Colitis: differential diagnosis and treatment.

Equine colitis characterised by diarrhoea and/or pain may be caused by a wide variety of bacterial, viral, protozoal agents and toxins. The causative agent of Potomac horse fever, Ehrlichia risticii, is the most recently recognised cause of colitis. Salmonella, the agent typically associated with colitis, also causes abdominal pain (colic) of variable intensity. Acute colitis is also caused by colitis X, various antibiotics, endotoxic shock and peritonitis caused by arterial infarction. The principles of therapy for each of these, together with means of differential diagnosis, are presented.