Evaluation of a radial immunodiffusion test for diagnosing brucellosis in sheep and its possible value for differentiating infected from Brucella melitensis REV 1 vaccinated sheep.

The efficiency of 4 serological test: Rose Bengal (RB), complement fixation (CF), gel diffusion (GD) and radial immunodiffusion (RID) for diagnosing Brucellosis in sheep was compared. RID and CF were also used to evaluate sheep serological response following REV 1 vaccination. Crude smooth lipopolysaccharide (LPS-S) and Polysaccharide B antigens obtained from B. melitensis 16 M were used in GD and RID tests respectively. In experiment 1, two hundred and sixty five sera from adult unvaccinated sheep were studied. The animals used belonged to 4 different flocks, in which was bacteriologically proved the existence of B. melitensis infection. RB positive reaction was obtained in 122 sera being 100, 87 and 91 of these, positive to CF, GD and RID respectively. In experiment 2, one hundred and one ewes from 5 to 10 months of age (and CF negative) were subcutaneously inoculated with 2.10(9) viable Rev 1 organisms. All animals were bled at 1, 2, 5, 10, 20, 24, 28 and 52 weeks after being vaccinated, and their serological response to CF and RID tests was studied. The percentage of CF reactors between the 24th and the 52nd weeks decreased from about 30% to less than 8%. The RID reactors in weeks 24 and 52 were 1% and 0% respectively when a concentration of 15 micrograms of Polysaccharide B per ml of gel was used.