How to Treat Ringworm on a Dog. Part of the series: Dog Health Treatment & Advice. Treating ringworm on a dog, which is not a worm at all, requires a DTMF or fungal culture at the veterinary office, followed by an antifungal treatment and antiringworm shampoos. Cure ringworm in a dog with health information from a veterinarian in this free video on pet care.