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By now, most people have heard of toxoplasma gondii, the parasite that turns people into crazy cat ladies. At least, that’s the view of it that has made it a popular subject in the science news and at dinner parties where talking about cat shit is acceptable.
T. gondii is one of those parasites that fascinate us because it seems to have mind-controlling powers, it can affect humans, and the vector is a lovable little beast that inhabits many of our homes. It’s the perfect recipe for parasite popularity!
T. gondii infects mice, but it can only reproduce in the digestive track of cats. So, it infects the mouse brains and makes them less afraid of cat pee and more likely to be forgetful, which makes the mice more likely to be eaten. The parasite then lays eggs, which are subsequently pooped out by the cats. Humans can get infected when they handle and that poop or breathe in its fumes, either while cleaning a litter box, or gardening, or playing in a sandpit (aka the feline public toilet), or doing some other weird thing that involves cat poop. I don’t know your life.
It’s a pretty successful parasite at this point thanks to all the cats we idiot humans have let roam outside where they have easy access to infected rodents. Reminder! Have your cat spayed or neutered, and keep him or her inside where it’s warm and safe and there are no small animals to murder and no cars to be murdered by.
So now a lot of humans are wandering around with T. gondii, which past studies have suggested could have similar effects as in mice. Not the part about being afraid of cat pee, but the memory problems and risk-taking behaviors, plus psychological issues like schizophrenia, severe depression, and obsessive-compulsive disorder.
All of this is news again thanks to a fairly large new study involving more than 800 38-year olds in New Zealand. Contrary to previous studies, this one found no correlation between toxoplasma gondii infection and any psychological issue, except for a very, very tenuous possible correlation with suicide attempts and a single memory test. There was zero difference in personality, depression, schizophrenia, criminal convictions, traffic accidents, and IQ.
It’s worth noting that this single study doesn’t cancel out all the previous studies that did find correlations. The data came from a cohort study following more than 1,000 New Zealanders, meaning that 200 people didn’t have their blood analyzed for T. gondii because they either didn’t show up, were already dead, or the blood analysis was botched. Among these missing people, they were statistically more likely to have schizophrenia, major depression, or a criminal conviction. If their results had been included, maybe the study would have had a slightly different conclusion.
Also remember that possible psychological effects aside, T. gondii can cause serious problems, especially for people who are pregnant or immunocompromised. Those problems are not at all in question, so even if further research supports that the psychological effects aren’t a big deal, you still shouldn’t be playing catch with feral cat turds. It’s dangerous, and also extremely disgusting, and also what’s wrong with you? Stop that.