title: Effects of age at vaccination on efficacy of Brucella abortus strain RB51 to protect cattle against brucellosis.
abstract: OBJECTIVE
  To establish that female calves vaccinated with Brucella abortus strain RB51 at 3, 5, and 7 months of age are protected against infection and abortion when challenged exposed during their first pregnancy.
  
  
  METHODS
  Polled Hereford heifer calves obtained from a brucellosis-free herd.
  
  
  METHODS
  Calves were inoculated SC at 3, 5, or 7 months of age with strain RB51 (n = 26), strain 19 (n = 16), or sterile saline solution (n = 15). Calves were bred at 16 to 17 months of age and challenged exposed during the first pregnancy with virulent B abortus strain 2308.
  
  
  RESULTS
  After vaccination, none of the heifers given strain RB51 developed serum antibodies that reacted in the standard tube agglutination test, but reacted in a dot-blot assay, using RB51 antigen. B abortus was cultured from biopsy specimens of superficial cervical lymph nodes in the RB51 and S19 vaccinates at 10 weeks, but not at 12 weeks after vaccination. All 4 heifers that had been vaccinated with RB51 at 3 months of age were protected against infection and abortion when challenged exposed. Vaccination at 5 and 7 months of age gave equivalent protection. Heifers given strain 19 were 95% protected and controls (given saline solution) had a high influence of infection and abortion.
  
  
  CONCLUSIONS
  Strain RB51 is protective at doses comparable to those of strain 19 in calves 3 to 10 months of age.
  
  
  CONCLUSIONS
  Immunogenicity and failure to induce antibodies that interfere with the serologic diagnosis of field infections of B abortus make strain RB51 an effective vaccine.
authors.affiliation: USDA, Agricultural Research Service, Ames, IA 50010, USA.
authors.forename: N F
authors.initials: NF
authors.lastname: Cheville
authors.forename: S C
authors.initials: SC
authors.lastname: Olsen
authors.forename: A E
authors.initials: AE
authors.lastname: Jensen
authors.forename: M G
authors.initials: MG
authors.lastname: Stevens
authors.forename: M V
authors.initials: MV
authors.lastname: Palmer
authors.forename: A M
authors.initials: AM
authors.lastname: Florance
mesh_terms: D000034:Abortion, Veterinary / Q000517:prevention & control*; D000367:Age Factors; D000818:Animals; D000907:Antibodies, Bacterial / Q000097:blood; D000917:Antibody Formation; D001428:Bacterial Vaccines; D001706:Biopsy; D002003:Brucella abortus / Q000276:immunology* / Q000302:isolation & purification; D002007:Brucellosis, Bovine / Q000276:immunology / Q000517:prevention & control*; D002417:Cattle; D005260:Female; D008198:Lymph Nodes / Q000382:microbiology; D011247:Pregnancy; D014611:Vaccination / Q000662:veterinary*
chemical_list: D000907:Antibodies, Bacterial; D001428:Bacterial Vaccines