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I read this article in The Atlantic not too long ago and it is FASCINATING.  It’s a bit long, but you should totally give it a read.  Like I said, FASCINATING.

So, I’ve long known that certain parasites can infect the host in ways that cause them to act contrary to how they’re expected.  You’ll see articles about them pop up from time as zombie ants or zombie spiders or zombie fish or zombie lots of insects and lower order animals.  The parasite that infects the host somehow causes the host to act in ways generally to its detriment while benefiting the parasite.  Really an underhanded way of doing things, says I.  But still, it’s fascinating.

Now, it’s not too hard to believe that something like that can happen to say, an ant.  An ant’s brain isn’t terribly complex.  It probably doesn’t take much to get an ant to throw off its normal constraints in life to seek the highest branches to be better eaten by some predator.

But what about a higher order animal?  What about a relatively large-brained dog?  It’s harder to imagine some parasite controlling the mind of your dog and getting him to do something other than what he would normally do.  But have you considered the rabies virus?  It seems to be able to do some of that mind control business.  An infected dog, no matter how docile before the infection, becomes very aggressive in the late stages of the disease and is wont to bite others to spread the virus.  Seems mind controlly to me, don’t you think?  By the way, it’s pretty important to make sure your dog (and other pets) are up to date on their shots, including their rabies shot.  It’s really not a pleasant way to die for your dog or you, should you be bitten by your zombie dog.

Now, as far as that mind controlling business goes, the rabies virus isn’t really that spectacular of a case.  Stirring an animal into a rage isn’t really that impressive.  It’s pretty basic and primal stuff.  But how about a parasite that affects your personality?  What if there’s a parasite that changes you from an introvert to a raging extrovert?

Well, there isn’t one.  But the article talks about Toxoplasma gondii (Toxo), sometimes found in cat feces, a protozoan parasite that can subtly (no raging extroverts here) shift a human’s personality. When Toxo has infected a rodent, it changes the behavior of said rodent to become more fearless and more attracted to cats, since Toxo needs a cat to complete its life cycle.  When Toxo infects a human, likely accidental, there is a small change in personality, which seems to be a by-product of a heightened sense of anxiety.  Human males, when anxious, become withdrawn and more hostile.  Human females, when anxious, become more social and seek friends (extroverted).  Both males and females become less attentive and have slower reaction times.

All this is quite interesting, but what’s the purpose of this mind altering?  Well, in humans, we don’t really know.  It’s not like family cat is going to eat someone infected with Toxo, like it would an infected rat.  But it could affect us in other ways.  It was shown in studies that people affected by Toxo tend to get into more accidents because of that delayed reaction time thing.  Also, it’s been shown that the parasite can manipulate dopamine levels in the host’s brain and could very well be one of the agents that trigger schizophrenia, a disease that is heavily influenced by dopamine levels.  It seems that schizophrenia gained a foothold when keeping cats as pets started to become fashionable.  Hmm…

Fascinating, wot?  It’s too bad that this might be considered fringe science right now, i.e. not too many scientists are researching this phenomenon.  I’d really like to read more about it.


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