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Are These Unsightly Bumps as Awful as They Look?

Analysis by Dr. Karen Shaw Becker

Story at-a-glance -

  • Warts, or papillomas, typically affect young, immunosuppressed and older dogs
  • Since these growths are benign, they should really only be removed if they’re impinging on a dog’s quality of life
  • It can be helpful to view harmless papillomas on dogs as a window into their immunologic health
  • Since papillomatosis can be a sign that a dog has been over-vaccinated, it’s another reason to have your pet titer tested in lieu of automatic revaccination

The medical term for warts is papillomas, because papilloma viruses — a group of DNA viruses — are responsible for the cauliflower-looking skin and mouth lesions that occur in dogs. The viruses typically affect three types of dogs:

  1. Young dogs, who tend to develop outbreaks of oral papillomatosis
  2. Immunosuppressed dogs, especially dogs who've received corticosteroids, for example, prednisone, or any drug that suppresses the immune system
  3. Older dogs, who often develop warts as they age

In veterinary medicine, we assume all dogs are exposed to papilloma viruses, but these opportunistic viruses tend to cause warts only in dogs with immune systems that aren't 100% healthy or dogs who are stressed. The good news is canine warts don't affect other species, so there's no need to worry that other members of your family, including kitties, will pick up the virus.

Dogs at Highest Risk for Papillomatosis

Young dogs usually develop oral papillomatosis (oral warts) that on very rare occasions can also cause warts to grow in the mucous membranes of the eye. These wart clusters often have a fleshy, cauliflower-like appearance.

The virus is most commonly spread by direct contact between dogs, such as when they lick or mouth each other, or share a toy. Oral papillomatosis typically occurs in dogs under 2 years of age whose immune systems are still immature, meaning their bodies aren't yet capable of mounting an effective immune response to eliminate the virus. Dogs who are immunoglobulin A (IgA)-deficient are also at risk.

Oral warts often spontaneously regress after a few months when the dog's immune system matures, recognizes the virus and resolves the outbreak.

However, in severe cases of oral warts in dogs with congenital immunodeficiency or IgA-deficiency, the body may not even recognize an immune response is required, so the virus rages on unchecked and the lesions in the mouth don't heal. These poor puppies can have literally hundreds of warts in their mouths, making it nearly impossible to eat or drink without excruciating pain.

Puppies and adult dogs who acquire severe oral papillomatosis should have their immunoglobulin levels checked immediately and begin oral immunotherapy and specific nutritional therapy to assist their bodies in fighting off not only the papilloma virus, but other potential pathogens.

Dogs with oral papillomatosis should be separated from other dogs until all the lesions have cleared. Diagnostic testing isn't necessary in most cases because veterinarians can clearly recognize the classic appearance of the warts in the mouth.

When to Consider Wart Removal

Because these growths are benign (they look terrible, but they're not cancerous), my rule of thumb is to remove them only if they're causing quality of life issues for the dog. This would include situations in which, for example, a dog is repeatedly licking, chewing or scratching at the wart until it bleeds.

Sometimes warts develop in between the toes, causing a dog to limp. This is another quality of life situation in which surgical removal is the best option.

Fortunately, warts only grow to a certain size and then stop. If a skin lesion, lump or bump on your dog seems to be growing or changing, it's time to visit your veterinarian. In very rare cases, warts can turn into cancerous skin lesions called squamous cell carcinomas. These lesions don't stop growing or changing. Any skin lesion that is continually changing should be closely monitored by you and your veterinarian. But again, this type of wart is quite rare.

If you want a definitive diagnosis, I recommend asking your veterinarian to perform a fine-needle aspiration of the growth to confirm that it is indeed a wart.

Unfortunately, many veterinarians recommend that all skin lesions, even benign skin tags and papillomas, be surgically removed. We're actually taught in veterinary school to remove all benign growths that bother clients. The vet makes good money removing these benign warts, and the dog owners buy themselves peace of mind.

This is unnecessary surgery I don't recommend, unless, as I mentioned, the wart is impinging on the dog's quality of life. Many older dogs, in addition to developing warts, also develop nonviral benign skin tumors such as sebaceous adenomas or epitheliomas. These growths are harmless in most cases (I call them "age spots").

I tend to follow Dr. Richard Pitcairn's approach to warts, which is to use them as a measure of a dog's immune function. Because warts are usually painless and only annoying to dog owners, I recommend monitoring them as a reflection of what's happening internally in dogs in terms of their immunologic health.

It's also important to realize that removing warts doesn't remove the virus from your dog's body. Unless the immune function problem is addressed, he'll continue to develop warts.

Vaccine-Wart Connection

Vaccines have been implicated as a cause of papillomatosis. This is another reason that I constantly advise against over-vaccinating. Warts can be an indication an animal has received too many vaccines or has had a negative reaction to vaccines. Eliminating or reducing the number of unnecessary vaccines your dog receives is a great first step in reducing the potential for papillomatosis. Ask your veterinarian to titer test instead of automatically revaccinating.

Since we assume all dogs have been exposed to the papilloma virus, the goal is to keep your pet's immune system healthy by reducing vaccines, feeding a species-appropriate, fresh food diet, and providing clean air and water and a nontoxic living environment.