Evaluation of efficacy of an inactivated vaccine against bovine respiratory syncytial virus in calves with maternal antibodies.
OBJECTIVE
To assess short- and long-term efficacy of an inactivated bovine respiratory syncytial virus (BRSV) vaccine administered i.m. to calves with maternally derived antibodies.


METHODS
28 two-week-old calves with neutralizing, maternally derived antibodies against BRSV.


METHODS
For evaluation of short-term efficacy, 6 calves were vaccinated i.m. at 2 and 6 weeks of age and challenged intranasally and intratracheally along with a matched group of 4 unvaccinated control calves at 10 weeks of age. For evaluation of long-term efficacy, 2 groups of 6 calves each were vaccinated i.m. at 2, 6, and 18 weeks of age or 14 and 18 weeks of age; these calves were challenged intranasally and intratracheally along with 6 matched unvaccinated control calves at 43 weeks of age. Serum virus neutralizing antibody titer, clinical reactions, and virus shedding in nasal mucus and lung washings were assessed.


RESULTS
None of the vaccination regimens resulted in a significant increase in serum virus neutralizing antibody titer. As judged by virus shedding in nasal mucus and lung washings, vaccinated calves were protected against challenge, compared with unvaccinated control groups. Clinical signs attributable to challenge were coughing (short-term efficacy study) and tachypnea and dyspnea (long-term efficacy study). The severity and incidence of disease were significantly lower in the vaccinated groups, compared with that in the unvaccinated groups.


CONCLUSIONS
Through vaccination, it is possible to protect vulnerable calves with maternal antibodies against BRSV infection and reduce respiratory tract disease.
Patel
Jay R
JR
Intervet UK Ltd, The Elms, Thicket Road, Houghton, Huntingdon, Cambridgeshire, UK, PE28 2BQ.
Didlick
Susan A
SA
D000818:Animals; D000914:Antibodies, Viral / Q000097:blood; D002417:Cattle; D002418:Cattle Diseases / Q000276:immunology / Q000517:prevention & control*; D007112:Immunity, Maternally-Acquired / Q000276:immunology; D008168:Lung / Q000821:virology; D009297:Nasal Mucosa / Q000821:virology; D018357:Respiratory Syncytial Virus Infections / Q000276:immunology / Q000517:prevention & control / Q000662:veterinary*; D022261:Respiratory Syncytial Virus Vaccines / Q000008:administration & dosage / Q000276:immunology / Q000592:standards*; D018112:Respiratory Syncytial Virus, Bovine / Q000276:immunology*; D013997:Time Factors; D015164:Vaccines, Inactivated / Q000008:administration & dosage / Q000276:immunology / Q000592:standards; D017201:Virus Shedding / Q000276:immunology
D000914:Antibodies, Viral; D022261:Respiratory Syncytial Virus Vaccines; D015164:Vaccines, Inactivated