It's a common parasite carried by cats. It infects mice, then causes the mice to be attracted to the smell of cat pee. The mice loose their fear of cats and actively seek them out. Cats, naturally, don't pass up a free meal and eat the infected mice, getting infected themselves in the process. The good news is toxoplasmosis is only transmitted through cat feces and causes no harm to the cat or human that may be infected. It only makes rodents suicidaly attracted to cats and cat owners are less likely to be botherd by the smell of cat pee after being infected. There is a theory that the majority of cat owners are already infected and extreme cases combined with existing mental illnesses is what causes crazy cat ladies to be a thing.

If I knew how I would probably win a Noble price in medicine. T. Gondii is one of those parasites that can influence their hosts behavior. One of its pit stops in its life cycle are rodents like rats and mice. Its end host are cats. Now any rodent is smart enough to fear and avoid an apex predator like cats. Fresh cat pee is like a big red flashing neon warning sign to them inducing fear. Somehow Toxoplasmosis can rewire a rodent’s brain to dampen or even eliminate fear of cats going so far as to seeking out cats. I’d like to imagine it just like our obsession with big cats in one of those touristy “petting zoos” making people ignore the fact that a tamed tiger can still maul you in a heart beat.

Scientists believe Toxoplasmosis can alter human brains as well. To what extent nobody knows. Maybe it explains the crazy cat lady trope. There are at least some studies that show that people infected with T.Gondii rate cate urine more pleasant and that they have worse memory at an older age.

And also this is Reddit and I was being facetious! ;P

cats release it to make humans more subservient to them