Recent studies shed light on how a prevalent brain parasite, known as Toxoplasma gondii, can interfere with brain functions, even when it infects only a handful of neurons. This microscopic parasite affects about one-third of the global population and disrupts communication between brain cells. The researchers involved in this study are optimistic that their discoveries could pave the way for improved detection and treatment of this chronic infection in the brain.
Toxoplasma gondii is quite the opportunist; it can infect nearly any warm-blooded animal, particularly favoring brain cells as its home. Once someone becomes infected, the parasites can create cysts in neurons that might persist throughout a person’s life. Interestingly, many don’t even realize they’re infected—it’s estimated that around 10 to 30 percent of people in the U.S. are unwitting hosts.
The parasite typically comes from undercooked meat or contact with cat feces. While many infected individuals show no symptoms, others may experience flu-like effects, such as fever, muscle aches, headaches, and fatigue. Swollen lymph nodes, especially in the neck, can also occur. However, these symptoms aren’t unique to Toxoplasma gondii and can be associated with various infections. Those with compromised immune systems may face more serious issues like confusion, blurred vision, and unsteady movements.
Interestingly, some studies have even suggested that contracting the parasite might surprisingly enhance one’s dating prospects, but that’s a topic for another day.
In most instances, a person’s immune system keeps the parasite at bay, but it can remain hidden in the brain for years, sometimes even decades.
Currently, the methods we have for diagnosing the infection rely on identifying antibodies to see if someone has been exposed to Toxoplasma gondii. Unfortunately, this doesn’t clarify whether the parasite is still lurking in the brain or how it might impact brain functions. However, there might soon be a shift in this approach.
Researchers from the University of California, Riverside, discovered that infected neurons produce fewer extracellular vesicles (EVs). These tiny membrane-bound packets are essential for cellular communication.
Emma H. Wilson, a professor of biomedical sciences at the Riverside School of Medicine and the study’s lead, explained, “This disruption in EV signaling can interfere with how neurons and glial cells, especially astrocytes, maintain a healthy brain environment.”
She further noted, “Even a few infected neurons can alter the neurochemical balance in the brain, indicating that communication between neurons and glial cells is crucial yet vulnerable to interference from parasites.”
The implications of this study could mean that EVs may serve as biomarkers, potentially isolatable from a person’s blood.
The existing research largely utilized mouse models and human cells in lab environments. In healthy mouse brains, astrocytes regulate neurotransmitters like glutamate to prevent excessive neuron excitation. However, when Toxoplasma gondii infects neurons, these messages are compromised, leading to an imbalance of glutamate that could cause seizures, neural damage, or changes in brain connectivity.
Wilson remarked, “The parasite might have a more significant influence on neurological and behavioral issues than we previously considered.”
Now, Wilson and her team aim to analyze human blood samples for EVs associated with the parasite. They’re also interested in understanding how glial cells identify and react to the proteins from the parasite, which could open doors to innovative therapies or even vaccines down the line.
“Our brains might have inherent defenses that can spot and respond to neurons infected by Toxoplasma gondii,” she added. “If we can find ways to bolster that mechanism, we could better shield vulnerable individuals.”
Despite its effects, there’s a lot of misunderstanding about Toxoplasma gondii.
Wilson reassured, “There’s no reason to avoid someone who is infected; most live symptom-free lives.”
“However, pregnant individuals should exercise caution, as first-time infection during pregnancy can lead to severe birth defects. Practicing proper food safety and hygiene is key: cook meats thoroughly, wash vegetables well, and always wash hands after handling cat litter, especially from younger cats, which tend to shed the parasite more frequently.”
This research has been published in PLOS Pathogens.
