THE EFFECT OF CALFHOOD VACCINATION WITH STRAIN 19 ON THE SEROLOGICAL DIAGNOSIS AND ERADICATION OF BOVINE BRUCELLOSIS

Data from 42,224 cattle from 694 herds collected during the brucellosis eradication campaign were used to examine the effects of calfhood strain 19 vaccination. The prevalence of infection in vaccinated herds was 1.8% compared with 9.1% in non-vaccinated herds (p< 0.005). The mean titre in the former group was lower (p< 0.001). Vaccinated herds required 3.3 herd tests to achieve a provisionally free status compared with 4.8 in non-vaccinated herds (0.001 < p < 0.005). Vaccination did not significantly reduce the number of herd tests in herds with less than 100 breeding females. In tests after the initial herd test only 0.5% reactors were found in vaccinated herds compared with 6.9% in non-vaccinated herds (p< 0.005). There were 0.9% false positive to the Rose Bengal plate test in non-vaccinated and 2.1% in vaccinated animals (p< 0.005) in non-infected herds. In infected herds this percentage was 3.0% and 4.2% respectively by (p< 0.05). In the non-infected herds there were 0.04% false positives to the complement fixation test out of 10,506 non-vaccinated cattle tested and 0.2% out of 24,734 vaccinated cattle.