Detection and isolation of coronavirus from feces of three herds of feedlot cattle during outbreaks of winter dysentery-like disease

A winter dysentery-like syndrome was observed in, 6- to 9-month-old cattle in 3 feedlots (herds 1 to 3) in Iowa in 1999. Clinical signs in affected cattle included acute onset of diarrhea with high morbidity. Frank blood in dark (brown-black) fluid feces, signs of respiratory tract disease, including dyspnea, coughing, and nasal discharge, and high rectal temperatures were observed in some cattle in all 3 herds. The morbidity rate for diarrhea in these cattle was 100, 100, and 22% and the mortality rate was 1.7, 0, and 3.6% for herds 1 to 3, respectively. An ELISA and immune electron microscopy (IEM) were used for detection of bovine coronavirus (BCV) antigen and particles, respectively, in 16 of 25 and 20 of 25 fecal samples submitted. Using ELISA, 2 of 3 nasal swab specimens collected from calves in herd 2 had positive results for BCV. During necropsy, 3 calves had large blood clots and frank blood in the lumen of the spiral colon and rectum. Histologic lesions were primarily restricted to the large intestine and included epithelial necrosis, dilatation, and metaplasia of the crypts of the colon and rectum. The crypt epithelium tested positive for BCV antigen by use of a monoclonal antibody to BCV Two BCV strains were isolated in cell culture from 6 fecal samples that had positive results when tested by use of ELISA and IEM. Bovine viral diarrhea virus (BVDV) was isolated from lung and lymph nodes from both. calves that died in herd 1 but not from the calf that died in herd 3. Diagnosis of BCV associated. with winter dysentery-like syndrome in these feedlot cattle was confirmed by use of ELISA and IEM on fecal samples and nasal swab specimens collected from affected cattle and by use of immunohistochemistry on intestinal sections collected from calves during necropsy. The BVDV may have contributed to the disease syndrome and mortality seen in herd 1, but it was not detected in the other 2 herds. Feedlot cattle with acute onset of bloody diarrhea should be tested for BCV.