Further observations on enterovirus infection in specific-pathogen-free turkey poults.

To evaluate sites of enterovirus replication and to characterize the resulting lesions, twenty 4-day-old specific-pathogen-free (SPF) turkey poults were orally inoculated with an enterovirus. Twenty uninoculated SPF poults served as controls. Inoculated poults were depressed, had ruffled feathers, watery droppings, and pasted vents. Gross lesions were dilated thin-walled ceca with foamy yellow fluid. Immune electron microscopy of the gastrointestinal tract contents revealed an enterovirus with an average diameter of 23.5 nm. Immunoperoxidase and indirect immunofluorescent antibody assays revealed intracytoplasmic staining in enterocytes of the duodenum, jejunum, and ileum. This correlated with the scanning electron microscopy findings, which showed the most lesions in the jejunum and ileum. The ileum had prominent cell outlines because of rounded, distinct, bulging epithelial cells. Histopathology revealed slight shortening of villi and increased crypt depth in the intestines of inoculated poults. Our findings indicate that the small intestine is the site of turkey enterovirus replication, and the gross and microscopic changes observed are determined to result from viral damage to the enterocytes.