For questions/concerns about this disease in humans, please call your doctor or the Montana Department of Public Health and Human Services (DPHHS).
For questions about this disease/parasite in wildlife, please call the FWP Wildlife Health Lab at 406-577-7882.
Benign masses known as papillomas or warts present on the skin and mucous membranes of cervids are most often often caused by the papillomavirus group of viruses (Miller et al, 2003). Papillomas are firm, fleshy, nodular masses attached only to the skin and varying in diameter from 10 to more than 100mm. Some are covered with gray or dark skin which often is scratched and bleeding. Others have a black, dry, hard surface that may be fissured much like the head of a cauliflower. Larger papillomas tend to be pendulous because of their weight and stem-like attachment to the skin. Papillomas can occur anywhere on the animal’s skin, but are more common on the head, neck, and shoulders (Adrian, 1981). They may be single or multiple. A heavily infected deer may have 25 or more. Occasionally they are so numerous and close together that they join into a coalescent mass (Michigan, 2010).
Papillomas have been reported in cervid species over much of their respective North American ranges (Michigan, 2010).
Papilloma viruses tend to be species specific. The virus that causes papillomas in cervids are seen in both white-tailed deer and mule deer, and occasionally in elk, pronghorn, and moose. Though similar diseases exist in other species, deer will not spread their fibromas to pets, livestock, or other species. Other papilloma viruses of wildlife cause oral papillomas of wild canids, papillomas of the skin of rabbits, and fibromas of squirrels (Adrian, 1981).
Transmission likely occurs through direct contact between broken skin and infectious material, either from a fibroma of an another infected cervid or from vegetation that has come in contact with an infected animal. Rutting among males or rubbing of antlers to shed velvet may also play a role in transmission. Virus also may be spread via the bit of blood-feeding insects.In general, the viruses that cause papillomas are quite species-specific and are unable to be transmitted to members of an unrelated species.
Affected animals have hairless wart-like growths on their skin. Growths can be quite variable in number (few to numerous), size (very small, 1-2 mm, to huge, 8–10 cm), coloration (light to dark) and texture (smooth to “cauliflower-like” in appearance) (Miller et al, 2003). On cross section, papillomas show a white, tough core of uniform texture covered with a rind of varying thickness and color. Those with a thin layer of skin show a thin and lightly pigmented rind, while those with a hard fissure external surface have a thick dark rind (Michigan, 2010). They are often found around the eyes and neck, but may also be on the body or legs. The growths are generally limited to the skin and are easily removed during skinning. Papillomas frequently regress over time, and once the animal has recovered from them, there appears to be resistance to reinfection (Adrian, 1981). Animals are generally in good body condition but may become weak and debilitated in unusual cases if the number and size of papillomas becomes unusually large or when tumors interfere with vision, mobility, or eating(Miller et al, 2003).
The virus is species specific and deer fibromas are not known to affect humans.
In general, papillomas do not affect quality of the meat. If the papilloma extends into the underlying muscle, the area surrounding the mass should be trimmed and discarded.If you harvest an animal and are unsure whether it is safe to eat, contact your local FWP staff for guidance soon after the animal is harvested.
Adrian, W.J., editor. 1981. Manual of Common Wildlife Diseases in Colorado. Denver: Colorado Division of Wildlife.
Michigan Wildlife Disease Manual. 2010. Michigan Department of Natural Resources. Website
Miller, M.J.R., R.D. Dawson, and H. Schwantje. 2003. Manual of Common Diseases and Parasites of Wildlife in Northern British Columbia. University of Northern British Columbia.