Comparison of serological methods for the detection of B. abortus antibodies in sera from vaccinated and non-vaccinated cattle.

A total of 4551 sera from 863 Strain 19 vaccinated and non-vaccinated adult cattle, independent of disease status, were tested by five serological methods to detect the presence of antibodies to B. abortus. Results from Standard Agglutination Tube (SAT), Buffered Brucella Antigen or card (CT), Complement Fixation (CF), Enzyme Linked Immunosorbent Assay (ELISA) and Rivanol (Riv) methods were compared. There was a 95% probability for agreement among CT negative sera, between serological methods, for all groups of vaccinated and non-vaccinated cattle. The agreement between tests with Riv Positive sera, excluding the calfhood and adult vaccinated group tested by the CF method, was 91-100%. The probability of a serum which was serologically negative by other methods being Riv negative was 98%. The usefulness of serological results from Riv (greater than or equal to 1/50) tests for classifying the reactor status of cattle are of doubtful supplemental value to confirm card test positive results. Vaccination history is an important consideration when evaluating serological data on cattle sera particularly from SAT and CF methods.