Photo by KiVEN Zhao on Unsplash

The Parasite Behind the Cat Lady

Cindy and I were sitting in our hot tub the other night, talking with a couple of friends from England, when the topic of cat ladies came up. That was probably because my friend Daniel is the quintessential cat lady. I asked, “Do you know about the theory of toxoplasmosis being the cause of cat ladies?” Dan asked, “Toxo what?” After explaining it to them, I realized that not many people know about this, so here goes.

Toxoplasma gondii is a parasite that reproduces only in cats and gets distributed in cat poop as cysts. The lifecycle of the parasite depends on it getting ingested by, and thereby infecting, other warm-blooded creatures, where it wreaks various forms of neurological havoc. The parasite can be acquired by humans through undercooked food or through handling of cat poop (such as when cleaning a cat litter tray).

The parasite can also be passed from a human mother to her child during pregnancy. If an unborn fetus gets infected by the toxoplasma parasite then it may die or end up severely brain damaged. This is the reason that pregnant ladies are instructed by their doctors to not empty cat litter trays or dig around in flowers beds while doing gardening; cats like to poop in flower beds.

The natural life-cycle of the toxoplasma parasite includes a rat eating the poop of an infected cat. When the rat gets infected, the parasite makes its way to the brain of the rat where it damages it in just the right way to make the rat love cats. An infected rat will have so much love for cats that it will approach them in a friendly manner, hoping to play, or at least just to get a closer look. Or maybe it just makes them a lot less scared of cats than they would normally be. This behavior leads, of course, to the rat being ingested by the cat. If that cat was not already infected with the parasite, then the parasite will have propagated to a new host in which it can reproduce.

There is a strong correlation between cases of schizophrenia in humans and the presence of antibodies to the toxoplasma parasite. The prevalence of schizophrenia has also grown in lock-step with the domestication of cats. Some people theorize that the parasite, confused by the anatomy of the human brain, modifies it not to make us just love cats, but to make us go full-on, batshit crazy. I wonder if some or all of the infected rats would also spout word-salad, if only they could talk.

I discovered a few additional interesting tidbits of information while researching this article: (1) the drugs used to treat schizophrenia inhibit the replication of the parasite; (2) toxoplasma infection is also correlated with obsessive-compulsive disorder, bipolar disorder, and an increased propensity to be involved in road-traffic accidents; and (3) infection with the parasite seems to protect against multiple sclerosis.

Which brings us, finally, to cat ladies, or should I say to crazy cat ladies. Although the correlation between cat-lady syndrome and infection with the toxoplasma parasite has not been studied, it doesn’t take a great leap of imagination to generate a powerful hypothesis: toxoplasma gondii makes cat ladies. Why else would anyone give up everything in life to focus only on loving cats? Well, because they’re the cutest, of course.