Dogs and cats are affected by several different types of warts. Oral papillomas are one particular type of warts that occur in and around the mouth of dogs.
SIGNS Oral papillomas vary in appearance from flat white spots to flowery or cauliflower-like nodules. By definition they occur in the mouth and on the lips, but occasionally they will also appear on the skin of the face and the margins of the eyelids. Most dogs will have one to several warts; rarely, a dog's mouth will be filled with them. In this uncommon version of the problem, signs include bleeding, halitosis, and difficulty chewing.
CAUSES AND RISK FACTORS Canine oral papillomas are caused by a virus and are contagious from dog-to-dog. (They are not zoonotic; that is, they are not contagious from dogs to people or other animals.) Most affected dogs are young to middle-aged and have some notable contact with other dogs, such as playing at doggie daycare. Infrequently a dog will develop oral warts when it has had no obvious contact with other dogs.
DIAGNOSIS The diagnosis is made by the history and the physical exam. Biopsy is usually not necessary to distinguish oral warts from other similar problems.
TREATMENT Oral warts will resolve without treatment. The time of exposure until the time the warts appear is usually 1 to 8 weeks. Regression usually occurs within 3 months as the patient develops an appropriate immune response. Once recovered, dogs are rarely reinfected; immunity appears to last for life.
Surgical removal of the warts is indicated if they aesthetically troublesome to the owner, or if they are so numerous that they are causing difficultly chewing and swallowing, bad breath, and drooling. Surgical biopsy is done if there is any doubt about the diagnosis that is made based on the history and physical exam.
A number of different medical treatments have been tried with limited or no success. Some success has been achieved with vaccines but there are none that are currently commercially available.
PREVENTION AND PROGNOSIS For practical reasons, it is difficult or impossible to prevent exposure. Not all dogs that are exposed will develop warts and those that do will be affected to varying degrees. However, almost every exposed dog will eventually develop an appropriate immune response and the problem will resolve.