Evaluation of the currently used diagnostic procedures for the detection of Brucella melitensis in sheep

A study was conducted to determine whether the use of the enzyme-linked immunosorbent assay (ELISA) improves detection of brucellosis in individual sheep. Sera from 132 sheep that aborted due to B. melitensis were used to assess the efficacy of the ELISA to detect brucellosis in sheep. ELISA results were compared with those of the serum agglutination test (SAT), complement fixation test (CFT), Rose Bengal Plate test (RBPT) and the skin delayed-type hypersensitivity (SDTH). Sera from 11132 sheep free from brucellosis were tested with the ELISA to determine its specificity. The results show little difference in diagnostic efficacy between SAT, CFT, RBPT and the SDTH test, although the skin test indicated infection in some seronegative sheep. A combination of CFT and SAT, or CFT and RBPT, or CFT and SDTH tests indicated brucellosis in 75-88% of the infected animals, whereas the ELISA indicated infection in 97-100% of those animals. Seventeen (0.2%) from the 11132 negative sheep sera tested positive with the ELISA, indicating a 99.8% specificity. We concluded that screening sheep for brucellosis with ELISA improves Brucella diagnosis, and in areas of low prevalence it will help to maintain flocks of sheep free from brucellosis