Ovine brucellosis (OB) is a bacterial disease of sheep that causes infertility in rams, resulting in low scanning or lambing percentages. OB is caused by the bacterium Brucella ovis. Usually, infection spreads between rams through homosexual behaviour.
Ewes rarely become infected, but can infect clean rams by exposing them to infected semen in the vagina from a recent mating. The lesions of OB can be palpated in the testes and epididymis of infected rams during pre-joining checks of rams. Infection causes inflammation and swelling of the tail of the epididymis; testes can be swollen or shrunken, and may feel hard or irregular on palpation.
OB can be eradicated from your flock by using a blood testing and cull program. Once your flock is free, monitoring through pre-joining checks of rams is vital to maintaining an OB-free flock.
Victoria has a voluntary accreditation scheme for ram breeders. OB-free accreditation requires two successive negative blood tests of all rams at an interval of not less than 60 days and not more than 180 days, and then routine testing of the ram flock. Contact your Agriculture Victoria office for further information on OB accreditation.
Purchasing replacement rams from OB-free accredited producers reduces the risk of OB entering your property. Other biosecurity measures, such as good boundary fences, quarantining new introductions and requesting a National Sheep Health Statement from the vendor, help to maintain a clean, healthy flock.
If you think your flock may have a problem with OB, please contact your private veterinarian or local Agriculture Victoria office for further information.
Rachael Holmes, District Veterinary Officer, Agriculture Victoria Bendigo