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Ringworm in Dogs? - Symptoms, Treatment, Prevention

Ringworm, medically called Dermatophytosis, is an infection of the skin, nails and hair and is parasitic fungal in cause. The organisms that cause it are Microsporum gypseum, Microsporum canis and Trchophyton mentagrophytes. It is a disease that can affect any mammal not just your dog and is found more often in younger dogs than senior ones. While cases of this can be found globally, more occur in climates that are humid and hot despite the fact that it seems most cases occur in the autumn and winter months. The fungus can live on the animal or in its living environment in the form of spores shed there by infected animals. Those spores can live for over eighteen months. It is not a common disease, affecting less than 3% of dogs with skin problems.


If you suspect your dog has Ringworm it is important to take care as it is transmissible between dogs and people. People who have weakened immune systems such as those undergoing treatments like chemotherapy or those with HIV are more vulnerable but anyone could potentially catch it. Therefore it is important to wear gloves when you are taking care of your dog if he has Ringworm and wash up properly after. Your vet will be able to talk to you about this further.

How does your dog get Ringworm

As mentioned there are three possible fungi that can cause ringworm and if your dog already has a weakened immune system he is more susceptible. It also means the infection is likely to be more severe. Places where there are a lot of animals close together put your dog more at risk. Also if he is placed somewhere where there is poor management, poor nutrition, a lack of proper quarantine can also increase those odds.

It is transmitted when your dog comes into direct contact with an animal already infected or when they come in contact with an item like bedding that has been contaminated with spores. Those spores might be on brushes, bedding, grooming equipment or just in the general environment of somewhere your dog has recently been or stayed. Because those spores can live for a long time your dog could pick it up from anywhere that other animals have been in the last 18 months.

Most dogs with a normal and healthy immune system have some resistance to this disease and symptoms therefore do not develop. Younger dogs and puppies are more likely to be affected as they have not yet developed that resistance.


Symptoms to be looked for in a dog with Ringworm include;

Scales or dandruff

Lesions that are round, nodular and raised

Skin may darken

Skin may redden

Hair or fur looses its healthy look

Loss of hair which may be circular or patchy



The lesions may ooze

Claw folds may be inflamed

It is possible for a dog to be a carrier but not have any symptoms of the disease. These dogs are still contagious to other mammals though.

At the Veterinarian

When you suspect Ringworm or your dog is showing similar symptoms you need to take him to your vet, though it may be a good idea to warn them it is possible this is a contagious disease. Once there he or she will discuss your dog's medical background with you including whether he has been in contact with other infected mammals or been in any dog facilities recently. Then they will perform a physical and other tests to work out what is happening.

Test they might perform include doing a fungal culture on some skin clippings, examining a sample of hair with a microscope and a biopsy of the skin. There is also a popular method called Wood's lamp which uses black light under which some species of fungi will glow. This is not always accurate on its own though as some common species of the fungi do not glow and some dogs may have spores but not have the symptoms. Another test is to pluck hairs around a lesion and then examine them in a preparation of KOH under a microscope. But the most accurate and best way to get a confirmed diagnosis is the culture approach.

Treating Ringworm

Usually this can be treated with anti-fungal medications at home but it is important to keep your dog quarantined until he is no longer contagious. Often the medication has to be applied directly to the dog's skin so an Elizabethan collar may be needed around his neck to stop him from licking off the meds. The lesions can take up to 4 months to heal on otherwise healthy dogs.

Dogs with more severe cases may need to be kept in the clinic at first and there will be several treatments going on to help him. Isolated lesions will have the fur clipped around them and then lesions are treated topically twice a day with a topical anti-fungal medication. Generalized or severe lesions may need further treatment of anti-fungal shampoos or dips to be done very two to four days. Some vets may feel the need to prescribe oral anti-fungal medication such as griseofulvin or itraconazole. This needs to be given for several months and the vet will need to monitor your dog as there is a potential for it becoming toxic to your dog.

Your vet will in all probability continue to take fungal cultures through the treatment to monitor him. At least one culture result needs to come back negative before treatment can be stopped. For severe cases vets may want to get two or threes consecutive negatives before considering this. Blood counts will also be performed regularly to make sure the anti-fungal treatment is not damaging his liver.



Make sure your dog stays in quarantine and all other animals and humans are kept away from him. It may be a good idea to have your other pets tested just in case to prevent a cycle of infection and prevent infecting others outside your home. If there is a chance you have mice or rodents in the home they could spread the disease further and you should take steps to deal with these pests.