How Toxoplasma Affects Human and Animal Behavior

[ Sun. Jun. 13. 2010 ]

The Economist has recently featured an interesting article on the behavioral effects that parasitic protozoa Toxoplasma gondii has on its mammalian hosts. Many of these effects have been recognized for years, and some of us here at Medgadget been privy to Toxoplasma news, thanks to a friend at Stanford who works with Dr. Robert Sapolsky, a leading researcher in the field. First of all, there is strong evidence that urine from cats is sexually attractive to rats infected with Toxoplasma. Then there seems to be a connection between Toxoplasma gondii and schizophrenia, lack of interest in the novelties of life, and a noted correlation with people getting into more car accidents. It seems that the nature of this parasite's life cycle has created a strange symbiotic, psychological relationship between it and its typical feline and rodent hosts. The Economist provides a handy overview of the latest knowledge around this topic.

If an alien bug invaded the brains of half the population, hijacked their neurochemistry, altered the way they acted and drove some of them crazy, then you might expect a few excitable headlines to appear in the press. Yet something disturbingly like this may actually be happening without the world noticing....

One reason to suspect [that some people have their behaviour permanently changed] is that a country's level of Toxoplasma infection seems to be related to the level of neuroticism displayed by its population. Another is that those infected seem to have poor reaction times and are more likely to be involved in road accidents. A third is that they have short attention spans and little interest in seeking out novelty. A fourth, possibly the most worrying, is that those who suffer from schizophrenia are more likely than those who do not to have been exposed to Toxoplasma.

Nor is any of this truly surprising. For, besides humans, Toxoplasma has two normal hosts: rodents and cats. And what it does to rodents is very odd indeed.