[Tyzzer's disease].

Tyzzer's disease occurs as an epizootic disease in a number of mammals including rabbits and is characterized by sever diarrhoea and high mortality. Lesions consist of necrotic and hemorrhagic enteritis and are observed mainly in the distal digestive tract (ileum-caecum-colon). Congestion and vivid reddening of the caecum and marked serosal and submucosal oedema are present. Typical hepatic lesions, i.e. necrotic and miliary foci of the liver are generally absent in acute phase of the disease in rabbits. The diagnosis of Tyzzer's disease is difficult to establish and is based on the histologic demonstration of the causative agent Bacillus piliformis within the cytoplasm and nucleus of viable cells around necrotic area of the liver or intestine. Cultivation of this pleomorphic organism in cell-free media has been unsuccessful. Hence, taxonomic position of B. piliformis remains questionable. It is possible that Tyzzer's agent is an anaerobic, Extremely Oxygen Sensitive (EOS) bacteria closely similar to Fusobacterium. Failure to cultivate B. piliformis in vitro makes its study difficult and the role of this organism in the outbreaks of diarrhoea remains unclear. We believe that like in "swine dysentery", strong modifications of the intestinal flora facilitated by disorders of some factors particular to the animal--such the impairment of the mechanisms of immunity--or the perturbations of the environmental conditions are important even in the genesis of Tyzzer's disease and that the difficulty of diagnosis probably minimize the incidence of this organism in breeding.