Corynebacterium equi Enteritis in Foals

Corynebacterium equi is a pathogen associated with respiratory disease in the foal. This paper discusses two cases of Corynebacterium equi infection, one acute and one chronic, in which the major damage was intestinal. Necrosis of Peyer's patches was the only lesion seen in the small intestine of both foals. The foal with acute disease had distinct green-tan focal necrosis and thickened mucosa of the large intestine. In the foal with chronic disease, the mucosa of the large intestine was thickened, rugose, and mottled red-tan. Histologically, the predominant lesions were villous atrophy, mucosal necrosis, mesenteric lymph node necrosis and large numbers of periodic acid Schiff (PAS)-positive macrophages filled with gram-positive pleomorphic bacilli. Electron microscopy of intestinal mucosa showed bacilli undergoing binary fission in macrophages and bacilli free in the lamina propria.