Comparative efficacy of modified-live and inactivated vaccines in boosting disease-sparing responses to bovine viral diarrhea virus challenge in neonatally mucosally primed weanling beef calves

Objective This study compares immune and clinical responses of bovine viral diarrhea virus (BVDV)- maternal antibody (MatAb)-positive beef calves primed with intranasal modified-live virus vaccine (MLV) and differentially boosted with a systemic MLV or an inactivated vaccine (KV). Animal Eighteen commercial Black Angus steers. Procedure Calves were mucosally primed at.24 h of age with an MLV and boosted by injection of a MLV (IN-MLV) or inactivated vaccine (IN-KV) at an average age of 54 d. Challenge occurred at weaning with a virulent non-cytopathic BVDV-2 strain, 24515. Results Clinically, the IN-KV group had a longer duration of fever, leukopenia, and viremia, whereas the IN-MLV group had greater BVDV Types-1 and -2 heterospecific antibody responses. Conclusion Altogether, these data indicated that systemic MLV boosting resulted in a more robust protection to BVDV Type-2 challenge at weaning. Clinical relevance Mucosal prime-boosting of neonatal calves provided protection against BVDV Type-2 challenge at weaning.