By David Martin –
When we opened our internet tubes this week, we were confronted with a fantastic view of what might be making people crazy for cats. (Keep in mind the two definitions of “fantastic”: extraordinarily good OR divorced from reality.) Follow the kitty trail carefully as there are many twists and turns.
A single-cell parasite called toxoplasma (full name is toxoplasmosis gondii) exists in many hosts, from meat to soil to cat feces. An enzyme in the cat’s intestine activates toxoplasma’s reproduction machinery, allowing the bug to make more bugs sexually instead of asexually, which is how the parasite has to reproduce outside of a cat. And that’s no fun. So … if the toxoplasma is released in the cat’s poop but can reproduce the fun way only by getting back into the cat’s intestine, how does the bug ensure it goes on that Vegas-like trip?
Lab studies have shown that once a mouse is infected with toxoplasma, the mouse’s brain becomes flooded with dopamine, which lowers fear and increases pleasure. Some mice also then become attracted to cat urine. Basically, little Mickey, once infected, isn’t so afraid of hanging around cats, which ends badly for the mouse but does put the toxoplasma back in the cat’s digestive system where the fun type of parasite sex can occur.
What about humans? About a third of the world’s population is infected with some form of toxoplasma, but for people with healthy immune systems, the parasite is apparently asymptomatic as an illness. Still, medical personnel recommend that women who are pregnant or trying to get pregnant should be extremely careful not to expose themselves to cat feces. If such women must change cat litter, they should do so with gloves while not touching their faces and washing hands afterward. Again, the parasite is usually easily handled by the pregnant woman’s immune system but, if not, it can cause severe problems for the child.
But even if our immune systems prevent us from becoming physically sick from toxoplasma, can the bug get into our brains and alter, however subtly, our behavior? According to the Medical Daily website, studies have found connections between toxoplasma and “schizophrenia, bipolar disorder, OCD, and aggression. The parasite can also slow reactions and decrease concentration, which may explain why people who get in traffic accidents are three times more likely to have gotten toxoplasma.”
But here’s the kicker: Just as infected mice become less cautious around cats, a person with a toxoplasma infection (and about a third of us have one) might be “brainwashed” to behave favorably toward cats. We don’t want to say that a parasite can make us crazy cat people, but … otherwise why would you be allowing Mr. Tiger to sleep next to you on your pillow?