FURTHER OBSERVATIONS ON THE INCIDENCE OF BRUCELLOSIS IN DAIRY CATTLE IN VICTORIA

Random blood sampling of 8,448 dairy cattle in two Shires of Victoria revealed that 194 (4.5%) serums, from south-eastern Victoria and 147 (3.6%) serums from northern Victoria were positive to the International tube agglutination test for Br. Abortus . Of these reactions at least 82 (1.9%) and 56 (1.4%) of the serums indicated that these animals were or had been infected with Br. Abortus .
The results show that 65% and 73% of the herds in the two areas did not contain Br. Abortus infected cattle. Two factors influenced the incidence of infected animals in herds. First the incidence of infected animals decreased with increasing length of time during which herd re-placement calves had been vaccinated with Br. Abortus strain 19. Second, the introduction of mature previously calved cows increased the incidence of infected animals.
Some discussion is given to the usefulness of the revaccination of animals and the control of brucellosis in Victoria with is possible effect on cattle meat export markets.