Clostridium piliforme Infection: Tyzzer’s Disease

Epizootics of Tyzzer's disease have been observed in Syrian hamsters in various parts of the world. The caus­ative agent, C. piliforme, is a spore-forming bacillus that multiplies only within cells.

Diagnosis

Clostridium difficile should be recoverable on anaerobic culture and its presence confirmed by PCR, but detection of toxin is essential to confirm cause. Due to the impor­tance of this disease in humans, there are a number of commercially available assays for detection of C. difficile A and B cytotoxins, using fresh intestinal contents or feces. Differential diagnoses include Tyzzer's disease, salmonellosis, and enteropathogenic E. coli infections.

Cecal Mucosal Hyperplasla of Unknown Etiology

Spontaneous cases of cecal hyperplasia have been observed in suckling and weanling hamsters. Diarrhea, runting, and high mortality were associated with the disease. At necropsy, ceca are congested, contracted, and opaque due to mucosal thickening (Fig 3.10).

FIG. 3.10. Cecal mucosal hyperplasia in a hamster. This syndrome is probably the aftermath of clostridial enteropathy. Source: Barthold et al. 1987. Reproduced with permission from American Association for Laboratory Animal Science.

Epizootiology and Pathogenesis

Hamsters may become infected by contact with affected animals or by contaminated bedding, which remain infectious with environmentally resistant spores for many months. Predisposing factors, such as poor sani­tation, intestinal parasitism, and inappropriate feeding practices, play a role in precipitating clinical outbreaks of the disease. Weanling hamsters are most often affected.

Pathology

At necropsy, there is a variable distribution of lesions. In some epizootics, lesions may be confined to either the liver or the intestinal tract. Multifocal hepatic necrosis is evident in some cases. Intestinal lesions, when evident grossly, usually involve the lower ileum, cecum, and colon and are associated with diarrhea and soiling of the perineum. Affected areas are edematous and dilated, with fluid contents. Microscopically, there are foci of hepatocellular necrosis with leukocytic infiltration. Intra­cellular bundles of bacilli are usually best demonstrated at the periphery of hepatic lesions. When lesions are present in the intestinal tract, there is edema of the lamina propria, with polymorphonuclear leukocyte infiltration and effacement of the mucosal architecture. There may be extension of the inflammatory process into the under­lying muscular layers. Typical bacilli are usually demon­strable within enterocytes in the region and in hepatocytes adjacent to necrotic foci (see Gerbil Chapter 4, “Clostridium piliforme Infection”). Focal granulomatous myocarditis, with conspicuous pale bulging nodules, has been associated with Tyzzer's disease in this species.

Diagnosis

Definitive diagnosis of acute Tyzzer's disease entails the demonstration of the typical intracellular bacilli in affected cells (enterocytes, hepatocytes, and myocytes), using Warthin-Starry or Giemsa stains. Differential diag­noses include clostridial enterotoxemia, salmonellosis, coliform enteritis, and Campylobacter enteritis. Both serologic and fecal PCR assays are commercially availa­ble, and are typically used for colony surveillance. PCR can be used to discriminate between rabbit and rodent C. piliforme, emphasizing the need to use the appropriate assay for the affected host species.