The development of oral lesions in lambs naturally infected with orf virus.

Stomatitis in sheep caused by orf virus can be confused with lesions of more economically significant diseases, including foot-and-mouth disease, but there is no published account of the sequential development of oral orf lesions in the sheep. This report describes the clinical appearance of such lesions during a natural outbreak of the disease in young lambs. Lesions were seen on the gingiva, the tongue and the dental pad/hard palate, and progressed from small erythematous papules to larger, often coalescing papules that in some cases were ulcerated. Resolution started within seven days and was complete within 22 days. The lambs continued to suck and thrive throughout the infection. Lesions at all stages were proliferative, providing a major differentiating factor between orf and other causes of stomatitis in sheep.