Clostridium piliforme, formerly Bacillus piliformis , is the causative agent of Tyzzer's disease. Prevalence remains high in laboratory rodent colonies. Possible explanations for this include the moderately contagious nature of the organism and the wide range of susceptible and naturally infected host species. With this in mind, transmission is thought to be via ingestion of infectious endospores in contaminated food or bedding. Inadequate sterilization of feed or bedding components may facilitate the entry of the pathogen into an otherwise well-managed rodent colony.
Most infections are subclinical.
Various host and environmental stressors may precipitate clinical disease. Clinical signs occur most commonly in suckling and weanling rodents and include sudden death, watery diarrhea, lethargy, and ruffled fur. Pathologic changes involve three main phases. These include the establishment of infection in the ileum and cecum, the ascension of the pathogen to the liver via the portal circulation, and hematogenous spread to other tissues such as the myocardium. This triad of organ involvement is the hallmark of Tyzzer's disease.