It has been suggested that the reservoir is actually a small rodent but this is not proven. Parapoxviruses Parapoxvirus infections are widespread in sheep, goats and cattle and relatively unimportant but common human infections occur. Infections in cattle and humans are usually referred to as pseudocowpox, paravaccinia or milker's nodes. Those in sheep and goats as orf. The viruses are closely related and the nomenclature of the human disease is based on the identity of the host form which the infection was acquired.
Infection occurs via small cuts and abrasions in all hosts and is usually localized.
Although the lesions are similar to the early lesions of cowpox and vaccinia, true macrovesicles do not form. In humans, lesions usually occur on the hand but may be transferred to the face. The virus may also be isolated in human, bovine and ovine cells but such investigations are not part of routine diagnostic virology. Parapoxvirus infections occur worldwide, and are of considerable importance. The lesions are surprisingly painless and thus there is probably substantial under-reporting.