I found a great inexpensive and Vet recommended Formula for treating Scratches Disease, it sounded a little strange but it works.
Clean Affected area very well with dishwashing soap, rinse well and let completely dry.
You Must Wear Gloves! Mix equal parts of DMSO Gel or Powder, Nitrofurazone and SafeGuard Wormer and apply twice a day to affected area.
Do not wrap area, moisture is not good, you will have to keep your Horse up in a stall or put in small dry paddock, I understand this ailment likes moisture and thrives in mud.
We noticed a vast improvement in 48 hours. Cured in 5 days without Sulfa Drugs, Vet said this formula works most of the time without the need of Sulfa Drugs.