Chronic inflammatory and lymphoproliferative lesions of the equine small intestine.

A retrospective study was made of 20 horses with severe and extensive chronic disease of the small intestine. Many of the animals had clinical evidence of malabsorption, with progressive loss of weight, hypoalbuminaemia and sometimes anaemia. All but two of the horses were Thoroughbreds. The pathology was diverse. Nine of the cases were alimentary lymphomas (Platt, 1986) and five had lymphocytic and eosinophilic infiltrations in the bowel wall which were considered to be probable reactions to parasitic invasion. One had acute thrombosis associated with partial occlusion of the anterior mesenteric artery by a verminous thrombus, superimposed on granulomatous lesions resulting from earlier ischaemic episodes. Two animals, from one stud, had dense mononuclear infiltration of the intestinal mucosa with villous atropy accompanying an unidentified acid-fast bacillary infection in the mesenteric lymph nodes and other sites. Three horses had granulomatous or lymphogranulomatous infiltration of the small intestine accompanied by marked mucosal and villous atrophy. One of these had multiple abscessation in part of the affected bowel. Only the three latter cases had lesions resembling those of equine granulomatous enteritis and the results of this study indicate the rarity of this condition in Thoroughbreds in Britain. The different types of lesion were only distinguishable by histological examination, since their clinical effects and gross pathology were not characteristic.