Here's what I know about this. Once it starts it is hard to stop. I have grew out 1 buck, taking him from the pen to the barn, from the pen to the barn. It started when he was 1 yr old. In the spring before he was three I moved him to the barn and grew him out and shot him that fall. One doe I had, the first one to ever do this, I pulled the stuff out over and over. I finally cut her jaw open and let the stuff fall out. Well that let everything fall out. I mthen knocked her out and cut all the extra flesh away and sewed it back up. I kept her alive to pull her fawns and eventually lost her from that. Everyone says its worms getting in there that causes it. I think that is BS. I think it is almost always started by an infected tooth, like someone else said. Now I just pull their teeth and put them in the barn and feed them pellets until healed. That has worked. By the way the buck scored in the 230's when we shot him.