Papillomas in Dogs

What is Canine papilloma virus?

Papillomas are small, generally benign growths or warts, that can be caused by canine papilloma virus (CPV). Papilloma viruses are species-specific (different papilloma viruses exist in other animals including humans, but cannot be transmitted from one species to another), as well as specific to the site of infection. They can be spread through direct contact, by contaminated objects such as bowls, toys, and floors, and possibly by insects.

CPV presents itself in three ways in dogs (see below). The most common type is the oral papilloma virus, caused by CPV-1. As implied in its name, oral papillomas affect the area around a dog’s mouth, including its lips and skin around its muzzle. The virus takes root in injured skin or a lesion to establish infection.

Multiple papillomas are generally seen in young dogs and puppies, as the dog’s immune system has not matured enough to fight off the virus. Single papillomas, on the other hand, are more common in older animals.

What are Papillomas in dogs?

Papillomas, also known as dog warts, are small growths caused by a viral infection that grows outwards and have a lumpy surface, often resembling small cauliflowers.

They typically appear as a cluster of multiple growths, although single growths are possible. These are the three types of papillomas found in dogs:

1. Canine mucous membrane papillomatosis – This most commonly affects the lips and mouths in young dogs. They can also affect the skin around the mouth and eyes. They appear suddenly, growing and spreading very quickly.
2. Cutaneous papillomas – These appear more frequently as single growths in older dogs. They are indistinguishable from other types of warts.
3. Cutaneous inverted papillomas – They are usually seen in young adult dogs. Most commonly, growths appear on the underside of the abdomen, but can also occur on the feet. 

Infrequently, viral papillomas can progress to squamous cell carcinomas, a type of skin cancer. Despite it being unusual, it is always a good idea to see a vet if you are unsure about a growth on your dog.  

Identifying Canine Papilloma Virus 

Most papillomas disappear on their own and become less frequent as the dog’s immune system matures. However, very severe cases can occur with those that are immunocompromised due to other diseases, such as lymphoma, making it hard to fight off the viral infection.

Other symptoms of CPV can occur when the growths in the dog’s mouth interfere with eating, chewing or swallowing. Oral warts can cause pain if the dog bites them whilst chewing, causing them to bleed and become infected.

Inverted papillomas that grow on the feet of a dog can also make it difficult for them when walking (similar to verrucas in humans).

Other wart-like lumps can occur anywhere on the body. They are generally slow-growing and occur alone, but can be otherwise identical to look at. They are usually benign and removal by surgery is curative.

How are papillomas diagnosed?

When there are multiple growths, this may be sufficient to make a diagnosis based on the appearance of the lumps and the age of the dog. If a growth is still present after three months, a biopsy is required to ensure that the lump is a viral papilloma.

When there are single growths, or if it is not clear from appearance whether the lumps are indeed papillomas, surgical removal and a biopsy will be performed. The lump is then sent to a laboratory for examination of the cells (histopathology) to give a definitive diagnosis.

How do you treat canine papillomas?

The disease is usually self-limiting, meaning that the growths will disappear within a few weeks to months. As the body can typically resolve the virus on its own, removal is often not necessary.

When it is necessary, due to the location or pain, treatment on the growth can include removal or reduction using electro or cryosurgery, or through traditional surgery. Once one or more of the papillomas are surgically removed,  the other papillomas may also start shrinking.

In very severe cases, in which the dog is struggling to swallow or breathe normally, wart vaccinations can be considered to help the body produce antibodies and fight the virus.

It is difficult to know how effective various treatments are because the disease will usually get better by itself in time.

How to prevent canine papillomas

To become infected, the dog generally has an immature immune system or has a suppressed immune system due to other diseases.

The virus can survive for at least 2 months at 4°C but only 2 hours at 37°C. Because the virus can be spread on toys, bowls and bedding, it is advisable to clean the pet’s environment and soak anything that has been in contact with affected dogs in hot water and, where possible, detergents that will kill viruses.

The incubation period (time from infection to signs of the disease) of papilloma viruses is 1-2 months.

Canine papillomas are highly contagious, so it is recommended to keep very young dogs and immunocompromised dogs away from any dogs showing signs of papillomas. Dogs are not deemed to be contagious once the growth(s) have started to shrink and disappear. 

Dogs who have recovered from canine papilloma virus cannot be re-infected with the same strain of the virus, but could still be susceptible to other strains.

If you believe your dog may be suffering from canine papilloma virus or their papillomas seem to be worsening, get in touch with Animal Trust to get expert advice today. Book a free consultation here.