BRUCELLA-ABORTUS STRAIN RB51 - A NEW BRUCELLOSIS VACCINE FOR CATTLE

For the last 50 years, the Brucella abortus strain 19 (S19) vaccine ha s been the only brucellosis vaccine approved for use in cattle in the United States. Vaccination with S19 combined with detection and slaugh ter of cattle that are infected with field strains of B. abortus have been critical elements of the Brucellosis Eradication Program since it s initiation in 1954. Cattle in 37 states are now free of bovine bruce llosis, and it is projected that the disease will be eradicated by 199 8. Identification of cattle infected with brucellosis can be complicat ed because the S19 vaccine induces antibody responses on brucellosis s erologic tests that cannot be differentiated from responses of cattle infected with field strains of Brucella. The B. abortus strain RB51 (S RB51) vaccine has recently been introduced (in 1996) and is anticipate d to replace the S19 vaccine. The SRB51 vaccine induces protective imm unity that is similar to that obtained following S19 vaccination but d oes not induce antibody responses that interfere with the serologic di agnosis of brucellosis. This article reviews the immunology and pathol ogy of the SRB51 vaccine as well as its efficacy in preventing brucell osis in cattle and other animals.