Clinical and immunologic responses of calves with colostrally acquired maternal antibody against parainfluenza-3 virus to homologous viral infection.

Exposure of colostrum-deprived calves and calves with colostrally acquired maternal antibody to aerosols of parainfluenza-3 (PI-3) virus resulted in signs of infection, leukopenia, and shedding of virus from the nasal passages. However, infection was not as severe in calves with colostrally acquired maternal antibody as it was in colostrum-deprived calves which did not have antibody to PI-3 virus before they were exposed. All calves responded immunologically to PI-3 virus, as indicated by resistance to challenge exposure and subsequent development of virus-neutralizing antibody. However, levels of serum and nasal secretion (NS) antibody at 30 days after viral exposure were lower in calves with colostrally acquired maternal antibody than in colostrum-deprived calves, and a serum antibody response in the former was primarily indicated by an anamnestic response after challenge exposure. After calves were challenge exposed to PI-3 virus, serum and NS antibodies were increased in all calves, but antibody titers were generally lower for calves that had colostrally acquired maternal antibody before their exposure than for those that acquired antibody only after PI-3 viral infection.