Clinical and immunologic responses of vaccinated and unvaccinated calves to infection with a virulent type-II isolate of bovine viral diarrhea virus.
OBJECTIVE
To determine efficacy of a modified-live type-I isolate of bovine viral diarrhea virus (BVDV) vaccine in protecting calves from infection with a virulent type-II isolate, and to determine which type of immune response (i.e., humoral or cellular) correlates with protection.


METHODS
Prospective study.


METHODS
28 neonatal Holstein and Holstein-cross calves.


METHODS
Within 18 hours of birth, calves received maternal colostrum or were fed pooled colostrum. On days 7 to 10 after birth, calves were determined to be seropositive (n = 16) or seronegative (12) for antibodies to BVDV on the basis of ELISA and virus neutralization test results. Seropositive and seronegative 10- to 14-day-old calves were then given a combined vaccine that contained a modified-live type-I isolate of BVDV or a similar vaccine that lacked protection against bovine viral diarrhea. All calves were inoculated intranasally approximately 21 days after vaccination with a virulent type-II isolate of BVDV. Clinical and immunologic variables, including clinical scores, rectal temperatures, results of CBC with lymphocyte subset analysis, antibody responses, and cell-mediated immune responses, were monitored for 14 days after inoculation.


RESULTS
Seronegative-unvaccinated calves developed severe disease and required euthanasia. Vaccination of seronegative calves with a modified-live type-I isolate had a disease-sparing effect as did passive transfer of colostral antibodies to BVDV. Clinical scores were not significantly different between seropositive-vaccinated and seropositive-unvaccinated calves after viral inoculation.


CONCLUSIONS
A single dose of a modified-live type-I isolate of BVDV vaccine protects young calves from clinical signs of disease associated with type-II isolates.
Cortese
V S
VS
Department of Veterinary Microbiology, Western College of Veterinary Medicine, University of Saskatchewan, Saskatoon, Canada.
West
K H
KH
Hassard
L E
LE
Carman
S
S
Ellis
J A
JA
D000818:Animals; D000914:Antibodies, Viral / Q000096:biosynthesis*; D001912:Bovine Virus Diarrhea-Mucosal Disease / Q000276:immunology / Q000517:prevention & control*; D002417:Cattle; D003126:Colostrum / Q000276:immunology; D001908:Diarrhea Viruses, Bovine Viral / Q000276:immunology* / Q000472:pathogenicity; D004797:Enzyme-Linked Immunosorbent Assay / Q000662:veterinary; D007111:Immunity, Cellular; D007112:Immunity, Maternally-Acquired; D007958:Leukocyte Count / Q000662:veterinary; D008213:Lymphocyte Activation; D009500:Neutralization Tests / Q000662:veterinary; D011446:Prospective Studies; D014611:Vaccination / Q000662:veterinary; D014765:Viral Vaccines / Q000276:immunology; D014774:Virulence
D000914:Antibodies, Viral; D014765:Viral Vaccines