Effect of serum and nasal neutralizing antibodies on bovine respiratory syncytial virus infection in calves.

Calves exposed to a bovine respiratory syncytial virus showed mild clinical signs of respiratory illness and responded serologically. The disease occurred in the presence or absence of circulating antibodies, but there was no evidence of exacerbation of the disease due to preexisting serum antibody. Nasal secretory antibody appeared to protect the calves against the disease. Calves previously exposed to the virus were immune to challenge. The virus was recovered at a high frequency when specimens of nasal secretion (not subjected to freezing and thawing) were inoculated into susceptible cells within 1 hr after collection.