Toxoplasma Gondii
A protozoan parasite that enters the brain via cat-litter contact, living physically inside cysts in about one-third of humans, often asymptomatically for decades.
Toxoplasma gondii is a widespread protozoan parasite that infects mammals, including humans, primarily through contact with cat feces or contaminated food. Most immunocompetent hosts carry it asymptomatically in cysts, but it can cause severe disease in immunocompromised individuals, pregnant women, and newborns via congenital transmission.
What this means in real life
A person who cleans a cat's litter box without washing their hands afterward and then touches their face may ingest the parasite; most will never notice, but a pregnant woman could pass it to her fetus, potentially causing birth defects.
What it isn’t
It is not a virus or bacterium, and infection does not automatically cause illness or behavioral changes in most people. While some research explores links to behavior, the parasite does not reliably 'control' human minds.
Commonly misused online
Social media often exaggerates claims that the parasite makes people reckless or alters personality in dramatic ways. In reality, most infected people show no behavioral effects; any influence remains scientifically contested and subtle.