(How many of you keep a cat around to catch rats?)
When you boil it down to the basic facts, cats are the common denominator where toxoplasma gondii infection is concerned. The parasite is the reason why pregnant women are cautioned not to clean cat litter boxes, because exposure to the parasite can cause toxoplasmosis. In infants this can cause serious neurological defects, organ damage, or even death. But for the moment we want to focus on the cat connection.
Cats are the main repository of the disease because the organism requires a cat to enter the reproductive phase of its lifecycle. It most certainly can and does infect other animals though. One of the most profound effects of the infection occurs in rats and mice. These creatures are fearful of cat urine because it marks the presence of a predator, and a healthy rat or mouse will try to hide when presented with cat urine. In studies done on rodents infected with toxoplasma gondii however, the rodents were not afraid of the smell of cat urine. In fact, they were even drawn to it, seeking out the scent and lingering by it, even though to do so meant certain death.