Evaluation of concurrent shedding of bovine coronavirus via the respiratory tract and enteric route in feedlot cattle

Objective-To assess the relationship between shedding of bovine coronavirus (BCV) via the respiratory tract and enteric routes and the association wit h 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 obta ined were tested for antibodies to BCV, using antibody-detection ELISA. Inf ormation was collected on weight gain, clinical signs, and treatments for e nteric and respiratory tract disease during the study period. Results-Number of samples positive for bovine respiratory 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 n egative to BECV shed BRCV. Twenty-seven of 48 (56%) paired nasal swab speci mens and fecal samples positive for BECV were positive for BRCV. In contras t, 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 afte r transport shed BCV from the respiratory tract and in the feces. Fecal she dding of BCV was associated with significantly reduced weight gain. Develop ing appropriate control measures for BCV infections could help reduce the d ecreased weight gain observed among infected feedlot cattle.