RESUMO
With the goal of providing an additional tool for controlling bovine brucellosis in Brazil and evaluating the full calf dose in adult cattle, the efficacy of the rough Brucella abortus strain RB51 vaccine was tested in heifers. Thirty-three females of approximately 24 months of age were divided in two groups: one group (n=20) received the RB51 vaccine and the other group (n=13) were used as non-vaccinated control. Animals in the vaccinated group were split in two sub-groups. One sub-group (n=12) was vaccinated subcutaneously with 1.5x10(10) colony forming units (CFU) of RB51 at Day 0 of the experiment and the other sub-group (n=8) was vaccinated subcutaneously with 1.6x10(10) CFU of RB51 at 60 days of gestation (Day 260 of the experiment). All cattle were challenged between 6 and 7 months of pregnancy with 3x10(8) CFU of the virulent strain 2308 of B. abortus by the conjunctival route. Vaccination with RB51 vaccine did not result in the production of any antibodies against the O-side chain of lipopolysaccharide (LPS), as measured by conventional serological tests (rose bengal plate agglutination test (RBPAT), standard tube agglutination test (STAT), and 2-mercaptoethanol test (2ME)). A total of 25% cumulative incidence of abortions was found in the vaccinated group, whereas in the control group the cumulative incidence was 62%. B. abortus RB51 was not isolated from any sample, and no abortions were produced by RB51 vaccination of females at 60 days of pregnancy. The results indicate that vaccination with RB51 prevented 59.4% of abortions, 58.6% of cow infections, and 61.0% of fetal infections. The relative risk (RR) revealed that non-vaccinated animals have 2.462 (95% CI 1.029-5.889) times higher risk of aborting than RB51-vaccinated animals.
Assuntos
Aborto Animal/prevenção & controle , Vacina contra Brucelose , Brucella abortus/imunologia , Brucelose Bovina/imunologia , Brucelose Bovina/prevenção & controle , Complicações Infecciosas na Gravidez/veterinária , Animais , Anticorpos Antibacterianos/sangue , Vacina contra Brucelose/administração & dosagem , Vacina contra Brucelose/efeitos adversos , Vacina contra Brucelose/imunologia , Brucella abortus/patogenicidade , Bovinos , Feminino , Gravidez , Vacinação/veterináriaRESUMO
La cepa RB51 de B. abortus fue aislada mediante fases repetidas de cepa 2308 de B. abortus sobre medios conteniendo ripamficina y penicilina. Ya que RB51 no expresa nada, o cantidades mínimas, de la cadena lateral O del lipopolisacárido, el ganado vacunado con esta cepa permanece seronegativo ante las pruebas de diagnósticos convencionales de brucelosis.
Presentación realizada en la Reunión de Consulta de Expertos de la OPS/OMS sobre Vacunas y Estrategias de Vacunación en los Programas de Control y Erradicación de la Brucelosis; 16-18 noviembre 1999.