Ovine Brucellosis

Ovine Brucellosis (OB) is a bacterial disease confined to sheep, characterised by infertility in rams. Infected rams produce semen of lower quality, making them sub-fertile or sterile and the effect on flock fertility depends on the percentage of infected rams and flock breeding management.

The effects of OB are often unrecognised, especially where marked fluctuations in fertility occur for other reasons.

Identifying and diagnosing ovine brucellosis

Testicles should be firm, springy on palpation with scrotal circumference above 28cm with no abnormal lumps on palpation. The lumps caused by OB are generally in the lower part of the testicle.

If your rams have abnormal lumps on their testicles, get a blood test to check for ovine brucellosis.

Prevention strategies for ovine brucellosis

  • Purchase sires only from studs accredited as OB-free.
  • If not purchasing from accredited studs, keep newly purchased rams separate and test prior to mixing with your flock.
  • Keep rams in small groups with the younger and older rams separated.
  • Ewes can spread OB so keep rams isolated from ewes until their disease status is established.
  • Palpate ram testicles to check for lumps prior to purchase and before joining.
  • Seek veterinary advice if you notice lower lambing percentages, longer lambing periods or abnormal lumps in the testes.
  • Establish the OB status of your flock before introducing OB-free sires and maintain ram-proof fences to avoid visits from your neighbour’s rams

More information


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