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With so many parasites out there, it may be tempting to lump ringworm in the same category as hookworms, whipworms, roundworms, and tapeworms. Despite its name, however, ringworm is not actually a worm—it’s a fungus. This fungal infection is common all over the world and infects almost all species of domestic animals, including dogs. It’s important for dog owners to know the symptoms, causes, and treatment options for ringworm.

What Is Ringworm?

Ringworm, as the fungus is commonly called, is named for the round, raised, red ring appearance usually seen in human ringworm infections. Ringworm, scientifically known as dermatophytes, is a collection of pathogenic fungi. In dogs, 70% of ringworm cases are caused by the fungus Microsporum canis and 20% are caused by the fungus Microsporum gypseum. Just 10% of cases are caused by Trichophyton mentagrophytes.

The fungus grows and lives in the outermost layer of skin and in the hair follicles of infected dogs. It also occasionally grows and lives in their nails. The infection is superficial, and in most cases only affects a few areas of the dog’s body. Puppies, senior dogs, and immunocompromised dogs sometimes suffer from more widespread ringworm infections.

Golden Retriever getting comforted while lying on a table at the vet.
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How Is Ringworm in Dogs Spread?

Ringworm in dogs spreads through direct contact with the fungus. This can happen when a dog comes in direct contact with an infected animal or person. It can also spread when a dog touches a contaminated object like a couch, comb, food bowls, bedding, or carpet. The fungal spores responsible for the spread can remain viable for up to 18 months. They typically spread through shedding or breaking of infected hairs.

Symptoms of Ringworm in Dogs

Ringworm isn’t a life-threatening disease, but it’s very contagious and does require the intervention of a veterinarian. Knowing the symptoms of ringworm in dogs can help you catch the disease before it passes to humans or other pets.

In dogs, ringworm usually presents as circular areas of hair loss throughout the body. These lesions may start to heal in the center as they enlarge, creating a patchy appearance, and may become inflamed or scabbed.

Ringworm usually does not itch. The affected hair follicles are brittle and break easily, which helps spread the disease throughout your home. In some cases, the fungus infects the claws, making them brittle and rough.

Contact your veterinarian if your dog experiences any or all of these symptoms:

  • Circular areas of hair loss
  • Dry, brittle hair
  • Scabby, inflamed skin
  • Rough, brittle claws

Hair loss, changes in coat appearance, or inflamed skin could be a sign of another condition. Skin problems are associated with many serious underlying conditions in dogs, like Cushing’s disease, hypothyroidism, or a nutrient imbalance. They could also be symptoms of other skin conditions like allergies, a different parasite, or an infection.

German Shepherd Dog getting its paw checked by the vet.
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Can Other Animals Get Ringworm?

Cats can get ringworm, too. The fungus responsible for most cases of ringworm in dogs, Microsporum canis, is also responsible for 98% of ringworm in cats. Since many dog owners also have cats in the home, this means that the risk of the fungus spreading from cats to dogs and dogs to cats is relatively high.

Most species of domestic animals can get ringworm, including livestock, so talk to your vet about the risk of spreading ringworm between your pets and other animals.

Can Humans Get Ringworm?

You might be familiar with ringworm by a different name, like “athlete’s foot.” Ringworm in dogs isn’t just a problem for your pup. Humans can get Microsporum canis, too, which is another reason why it’s important to take this condition seriously. Young children, the elderly, and those with compromised immune systems are at an increased risk of contracting ringworm from dogs. However, anyone can contract this unsightly and uncomfortable parasite.

In humans, ringworm presents as a roughly circular rash that’s often red and itchy. If you or a family member notices a rash on your body after your dog has been diagnosed with ringworm, contact your primary care physician.

Australian Cattle Dog having its eyes checked by the vet.
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Treatment of Ringworm in Dogs

Your vet will diagnose your dog with ringworm by performing a diagnostic test, as well as a physical exam. They may take a sample of hair or skin cells for a fungal culture or examine infected hairs under a special ultraviolet light called a Wood’s lamp.

Once ringworm is diagnosed, your vet will discuss a treatment plan for your dog. This treatment plan depends on the severity of the case, the number of pets in the household, and whether or not there are children or immunocompromised adults in the home.

Treating ringworm in dogs usually consists of three steps:

  1. Topical therapy
  2. Oral medications
  3. Environmental decontamination

Topical Therapy for Ringworm

Your veterinarian will probably recommend a topical therapy, like a cream, ointment, or medicated shampoo to help treat and control the infection. Your vet might also suggest clipping long-haired dogs to speed up treatment and shaving the hair from affected areas. Topical therapy can take several months to fully eliminate the infection, but does help prevent environmental contamination.

Oral Medications for Ringworm

Oral therapy is usually used in conjunction with a topical therapy. Anti-fungal oral medications help fight the infection and, like topical therapy, need to be administered for a minimum of six weeks, but in some cases could take months to take full effect.

Your vet will likely ask you if you have any other pets in the household. They might advise that you test and treat them for ringworm, as well, even if they are not currently showing signs of a ringworm infection. It’s also very important that owners continue to treat for ringworm for the prescribed period of time. Just because the clinical signs go away doesn’t mean that your dog is no longer contagious. Your vet will most likely want to retest your dog for ringworm before giving you the “all clear.”

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Environmental Decontamination

The spores that live inside the hair follicles remain contagious for months at a time, surviving on couches, grooming tools, bedding, furniture, and clothing. Cleaning up all this hair is a part of treatment, but as many dog owners know, also a bit of a challenge.

Some owners keep their dogs in rooms that are easy to clean during the time they are infected with ringworm. This makes it easier to eliminate stray hairs and to mop with a disinfectant recommended by your veterinarian. If you can’t contain your dog to hard floors, daily vacuuming with a pet hair vacuum and removal of hair from furniture and surfaces can help prevent ringworm from spreading.

Preventing Ringworm in Dogs

Most owners don’t have to worry about ringworm prevention on a regular basis unless they’ve already had a case of ringworm in one or more pets. The best ways to prevent reinfection of ringworm in dogs are to fully cleanse the environment of the home and any tools and bedding that the animals regularly come into contact with, and to follow the instructions of your veterinarian.

Knowing the symptoms of ringworm in dogs can help you prevent the spread of ringworm from dogs to people or other pets. For more information about ringworm or if you suspect that your dog might have ringworm, contact your veterinarian.

Related article: How to Remove a Tick From Your Dog