New research reveals that a common parasite known as Toxoplasma gondii, often spread by cats, may significantly disrupt brain function—even when only a small number of brain cells are infected. Scientists at the University of California Riverside have found that this parasite can impair how neurons communicate, potentially affecting overall brain health.
The findings, published following detailed experiments on mouse neurons, add weight to ongoing concerns about the
behavioral and neurological impacts of toxoplasmosis in both animals and humans.
How the Parasite Works in the Brain
T. gondii is a protozoan parasite that can infect nearly all warm-blooded animals, but it reproduces only in cats. Once in the host’s body—often through undercooked meat or exposure to cat feces—the parasite travels to the brain and embeds itself in neurons. There, it can remain for years, sometimes decades, without being detected.
Earlier studies have raised concerns that T. gondii may influence host behavior. For instance, infected rodents have been shown to lose their fear of cats, possibly increasing the chances of the parasite returning to its feline host. While these behavioral links remain controversial in humans, this latest study shifts the focus to clear physical changes in the brain.
Clear Physical Impact, Not Just Behavior
Unlike previous research that looked at behavioral outcomes, this study examined the direct cellular effects of the infection. Researchers noted:
Reduced EV Production: Infected neurons released significantly fewer extracellular vesicles.
Altered EV Content: The EVs produced by infected cells had different chemical compositions compared to healthy cells.
Astrocyte Reaction: Neighboring astrocytes responded to these changes by modifying gene expression—producing more immune-response molecules and less of the transporter responsible for clearing excess glutamate.
Glutamate is a neurotransmitter that plays a crucial role in brain activity. When levels become too high, it can lead to seizures, inflammation, or permanent neural damage—all complications that are occasionally seen in severe toxoplasmosis.
A Widespread, Often Overlooked Infection
Toxoplasmosis is remarkably common. In some regions, up to 80% of people may carry the parasite without knowing it. In the U.S., estimates range from 10% to 30%. While many infected individuals show no symptoms, the infection poses higher risks for pregnant women, infants, the elderly, and people with weakened immune systems.
In vulnerable individuals, toxoplasmosis can lead to serious complications such as brain lesions, seizures, and even death. Public health experts have long urged basic hygiene and food safety to prevent infection.
How to Reduce the Risk of Toxoplasmosis
To protect against toxoplasmosis, experts recommend several practical steps:
Cook Meat Thoroughly: Avoid rare or undercooked meats, especially pork and lamb.
Wash Fruits and Vegetables: Clean fresh produce thoroughly to eliminate potential contamination.
Handle Cat Litter Safely: Always wash your hands after scooping litter and consider wearing gloves. Pregnant women should avoid this task altogether.
Practice Kitchen Hygiene: Clean cutting boards, knives, and countertops after handling raw meat.
Hope for Better Protection
While the study does not suggest that all infected individuals are at immediate risk of neurological problems, it highlights how even low-level infections could disrupt brain processes. Future research may focus on how the immune system detects and manages infected neurons.
“Our brains have built-in defenses that may recognize and respond to neurons infected by T. gondii,” Dr. Wilson said. “If we can learn how to support or enhance that process, we may be able to better protect people—especially the most vulnerable.”
The findings underscore the importance of taking toxoplasmosis seriously—not just for pet owners, but for anyone interested in maintaining long-term brain health.
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