Evaluation of serologic testing of rams in the management of Brucella ovis in a domestic sheep flock.

Brucella ovis is a bacterial pathogen present in most major sheep-producing regions of the world. The pathogen is associated with ram infertility, decreased ewe conception rates, and premature lambs. Twenty ELISA seropositive or indeterminate rams were culled from a B. ovis-positive flock, and donated to the Wyoming State Veterinary Laboratory for evaluation of infection. Tissues from each ram were collected at autopsy for additional testing, including bacterial culture, PCR, and histopathology. Of 17 seropositive rams, 11 rams were also positive by culture and PCR, and had evidence of mild histologic lesions; 1 seropositive ram was positive by culture with mild histologic lesions, but negative by PCR. Five seropositive rams were negative by culture and PCR and had no histologic lesions. Three indeterminate rams were negative by culture and by PCR and had no histologic lesions. The tissues in which B. ovis was most often detected included the epididymis, vesicular gland, and ampulla. Although this was a small study, the observation that 5 of 17 (29%) rams that were initially seropositive had no evidence of infection is interesting. A convalescent test for valuable seropositive animals prior to culling may be useful, and reproductive tissues may be evaluated postmortem if confirmatory testing is desired.