Tyzzer's disease (Bacillus piliformis) in Australian marsupials.

Tyzzer's disease (Bacillus piliformis infection) was diagnosed in nine marsupials (six possums, a koala, a wombat and a dasyurid). All but two of the possums were captive. Five of the seven marsupials, for which ages were recorded, were juvenile. Affected marsupials were either found dead or were showing non-specific illness for up to two days before death. Affected livers and hearts showed gross haemorrhage and scattered areas of white discolouration. Microscopically, areas of coagulative necrosis were often associated with neutrophilic infiltrates. Intracellular, slender, faintly basophilic rods were occasionally detected in HE-stained sections. Rods were shown by silver staining techniques to be associated with the lesions in all affected animals. These rods showed a beaded appearance when stained with methenamine silver and were consistently in packets within cells, on the peripheries of lesions and scattered sparsely and irregularly within the central necrotic regions.