Vaccination of cattle against brucellosis using either a reduced dose of strain 19 or one or two doses of 45/20 vaccine

Abstract

SUMMARY Three groups, each of 14 mature Jersey heifers, were vaccinated. They were mated about 2 months later and those that became pregnant were challenged at about 6.5 months of pregnancy by the conjunctival application of virulent Brucella abortus. Group 1 heifers received 2 doses of B. abortus 45/20 vaccine 2 months apart. Only 5 of the 14 heifers became pregnant, and of these 5 only one resisted challenge. Group 2 heifers received only one dose of 45/20 vaccine, 5 of the 10 challenged resisted infection. Group 3 heifers received 3 × 108 cfu of strain 19. Six of the 10 heifers challenged resisted infection. All of 5 non‐vaccinated control cattle became infected. It appeared advantageous to give only one dose of 45/20 rather than 2 as presently recommended. A single dose of 45/20 vaccine induced resistance to virulent B. abortus approximately equal to that given by the reduced dose of strain 19. One dose of 45/20 vaccine stimulated transient serological positivity in 2 of 28 heifers whereas the reduced dose of strain 19 gave rise to persistent titres in 2 of 14 vaccinated heifers.

Brucellosis Vaccines: An Overview

“…In fact, overall, htrA-deficient mutants produce spleenic bacterial loads comparable to their 11 wild-type counterparts. RecA mutants produce similar results as htrA mutants in early-and late-phase spleenic load (43).Two other types of proteins that have been put forth as possible virulence factors are siderophores and Cu-Zn superoxide dismutase (Cu-Zn SOD). Ironsequestration by siderophores may be an integral virulence factor in intracellular survival of Brucella species.…”