Abstract. Four cases of chronic eosinophilic gastroenteritis in horses are described. The disease was manifested clinically by weight loss, malabsorption and diarrhea or soft, formless feces. A chronic inflammatory reaction, with diffuse and focal eosinophilic infiltrates, was present in the esophagus, stomach, small and large intestine, and mesenteric lymph nodes. The cause of the lesion was not determined but was thought to be due to an ingested allergen, as the lesion is indicative of an on-going, immediate hypersensitivity reaction. One horse had generalized acanthosis, hyperkeratosis, and ulcerative coronitis.Chronic enteric disease in the horse, characterized by weight loss with or without diarrhea, has been reported in several countries [3, 5, 15, 17, 211. The enteric lesion in these horses was a chronic granulomatous inflammation. This paper describes a chronic eosinophilic enteritis that is pathologically distinct from the previously described chronic enteritides of horses.
Materials and MethodsFour young-adult horses with signs of weight loss, diarrhea, or both (table I) were presented to Murdoch University Veterinary Hospital over an 18-month period. The horses were unrelated and from different areas of Western Australia. Routine clinical, hematological, biochemical, and fecal examinations were done. Glucose absorption tests [20] were done on all horses and full-thickness intestinal biopsies were removed from two horses. The horses either died or were killed. At necropsy, tissues from all visceral organs and skin from horse 4 were fixed in 10% neutral buffered formalin, processed routinely in paraffin, and stained with hematoxylin and eosin (HE). Selected tissues also were stained with the periodic acid-Schiff technique, Gram-Twort, Ziehl-Neelsen, Warthin and Starry, Castaneda's, and toluidine blue stains.Several sections of duodenum, jejunum, ileum, cecum, colon, and mesenteric lymph nodes from two horses were fixed in 3% glutaraldehyde in 0.1 mol/l phosphate buffer at pH 7.4, were post-fixed in 1% osmium tetroxide in the same buffer and embedded in epon. Sections for light microscopy were cut 1-pm thick and stained with toluidine blue. Thin sections were cut from selected areas and stained with uranyl acetate and lead citrate for examination by electron microscopy.Intestinal contents, mesenteric lymph node, and liver from all horses were cultured aerobically on sheep blood agar and McConkey's agar. Intestinal mucosa and mesenteric lymph node from horse 4 were homogenized in normal saline following removal of surface contam-486
