Molecular and epidemiological characterization of a respiratory disease outbreak in pre-weaned beef calves associated with bovine coronavirus

Authors: Workman, Aspen; McDaneld, Tara; Kuehn, Larry; Clawson, Michael - Mike; LOY, JOHN - University Of Nebraska

Submitted to: Research Workers in Animal Diseases Conference Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: 9/19/2017
Publication Date: 12/5/2017
Citation: Workman, A.M., McDaneld, T.G., Kuehn, L.A., Clawson, M.L., Loy, J.D. 2017. Molecular and epidemiological characterization of a respiratory disease outbreak in pre-weaned beef calves associated with bovine coronavirus. Conference of Research Workers in Animal Diseases Conference Proceedings, December 3-5, 2017, Chicago, Illinois. Abstract #203. Available: https://crwad.org/crwad-2017/

Interpretive Summary:

Technical Abstract: Bovine coronavirus (BCV) is associated with respiratory tract infections in cattle of all ages; however, a temporal study to evaluate the effect of BCV immunity on virus shedding and bovine respiratory disease (BRD) incidence in pre-weaned beef calves has not been reported. Thus, we report here a prospective study in three herds of crossbred beef calves (n=817) with endemic BCV. Serial blood samples for measurement of serum anti-BCV antibody titers and nasal swabs for detection of BCV and other viral and bacterial BRD pathogens by real-time PCR methods were collected from all calves or subsets of calves at predetermined times from birth through weaning. The calves were monitored for BRD and those that developed respiratory disease were sampled and tested for common respiratory pathogens. Two hundred forty-eight of the 817 study calves (30.4%) were treated for BRD prior to weaning; 246 of those were from a single herd involved in two mass treatment events. Molecular diagnostic testing revealed that BCV shedding occurred in conjunction with the pre-weaning BRD outbreaks in that herd. However, between herd analyses revealed that levels of passively (maternal) or actively acquired anti-BCV antibodies did not associate with the incidence of pre-weaning BRD or BCV shedding. Thus, to account for potentially confounding factors that could have influenced BRD development in these herds, sequencing and phylogenetic analysis of the BCV strains circulating in each herd, and the prevalence and relative abundance of bacteria in the nasopharynx of sick and apparently healthy cattle were also evaluated. Mycoplasma species and Histophilus somni were identified in high abundance in the nasopharynx of cattle with BRD but not in apparently healthy animals. Our results indicate that BCV infection was associated with both subclinical and clinical disease; however serum anti-BCV antibody tiers were not associated with disease incidence. Co-infection with Mycoplasma sp. and Histophilus somni likely contributed to the disease outbreak characterized in this study.