By making a normally threatening scent sexy, T. gondii creates a fatal attraction in its host. So how does it perform this wicked feat? By going directly to the brain. Prior research suggests that T. gondii raises levels of dopamine in mouse brains by 15%; using drugs to block dopamine in turn eliminates infected animals’ attraction to cat urine.
(Scarily, there are a number of parasites in nature that produce behavior that is detrimental, even deadly, to the host, while helping the parasite survive. If you want to know the sickening but fascinating details, Discover’s Carl Zimmer, author of Parasite Rex, is the best journalist on this beat.)
T. gondii may have behavioral effects in humans too, though the research is preliminary. A recent study in Mexico found that people with schizophrenia, a disorder that is associated with elevated dopamine activity in the brain, were four times more likely than healthy controls to be infected with the parasite; other recent research has found no effect, however.
More controversially, research has linked T. gondii infection to normal variations in human personality. One large study found that infected women were warmer and friendlier than non-infected women, while infected men were more suspicious and antisocial. Infected people also have a higher risk of being involved in car accidents, according to two studies.
So does T. gondii also cause cat ladies to collect furry felines? No research appears to have been done directly on this subject, though one study did find a connection between the bug and obsessive-compulsive disorder, of which animal hoarding is one form.
As for me, I just like my kitty because she’s pretty.