QUESTION:

Does anyone have an explanation for the small black lumps that appear  on whitetail deer? They are usually no larger than a quarter and often fall off by autumn.

What are they and do they have any negative affect on deer? Do other

species of deer get these as well?

ANSWER:

Skin fibromas  (also called papillomas or fibropapillomas) are black warts or tumors on the skin ranging in size from less than an inch to over 8 inches in diameter.  These tumors are caused by a virus and can proliferate in clusters covering large areas of the animal's body in the most severe cases. 

Robinette and others (in a 1977 publication) reported that out of "thousands" of mule deer examined in Utah, they found only 3 fibromas larger than 3-4 inches in diameter.  This disease is thought to be spread through contact and infection via biting insects and does not seriously affect the deer's survival unless it significantly impairs normal feeding, hearing, or sight. 

The fibromas have been reported to disappear completely and the animal may then be immune to further infection.  These unsightly growths usually cause concern when encountered in the field, but they pose no health hazard to those handling the deer.  These tumors are usually attached only to the skin and do not affect the underlying tissue or preclude the consumption of the meat. 

Jim Heffelfinger

Regional Game Specialist

Arizona Game and Fish Department

and Adjunct Professor, University of Arizona

QUESTION:

Do these papillomas have any genetic connection? It has seemed to me that they occur generally in one particular genetic line. How would this then tie in with viral transmission?

ANSWER:

Papillomas can be transmitted in different ways; through insects, direct contact, etc. (Example- Some papillomas seen in dairy cows, were found to be spread by the person milking one cow and moving on to the next.) We do not know all there is to be known about transmission, but it has proven to be viral. There may be a genetic predisposition to certain viruses. There is a definite genetic basis for which animals get infected and those that do not. Some animals just may be much less susceptible. There has not been a lot of scientific research into this particular species (deer), but it all seems to line up.

Dr. Sean Haas, DVM

Lakeland Veterinary Clinic

North Battleford, SK.