High mortality and growth depression experimentally produced in young turkeys by dual infection with enteropathogenic Escherichia coli and turkey coronavirus

Six-day-old turkeys were inoculated with turkey coronavirus (TCV) and an enteropathogenic Escherichia coli (EPEC) (isolate R98/5) that were isolated from poult enteritis and mortality syndrome (PEMS)-affected turkeys. Turkeys inoculated with only R98/5 did not develop clinically apparent disease, and only mild disease and moderate growth depression were observed in turkeys inoculated with only TCV. Turkeys dually inoculated with TCV and R98/5 developed severe enteritis with high mortality (38/48, 79%) and marked growth depression. R98/5 infection resulted in attaching/effacing (AE) intestinal lesions characteristic of EPEC: adherence of bacterial microcolonies to intestinal epithelium with degeneration and necrosis of epithelium at sites of bacterial attachment. AE lesions were more extensive and were detected for a prolonged duration in dually inoculated turkeys compared with turkeys inoculated with only R98/5. An apparent synergistic effect in dually inoculated turkeys was indicated by increased mortality, enhanced growth depression, and enhanced AE lesion development. The results suggest that TCV promoted intestinal colonization by R98/5; however, R98/5 did not appear to alter TCV infection. The present study provides a possible etiologic explanation for PEMS.