Orf, also known as contagious ecthyma, is a parapoxvirus infection of sheep and goats that causes blistering lesions on the lips, nostrils, udders or toes of affected animals. Contagious ecthyma is an important disease in camels, contributing to calf debility and eventually to high calf mortality. It is a zoonotic infection transmitted to humans through contact with an infected animal or fomites. In humans, Orf manifests as an ulcerative skin lesion sometimes resembling bacterial infection or neoplasm. Human infection typically is associated with occupational animal contact.