CSU ext
Warts or papillomas - (papilomastosis) is a common viral contagious disease of young animals that can resemble ringworm lesions.
How is it transmitted?  
Direct contact with an infected animal. Warts are species specific, meaning that they are not transmitted from sheep to cattle or horses to people, etc.
Warts maybe indirectly acquired from surfaces (blankets, grooming equipment, posts, feed bunks).
cow warts
Warts on a cows head and neck
What are the signs in animals? Warts are generally painless raised, "wartlike" lesions and may occur anywhere on the skin. warts on horse
Warts on a horses chest
What are the symptoms in humans? Humans can acquire warts from other people and not from animals. close up wart
Close up of a wart
More information at Merck Vet Manual:
http://www.merckvetmanual.com/mvm/index.jsp?cfile=htm/bc/23112.htm&word=papillomas