Lawsonia intracellularis-like organism infection in a miniature foal.

A 7-month-old foal was admitted to the hospital with a history of lethargy, weight loss, mild diarrhea, and anorexia. A diagnosis of proliferative enteritis caused by Lawsonia intracellularis-like organisms was made after necropsy and histologic examination of the small intestine. Although infection with L intracellularis-like organisms is a rare cause of enteritis in foals, it should be considered in the differential diagnosis, especially if the foal was housed in the proximity of pigs or pig feces. Antemortem diagnosis remains challenging because isolation of the organism in fecal material requires cell culture, and histologic evaluation of intestinal biopsy specimens may be unrewarding because of the lack of information regarding the frequency and distribution of lesions in horses. Alternatively, use of immunochemical stain, dot-blot technique, and polymerase chain reaction provide specific diagnostic tests that can be performed on fecal material. Postmortem diagnosis relies on histologic examination of infected tissues and use of immunofluorescence and polymerase chain reaction.