Toxoplasma gondii 🧠 A Deep-Dive Into a Parasite That Quietly Alters Human Behavior Most people understand that parasites can affect digestion or immunity… but few realize that some can reach all the way into the brain and subtly shift mood, cognition, and even behavior. One of the most fascinating — and most common — examples is Toxoplasma gondii . 🦠 What Is Toxoplasma gondii ? T. gondii is a single-celled parasite commonly found in: Cat feces Contaminated soil Undercooke