What I know about it comes from studying, in very general terms, possible bioterrorism weapons. The spores are inhaled into an animal when it has its nose close to the ground. The spores multiply in the animal and then are exhaled onto the ground where the animal is feeding. From what I understand, the closer the animal's nose is to the ground, and the more animals that are in a certain small area, the more likely the disease will spread. Apparently it has to be in a pretty concentrated area to spread in epidemic form. This is why it is more likely to be spread at a feeder or corn pile than deer eating browse or in a food plot.