Suspected actinobacillosis manifested by facial enlargement in a heifer.

Actinobacillosis was the suspected cause of severe, bilateral facial enlargement of 8 months' duration in a 2.5-year-old Holstein heifer. Serum protein electrophoresis revealed a polyclonal gammopathy. Necropsy findings indicated that facial swelling was caused by fibrosis between the skin and underlying bone. Lesions were characterized microscopically by scattered pyogranulomas containing eosinophilic, club-like colonies surrounding gram-negative bacterial rods. The lesion was compatible with diagnosis of actinobacillosis. It is unusual for severe bilateral facial enlargement to be associated with actinobacillosis.