Courtesy of Dr. Max Bonniwell, Oban, Scotland.
Sheeppox and goatpox are serious, often fatal, diseases characterized by widespread skin eruption. Both diseases are confined to parts of southeastern Europe, Africa, and Asia. The poxviruses of sheep and goats (capripoxviruses) are closely related, both antigenically and physicochemically. They are also related to the virus of lumpy skin disease. Reports on the natural susceptibility of sheep to the virus of goatpox and vice versa are conflicting; at least some strains seem capable of infecting both species.
The incubation period of sheeppox is 4–8 days and that of goatpox 5–14 days. The clinical picture is similar in the two diseases but is generally less severe in goats. Fever and a variable degree of systemic disturbance develop. Eyelids become swollen, and mucopurulent discharge crusts the nostrils. Widespread skin lesions develop and are most readily seen on the muzzle, ears, and areas free of wool or long hair. Palpation can detect lesions not readily seen. Lesions start as erythematous areas on the skin and progress rapidly to raised, circular plaques with congested borders caused by local inflammation, edema, and epithelial hyperplasia.
Courtesy of Dr. Max Bonniwell, Oban, Scotland.
Although microvesicles are present histologically, vesicles and pustules are not evident clinically. Virus is abundant in skin lesions at this stage. As lesions start to regress, necrosis of the dermis occurs and dark, hard scabs form, which are sharply separated from the surrounding skin. Regeneration of the epithelium beneath the scabs takes several weeks. When scabs are removed, a star-shaped scar, free of hair or wool, remains. In severe cases, lesions can develop in the lungs. In some sheep and in certain breeds, the disease may be mild or the infection inapparent.
It has been suggested that transmission may be airborne, by direct contact with lesions, or mechanically by biting insects.
The disease in either species must be differentiated from the milder infection, contagious ecthyma (orf), which mainly causes crusty, proliferative lesions around the mouth.
Infection results in solid and enduring immunity. Live, attenuated virus vaccines induce longer immunity than inactivated virus vaccines.
