Histiocytic or Proliferative Enteritis

Etiology:  Lawsonia intracellularis is a Gram-negative, obligate intracellular bacterium, and non- spore-forming rod [1].

Incidence:   Infection is rare and is observed in all age groups of laboratory rabbits.

Transmission:  Transmission is most likely fecal-oral.

Clinical Signs:  Rabbits develop a semi-fluid, often mucous, diarrhea and lose weight.

Pathology:  Gross lesions include fluid cecal contents and mild thickening of the ileal or cecal wall.  Microscopic lesions include proliferative enterotyphlitis with mucosal erosions, crypt epithelial hyperplasia, and infiltration of the submucosa with macrophages, lymphocytes, and occasionally multinucleated giant cells.

Diagnosis:  PCR for this agent can be used on feces, fresh tissue, or tissue blocks.  Microscopic lesions with small, curved coccobacilli can be demonstrated in the apical portion of enterocytes by silver histochemical stains.

1.            Watarai, M., et al., Cultivation and characterization of Lawsonia intracellularis isolated from rabbit and pig. J Vet Med Sci, 2008. 70(7): p. 731-3.