Leprosy is a bacterial infection that affects humans and if left untreated will go on to cause severe damage to the skin, nerves, extremities and eyes; eventually leading to them going numb and allowing them to get secondary infections which may result in the loss of the appendage.
Very few infections affect multiple species of animal, but leprosy is one of the few that actually can as it is able to infect both humans and, for some reason, Armadillos.