Development, testing and commercialization of a new brucellosis vaccine for cattle.

Vaccines used against brucellosis do not generally protect completely against infection or abortion. Genetic analysis has revealed differences in arrangements of DNA sequences between these vaccine strains and the virulent parent strain and permits the specific identification of field isolates of B. abortus as wild-type or vaccine strain. B. abortus strain 19 is a low-virulence, live vaccine developed for use in cattle. Although it is effective, strain 19 vaccine had a tropism for the placenta and caused abortion when given to pregnant cows, was infectious for humans, and caused serologic responses in calves that could not be differentiated from those in cattle infected with natural field strains. In the mid-1980s the need for a new vaccine emerged when the USDA increased its efforts in brucellosis eradication. In the 1990s, research on biosafety, vaccine efficacy and field application rapidly established the fact that strain RB51 is protective in cattle at doses comparable to those of strain 19. Thus, Brucella abortus strain RB51 is the vaccine of choice against brucellosis of cattle in the United States. Studies have established the relative efficacy of strain RB51 vaccine on bison, and the vaccine has also been accepted for use in commercial bison herds in the U.S.