The immune response of guinea pigs and buffalo calves to the locally prepared Brucella abortus strain 19 vaccine.

Brucella abortus vaccine was prepared from strain 19 imported from Germany. The vaccine induced a good immune response in guinea pigs as evidenced by a serological titre of 328 international units (IU)/ml 10 days post-vaccination. Vaccinated guinea pigs also withstood an experimental challenge of 5,000 colony-forming units of a locally isolated virulent B. abortus strain. This vaccine, containing 7 x 10(10) viable organisms, induced a significant immune response in 8 to 10.5 month old female buffalo calves. Significant serum agglutination test (SAT) titres were seen on day 7 following vaccination. The highest SAT titres were observed on day 14 post-vaccination and the titres started declining thereafter. The rate of decrease was slow from day 14 to day 49 post-vaccination; however, a rapid decrease in titres was seen from day 49 to day 91 post-vaccination. Negligible SAT titres were observed on day 91 post-vaccination. Specific immunoglobulin G titres, as measured by 2-mercaptoethanol treated SAT, also followed a similar trend and the titre of all five of the calves that were vaccinated became zero on day 91 post-vaccination.