not necessarily sexual transmission. many diseases can be spread by contact with blood and other bodily fluids. even today, rabbits, bears, wild hogs, and other animals harbor things you don't want. armadillos, for example, can pass along leprosy, as they and humans are the only repositories of the disease. you don't have to fuck them to catch their ailments...Said he would leave it up to us to figure out how it was contracted by Humans.