 8, 2013
A new discovery about the malaria-related parasite Toxoplasma gondii—which can threaten babies, AIDS patients, the elderly and others with weakened immune function—may help solve the mystery of how this single-celled ...

Parasite uses the power of sexual attraction to trick rats into becoming cat food

August 17, 2011
(PhysOrg.com) -- Could it be love? Rats infected with the parasite Toxoplasma seem to lose their fear of cats – or at least cat urine. Now Stanford researchers have discovered that the brains of those infected, fearless ...

Recommended for you

Anti-malaria drug shows promise as Zika virus treatment

November 17, 2017
A new collaborative study led by researchers at Sanford Burnham Prebys Medical Discovery Institute (SBP) and UC San Diego School of Medicine has found that a medication used to prevent and treat malaria may also be effective ...

Decrease in sunshine, increase in Rickets

November 17, 2017
A University of Toronto student and professor have teamed up to discover that Britain's increasing cloudiness during the summer could be an important reason for the mysterious increase in Rickets among British children over ...

Scientists identify biomarkers that indicate likelihood of survival in infected patients

November 17, 2017
Scientists have identified a set of biomarkers that indicate which patients infected with the Ebola virus are most at risk of dying from the disease.

Research team unlocks secrets of Ebola

November 16, 2017
In a comprehensive and complex molecular study of blood samples from Ebola patients in Sierra Leone, published today (Nov. 16, 2017) in Cell Host and Microbe, a scientific team led by the University of Wisconsin-Madison has ...

Study raises possibility of naturally acquired immunity against Zika virus

November 16, 2017
Birth defects in babies born infected with Zika virus remain a major health concern. Now, scientists suggest the possibility that some women in high-risk Zika regions may already be protected and not know it.

A structural clue to attacking malaria's 'Achilles heel'

November 16, 2017
Researchers from The Scripps Research Institute (TSRI) and PATH's Malaria Vaccine Initiative (MVI) have shed light on how the human immune system recognizes the malaria parasite though investigation of antibodies generated ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.