Laboratory Diagnosis of Brucellosis

Abstract

This chapter addresses the different methods used to diagnose brucellosis. Rapid diagnosis of the disease is essential for its control and to protect public health. Basically, there are two types of tests, the direct tests, which detect the presence of Brucella and are used in clinical situations where the animals are affected and show clinical signs, and indirect tests that are mainly used for screening to detect subclinical conditions. These are widely used as part of control and eradication programs. Main aspects of direct tests are described, namely bacterial isolation and identification and molecular methods: conventional and real-time PCR, multiple locus variable-number tandem repeat analysis, multi-locus sequence typing and luminex xMAP technology. Regarding indirect tests, serological tests are prefered: milk ring test, buffered Brucella antigen tests, namely rose Bengal test and buffered plate agglutination test, serum agglutination test, complement fixation test, indirect and competitive enzyme-linked immunosorbent assays, fluorescence polarization assay, immunoprecipitation tests and lateral flow immunochromatography. Another indirect test, interferon-gamma release assay, performed on whole blood and brucellin skin tests are discussed. Concerning sensitivity (DSe) and specificity (DSp) of the methods, none of the tests are Brucella species-specific, but some of those, specifically the buffered agglutination tests, set a high standard with regards to the DSe/DSp. Although no current serological test provides enough DSe for the 100% DSp required, some test combinations can be of great help.