Comparative efficacy of an experimental S45/20 bacterin and a reduced dose of strain 19 vaccine against bovine brucellosis.
Yearling beef heifers were vaccinated with 2 doses of an experimental Brucella abortus S45/20 bacterin or a reduced dose of strain 19 (S19) vaccine, or were used as nonvaccinated controls. None of the vaccinated heifers was positive by the acidified plate, Rivanol, complement-fixation, or card tests 5 months after inoculation. Sixteen of 21 heifers given S45/20 bacterin with trehalose dimycolate adjuvant had delayed hypersensitivity when skin was tested 7 months after initial vaccination, whereas none of the S19 vaccinates or controls was reactive. After natural breeding, pregnant heifers were challenge exposed at 3.5 to 5 months of gestation with 2.5 X 10(7) viable B abortus S2308 organisms in the conjunctival sac. Abortions occurred as follows: 16/19 (84.2%) of heifers given S45/20 bacterin, 6/12 (50.0%) of heifers vaccinated with S19, and 17/18 (94.4%) of the nonvaccinated controls. Of the 10 heifers that calved normally, only 3 (1 in each group) were seropositive. A correlation was not seen between skin hypersensitivity and acquired resistance. Possible reasons for the poor protection with a reduced dose of S19 vaccine and the failure of S45/20 bacterin to enhance cellular resistance are discussed.
D000034:Abortion, Veterinary / Q000517:prevention & control*; D000276:Adjuvants, Immunologic / Q000494:pharmacology; D000818:Animals; D002004:Brucella Vaccine / Q000008:administration & dosage / Q000276:immunology / Q000494:pharmacology*; D002007:Brucellosis, Bovine / Q000276:immunology / Q000517:prevention & control*; D002417:Cattle; D003311:Cord Factors / Q000494:pharmacology; D004342:Drug Hypersensitivity / Q000662:veterinary*; D005260:Female; D006968:Hypersensitivity, Delayed / Q000139:chemically induced / Q000662:veterinary*; D007117:Immunization, Secondary / Q000662:veterinary; D011247:Pregnancy; D011251:Pregnancy Complications, Infectious / Q000517:prevention & control / Q000662:veterinary*; D014611:Vaccination / Q000662:veterinary*
D000276:Adjuvants, Immunologic; D002004:Brucella Vaccine; D003311:Cord Factors