Ovine brucellosis: repeated vaccination with Rev 1 vaccine and the prevalence of the disease in the Winburg district.

The effect of repeated vaccination of ram lambs with Brucella melitensis Rev 1 vaccine was studied in relation to complement fixation titres. The presence of Brucella organisms in semen and changes in neutrophil densities of the semen were also studied. A survey of the incidence of ovine brucellosis in the Winburg district on the basis of a clinical examination of rams and the complement fixation test is also reported on. Repeated vaccination of ram lambs with Rev 1 vaccine resulted in high complement fixation titres for Brucella abortus in all cases and slight Brucella ovis titres in some cases. Neither Brucella organisms, nor increased numbers of neutrophils could be found in semen samples collected from the experimental animals. The incidence of ovine brucellosis in commercial and stud flocks in the Winburg district was in the order of 2%. As a fairly high incidence of brucellosis occurred in 2 stud Döhne merino flocks where ram lambs are vaccinated with Rev 1 at weaning, the administration thereof in this breed should take place at an earlier age. A second dosage at weaning should not have any disadvantageous effects. In order to protect newly vaccinated ram lambs from contracting brucellosis from older, infected cases, the separation of age groups is essential. The incidence of clinically detectable testicular lesions in rams from the Winburg district was in the order of 2%.