Warts (Papillomatosis) in Cats

Papillomatosis is caused by a papillomavirus. Papilloma viruses are a group of DNA viruses that disrupt normal cell division. Instead of dividing normally to create smooth tissue, the cells divide more frequently and in abnormal patterns, creating bumps. Usually, the cat’s immune system stops the virus from replicating, and cats carry the papillomavirus without the bumps developing. In rare cases, the immune system fails to react appropriately and warts or skin plaques develop.

Cats with small clusters of bumps in their mouths or individual flat, scaly bumps on their skin require prompt veterinary attention.

The severity of papillomatosis depends on the location of the papilloma and how long it is left untreated.

In the case of cutaneous papilloma, individual bumps that are scaly appear on the head, neck or limbs. These bumps typically do not bother cats. In some cases, the papillomas are flat and plaque-like.

In the case of oral papilloma, tiny bumps appear in clusters in the mouth on the gums, tongue, throat, or roof of the mouth.

The ability of the papillomavirus to disrupt cell division also means that left unchecked, it can develop into a cancer, typically a squamous cell carcinoma.

Papillomatosis is rare in cats, although infection with papillomavirus is common. Typically, a cat’s immune system keeps the virus from progressing to the stage where it becomes symptomatic, and therefore papillomatosis never develops. In some cases, particularly in young cats or cats with compromised immune systems, such as those with FIV or FeLV, the virus replicates sufficiently to cause the characteristic bumps known commonly as warts. Outdoor cats and cats kept in dense populations are more at risk of contracting viruses, including papillomaviruses.

Cats contract the papillomavirus through direct contact with infected cats or objects that infected cats have touched. Transmission requires open or fragile skin. Cats cannot contract the papillomavirus from other species or from humans.

Warts may appear as an individual bump on the skin, or a cluster of bumps in the mouth. These bumps tend to have a “frond-like” or “cauliflower-like” appearance to the surface.

Cats with individual bumps on their skin or clusters of bumps in their mouths require prompt veterinary care to distinguish these symptoms from those of other, more harmful conditions, including cancer. Diagnostic tools include:

• Physical examination
• Fine needle aspiration
• Biopsy

Papillomatosis in cats is frequently associated with immunosuppressive conditions such as feline leukemia virus and feline immunodeficiency virus. Blood tests for these infections are recommended as part of the diagnostic process.

Typically, papillomatosis resolves on its own in a month or two. Sometimes, the papilloma is crushed on purpose to trigger an immune response to expedite recovery.

Close observation of the papilloma is required until papillomatosis resolves. In cases where the papillomatosis does not resolve itself in 3 months, surgery to remove the wart is recommended in order to prevent progression to cancer.

Cats should be prevented from scratching, biting, or licking papillomas to avoid rupture and subsequent infection.

In cases where papillomatosis resolves on its own, it typically takes 1 to 2 months for recovery. In these cases, the prognosis is excellent. If surgery is required, the prognosis is good. If left untreated and cancer develops, the prognosis is guarded.

Prevention requires avoidance of cats or objects that carry the papillomavirus. Cats kept indoors and away from other cats are at less risk.

Papillomatosis is rare in cats, even though cats are commonly infected with papillomavirus.

• Benign neglect
• FIV/FeLV testing
• Surgery