Acute febrile diarrhoea in adult horses

Background

Acute diarrhoea in adult horses is almost exclusively attributable to large intestinal dysfunction, reflecting disruption of the normal balance between secretion and absorption of fluids and electrolytes. Various processes may contribute to large intestinal dysfunction including increased water and solute secretion (commonly caused by inflammatory processes and pathogen derived enterotoxins), dysmotility (again caused by inflammatory processes and pathogen derived enterotoxins), malabsorption (reflecting decreased functional absorptive surface area) and osmotic overload (such as carbohydrate overload). Since the adult equine large intestine normally reabsorbs approximately 100 l fluid daily, acute diarrhoea may result in significant loss of water and electrolytes and disturbance of acid–base homeostasis. Healthy adult horses produce approximately 11–13 kg faeces/ day, while some acute colitis cases produce >90 l (kg) diarrhoea. Many of the disorders causing diarrhoea also lead to loss of the integrity of the large intestinal epithelium, which normally plays a key role in preventing entry of luminal microorganisms and limiting absorption of other potentially injurious luminal agents including endotoxin and ammonia. Loss of epithelial integrity can also lead to significant loss of protein or blood into the lumen. The fever occurring in many diarrhoeic horses can therefore reflect endotoxaemia, a systemic inflammatory response, bacteraemia or septicaemia, all of which may result from a loss of epithelial barrier function. Alternatively fever may be a direct result of the primary disease process, such as occurs in bacterial and viral colitis.  […]