A method for reproducing fatal idiopathic colitis (colitis X) in ponies and isolation of a clostridium as a possible agent.

Severe colitis was induced in two ponies after oral pretreatment with clindamycin and lincomycin, followed by intestinal content from two horses which had died from naturally-occurring idiopathic colitis. Two ponies treated with antibiotic alone, and two ponies treated with intestinal content alone, were unaffected. In a further study, three ponies treated on separate occasions with lincomycin, administered orally, died or were destroyed 67 to 72 h after initial treatment. No established salmonella, yersinia or campylobacter pathogens were isolated from these ponies, but a clostridium closely resembling Clostridium cadaveris was isolated as the predominant clostridium from them all and from the colonic content of one of six horses which died from naturally-occurring idiopathic colitis. It was not isolated from six horses with non-fatal diarrhoea. This clostridium is a candidate as an agent of some cases of fatal colitis in horses.