Case Report J Vet Intern Med 2000;14:630–632 Surgical and Medical Treatment of an Arabian Filly with Proliferative Enteropathy Caused by Lawsonia intracellularis John Schumacher, Jim Schumacher, Mark Rolsma, Kenny V. Brock, and Connie J. Gebhart A 3-month-old, 150-kg Arabian ﬁlly was examined at Auburn University’s Veterinary Teaching Hospital because of signs of abdominal pain that had been present for 1 week. The ﬁlly lived with 8 other horses on 3 acres in a residential neighborhood. When the ﬁlly was 3 days old, she developed diarrhea that resolved after 2 weeks of treatment with trimethoprim-sulfamethoxazole (15 mg/kg PO q12h). Pyrantel pamoate was administered when the ﬁlly was 1 month old, fenbendazole was administered when she was 2 months old, and pyrantel tartrate was adminis- tered daily thereafter for treatment and prevention of infes- tation with intestinal nematodes. The ﬁlly was weaned when she was 2 ½ months old because her dam experienced severe weight loss during lactation. Signs of abdominal pain were observed 1 week after weaning. Signs of abdominal pain were mild initially and could be ameliorated with once or twice daily IV administration of ﬂunixin meglumine (1.1 mg/kg). Cimetidine (18 mg/kg PO q12h) also was administered because gastric ulceration was suspected to be the cause of the signs of abdominal pain. Despite this therapy, signs of abdominal pain became more frequent and more pronounced. At admission, the ﬁlly was slightly thin but otherwise appeared to be in good condition. Vital signs were within the normal range, and signs of abdominal pain initially were not observed. Results of a CBC and serum creatinine con- centration were within the reference range, but the serum protein concentration was low (4.2 g/dL; normal,  5 g/ dL). 1 Other serum biochemistry tests were not performed. Gastric ulcers were not observed during gastroscopy. During abdominal ultrasonography, several segments of small intestine appeared to be distended with ﬂuid, and al- though not measured, other segments appeared to be mark- edly thickened (Fig 1). While being examined, the ﬁlly showed signs of abdominal pain, which resolved after ad- ministration of ketoprofen (2.2 mg/kg IV). Inﬂammatory bowel disease was suspected to be the cause of abdominal pain, and an exploratory celiotomy was performed. Gentamicin sulfate (5 mg/kg IV) and procaine penicillin From the Department of Large Animal Surgery and Medicine (John and Jim Schumacher) and the Department of Pathobiology (Rolsma, Brock), College of Veterinary Medicine, Auburn University, Auburn, AL; and the Department of Veterinary Pathobiology (Gebhart), Uni- versity of Minnesota, St Paul, MN. Reprint requests: John Schumacher, DVM, Department of Large An- imal Surgery and Medicine, Auburn University, Auburn, AL 36849- 5522; e-mail: schumjo@vetmed.auburn.edu. Submitted March 10, 2000; Revised June 27, 2000; Accepted July 26, 2000. Copyright  2000 by the American College of Veterinary Internal Medicine 0891-6640/00/1406-0012/$3.00/0 (22,000 U/kg IM) were administered before surgery. Vis- cera were examined through a 10-cm ventral midline celi- otomy. The wall of the distal third of the small intestine, including the ileum, was thickened, and ﬂuid and ingesta ﬁlled the small intestine proximal to the thickened segment. The midportion of the jejunum proximal to the grossly thickened portion of intestine was anastomosed (side-to- side) to the cecum so that ingesta could bypass the grossly thickened section of small intestine. A small section of the jejunal wall at the site of the anastomosis was removed for histologic examination. The thickened ileal wall was also biopsied. Administration of gentamicin sulfate (5 mg/kg IV q12h) and procaine penicillin (22,000 U/kg IM q12h) was contin- ued for 3 days after surgery. The ﬁlly was allowed to eat grass hay 12 hours after surgery but showed signs of mild abdominal pain soon after eating. These signs resolved after administration of ﬂunixin meglumine (1.1 mg/kg IV) and 0.5 L of mineral oil (by nasogastric tube). Signs of colic were not observed after this time. After treatment for colic, the ﬁlly was allowed to eat pelleted feed and 8 hours later was allowed to eat grass hay. Mineral oil (0.5 L) was ad- ministered PO once daily for 2 more days. Oocysts of Eimeria leuckarti were observed during his- tologic examination of the thickened intestinal tissue and on Sheather ﬂotation of feces on day 2 after surgery and prompted a change in antimicrobial therapy to trimetho- prim-sulfamethoxazole (15 mg/kg PO q12h), which was ad- ministered for 5 days. No other postoperative complications were observed, and the ﬁlly was discharged 6 days after surgery. At the time of discharge, serum protein concentra- tion was 3.9 g/dL. Marked shortening and blunting of intestinal villi were seen during histologic examination of grossly thickened je- junum. Crypts were elongated and lined by thickened, hy- perplastic epithelium. The lamina propria, especially around crypts, was expanded by moderate numbers of macrophag- es, lymphocytes, and plasma cells. Eosinophils were noted occasionally. The lamina propria contained moderate num- bers of several stages of a coccidian parasite, assumed to be E leuckarti. The intestinal lesions resembled those of porcine proliferative enteropathy, 2 and tissues were reex- amined with Steiner stain. In these specimens, large num- bers of curved bacilli assumed to be Lawsonia intracellu- laris were found within the apical cytoplasm of many ep- ithelial cells of the crypts (Fig 2). Similar, but milder, le- sions were seen during histologic examination of grossly normal jejunum removed from the site of anastomosis. DNA was extracted from sections of formalin-ﬁxed intes- tine, and a polymerase chain reaction (PCR) assay for the detection of L intracellularis, as previously described, was