But don’t rush to evict your pet. Most people infected with T. gondii probably got it from undercooked meat.
A wily parasite well known for influencing the behavior of its animal hosts appears to play a troubling role in humans, increasing the risk of suicide among women who are infected, new research shows.
Chances are you or someone you know has been infiltrated by the parasite, called Toxoplasma gondii. Researchers estimate that T. gondii is carried by 10% to 20% of Americans, who can get it by changing litter used by infected cats or eating undercooked meat from an animal carrying the bug.
Despite its prevalence in humans, the protozoan is most famous for the strange effect it has on the brains of rats and mice.
The parasite’s optimal host is the cat — it can fully complete its reproductive cycle only in the feline intestinal tract. So T. gondii has developed an ingenious, and as yet unexplained, mechanism for ensuring survival: It turns rodents into willing cat food.
When a rat or a mouse is infected, it suddenly flips from being petrified of cats to being attracted to them. Studies have shown that the cells in the rodent brain that regulate sexual arousal become active when mice and rats get a whiff of cat urine, suggesting the smell turns them on. As a result, they drop their guard, the cats eat them — and the parasite wins the day, reproducing at will.
But studies in humans have suggested that rats and mice are not the only animals to undergo worrying behavioral changes in response to T. gondii infection.
The parasite has been linked to an increased risk of schizophrenia and bipolar disorder in humans. A few small studies have also suggested a relationship between suicide attempts and infection with T. gondii.