Enteritis due to Lawsonia intracellularis in hamsters
Andrew Brooks, Emily Martin, Emily Brouwer
Animal Health Laboratory, University of Guelph, Guelph, ON.
AHL Newsletter 2025;29(2):15.
Multiple cases of enteritis in hamsters due to Lawsonia intracellularis infection were diagnosed this spring at the AHL. Three of the cases were postmortem submissions and one case consisted of formalin-fixed viscera submitted for histopathology. The hamsters were between 3 to 6 months of age and exhibited various clinical signs, including diarrhea, lethargy, anorexia, respiratory difficulties and sudden death.
In the hamsters submitted for postmortem examination, gross lesions included necrosis and inflammation of the intestine, predominantly affecting the ileum, with variable involvement of the jejunum, cecum and proximal colon. The intestine was described as thickened, hyperemic and firm, with necrosis evident on the mucosal surface. Histologically, the intestinal lesions consisted of hyperplasia of the crypt epithelium (Fig. 1A), with thickening of the mucosa, variable degrees of necrosis and inflammation. A mixed population of extracellular bacteria was often present in the necrotic debris. In some cases, the necrosis was severe (Fig. 1B), and extended through the wall of the intestine resulting in peritonitis. Bacterial culture of the intestine was performed in two submissions: in one case no bacterial pathogens were detected, and in the other case, large numbers of E. coli and Fusobacterium varium were isolated. Salmonella, Campylobacter, Yersinia, Clostridium perfringens and Clostridium difficile were not isolated. Lawsonia intracellularis was detected by PCR in the three postmortem submissions, with Ct values ranging from 8.45 to 14.46.
Proliferative ileitis due to Lawsonia is common in hamsters, and can cause high morbidity and mortality. Disease occurs most often in young hamsters, especially during the post-weaning period, and predisposing factors may include transportation, dietary changes and overcrowding. Clinical signs may include lethargy, diarrhea and dehydration. Lesions typically involve the ileum and consist of hyperplasia of the intestinal crypt epithelium with variable degrees of necrosis and inflammation, as seen in these cases. Although the crypt proliferation is highly characteristic of this disease, further etiologic confirmation can be performed by demonstrating the presence of typical slender curved bacteria within the apical cytoplasm of enterocytes in a Warthin-Starry silver-stained section. Lawsonia infection can also be confirmed by immunohistochemistry or PCR.
Figure 1. Proliferative enteritis due to Lawsonia intracellularis infection in a young hamster. (A) Note the marked hyperplasia of the crypt epithelium (arrows) resulting in thickening of the mucosa. (B) In some cases, the necrosis (*) extended across the wall of the intestine. H&E stain.
Reference
1. Barthold SW, Griffey SM, Percy DH. Pathology of Laboratory Rodents and Rabbits, 4th ed. Wiley Blackwell, 2016:183-184.