Skeptophilia (skep-to-fil-i-a) (n.) - the love of logical thought, skepticism, and thinking critically. Being an exploration of the applications of skeptical thinking to the world at large, with periodic excursions into linguistics, music, politics, cryptozoology, and why people keep seeing the face of Jesus on grilled cheese sandwiches.

Tuesday, February 15, 2011

Cats and rats and brain parasites, oh my!

To further explore yesterday's topic of Reasons You May Be Mentally Ill, today's topic is: toxoplasmosis.

The subject came up in casual conversation with our dear friends Alex and Nancy a couple of days ago.  Alex and Nancy are wonderful dinner guests, in that (1) they always bring amazing desserts, (2) Nancy brings along her guitar and after dinner we spend a couple of hours playing music, and (3) they are polymaths of the sort for whom "toxoplasmosis" could come up as a topic for casual conversation, and no one would raise an eyebrow.  To say that conversations with Alex and Nancy are "wide-ranging" is an understatement that would be rivaled only by saying that Magellan "got around a bit."

You may know of the pathogen Toxoplama gondii in its connection to the recommendation by doctors that pregnant women not clean cat litter boxes.  The pathogen, which is neither a bacteria nor a virus but a protist, is carried by cats and excreted with the urine; and a pregnant woman who contracts toxoplasmosis risks birth defects in her unborn child.

What you may not know, however, is that there is a significant likelihood that you have toxoplasmosis right now.  In fact, if you have ever owned a cat, the probability probably stands close to 100%.

A recent study by Kevin Lafferty, of the University of California, suggests that as many as three billion people may have a dormant Toxoplasma infection.  Yes, dear readers, you read that right; that's three billion, as in a little less than half of the human population.  Turns out that Lafferty's research indicated that when you get toxoplasmosis, you get flu-like symptoms for a couple of days, and then the symptoms abate -- but for most of us, the protist goes dormant, and we carry around the parasite for life.

This is creepy enough, but wait'll you hear what it does to you.

Lafferty's research showed that the Toxoplasma organism invades, and becomes dormant in, your brain cells.  It's been known for years that toxoplasmosis in rats makes them bolder and less cautious around predators, which aids in the passage of the germ between rats and cats.  What wasn't known before Lafferty's study is that infection by the germ in humans also causes personality changes.

Now, it doesn't make us have a high affinity for cats, which would make sense, and would explain Crazy Cat Lady syndrome, in which some people think it's normal to own thirty cats, and somehow seem to become immune to the truly cataclysmic odor that their houses attain.  No, what actually happens is more subtle.  Apparently, if you have Toxoplasma, you're more likely to be neurotic.  People who tested positive for antibodies for Toxoplasma scored far higher on personality assessments in the areas of guilt-proneness, anxiety, and risk of depression.  These effects were so pronounced that Lafferty speculates that it could account for certain differences between cultures.

"In some cultures, infection is very rare," Lafferty said, "while in others, virtually everyone is infected.  The distribution of Toxoplasma gondii could explain differences in cultural aspects that relate to ego, money, material possessions, work, and rules."

I find this speculation fascinating.  The idea that my neuroses might not be due to my genes or upbringing, but because I'm carrying around a parasite in my brain, doesn't create the level of Icky-Poo Factor that you might expect.  Of course, I'm a biologist, and so I'm at least on some level accustomed to thinking about creepy-crawlies.  But the idea that some sort of a microorganism could affect my behavior strikes me as weirdly interesting, particularly since I've had at least one cat in my household for the past 25 years.

So, maybe our personalities aren't as static as we'd like to think -- they can be influenced by a great many circumstances outside of our control.  Add parasite infestations to that list.  And if that whole idea upsets you too much, take comfort in the fact that Lafferty's research has spurred medical researchers to try to find a drug that can destroy the germ.  Nothing's been certified for human use so far, so don't cancel your appointment with your therapist just yet, but there are a couple that are looking promising. 

Until then, you should probably shouldn't worry.  What's a few brain parasites among friends, after all?  In fact, just forget I brought it up.  Relax, go and sit in your recliner, and pet your cat, Mr. Fluffkins, for a while.

You'll feel better.  Trust me.


  1. YES! Finally an explanation for my OCD! But don't tell my hubby that I probably already have the little bugger in my system...that's the only way I can get out of cleaning litter boxes if we get pregnant again! I already got a blissful 10-month reprieve with Luke...looking forward to another litterbox-free period some day!

  2. p.s. I have no idea where that weird ID name came from...

  3. Wonderful news!!! I have a good friend who has a beautiful cat who was treated for this and its origin could not be explained. Now I have to tell her it was her all along. Geez. :-)