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Ovine Brucellosis

Diagrammatic illustration of ram's major reproductive organs
Reproductive organs of the normal ram
Illustration courtesy of the NSW Department of Primary Industries

Comparison of normal and infected ram testicle
On the left, a normal ram testicle and epididymidis. On the right, a testicle and epididymidis of an infected ram. Note the enlarged epididymidis, and the shrunken testicle.
Illustration courtesy of the NSW Department of Primary Industries

Ovine brucellosis (OB) is common in many sheep flocks across the state. In Crookwell, it is now less common due to the uptake in most studs of the Ovine Brucellosis Accreditation program, but care should still be taken to ensure rams are purchased only from accredited flocks.

All CVH vets are approved to test and accredit flocks through the Ovine Brucellosis Accreditation Scheme.

The disease

The causative organism, the bacterium Brucella ovis, is found in the semen of rams and causes epididymitis leading to ram infertility and sterility – sometimes in more than 50% of the rams in an individual flock. In ewes, the organism is found in foetal fluids and mammary glands (it can pass to lambs in the milk) and will cause abortion in a small percentage of ewes. Rams are primarily infected by exposure to infected semen (male to male sex) or less commonly, via vaginal discharges from infected ewes (following OB abortion). The economic costs can be significant, and there are three key factors that point to OB infection in a flock:

  • ram wastage
  • low lamb-marking percentages
  • extended lambing seasons.

Lesions occur in the testes, epididymides and accessory sex glands of infected rams. Palpation of testicles and the tail of the epididymides is critical to detection of OB, although some rams can be infected without obvious lesions. In a normal ram, the testicles and epididymides should feel even and symmetrical, with no obvious lumps or thickening. Refer to the image below, showing definite enlargement of one epididymidis, with the testicle on this side obviously shrunken. Be aware there are other causes of epididymitis, including Actinobacillosis.

Diagnosis of ovine brucellosis

Detecting OB in rams involves a combination of blood tests and palpation, but note that in some rams, the blood test may not be positive until 7 weeks after infection.

Eradication of OB

An eradication program includes:

  • A cull of all rams with epididymitis or other testicular abnormalities.
  • Blood tests for all remaining rams on the property (and selling for slaughter all rams testing positive).
  • Repeating the blood test in 60 days – it’s essential 2 consecutive negative tests are obtained (noting it can take up to 7 weeks for infection to test positive).
  • Keeping young rams segregated from older rams, and ensuring ram paddocks are secure from neighbouring rams.
  • Avoid running rams with lambing ewes – infection can be picked up easily if an infected ewe aborts.
  • Avoid buying rams from saleyards and make sure new rams come from properties free from OB – ie, they should be part of the NSW Ovine Brucellosis Accreditation Scheme. If in doubt, isolate for 60 days and blood test before introducing into your flocks.
  • Keep segregated for at least 60 days any rams returning from shows or sales, and blood test to ensure they are negative. Rams in shows and sales that are restricted to rams from OB-free flocks should not require these precautions.

For more detail, refer to ovine brucellosis information on the NSW Department of Primary Industries website.