Brucella abortus infection in the bull

Observations on 2 bulls from a brucella-infected property are reported. Bull 1 gave serological reactions to Br. abortus in both the SAT and CFT from day 0 to day 141. Br. abortus was not recovered from semen and the bull remained clinically normal. The serological status of bull 2 changed from negative to positive to negative over a 203 day period and remained negative for a further 74 days. Semen agglutinins were only detected on one occasion (20 iu). The first clinical sign observed was epididymitis followed by orchitis, which became apparent on day 122. Br. abortus was not recovered from semen but at autopsy, on day 363, Br. abortus biotype 1 was isolated from the right seminal vesicle and ampulla. The histology of the lesion is described. The literature relating to Br. abortus infection in the bull is discussed. Recommendations are made regarding the diagnosis of Br. abortus infection in bulls.