Onset of immunity of a quadrivalent vaccine against bovine respiratory diseases

Anotace: Four experiments demonstrated the onset of immunity at 42 days of a vaccine including the following components: bovine viral diarrhoea virus (BVDV), bovine respiratory syncytial virus (BRSV), bovine parainfluenza (Pi3) and Mannheimia haemolytica (MH). Colostrum-deprived calves were vaccinated at 2 and 5 weeks of age and challenged with virulent strains 6 weeks after the 1st vaccine injection. The challenge strains caused respiratory symptoms in unvaccinated animals, while the vaccinates were clinically protected and excreted much reduced quantities of viral particles in the viral challenge tests. The MH experiment also demonstrated protection in vaccinated animals against clinical signs, lung lesions, and presence of the pathogen in the lungs.