A microscopic parasite may be doing more inside the brain than we ever imagined.
Researchers at the University of California, Riverside have discovered that Toxoplasma gondii — a common parasite carried by roughly 30% of people in the United States — can interfere with how brain cells communicate, even when it infects only a small number of neurons.
Rather than causing widespread damage, the parasite appears to subtly rewire communication pathways.
The study found that infected neurons release fewer extracellular vesicles (EVs) — tiny molecular packets that neurons use to send messages to surrounding cells, including astrocytes. Astrocytes are critical support cells that regulate brain chemistry, balance neurotransmitters, and maintain overall neural stability.
When EV signaling drops, glutamate levels can rise.

Excess glutamate is dangerous — it has been associated with seizures, neuroinflammation, and long-term neural damage. Over time, this chemical imbalance may alter neural connectivity in ways scientists are only beginning to understand.
Most people infected with T. gondii never show symptoms, and the parasite often remains dormant for life. But this research suggests that its presence may not be entirely silent. Even low-level, chronic infection could influence how the brain regulates communication at the cellular level.
Perhaps most promising is the diagnostic breakthrough. Because standard antibody tests cannot detect whether the parasite is actively affecting the brain, researchers are now exploring extracellular vesicles as blood-based biomarkers. If successful, this approach could allow doctors to identify chronic brain infections earlier — and potentially intervene.