I was reading today about a new study that shows that rats infected with toxoplasma parasites are “controlled” by the parasite to perform acts beneficial to it. Some of these acts are decidedly suicidal for the poor rat, unfortunately, like being attracted to the smell of cat urine.
Toxoplasma has two basic life stages: their sexual stage can only take place in a cat, the asexual part of their life can take place in any mammal. So, if Toxoplasma wants to reproduce, it needs to get inside a cat. With rats, it does this by short-circuiting a key rat survival instinct- the one that keeps them away from areas where cat urine can be smelled. The cat eats the infected rat, the parasite gets to have sex, and everyone is happy…well, except maybe for the rat.
The exact mechanisms that the toxoplasma gondii protozoa uses to achieve this result are not yet understood. It also isn’t determined yet whether the parasite has any real impact on adult humans who might happen to pick it up. It is known, however, that a pregnant woman who picks up the bacteria will have a higher probability of giving birth to a child with schizophrenia…along with other problems like hydrocephalus and spontaneous abortion.
Its also known that about 15% of people in the United States show signs of having been infected with Toxoplasma parasites…and about 50% of people world wide (88% in France…I wonder what the French are up to?). The question is: are some mental disorders in humans caused by this parasite? Is the legendary French arrogance simply a result of the parasite trying to get citizens of France eaten by giant cats? Science may one day soon answer this and other pressing questions…
Humour aside, the ability of a simple parasite to selectively alter deep-seated mental behaviors for its own benefit is intriguing to say the least.