|Storz, J - LOUISIANA STATE UNIV.|
|Lin, X - LOUISIANA STATE UNIV.|
|Burrell, M - LOUISIANA STATE UNIV.|
|Truax, R - LOUISIANA STATE UNIV.|
|Loan, R - TEXAS A&M UNIVERSITY|
Submitted to: Journal of the American Veterinary Medical Association
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 21, 1999
Publication Date: October 1, 2000
Citation: Storz, J., Purdy, C.W., Lin, X.Q., Burrell, M., Truax, R.E., Briggs, R.E., Frank, G.H., Loan, R.W. 2000. Isolation of respiratory bovine coronavirus, other cytocidal viruses, and pasteurella spp from cattle involved in two natural outbreaks of shipping fever. Journal of the American Veterinary Medical Association. 216(10):1599-1604. Interpretive Summary: The shipping fever complex in market-stressed calves costs the feeder/stocker industry $750,000,000 per year in acute and chronic sickness and death. Two viruses [infectious bovine rhinotracheitis (IBR), parainfluenza-3 (PI-3)] are known to precede and set off the bacterial infection of Pasteurella haemolytica serotype 1 which is responsible for much of the losses incurred with this disease complex. Good vaccines have been developed for IBR and PI-3 to help break the shipping fever complex if such vaccines are used prior to marketing. However, we now have good evidence that another virus infection, respiratory bovine coronavirus (RBCV) can also precede and set off the shipping fever complex. Heretofore, RBCV infection has never been reported with the shipping fever complex in beef cattle. The isolation of RBCV was made possible by the G clone of the human rectal tumor-18 (HRT-18) cells. The G clones are uniquely permissive for RBCV which do not replicate in other currently available bovine cell cultures. This accomplishment is very important to find another virus RBCV responsible for preceding and setting off the shipping fever complex. This discovery will necessitate that veterinary diagnostic laboratories acquire the G clone of cell in order to make the diagnosis that RBCV can be present in shipping fever complex. Its impact will be responsible for the development of RBCV vaccines and ultimately to the feeder calf industry for reducing the cost of shipping fever.
Technical Abstract: The objectives of this study were to trace respiratory virus infections under prospective, experimentally monitored conditions among market-stressed calves during the pathogenesis of shipping fever pneumonia in two severe epizootics. One hundred and five and 120 beef cattle of mixed breeds, with ages of 6 to 8 months and weights of 148 to 282 kg, experienced shipping fever epizootics in 1997 and 1998. All calves were processed (ear tagged, vaccinated for IBR and 7-way blackleg, nasal swabbed, blood sampled and weighed) at the order-buyer barn (OBB). In addition, the odd numbered calves were vaccinated for Pasteurella haemolytica (Ph1). The cattle were transported 1932 km from the OBB to a feedyard in Bushland, Texas, where the calves were monitored daily for clinical respiratory signs. If adverse clinical signs were observed and rectal temperatures were 40 deg C or higher, the calves were treated with antibiotics. In the feedyard, the calves were sampled weekly (4 wk) for blood and nasal swabs and they were also weighed. The nasal swabs were cultured for Ph1 and for known bovine respiratory viruses by inoculating three selectively permissive cell culture systems. The results are as follows: 93 of 105 calves and 107 of 120 calves developed respiratory tract disease in 1997 and 1998. Respiratory bovine coronaviruses (RBCV) were isolated from nasal swabs samples of 81 and 89 of the affected cattle during the early stages of both epizootics. Cattle with high antibody titers to BRCV early in the epizootics did not exhibit adverse clinical signs. Cattle at the OBB were highly susceptible to BRCV. The BRCV represented a high risk factor for the two shipping fever epizootics. This is the first report of BRCV being involved in shipping fever.