Tyzzer's disease in a dog.

A 5-week-old mixed-breed dog was examined because of emaciation and depression associated with chronic anorexia, diarrhea, and vomiting. Its rectal temperature was subnormal and it died on the day of admission. At necropsy, small focal lesions were distributed through the liver. Enteric alterations included catarrhal enteritis with fluid contents, excess production of mucus, and mucosal hyperemia. Microscopically, the hepatic lesions were disseminated foci of coagulative necrosis, with little or no associated inflammatory cell response. Numerous organisms morphologically consistent with Bacillus piliformis were demonstrated within viable hepatocytes at the periphery of the necrotic foci and in the intestinal mucosa. Numerous coccidial forms were found within the epithelial cells of the intestinal mucosa, which was focally necrotic.