Pathology of Bacillus piliformis infection in rabbits

Rabbits (92) died between April 1997 and March 1998 in the institute's rabb itry, On necropsy, 15 of these, belonging to all age groups, exhibited gros s lesions of necrotic hepatitis with pinpoint necrotic foci scattering unif ormly in the liver parenchyma, haemorrhagic typhlitis with serosal reddenin g involving adjoining parts of ileum and colon, and necrotic lesions in the heart. On histopathological examination, liver revealed small coagulative necrotic foci with leucocytic inflammatory cell reaction which demarcated f rom the surrounding viable hepatocytes. Caecal mucosa showed extensive necr osis and massive extravasation of erythrocytes; the lymphocytic and plasma cell reaction was also noticed predominantly. Caecal glands were hypertroph ied and filled with mucinous substance. Heart revealed necrotic streaks in the cardiac musculature. On Warthin- Starry staining, viable hepatocytes ar ound necrosis evinced intracellular clumps of long filamentous Bacillus pil iformis organisms as also in the caecal mucosal epithelial cells and cardia c myocytes. This is probably the first. detailed pathological study of Tyzz er's disease in Indian subcontinent.