Evaluation of an enzyme-linked immunosorbent assay for the detection of sheep infected and vaccinated with Brucella melitensis

Departamento de Sanidad Animal (Enfermedades Infecciosas y Epidemiologia), Facultad de Veterinaria, Universidad de Leon, Spain.

An indirect enzyme-linked immunosorbent assay (ELISA), using the lipopolysaccharide of the cell wall as an antigen, was used to detect Brucella melitensis antibodies in ovine serum. The test was carried out on 703 samples of field serums, which were also analyzed by the complement fixation (CF) test and the rose Bengal (RB) test. The ELISA results were more similar to those of the CF test (kappa = 0.89) than to the results of the RB test (kappa = 0.73). The ELISA also had high sensitivity (94.7%) and a somewhat lower specificity (90.4%). One group of 139 young brucellosis-free animals 3-6 months of age were vaccinated with B. melitensis rev. 1 at a dose of 1.2 x 10(9) live organisms. The ELISA detected a significantly lower number of reactors than the CF and RB tests (P < 0.001). The ELISA values remained below the cutoff level during the 9 months following vaccination.