Sore mouth disease has infected some bighorn rams in Yellowstone National Park/NPS, Jacob W. Frank

Some bighorn rams in Yellowstone National Park have contracted "sore mouth disease," a viral infection that can be transmitted to people through direct contact.

Sore mouth disease is common in farmed sheep and goats and widespread in wild bighorn sheep in the Rocky Mountains from Alaska to California. Typically spread from ewes to lambs, the disease can manifest itself as scabby sores around the mouth and face. Lesions disappear in 2-4 weeks, and animals typically heal without scarring.

Generally, affected animals recover but deaths can occur in severe outbreaks, especially with young animals who cannot feed, according to park staff. The virus has the greatest effect on lambs that refuse to nurse because of sore mouths. 

So far, only breeding age rams in the park have been observed with lesions. This is likely a result of frequent contact with each other and possibly infected ewes during the breeding season. 

The disease is difficult to control in bighorn sheep. In most situations, control efforts are not warranted since the disease is typically self-limiting as animals build up protective antibodies.

Park biologists will continue to monitor the infected animals.