This lesion is most consistent with necrotizing enteritis due to clostridial infection. Cultures were not done by the referring veterinarian but the morphology of the bacilli is consistent with Clostridium sp. Enteritis, necrotizing, peracute to acute, diffuse, severe, with edema, hemorrhage, emphysema, and myriad mucosal adherent bacilli, breed unspecified, equine, etiology consistent with Clostridium spp. Clostridial enterotoxemia is usually caused by Clostridium perfringens , a gram-positive, anaerobic, commensal bacillus. Alpha toxin is a lecithinase which degrades cell membranes.
Beta toxin appears to paralyze the gut.
Epsilon toxin is a proenzyme that is activated by enzymatic digestion by trypsin. Iota toxin is also a proenzyme that increases capillary permeability. Additionally, strains A, C, and D produce an enterotoxin. The villar mucosa is denuded of epithelium, often leaving only shrunken pegs of the lamina propria in place of the villi. The submucosa is expanded by edema and hemorrhage, and may contain neutrophils.