Ringworm can be effectively treated once the causative organism is identified. The goals of treating ringworm are to eliminate the infective fungal organisms from the dog’s skin, restore the skin and hair coat to a normal condition and prevent the spread of the infection to people and other pets in the household.
The best treatment protocol for ringworm is a three-step approach that involves applying topical medications, administering oral drugs and treating the external environment. Topical treatments are best if applied to the dog’s whole body, in the form of shampoos, rinses or dips. Affected areas should be clipped to remove any remaining hair before treatment. In severe cases, the entire dog may need to be shaved. Isolated lesions can be spot-treated with anti-fungal medications prescribed by a veterinarian, but most veterinarians still recommend treating the entire body with a disinfectant shampoo, followed by an antifungal rinse. Some of the topical solutions that are effective against ringworm include lime-sulfur (calcium polysulfide or sulfur sulfide), chlorhexidine + miconazole, chlorhexidine + ketoconazole and enilconazole. Topical treatment should continue for at least 4 to 6 weeks, and at least 2 weeks beyond the time when the dog’s clinical signs go away.
Oral antifungal drugs are available by prescription from the dog’s veterinarian. These include griseofulvin, ketoconazole, itraconazole, lufenuron and terbinafine, among others. Each of these medications has its own risk of side effects, some of which can be quite severe. Antifungal drugs should not be given to pregnant bitches, because they can cause or contribute to birth defects in puppies. Drug therapy usually continues for several months, until the dog has two consecutive negative fungal cultures. Some antifungal drugs are given daily for one week, then not given for the second week, then given daily for another week, and so on. Long-term treatment with antifungal drugs can be very expensive.
The dog’s living environment should be thoroughly cleaned, vacuumed, mopped and disinfected. Bedding, rugs and other salvageable items should be washed in a bleach solution. A Microsporum canis vaccination may be available but is rarely effective in preventing ringworm outbreaks. However, it may be useful as an adjunct to oral and topical treatment in severe cases.
The prognosis for dogs with ringworm infection is generally quite good. Most cases will spontaneously resolve in three or four months, but it is best to treat the infection aggressively because it is extremely contagious. The outlook for dogs with compromised immune function is more guarded. People with immunodeficiency disorders should be very careful around animals that are known to have a ringworm infection.