Viral Infections in Stocker Cattle and Their Implications for Bovine Respiratory Disease.

Bovine respiratory disease complex (BRDC) remains a leading cause of morbidity and economic loss in stocker cattle, particularly during the transition from weaning to feedlot placement. Virus-induced changes promote microbiome imbalance and facilitate secondary bacterial infections, leading to bronchopneumonia. The high transmissibility of these viruses, with basic reproduction numbers ranging from approximately 3 to 36, contributes to rapid spread under feedlot conditions. This article reviews the epidemiology, pathogenesis, transmission, diagnosis, and control of major viral pathogens associated with BRDC and highlights the importance of integrated management strategies, including stress reduction, biosecurity, vaccination, and early diagnostics, for effective disease control.