It is like a childhood disease. They get it and it will run its course. Goes away by itself. It is contagious. You can get it.
Most states will not let us show cattle with active ringworm or warts.
@kenny thomas I use Captan, a black powder fungicide, and I mix it with Vaseline. First, I take a curry comb and scrape all the dry scales crud off until you get to raw pink skin. May bleed slightly. Then smother it with the mixture. I put it on every time I'm near them. Maybe 2 or 3 times a day. Clears it right up.
Of course, you can go to drug store and just buy athlete's foot treatment. That is also a fungicide.