Now we know what makes the crazy cat lady crazy. A parasite called toxoplasma gondii, which causes a disease called toxoplasmosis, is transmitted from cats to humans. Cats defecate the parasite which, if picked up by a human, infects our neural circuitry. More than 20 percent of all Americans are infected with toxoplasmosis, though not everyone shows symptoms of infection.
In this video by educational YouTube channel Big Think, science and health expert Kathleen McAuliffe explains how the cat parasite and other parasites affect the brain. At least 100 known parasites manipulate their host's behavior to enhance their own transmission, according to McAuliffe.
Humans are most often infected with toxoplasmosis when changing a cat's litter box. While most people exhibit few, if any, symptoms of infection, those who are pregnant, have transplanted organs, or are undergoing chemotherapy are most vulnerable to side effects. The parasite can cause blindness in a developing fetus, and threaten people who are immunocompromised. A severe toxoplasmosis infection can damage the brain, eyes, or other organs.
And while it was thought that among healthy people, toxoplasmosis caused no health problems, some studies have shown that even a dormant infection can have consequences. Toxoplasmosis has been linked to mental illness, depression, suicide, and dangerous driving—possibly because infected people are less vigilant or have slower reaction times. McAuliffe notes that these are correlational studies, but it's possible a dormant infection can cause trouble for some.
Toxoplasma gondii, in particular, affects both rodents and humans, as Motherboard wrote about before. Studies have shown that rodents with toxoplasmosis are sexually attracted to the smell of cat urine, luring them to the cats, who eat them, hence allowing the parasite to then live once again inside the cat. The parasite also gives the rodent increased levels of testosterone in males, or progesterone in females, emboldening the rodent so that it lowers its guard and acts foolishly around cats.
So if you're scooping the litter box and feeling crazy or slow, feel free to blame your cat.
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