A wart, or papilloma, is caused by the canine papilloma virus. The papilloma virus is highly contagious to other dogs and is transmitted orally through saliva. In some instances, papillomas and the papilloma virus are genetically related to the dog's breed.
The papilloma virus, though highly contagious, is not transferable to humans or other species of animals such as cats. Remove any dog infected with the papilloma virus immediately from dog populations to prevent the spread of the virus. The canine papilloma virus incubates within the host for one to eight weeks before papillomas develop. Dogs who have a compromised immune system are especially susceptible to developing papillomas. Puppies are also more susceptible to developing them, because their immune systems are not fully developed.
Papillomas usually develop on a dog's abdomen, but can also be found in the mouth and around a dog's eyes, lips, legs, genitalia and feet. Papillomas are usually benign in nature, but can develop into skin cancer and cause discomfort for the animal when located in the mouth or on the feet. Dogs may also lick or chew papillomas, causing them to be at risk for a skin infection. In such instances, taking the dog to a veterinarian is necessary.