|Briggs, Robert - Bob|
Submitted to: Bovine Practitioner Journal
Publication Type: Proceedings
Publication Acceptance Date: 9/24/1998
Publication Date: N/A
Technical Abstract: Shipping fever (SF) of cattle results from stressful conditions favoring viral and bacterial infections of respiratory tracts that lead to severe respiratory distress with frequent fatal outcomes. The incidence and spread of respiratory viral infections of cattle developing SF were analyzed by a refined and sensitive virus isolation technology that detects sall viruses known to infect the bovine respiratory tracts including respiratory bovine coronaviruses (RBCV) which multiply in highly polarized epithelioid cells such as the G clone of HRT-18 cells in culture. Sequential nasal swab samples from 105 cattle of this epizootic were collected at an order-buyer barn and on three subsequent intervals of seven days in the feedlot. These samples were cultured for viruses and bacteria. The viral isolation attempts revealed that 64 cattle had RBCV infection at the order-buyer barn. Twenty-three additional cattle contacted this infection during transport to the feedlot so that 87 of them had this vira infection during the initial days of the epizootic. Ten cattle died and nine of them had RBCV infections. Seventy-nine of the remaining 95 cattle had to be treated for acute respiratory disease, and 69 of them had the RBCV infection. The 87 isolates of G-clone cell-dependent viral strains were identified as RBCV through cell fusion functions, specific hemagglutinins, and receptor destroying enzyme activities mediated through an acetylesterase. Samples collected on the two subsequent periods are currently under investigation. The strong evidence furnished through virus isolation indicates that RBCV are emerging as a frequent infection of cattle affected with acute respiratory tract diseases, and they evidently played a significant etiological role in this severe epizootic.