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Wildlife and Fish Health - Fibromatosis in Deer

Questions and Answers about Fibromatosis

Deer with Fibromatosis
-Photo courtesy of Dan Eastham-

What is fibromatosis?

Fibromatosis is a common skin disease of white-tailed deer, mule deer, black-tailed deer, and other Cervidae in North America.  There is evidence that the skin tumors, called fibromas, are caused by a papilloma virus.

What are the signs of fibromatosis in deer?

Large, warty growths, or fibromas appear as firm, round, nodular, hairless, pigmented skin abnormalities adhered to or incorporated within the skin of deer.  The masses occur most frequently around the eyes, mouth, face, neck, and forelimbs, and may appear as a single mass or numerous growths.  The tumors are typically small (less than 5 inches across), dark brown or black in color, and their surface may be abraded or bleeding and in some case infected. Most often, fibromas occur in deer less than 2 years of age, with a higher incidence of disease in bucks.    

How is the disease transmitted?

The manner in which the disease is transmitted is not entirely known.  However, it has been suggested that transmission occurs through direct contact between broken skin and infectious material, either from a fibroma of an another infected deer or vegetation that has come in contact with an infected deer.  Since more bucks are seen with the condition, rutting or fighting among males during the rut or rubbing of antlers to shed velvet may play a role in disease spread.  Biting insects may also be involved in disease transmission.

What is the significance of fibromas to deer? 

Deer with fibromatosis are generally unaffected by the condition, unless the location or size of the tumor impedes normal movement, feeding, or vision.  The tumors may be surgically removed, although treatment is not typically practical, and is usually unnecessary, as the disease is self-limiting and fibromas tend to regress over time.

Do deer that get the disease die?

Typically, deer are exposed to the virus at a young age and develop fibromas. If they are exposed again as an adult, they are less likely to get the disease a second time due to acquired immunity to the disease.  Fibromas are not a significant cause of deer deaths.

Can humans become infected with deer fibromas?

No, the virus is species specific and deer fibromas are not known to occur in or affect humans.  As fibromas only involve the skin and not underlying muscles or other structures, an infected animal’s meat is safe to eat.  However, if you have any question regarding the health of the animal or meat safety contact your local ODFW field office or wildlife health hotline at 1-866-968-2600.


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