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Study Finds Evidence of Bartonella Infection in Blood of Patients With Schizophrenia

May 03, 2021

A pilot study found evidence of Bartonella infection in the blood of participants with schizophrenia, fueling researchers’ hypothesis that there may be a connection between bacterial infection and neuropsychiatric disease.

Researchers published their findings online in Vector-Borne and Zoonotic Diseases and plan to confirm the results in a larger study.

“Specifically, there has been research suggesting that cat ownership is associated with schizophrenia due to the zoonotic parasite Toxoplasma gondii, but to date there has been no conclusive evidence in support of a causative role for this parasite,” said lead author Erin Lashnits, MS, DVM, PhD, DACVIM, University of Wisconsin, Madison. “So we decided to look at another cat-associated infectious agent, Bartonella, to see if there could be a connection.”

Using a case-control study design, researchers analyzed both clinical and cognitive assessments of 17 participants with stable, medically managed schizophrenia and a control group of 13 healthy adults. Participants completed questionnaires examining their symptom severity and potential Bartonella exposure. Researchers looked for evidence of Bartonella organism-specific DNA and antibodies at 14- and 21-day intervals from blood samples taken twice in one week and cultured in a growth medium.

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Twelve of the 17 patients (70.5%) with schizophrenia had Bartonella DNA in their blood compared to 1 one of 13 (7.7%) in the control group. Patients with schizophrenia and controls reported similar pet ownership and flea exposures on their questionnaires.

Bartonella is historically associated with “cat scratch disease,” which was thought to be a short-lived infection, researchers said. Flea and tick exposure can infect cats with Bartonella.

“Many of these patients have been undergoing care for years,” said coauthor Ed Breitschwerdt, DVM, DACVIM, North Carolina State Veterinary Medicine, Raleigh. “What we’re starting to see is a pattern—Bartonella can persist for a long time. And for the subset of people who can’t eliminate the infection, the bacteria can cause chronic or progressive illness.”

“It is important to remember that our study was by design not able to demonstrate a causal link between Bartonella infection and schizophrenia,” said corresponding author Flavio Fröhlich, PhD, University of North Carolina at Chapel Hill Neuroscience Center. “However, we believe this initial observational study strongly supports the need for follow-up research.”

—Meagan Thistle


Lashnits E, Maggi R, Jarskog F, et all. Schizophrenia and Bartonella spp. infection: a pilot case-control study. Vector Borne and Zoonotic Diseases. 2021 Mar 15;[Epub ahead of print].

Pilot study finds evidence of Bartonella infection in schizophrenia patients [press release]. Chapel Hill, NC: North Carolina University; March 26, 2021.

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