Protection against infection and abortion induced by virulent challenge exposure after oral vaccination of cattle with Brucella abortus strain RB51.
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.
Elzer
P H
PH
Department of Veterinary Science, Louisiana State University Agricultural Center, Baton Rouge 70803, USA.
Enright
F M
FM
Colby
L
L
Hagius
S D
SD
Walker
J V
JV
Fatemi
M B
MB
Kopec
J D
JD
Beal
V C
VC
Schurig
G G
GG
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
D001428:Bacterial Vaccines