Bacterial and viral enterocolitis in horses: a review

Abstract

Enteritis, colitis, and enterocolitis are considered some of the most common causes of disease and death in horses. Determining the etiology of these conditions is challenging, among other reasons because different causes produce similar clinical signs and lesions, and also because some agents of colitis can be present in the intestine of normal animals. We review here the main bacterial and viral causes of enterocolitis of horses, including Salmonella spp., Clostridium perfringens type A NetF-positive, C. perfringens type C, Clostridioides difficile, Clostridium piliforme, Paeniclostridium sordellii, other clostridia, Rhodococcus equi, Neorickettsia risticii, Lawsonia intracellularis, equine rotavirus, and equine coronavirus. Diarrhea and colic are the hallmark clinical signs of colitis and enterocolitis, and the majority of these conditions are characterized by necrotizing changes in the mucosa of the small intestine, colon, cecum, or in a combination of these organs. The presumptive diagnosis is based on clinical, gross, and microscopic findings, and confirmed by detection of some of the agents and/or their toxins in the intestinal content or feces.

Clostridial Diseases of Horses: A Review

“…This is attributed in large part to the trypsin inhibitors in colostrum resulting in low levels of intestinal trypsin activity in the intestine of neonatal animals. In horses, C. perfringens type C associated disease is most common in foals, with sporadic cases reported in adults [10,13].…”

“…Infection can occur due to environmental contamination or exposure to infected feces. It has also been postulated that foals can become infected from the teats of their dams [13]. In foals, the presence of trypsin inhibitors in colostrum prevents the lysis of CPB; the pathogenesis of C. perfringens type C-associated disease in adult animals is less clear.…”

“…In more chronically affected animals, clinical signs often include diarrhea, dehydration, weight loss, and weakness. Neurologic signs and sudden death can also occur [13].…”

“…Gross pathology. Gastrointestinal lesions can be segmental or diffuse and affect any portion of the intestinal tract (small intestine, cecum, or colon) [13]. Gross lesions include hyperemia/hemorrhage of the mucosa and serosa, transmural thickening, edema, emphysema, ulceration, and occasionally pseudomembrane formation (Figure 1A,B) [10].…”

“…Microscopic lesions associated with C. perfringens type C infection are characterized by a hemorrhagic and necrotizing enteritis and/or colitis [12,13]. In affected sections of the intestine, there is coagulative necrosis of the intestinal mucosa with loss of normal villous architecture and the mucosal epithelium, collapse of the crypts, hemorrhage, congestion, edema, and mucosal or submucosal thrombosis (Figure 1C) [10,13]. Fibrinonecrotic pseudomembranes are appreciated microscopically in some cases (Figure 1C).…”