title: Protection against infection and abortion induced by virulent challenge exposure after oral vaccination of cattle with Brucella abortus strain RB51.
abstract: OBJECTIVE
  To determine efficacy of orally administered Brucella abortus vaccine strain RB51 against virulent B abortus challenge exposure in cattle as a model for vaccination of wild ungulates.
  
  
  METHODS
  20 mixed-breed beef cattle obtained from a brucellosis-free herd.
  
  
  METHODS
  Sexually mature, Brucella-negative beef heifers were vaccinated by mixing > 10' viable RB51 organisms or diluent with their feed. Heifers were fed individually and consumed their entire ration. Each heifer received approximately 3 X 10' colony-forming units (CFU). Six weeks after oral vaccination, heifers were pasture-bred to brucellosis-free bulls. At approximately 186 days' gestation, heifers were challenge exposed conjunctively with 107 CFU of virulent B abortus strain 2308.
  
  
  RESULTS
  Vaccination with the rough variant of B abortus RB51 did not stimulate antibodies against the O-polysaccharide (OPS) of B abortus. After challenge exposure and parturition, strain 2308 was recovered from 80% of controls and only 20% of vaccinates. Only 30% of the vaccinates delivered dead, premature, or weak calves, whereas 70% of the controls had dead or weak calves.
  
  
  CONCLUSIONS
  Cattle vaccinated orally with the rough variant of B abortus strain RB51 develop significant (P < 0.05) protection against abortion and colonization and do not produce OPS-specific antibodies. Clinical Relevance-Results encourage further investigation into use of strain RB51 to vaccinate wild ungulates (elk and bison) orally.
authors.affiliation: Department of Veterinary Science, Louisiana State University Agricultural Center, Baton Rouge 70803, USA.
authors.forename: P H
authors.initials: PH
authors.lastname: Elzer
authors.forename: F M
authors.initials: FM
authors.lastname: Enright
authors.forename: L
authors.initials: L
authors.lastname: Colby
authors.forename: S D
authors.initials: SD
authors.lastname: Hagius
authors.forename: J V
authors.initials: JV
authors.lastname: Walker
authors.forename: M B
authors.initials: MB
authors.lastname: Fatemi
authors.forename: J D
authors.initials: JD
authors.lastname: Kopec
authors.forename: V C
authors.initials: VC
authors.lastname: Beal
authors.forename: G G
authors.initials: GG
authors.lastname: Schurig
mesh_terms: D000034:Abortion, Veterinary / Q000517:prevention & control*; D000284:Administration, Oral; D000818:Animals; D000917:Antibody Formation; D001428:Bacterial Vaccines / Q000008:administration & dosage; D002003:Brucella abortus / Q000276:immunology* / Q000472:pathogenicity; D002007:Brucellosis, Bovine / Q000276:immunology* / Q000517:prevention & control; D002417:Cattle; D005260:Female; D007743:Labor, Obstetric; D011247:Pregnancy; D014774:Virulence
chemical_list: D001428:Bacterial Vaccines