Efficacy of a non-adjuvanted, modified-live virus vaccine in calves with maternal antibodies against a virulent bovine viral diarrhea virus type 2a challenge seven months following vaccination

Abstract

In the presence of maternal antibodies, 26 calves three days of age were either vaccinated (n=15) with a single dose of a non-adjuvanted, pentavalent, modified-live vaccine containing bovine herpes virus-1, bovine respiratory syncytial virus, bovine viral diarrhea virus 1a (BVDV1a), bovine viral diarrhea virus 2a (BVDV2a), and bovine parainfluenza-3, or sham vaccinated with sterile saline (n=11). At approximately seven months post-vaccination, when vaccinates and non-vaccinates were seronegative to BVDV1a and BVDV2a antibodies, all calves were intranasally challenged with a virulent BVDV2a (strain 1373). Clinical signs of BVDV infection were monitored beginning three days prior to challenge and concluded on day 21 after challenge. Calves vaccinated in the face of maternal antibodies (IFOMA) were less impacted by the challenge. Based on clinical parameters, vaccinates had reduced clinical scores, rectal temperature, weight loss, and mortality compared to sham-vaccinated animals. Vaccinated animals had higher levels of circulating white blood cells and fewer animals were viremic than sham-vaccinated animals. This study demonstrated that a calf as young as three days of age when vaccinated IFOMA can be protected against a virulent BVDV2a challenge with a non-adjuvanted, pentavalent vaccine.