Can Cat Poop Make You Crazy?

  • By Michael Rivera
  • Posted 06.13.18
  • NOVA

Toxoplasma gondii is a parasite that invades the brains of mice and organs of cats, resulting in a disease called toxoplasmosis. This parasite can also infect humans by way of cat feces. Although Toxoplasma research is still in its early stages, scientists estimate that one-third of the human population has been infected.

Running Time: 03:23


Can Cat Poop make you Crazy?

Published June 13, 2018

Onscreen: Can a parasite found in kitty litter take over the brain? Definitely. If the brain belongs to a mouse.

Emma Wilson: Normally, if a mouse smells cat urine, sensing its predator. It's going to run in the opposite direction.

Onscreen: Emma Wilson studies a parasite called Toxoplasma gondii, found in cat poop. If a mouse eats that poop, the parasite invades its brain.

Wilson: When that mouse is infected, the mouse is attracted to the smell of the cat urine instead of running away from it.

Onscreen: The mouse is now more likely to be eaten, which is exactly what the parasite wants. Toxo can only reproduce if it reaches a cat’s gut.

Wilson: That's going to continue the life cycle of the parasite.

Onscreen: This mouse is safe, but how can a parasite change a mouse’s actions? This is a single mouse neuron invaded by a round cyst full of toxo parasites…”inside the cell.” The body’s immune system then goes on the attack.

Wilson: The cyst contains hundreds and hundreds of parasites, and it slowly grows over time inside the cell.

This is an image of a live mouse brain, and these red circles are Toxoplasma parasite cysts. And every green dot is an immune cell.

Onscreen: Inflammation and swelling cause a build up of a near transmitter, called glutamate, and that could damage brain circuitry.

Wilson: Glutamate is involved in almost every single aspect of brain function. It really goes up in the infected brain. And that starts to interfere with cell signaling and that might explain changes in behavior.

Onscreen: And the creepy thing? It isn’t just mice…”with this parasite.” You don’t have to eat mice to get toxo. You can get it from raw meat, unwashed vegetables, or from handling kitty litter. And few ever know the parasite is in their bodies.

Wilson: What is fascinating is that so many people are infected with toxoplasma. A third of the world's population is infected with this parasite.

Perhaps we feel a little achy and that might be the only indication that you are infected.

Onscreen: Toxo infection can be dangerous to humans, sometimes causing premature birth or miscarriage. But claims that it might cause “Cat Lady Syndrome” or violent behavior in adults are difficult to prove. Toxo research is still in its early stages, but some think the parasite could be involved in diseases we’re only beginning to understand, like schizophrenia.

Wilson: The origins of schizophrenia are very poorly understood, but there's correlative evidence that people with schizophrenia are much more likely to be infected with toxoplasma. Possibly, a parasite in your brain, if it alters the chemistry of that brain, could trigger some genetic, underlying neurological disease that we have very little understanding of currently.



Digital Producer
Michael Rivera
Produced, and Directed by
Peter Yost
© WGBH Educational Foundation 2018

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