Instead, Conniff advocates keeping all felines indoors, which he predicts many cat-owners will begin to take seriously as the rates of death and disease become increasingly frightening for animals and the humans who love them. "Cats are three to four times more likely than dogs to carry rabies, according to the Centers for Disease Control and Prevention," he writes. "They also share many other parasites or infectious microbes with humans, including roundworms, hookworms, giardia and campylobacter. When cats live outdoors it is almost impossible to predict what they will bring home next." And that, Conniff says, is reason enough to keep them home in the first place.