Enterohepatitis in Mongolian gerbils (Meriones unguiculatus) inoculated perorally with Tyzzer's organism (Bacillus piliformis).

Enterohepatitis was produced in Mongolian gerbils by intragastric inoculation with Tyzzer's organism from natural infection of a gerbil. Death occurred in 50 to 60% animals 5 to 7 days postinoculation (p.i.). On day 3 p.i., when a few necrotic foci appeared in the liver, a large amount of bacterial antigen was present within ileocecal enterocytes and reticuloendothelial cells of the Peyer's patches. Neutrophil and monocyte infiltration was found in the lamina propria. On day 5 or 6 p.i. there was severe necrotizing and hemorrhagic ileotyphlocolitis. Bacterial antigen was abundant within not only enterocytes, but also smooth muscle cells of the ileum and jejunum as well as reticular cells of the mesenteric lymph nodes. On day 7 p.i. the intestinal lesions subsided in the presence of fewer bacteria, while necrotizing hepatitis became well developed. The results indicated that Mongolian gerbils were highly susceptible to the oral route of infection with the Tyzzer's organism.