What I would try. I'm no vet, but this works wonders for most necrotic sores that isn't venting out. 50/50 castor oil and coconut butter. (I put a couple drops of tea tree oil in for good measure) Coco butter will kill just about any fungus or bacteria, promotes healing, and will smoother mites. The castor oil will promote blood flow and help it begin to heal. If it starts bleeding, back off the castor oil. Be careful around pregnant ladies with the castor oil, and wear gloves or it can give you the trotts, (it would take a lot through the skin) Also, I throw a cinnamon stick, 1/4 teaspoon turmeric, 3 crushed cardamom pods in about 3 gallons when I water, really good natural antibiotic properties, our birds, (chickens, ducks, geese,and turkeys), prefer it to plain water. Seems to keep my turkeys in tip top, the water doesn't sour, and I don't know of any adverse effects. Good luck!