What causes ulcerations and scabs around the lips and in the mouth of a sheep and can spread to the udder of a ewe?

The condition described in the question refers to ulcerations and scabs around the lips and in the mouth of a sheep, which can indeed extend to the udder of a ewe. This presentation aligns with sore mouths, also known as orf or contagious ecthyma, which is caused by a viral infection. Sore mouths typically manifest as sores and scabs that can affect young lambs and ewes, particularly during times of high contact in communal grazing or feeding scenarios. The lesions can be painful and may impede feeding, and in nursing ewes, they can spread to the udder, complicating the nursing of lambs.

In contrast, other conditions such as foot rot primarily affect the feet and do not cause lesions in the mouth area, while pink eye involves the eyes and surrounding tissues rather than the mouth. Contagious ecthyma, while it is similar and can also cause sores on the lips and in the mouth, is more commonly associated with a generalized outbreak that can affect many animals through direct contact. Therefore, identifying sore mouths as the direct cause of the described symptoms is crucial for understanding and managing the health of sheep effectively.