A brief review of diagnosis of bovine brucellosis by detection of antibody

Brucellosis has been presumptively diagnosed by serological testing since 1897. The early test used, the agglutination test, was found to be of low specificity. Attempts to decrease the nonspecific reactions was made by physical treatment of the test serum, addition of reducing agents to the serum and acidifying the antigen. All these treatments destroyed or inactivated macroglobulins, the cause of false agglutination reactions. Because of its sensitivity, ease of performance and low cost, modified agglutination tests are still widely used for both screening and to a lesser extent for confirmation of antibodies to Brucella abortus. To compensate for the relatively low specificity of the agglutination tests, confirmatory tests were developed. These tests included the complement fixation test and precipitation tests both of which provided higher specificity. These tests, however, while technically cumbersome, expensive and slow, were suitable for use as confirmatory tests after screening with an agglutination test. Primary binding assays were introduced because they do not have most of the shortcomingss associated with the conventional serological tests. Initially, primary binding assays and in particular the indirect enzyme immunoassay, proved to have a series of other problems, including relatively low specificity, high cost and technical problems especially with the high reagent dilutions used. The latter problem was overcome to a large extent by providing the assay in a kit form which also allows standardization of the assay on a large scale. The former problems have been overcome by introduction of mass-produced, better reagents and introduction of different assay formats such as the competitive enzyme immunoassays. Will the primary binding assays replace the conventional tests for brucellosis? Increased test accuracy, extensive standardization of assay procedures and reagents, better validation procedures, better quality control, cost reduction, the ability to differentiate between vaccine and field strain induced antibody and increased acceptance will undoubtedly lead to extensive use of primary binding assays.