By Deb Haines
Papillomas are benign growths caused by the canine papillomavirus . The oral mucosa and commissures of the lip are most frequently involved, but the growths (usually multiple but sometimes single) can involve the palate and oropharynx. Papillomas are most common in young dogs and appear suddenly, with rapid growth and spread. Signs are seen when the growths interfere with prehension, mastication, or swallowing. Occasionally, if the growths are numerous, the dog may bite them when chewing, causing them to bleed and become infected. They may regress spontaneously within a few weeks to months, and removal is generally not necessary. If necessary, the exophytic lesion can be debulked with electro- or radiosurgery or by sharp resection. Surgical removal of one or more of the papillomas may initiate regression. The use of commercial or autogenous vaccines should be considered in very severe cases in which the dog cannot swallow or breathe normally. The self-limiting character of the disease makes evaluation of any treatment difficult. Severe oral papillomatosis may be seen in immunocompromised dogs with lymphoma.
What Do these Papillomas Look Like?
By far, the most common type of viral papilloma in dogs is near the mouth, caused by CPV1 (canine papilloma virus-1). Viral papillomas are classically fimbriated, meaning they are round but often have a rough, almost jagged surface reminiscent of a sea anemone or a cauliflower. They occur usually on the lips and muzzle of a young dog (usually less than 2 years of age). Less commonly, papillomas can occur on the eyelids and even the surface of the eye or between the toes. Usually they occur in groups rather than as solitary growths so if one growth is noted, check inside the mouth and lips for more.
When the viral papilloma has a classic appearance like the ones shown above, biopsy is usually not needed to identify the growth. In cases where there is uncertainty, however, biopsy will settle any questions. The good news is that most oral viral papilloma cases are mild and resolve on their own within 2 months.
How is this Virus Transmitted?
The infection is transmitted through direct contact with the papillomas on an infected dog or with the virus in the pet’s environment (on toys, bedding, food bowls etc.). The virus requires injured skin to establish infection; healthy skin will not be infected. The incubation period is 1 to 2 months. This virus can only be spread among dogs. It is not contagious to other pet species or to humans, and it appears not to be contagious after the lesion has regressed. Recovered dogs cannot be infected with the same strain of virus but there are several viral strains.
To become infected, the dog generally needs an immature immune system, thus this infection is primarily one of young dogs and puppies. Dogs taking cyclosporine orally to treat immune-mediated disease may also have an outbreak of papilloma lesions.
Are Viral Papillomas Dangerous?
Not really. They should go away on their own as the dog’s immune system matures and generates a response against the papillomavirus. The process of regression usually takes 1 to 2 months. If lesions are still there after 3 months, treatment is recommended (see below) and a biopsy may be needed to confirm that the growth really is a viral papilloma. Severe cases can actually interfere with chewing and swallowing but such heavy involvement is unusual.
Sometimes oral papillomas can become infected with bacteria from the mouth. Antibiotics will be needed in such cases to control the pain, swelling, and bad breath.
In most cases, treatment is unnecessary; they simply go away on their own. Occasionally an unfortunate dog will have a huge number of papillomas, so many that consuming food becomes a problem. Papillomas can be surgically removed or frozen off cryogenically. Sometimes crushing several growths seems to stimulate the host’s immune system to assist in the tumor regression process. In humans, anti-viral doses of interferon have been used to treat severe cases of warts and this treatment is also available for severely infected dogs though it is costly and yields inconsistent results.
More recently, a topical medication called imiquimod has been used in both canine and human infections to help boost immune-mediated inflammation and thus facilitate destruction of the virus by the body. Imiquimod is being prescribed increasingly for dogs with viral papillomas. Skin irritation is frequently noted adjacent to the growth when imiquimod is in use, but this is generally regarded as a sign that the growth is regressing and the medication is working.
Other Types of Papillomas
The oral papilloma is by far the most common canine viral papilloma but it is certainly not the only kind. There are other papilloma viruses besides CPV-1. Here are other types of viral papillomas:
Cutaneous Inverted Papillomas: (Also Called Endophytic Warts)
These are caused by the CPV-2 papilloma virus as well as other papilloma viruses. They can appear as single nodules on the belly (1/2- 1 inch across) with a small central pore or they can be disseminated like a lumpy rash. They can also form between the dog’s toes.
Papillomavirus Pigmented Plaques:
These are caused by several of the “Chi canine papilloma viruses” and usually affect pugs and miniature schnauzers. They dark, scaly and of variable size and are usually found on the belly. Unlike other papillomas, these do not regress on their own except in pugs. They are capable of transforming into malignancy.
These are caused by the CPV-2 papilloma virus as well as other papilloma viruses and grow on the foot pads and between the toes. They tend to be painful and have potential to transform into malignancy.
These non-oral papillomas do not possess the classic fimbriated appearance of the oral papilloma and are likely to require biopsy for identification. As with oral papillomas, though, they can be expected to regress in most cases within a 2 month time frame. If they do not, the same treatments noted above can be applied.
PVC Vets Questions and Answers
- Dog was found half a month ago. Biopsy done (need your second opinion on this please). It has been 15 days since rescuing this dog and as you can see from the photos the growth is progressing. Have we missed anything? Can you see anything we haven’t noticed on the biopsy results/cytology? Pics and Path report below
Answer….. Dr. Meghann Jo… speak to your vet,You can use interferon or azithromycin to try and get it to resolve faster since it is a severe case. Oral papilloma virus is usually self limiting and goes away on its own.
2) Paw issue has progressed even further and am looking for additional eyes to help us figure this out. Pic belowAnswer..Dr. Lea A Mayer …. I think that your pup suffers from pododermatitis.Pododermatitis means inflammation of the feet, and is considered to be more of a description, than an actual disease. Many underlying disorders result in pododermatitis.The most common cause of pododermatitis is allergy, especially atopy (environmental allergy) and food allergies. The allergy can cause inflammation of many areas of the skin, including the feet. Many pets with a pododermatitis can then develop a secondary bacterial or yeast infection.In addition to allergies, other causes of pododermatitis includes a form of mange (Demodex), fungal infections (ringworm or dermatophytosis), dilated (cystic) hair follicles, sterile granuloma, and autoimmune disorders such as pemphigus foliaceus. Foreign bodies such as plant awns or fox tails are frequently the cause of pododermatitis, although this will most often affect only one foot. There are also internal diseases, such as a failure of the liver, which can cause destruction (necrosis) of the foot pads, or hormonal disorders such as hypothyroidism or Cushing’s disease, which can make animals more proneto develop infections.Any allergic pet should be considered prone or susceptible to developing pododermatitis. In addition animals outside with greater exposure to foxtails, and ringworm in the soil are also at greater risk. Larger dogs may also be at greater risk of developing infections from hair shafts which have been pushed under the skin (similar to an ingrown hair), which can cause inflamed lumps between the toes.3) my dog has a couple cauliflower like growths on her. Vet has seen them & thinks papilloma virus. The one on her nose is small and unchanged but the one on her chest is growing outward and has started to bleed.Answer… Dr. Anamana Cr… I’d remove it because of the bleeding and risk of infection. If it seems more concerning at time of removal (once vet is in the tissue and examining it more closely), you can ask to have the tissue sample submitted for histopathology. Pic below
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