Sheeppox and goatpox are serious, often fatal, diseases of sheep and goats. Sheeppox and goatpox are characterized by widespread skin eruption and respiratory disease. Diagnosis is usually based on PCR assay. Live attenuated virus vaccines against sheeppox and goatpox are available.
Sheeppox and goatpox are serious, often fatal, diseases of sheep and goats characterized by widespread skin eruption and respiratory disease.
The viruses that cause sheeppox and goatpox are capripoxviruses, closely related to lumpy skin disease virus.
Although sheeppox and goatpox viruses are different species, some strains can infect both sheep and goats. Other animal species seem not to be susceptible to these viruses.
Sheeppox and goatpox are not zoonotic.
Both diseases are found in North Africa, as well as across the Middle East, the Indian subcontinent, and Asia. They are also found in Georgia, Greece, Bulgaria, and Romania. Past introduced outbreaks in Spain and North and South America were successfully eradicated.
The incubation period of sheeppox and goatpox is usually between 8 and 14 days; however, it can be shorter after direct dermal inoculation via an insect bite.
Clinical signs of sheeppox and goatpox are similar but generally less severe in goats.
Fever and a variable degree of systemic disturbance develop, and some susceptible European breeds suffer high mortality rates before skin lesions develop. Eyelids become swollen, and mucopurulent discharge crusts the nostrils. Widespread skin lesions develop and are most evident on the muzzle, ears, and other areas free of wool or long hair (see ).
Courtesy of Dr. Max Bonniwell.
Palpation can reveal sheeppox or goatpox lesions that are not readily evident. 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.
Virus particles are abundant in skin lesions at this stage of sheeppox or goatpox. 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 scabs takes several weeks. When scabs are removed, a star-shaped scar, free of hair or wool, remains.
In severe cases of sheeppox or goatpox, lesions can develop in the lungs. In some sheep, however, the disease is mild or inapparent.
The severity of sheeppox or goatpox varies with the virus strain, the breed of the host (indigenous breeds are usually far less susceptible than European breeds of sheep and goats), and concomitant infections, such as peste de petits ruminants.
Sheeppox and goatpox viruses survive well in the environment, and they are found not only in skin lesions and scabs but also in nasal and oral secretions. Thus, within a herd and over short distances, virus transmission is mainly airborne. However, the virus can also be transmitted via direct contact with lesions or mechanically, both on nonbiological fomites and by biting insects.
Diagnosis of sheeppox and goatpox is usually based on PCR assay; however, antigen-capture ELISA, along with characterization of the viruses by culture and genome sequencing, has also been used.
Sheeppox and goatpox must be differentiated from the usually milder infection contagious ecthyma, which mainly causes crusty, proliferative lesions around the mouth.
Live attenuated virus vaccines against sheeppox and goatpox are commercially available and induce good immunity and protection. However, concerns over reversion to virulence and vaccine spread mean that they are used only in areas where the disease is considered endemic.
No available vaccines currently support DIVA (differentiating infected from vaccinated animals)–based approaches to vaccination against and eradication of sheeppox or goatpox. Emergency control therefore depends on rapid identification, isolation and culling, and prevention via movement restrictions and strict biosecurity.
