What is "sore mouth" (contagious ecthyma, orf)?

Sore mouth in goat kid.
Photo courtesy Edie Lederman, MD.

"Sore mouth," also known as "scabby mouth," or contagious ecthyma, is a viral infection caused by a member of the poxvirus group and is an infection primarily of sheep and goats.

Geographically, "sore mouth" infection is commonly found throughout the world. According to the United States Department of Agriculture Animal and Plant Health Inspection Service's National Animal Health Monitoring System (USDA APHIS NAHMS) 2001 sheep survey, 40 percent of U.S. operations reported sore mouth infecting their flocks in the previous three years.