A 4-day-old cockatiel that died suddenly had a pale, mottled liver at
necropsy. Extensive necrosis and numerous bacilli were present microsc
opically in the liver. The organism was identified as Bacillus pilifor
mis, the causative agent of Tyzzer's disease, by special staining and
electron microscopy. This is the first report of Tyzzer's disease in a
n avian species.