Abstract
Rectal prolapse was the presenting clinical finding in a group of juvenile emus (Dromaius novaehollandiae). Gross findings included severely thickened and rugose distal rectal mucosae. Histologically, there were thickened villi, enterocyte hyperplasia, dilated glands filled with mucus and heterophils, and a dense infiltrate of heterophils, macrophages, lymphocytes, and plasma cells in the lamina propria. Examination of Warthin-Starry silver-stained sections revealed numerous apically located comma-shaped intracytoplasmic bacteria approximately 1X3 μm in size. Campylobacter-like organisms morphologically compatible with ileal symbiont intracellularis now known as Lawsonia intracellularis were seen via electron microscopy. Bacteria were further characterized by indirect immunofluorescence using a monoclonal antibody specific for the 25-27-kd outer membrane protein of L. intracellularis.