What is Ringworm?

Ringworm has nothing to do with worms; it is a skin disease caused by fungi. The name is derived from the fact that this disease can cause ring-shaped skin irritation. Several different fungi can cause ringworm. When dogs are infected, roughly 70% of them have been infected by Microsporum canis, 20% by Microsporum gypseum and 10% by Trichophyton mentagrophytes. In dogs, the two most common symptoms of Ringworm are scaly skin and hair loss.

Ringworm diagnosis

Veterinarians often use a so called Wood’s lamp to diagnose dermatophytosis, but it is not 100% accurate. For a more definite ringworm diagnosis, a DTM culture must be carried out. The vet can brush the coat of the dog with a new toothbrush and use the sample to create a culture.

Ringworm symptoms in dogs

The most common Ringworm symptoms in dogs are scaly patches with broken hairs, and sometimes the patches will become hairless. Dogs can also get folliculitis and furunculosis with pustules and papules, either regionally or over big parts of the body. A special form of dermatophytosis in dogs is the kerion reaction, a focal nodular form of dermatophytosis. When adult dogs become infected with ringworm, is rarely develops into generalized ringworm – they are usually strong enough to limit the infection to one or a few parts of the body. Adult dogs with weak immune systems can however develop generalized ringworm.

Ringworm treatment for dogs

When ringworm affects adult and otherwise healthy dogs, the disease is often self-limiting. Most owners do however prefer to take their dog to the vet since treatment can make the disease vanish more rapidly. Prompt treatment is also a good way of preventing the fungi from spreading, since this disease is quite contagious. A lot of animals, including cats, can get ringworm, and it can also spread to humans.

It is possible to use whole-body topical therapy for dogs infected with ringworm, but using this is controversial and a lot of veterinarians avoid it unless the infection is really severe and widespread. Whole-body treatments often come in the form of shampoo or topical rinse. One of the most commonly used rinses is Enilconazole.

As long as the ringworm consists of local lesions, dogs can be treated with topically applied Clotrimazole or Miconazole on the affected areas. If the situation is severe, or if long hairs make topical treatment difficult (more common among dogs than cats), systemic treatment can be necessary. Two drugs effective against ringworm in dogs are Terbinafine and Itraconazole. The normal Terbinafine dose for dogs is 30 mg per kilogram bodyweight once a day, while you only need to use 5-10 mg/kg of Itraconazole per day.

The dog can for instance be given a microsized formulation of Griseofulvin; the standard dose is 25 to 100 mg/kg, administered once per day or in the form of several divided doses. It should be noted that this dose is higher than the dose approved by the American Food and Drug Administration. When a dog is given Griseofulvin, stomach problems are a common side effect.

During the last few years, Lufenuron has been tested as a possible cure for ringworm in dogs, but the results have not been confirmed by controlled studies and it can therefore not be recommended. Hopefully, it will turn out to be a good cure for ringworm in dogs that we can make use of in the future.

Regardless of whether your dog received a systemic or topical treatment for ringworm, it is important not to stop treating it simply because the symptoms vanish. Ringworm should always be treated 2-4 weeks past clinical cure, or until your veterinarian has brushed your dog and determined that disease is completely cured. In some cases, you have to medicate your dog for several months since it takes time before the symptoms starts to go away. 

Ringworm vaccination for dogs

There is currently no available ringworm vaccination for dogs, but a ringworm vaccine consisting of a killed fungal cell has been approved for use on cats. This vaccine is capable of hastening the clinical resolution for Microsporum canis in cats. The vaccine can also decrease the severity of ringworm infections in kittens, but unfortunately not the frequency.

Fungal Infections in dogs: (click for more info)
Blastomycosis in dogs
Cryptococcosis in dogs
Histoplasmosis in dogs
Phycomycosis in dogs
Pythiosis in dogs
Ringworm in dogs
Sporotrichosis in dogs