How to avoid being the lonely old crazy cat lady

One thing I love learning is the scientific reasoning behind myths. Everyone believes them but no one knows why they're true. Everyone knows the urban legend about being alone and getting a bunch of cats and becoming a crazy old lady. Well here's why it could be true....

Toxoplasma gondii is a bacteria that is common in humans. But only 1% of those infected are ever diagnosed. That's because your average immune system can handle it and it just forms a cyst somewhere out of the way. It can be dangerous around pregnant ladies and immunocompromised people (like if you have AIDS or a transplant). Problems can also arise if cysts form in the brain.

Ironically, the bacteria only undergo replication in the cat digestive system. That's another reason its not so harmful in humans: it can't grow there successfully. After it grows and reproduces in the cat digestive system it gets excreted with the rest of the stuff in the digestive system.

So imagine this scenario: you are an old lady (old = less effective immune system) with 7 cats. Maybe you don't clean out the litter box every day, so maybe a piece of cat crap gets stuck on a cat's paw. The cat walks on a counter leaving T. gondii behind. You eat the bacteria by accident with the sand which you made on the counter. The bacteria makes a cyst in your brain.

The icing on the cake is that T. gondii in the brain has been linked to schizophrenia and has significant behavioral changes in rats exposed to the bacteria.

MRI of AIDS patient with cyst

So there you have it. If you are old, don't get a bunch of cats cause you just might end up crazy.

Info from: Schaechter's Mechanisms of Microbial Disease and Survival of the Sickest and 10-1-07 UM lecture in Medical Microbiology