Level and duration of serum antibodies in cattle infected experimentally and naturally with bovine virus diarrhoea virus

Neutralising serum antibodies against bovine virus diarrhoea virus (BVDV) w ere monitored for three years in 35 cattle that were infected with the viru s as calves; 24 of the calves were inoculated intramuscularly or intranasal ly, and 11 contracted the infection naturally. All the experimentally infec ted calves seroconverted within 14 to 28 days after inoculation, and all th e animals still had high serum levels of antibodies to BVDV three years aft er infection. Determinations of antibody levels in milk and blood samples e xcluded the possibility that the calves had been reinfected with BVDV durin g the study.