A complement fixation method for quantitative differentiation of reactions to 45/20 vaccine and Brucella infection

Brucella complement fixing antibodies may be titrated independently in adult vaccinated (strain 45/20) and in naturally infected cattle by serological tests utilizing a specially prepared antigen. Serum samples are subjected to the standard complement fixation test for the diagnosis of brucellosis (MacKinnon 1963) and subsequently retested by the same method but with a saline extract antigen prepared from strain 45/20 Brucella abortus. The results obtained in the two tests are compared in five specific categories of brucella reactors. An evaluation and discussion of the test method, on the basis of the results obtained, indicates that informed diagnoses can be made in parallel with a continuous adult vaccination programme.