An epizootic of diarrhea in a rabbit colony. Pathology and bacteriology

Thirteen adult rabbits and 15 weanling rabbits exhibiting signs of diarrhea were subjected to pathological and bacteriological examination. The lesions in 11 of the adult rabbits consisted of a cecocolitis that was characterized by edema of the gut wall, necrosis of the mucosa, and serosal hemorrhages. Also, five of these 11 rabbits exhibited liver lesions consistent with Tyzzer's disease. Lesions in the weanling rabbits were minimal with only two animals exhibiting focal necrosis of the mucosa and one animal exibiting necrosis of the mesenteric lymph nodes. All animals of each age group exhibited pneumonitis. Escherichia coli was present in high numbers (approximately 10(12) organisms per g dry wt contents) in the cecum of eight of 13 adult and 12 of 15 weanling rabbits. Thirteen of these isolates were serotype O128:B12. Preliminary attempts to reproduce the disease in young adult rabbits by a series of per os inoculations of an isolate of E. coli (serotype O128:B12) plus intramuscular inoculation of prednisone resulted in the induction of diarrhea in two of four rabbits. The gross and histological lesions in these two animals were similar to those of the spontaneously occurring cases, consisting of edema of the cecal wall, necrosis of the mucosa, and serosal hemorrhages. Numerous white spots of focal necrosis occurred in the liver. No intracellular organisms resembling Tyzzer's disease agent were evident in any sections examined. Inoculation of either E. coli or prednisone alone did not induce diarrhea. Subsequent attempts to reproduce the disease by these methods were unsuccessful. In spite of this inability to repeat the experimental results, it was felt that this study indicated a possible role of E. coli in rabbit diarrhea, either as an etiological agent or as a secondary invader.