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.
泰泽氏病在包括兔子在内的多种哺乳动物中呈流行性疾病发生，其特征为严重腹泻和高死亡率。病变包括坏死性和出血性肠炎，主要见于消化道远端（回肠 - 盲肠 - 结肠）。盲肠充血、明显发红，浆膜和黏膜下显著水肿。在兔子疾病的急性期，通常不存在典型的肝脏病变，即肝脏的坏死性和粟粒状病灶。泰泽氏病的诊断难以确立，其依据是在肝脏或肠道坏死区域周围活细胞的细胞质和细胞核内发现病原体毛样芽孢杆菌的组织学证据。在无细胞培养基中培养这种多形性微生物未获成功。因此，毛样芽孢杆菌的分类地位仍存疑问。泰泽氏病原体可能是一种与梭杆菌极为相似的厌氧、极端氧敏感（EOS）细菌。无法在体外培养毛样芽孢杆菌使得对其研究困难，且该微生物在腹泻暴发中的作用仍不清楚。我们认为，如同“猪痢疾”一样，动物特有的某些因素紊乱（如免疫机制受损）或环境条件扰动所促成的肠道菌群强烈改变，即便在泰泽氏病的发生过程中也很重要，而且诊断困难可能使该微生物在养殖中的发生率降至最低。
