Abstract
Histopathological examination was conducted on 16 horses affected with colitis X. Characteristic lesions of the disease were exfoliation of the mucosal epithelial cells and hemorrhagic necrosis of the ceco-colonic mucosa, fibrin thrombus formation of the capillary and venules, especially in the intestinal mucosa, congestive edema of the lungs, and widespread necrosis of tubular epithelial cells with hyalin casts in the kidneys. These lesions support the morphological ground to the hypothesis that endotoxin shock is immediate cause of colitis X. As one of a possible predisposing events to the shock, involvement of systemic infectious disease; especially viral infection was suggested by interstitial pneumonia observed in 15 cases and reticulum cell proliferation with occasional formation of multinucleated giant cell in the lymphoid follicles of the large intestine, spleen, and lymph nodes in most cases.
