Naturally occurring Bacillus piliformis infection (Tyzzer's disease) in guinea pigs.

Two juvenile male Hartley guinea pigs (Cavia porcellus) were found dead 36 hours after receipt from a commercial source. Both guinea pigs had dependent, subcutaneous edema and excess serous fluid in their thoracic and abdominal cavities. Their livers were mottled and the cecal walls were reddened focally. Histopathologic exam revealed nests of Bacillus piliformis within the absorptive epithelial cells of the ileum, cecum and colon. Vegetative organisms and spore-like structures were observed in the cytoplasm of intestinal epithelial cells by electron microscopy. A diagnosis of Tyzzer's disease was made.