We actually brought ringworm onto our farm by purchasing a tractor from a dairy. Since our herd had not had it previously - everything ended up breaking out with it - cows included.
I also say to let them get it now. When you say the same animal has gotten it a 2nd time, do you mean a new spot withing ? a month? of the first one that healed?? They can keep breaking out for a long time, but once they quit (could be months - but not normally more than a month), they should not EVER get it again. Like people, there is ALWAYS an exception to the rule - but should be rare.