1436 AJVR, Vol 62, No. 9, September 2001 B ovine coronavirus (BCV) was first identified as a possible cause of diarrhea in calves in 1972 1 and is now recognized as a primary pathogen in diarrhea of neonatal calves 2-6 and epizootic diarrhea of adult cat- tle. 3,7-11 Bovine coronaviruses replicate in the differenti- ated epithelium of the small and large intestines as well as the respiratory tract. 12-16 Feedlot cattle are exposed to a multitude of infec- tious agents during transport from ranch to auction market to feedlot. 17-19 Infection by viruses and bacteria is common among these cattle, and although cattle do not always have signs of clinical disease, mild to severe respiratory tract disease associated with the bovine res- piratory disease complex is common. Recently, investi- gators have detected and isolated BCV from nasal swab specimens obtained from feedlot cattle. 20-23 Cattle shed- ding BCV via the nasal passages at time of arrival in a feedlot have an increased risk for developing respirato- ry tract disease. 24 In 1 study, a high mortality associated with BCV infection was observed. Although BCV infects epithelial cells in the intesti- nal and respiratory tracts of calves, 12-16 the prevalence of enteric infections attributable to BCV, the association between shedding of BCV via the respiratory tract and enteric routes, and the rate of seroconversion to BCV are unknown in feedlot cattle. To define epidemiologic characteristics of BCV-induced enteric and respiratory tract infections of feedlot cattle and the association of BCV with respiratory tract and enteric infections, we evaluated cattle entering a local feedlot in Ohio. Information collected on clinical signs, treatment rates for respiratory tract and enteric disease, and average daily weight gain was used to identify associations between these variables, shedding of bovine respirato- ry coronavirus (BRCV) and bovine enteric coron- avirus (BECV), and seroconversion to BCV. Materials and Methods Animals—Fifty-six crossbred steers between 6 and 7 months old were included in the study. They were in a group of 216 cattle purchased from a mixed-source livestock auc- tion market in West Virginia and transported to the feedlot of the Ohio Agricultural Research and Development Center in Wooster, Ohio. Sample Collections—Paired nasal swab specimens and fecal samples were collected from cattle at time of arrival (day 0) and 4, 14, and 21 days after arrival in the feedlot, using a technique described elsewhere. 20 Briefly, samples were obtained from 56 cattle in a newly arrived group. These 56 comprised cattle with apparent respiratory tract and enteric disease as well as those that appeared to be clinically normal. Using sterile cotton-tipped applicators, swab specimens were obtained from both nostrils of each calf; swabs then were placed in tubes containing 4 ml of maintenance medium. 20 Tubes were vortexed, swabs were removed, and samples were centrifuged (1,000 X g for 11 minutes). Supernatants were collected and frozen at –70 C for subsequent testing by use of an ELISA and virus isolation techniques. 20 Fecal samples Received Jul 3, 2000. Accepted Oct 23, 2000. From the Food Animal Health Research Program, Ohio Agricultural Research and Development Center, the Departments of Veterinary Preventive Medicine (Cho, Hoet, Saif) and Animal Science (Loerch), The Ohio State University, Wooster, OH 44691; and the Department of Veterinary Preventive Medicine, The Ohio State University, Columbus, OH 43210 (Wittum). Supported in part by state and federal funds appropriated to the Ohio Agricultural Research and Development Center (OARDC) including an OARDC Competitive Research Enhancement matching grant. Address correspondence to Dr. Saif. Evaluation of concurrent shedding of bovine coronavirus via the respiratory tract and enteric route in feedlot cattle Kyoung-Oh Cho, DVM, PhD; Armando E. Hoet, DVM; Steven C. Loerch, PhD; Thomas E. Wittum, PhD; Linda J. Saif, PhD Objective—To assess the relationship between shed- ding of bovine coronavirus (BCV) via the respiratory tract and enteric routes and the association with weight gain in feedlot cattle. Animals—56 crossbred steers. Procedures—Paired fecal samples and nasal swab specimens were obtained and were tested for BCV, using antigen-capture ELISA. Paired serum samples obtained were tested for antibodies to BCV, using antibody-detection ELISA. Information was collected on weight gain, clinical signs, and treatments for enteric and respiratory tract disease during the study period. Results—Number of samples positive for bovine res- piratory coronavirus (BRCV) or bovine enteric coro navirus (BECV) was 37/224 (17%) and 48/223 (22%), respectively. Some cattle (25/46, 45%) shed BECV and BRCV. There were 25/29 (86%) cattle positive for BECV that shed BRCV, but only 1/27 (4%) cattle neg- ative to BECV shed BRCV. Twenty-seven of 48 (56%) paired nasal swab specimens and fecal samples pos- itive for BECV were positive for BRCV. In contrast, only 10/175 (6%) paired nasal swab specimens and fecal samples negative for BECV were positive for BRCV. Only shedding of BECV was associated with significantly reduced weight gain. Seroconversion to BCV during the 21 days after arrival was detected in 95% of the cattle tested. Conclusions and Clinical Implications—Feedlot cattle infected with BCV after transport shed BCV from the respiratory tract and in the feces. Fecal shedding of BCV was associated with significantly reduced weight gain. Developing appropriate control measures for BCV infections could help reduce the decreased weight gain observed among infected feedlot cattle. (Am J Vet Res 2001;62:1436–1441) Unauthenticated | Downloaded 08/14/22 04:51 AM UTC