Naturally occurring Tyzzer's disease as a complication of distemper and mycotic pneumonia in a dog.

Tyzzer's disease, distemper, and mycotic pneumonia were diagnosed at necropsy of a 6-week-old mixed breed pup. The illness was characterized by lethargy, poor appetite, dysentery, and convulsions, the latter developing just prior to death. The necropsy findings included pale, dilated large intestine and swollen, dark liver. Histologically, multifocal hepatic necrosis, similar to that of Tyzzer's disease in other species of animals, was observed. Bacillus piliformis was found in hepatocytes and necrotic areas of the liver.