Contagious ecthyma (ORF)
Contagious ecthyma (also known as orf and sore mouth) is a quite common disease of sheep and goats caused by a poxvirus. The classic clinical signs are crusty scabs affecting the mucocutaneous junction of the nose and mouth. There may also be proliferative lesions affecting the oral mucosa.47 The oral lesions are usually seen in young animals born into endemic herds. Immun
ologically naïve older animals may develop clinical signs when exposed to clinically normal carrier animals.48 Orf lesions are differentiated from oral lesions of FMD and Bluetongue by the clinical signs of crusty scabs as opposed to erosions and ulcerative lesions. The clinical signs of contagious ecthyma are usually self-limiting in 3 to 6 weeks. Severely affected animals may require supportive care and assisted feeding if the mouth is sore enough to prevent nursing or if ewes have udder lesions significant enough to prevent the young from nursing. Humans can be infected by the virus as well as act as vectors transmitting the virus from one animal to another so extreme care should be taken to use protective gloves when handling affected animals.49,50
Animals usually show immunity for 2 to 3 years after a clinical case of orf although some may show clinical signs 1 year after disease. Lesions are usually milder and respond more quickly during subsequent infections.36 Eighteen outbreaks of orf over 4 years in India (6 sheep, 12 goat) had morbidity rates of 18.93% for goats and 21.50% in sheep while mortality rates were 2.53 and 1.10% in those species, respectively. Kids were more likely to have lesions on the gums and tongue than older animals.51 Contagious ecthyma is endemic in northeastern Brazil.52 One lamb flock affected by an orf outbreak in addition to the signs of crusty nostrils, lips, and muzzle had significant facial swelling with pitting edema. The disease ran its course but the healed animals showed some hair loss at the sites of the facial edema.53 While most cases of orf have healing of the clinical lesions in weeks there is a report of sheep showing clinical signs for as long as 6 months. The scabs of the chronic form were well adhered to the skin and caused bleeding when removed.54
One survey of 48 goat flocks in Argentina found that 81.2% identified contagious ecthyma as an infectious disease problem on the premises.55 There has been a report of orf in five sheep from three flocks in the United States that exhibited proliferative skin lesions on the limbs that were painful to touch and caused the sheep to be reluctant to move. The lesions did not spontaneously resolve as is the case with most cases of orf. The disease also appeared to be less contagious than classic orf in sheep. All these animals were euthanized after lack of response to imperative treatment with antibiotics and topical medications, or spontaneous resolution of signs. This stresses that while this disease is usually diagnosed on clinical signs and course of disease, not all cases are classic.56
Contagious ecthyma has been reported in several species of cervidae and there are case reports of human disease (orf) that have been contracted from exposure to cervidae.29 Pox virus has also been reported from white-tailed deer in Florida.29 Diagnosis is rare and treatment is limited to benign neglect unless secondary bacterial infection is suspected, in which case systemic antibiotics may be helpful. Prevention through vaccination may be helpful in affected herds, but proof of disease and the subsequent use of either sheep vaccine or an autogenous vaccine should be carefully considered before implementing.
