Transmission electron micrograph (TEM) of Orf virus "C" form. Orf is an exanthemous disease caused by a parapox virus and occurring primarily in sheep and goats. It is also known as contagious pustular dermatitis, infectious labial dermatitis, ecthyma contagiosum, thistle disease and scabby mouth. Orf virus is zoonotic - it can also infect humans. Parapoxvirus is a genus of viruses, in the family Poxviridae, in the subfamily Chordopoxvirinae. Like all members of the Poxviridae family, they are oval, relatively large, double-stranded DNA viruses. Parapoxviruses have a unique spiral coat that distinguishes them from other poxviruses. Parapoxviruses infect vertebrates, including a wide selection of mammals, and humans. Not all parapoxviruses are zoonotic. Notable zoonotic hosts of parapoxviruses include sheep, goats, and cattle. Cropped from larger image.