Pathomorphology of the intestinal mucosa in diarrheic calves.

The intestinal mucosa was examined in twelve 2–5-week-old calves with a spontaneous intestinal disorder, 8 with diarrhea and 4 convalescents. The calves were fed a defined milk replacer. Light microscopy including morphometry, showed villous atrophy and crypt elongation. Villous epithelial cells had decreased height, and epithelial cells of the posterior small intestine contained an increased amount of fat droplets. Accumulation of neutrophils in crypts was frequent. Scanning electron microscopy revealed blunt villi with increased numbers of necrotic cells in the extrusion zone at the tips of the villi. The convalescents had generally milder changes, particularly in the anterior small intestine. The probable etiological factors included a rotavirus and chlamydial infection, and it is concluded that these agents together with other possible noxious influences were responsible for the increased necrobiosis of apical senescent villous epithelial cells, resulting in villous atrophy and crypt hyperplasia.