A lot of dairies in Texas have them. Cow traders have spread them all over the area. Usually occurs on back feet and sometimes called "strawberry wart" as it will almost have the appearance of a strawberry with long coarse hairs growing out of it. Nasty looking things. Those things will literally cripple a cow overnight. Not much to treat them with that I'm aware of. Most folks usually have a hoof trimmer come by, put them on the trimming table and just cut the wart out then apply some kind of homemade remedy and cover with vet wrap.
It's common in dairys, therre isn;t a permanent cure for them I don;t think. They're usually treated with terrimycin poweder and the foot wrapped. There are also a couple of spray/squirt on treatments. Check with some local dairys. Here is what Merck says about them. http://www.merckvetmanual.com/mvm/index ... dermatitis