"In some ways, Toxoplasma knows more about the neurobiology of fear than we do, because it can specifically alter it," Sapolsky said.
Because Toxoplasma reproduces in the small intestine of cats, the parasites are excreted in feces, which is presumably how rats get infected. Rats are known to be extremely curious, tasting almost everything they come in contact with. Toxoplasma is also frequently found in fertilizer and can infect virtually any mammal.
Approximately one third of the world's human population is infected with Toxoplasma. For most people, it appears to present no danger, although it can be fatal in people with compromised immune systems. It also can cross the placental barrier in a pregnant woman and lead to many complications, which is why pregnant women are advised not to clean cat litter boxes.
House said humans acquire the parasite by eating undercooked meat or "eating little bits of cat poop, which I suspect happens more often than people want to admit." Or know.
Although Toxoplasma has not been shown to have any ill effects in most people, one can't help but wonder whether it truly has no effect in humans.
"There are a couple dozen studies in the last few years showing that if you have schizophrenia, you are more likely to have Toxoplasma. The studies haven't shown cause and effect, but it's possible," House said. "Humans have amygdalae too. We are afraid of and attracted to things it's similar circuitry."
|Contact: Louis Bergeron|