Abstract: Actinobacillus strains are symbiotic bacteria colonizing the mucous membrane of animals. They can invade the body when wounds in oral mucosa or skin appear and then result in actinobacillosis. This disease is characterized by sporadic epidemic. In addition, improper feeding and management may also associate with the emergence of this disease, which always bring great losses for the livestock breeding industry. In this paper, the clinical symptoms, pathological changes, laboratory examination and differential diagnosis of a clinical case of lamb actinobacillosis emerged in a sheep farm in spring of 2019 in Hohhot were introduced in detail. Furthermore, the corresponding prevention and control measures were put forward for veterinary personnel and sheep farmers.

Key words: East Friensian lamb, mandibular swelling, Actinobacillus lignieresil