What Causes Warts?

Warts are caused by a virus known as papillomavirus.  There are many different types of papillomavirus - some of which only affect one species of animals, and others that may effect  more than one species.  These viruses are named according to the species that they affect: for example bovine papillomavirus affects cattle while equine papillomavirus mainly affects horses.  Within each species, there may also be different types of the virus: for example there are 6 types of bovine papillomavirus that are distinctive according to different proteins associated with the virus as well as the effects that they may cause in the animal.  Warts are generally thought to be a benign condition when they develop, but are contagious between animals that are susceptible to the same virus.


Transmission of Warts

Papillomavirus is spread between animals by direct contact of wart material from an infected animal getting into a break in the skin of an uninfected animal.  It is also possible that the virus can live inside wart material that is on an inanimate object such as a scratching post, brushes, milkers, etc. and then be transmitted onto the skin of an uninfected animal.  It is important to realize that infection only occurs when the virus can get into some kind of flaw or break in the skin.


Who Gets Warts?

Any animal runs the risk of getting papillomavirus and developing warts, but the risk is generally increased in young animals (who have a poorly developed immune system), animals that are crowded in close quarters with infected animals (this increases the likelihood of transmission between animals) and animals that are sick or stressed (thus having an already decreased ability for the immune system to respond properly).  Once an animal has been infected with papillomavirus, it can take several weeks to months before any warts appear.  During this time the virus is infecting cells, replicating, and infecting other cells in the area. 


Treatment/Duration of Infection

Warts caused by papillomavirus are considered to be self-limiting, meaning that they are benign and generally disapear on their own once the immune response of the animal has taken control of the situation.  The duration of infection varies according to the animal species affected..  If treatment is required, the options are fairly limited to cryosurgery or surgical removal.  See pages on individual animal species for more information.