Comparing clinical and immunologic response efficacy of systemic prime

Objective: This study compared the efficacy of mucosal prime and systemic boost vaccination of young beef calves to the current industry standard of systemic prime in the presence of maternal antibodies. Animals: April-born commercial crossbred beef calves (N = 22) were enrolled as neonates with a mean body weight of 37.7 ± 5.3 kg. Procedure: At birth, 11 calves (PRB) were intranasally administered a commercial combination modified live virus [bovine herpesvirus type 1 (BoHV1), bovine respiratory syncytial virus (BRSV), bovine parainfluenza virus type 3 (BPIV3)] mucosal vaccine and 11 calves (INJ) remained unvaccinated. At ~39 ±2 d of age, all 22 calves were subcutaneously administered a combination modified live virus systemic vaccine (BoHV1, BRSV, BPIV3, and bovine viral diarrhea virus types 1 and 2). At weaning (159 ±2 d of age), calves were challenged by coinfection with BRSV and BPIV3 and monitored 8 d for health and immunologic outcomes. Results: The INJ group had an increased risk of greater group cumulative clinical scores on Day 8 and rectal temperature > 39.5°C on Days 7 and 8 post-challenge. The INJ calves had lower arterial oxygenation than the PRB on Day 6, indicating more severe lung pathology. Shedding of BRSV and BPIV3 was greater on Days 5 and 7 for INJ compared to PRB. Conclusion: Mucosal priming and systemic boosting resulted in fewer lung lesions and less shedding of virus post-viral challenge at weaning than systemic priming of young calves. Clinical relevance: Prime-boost vaccination optimizes immune development toward weaning.