Ovine Brucellosis - time to check your rams

By Dr Sarah Maher - District Veterinarian, Dubbo

July 2020

Ovine brucellosis, we’ve all heard about it, we all know it causes ram infertility, but do you know enough to protect your business?

What is it?

Ovine brucellosis is an infection of the reproductive tract caused by the bacteria Brucella ovis. It causes infertility in rams and less commonly abortion in ewes. It is a disease of significance due to the economic loss experienced through low lamb marking percentages, prolonged lambing periods and ram wastage. Brucellosis is reported to have a prevalence of up to 30% in some areas of NSW.

How is it spread?

Infection is generally introduced to a flock through the introduction of infected rams, or through purchased or straying sheep. Brucellosis is spread when a clean ram mates with the same ewe as an infected ram mate. It can also be spread between rams through sodomy.

What are the effects?

Once infected B. ovis causes inflammation of the male reproductive organs which results in partial or complete sterility. This most commonly presents as lesions in the tail of the epididymis but can occur in the testicle or head of the epididymis. Palpable lesions occur in 40% of rams infected with brucellosis and is often one of the first signs of a problem. A blood test is required to confirm suspicion of brucellosis.

Treatment and management options

There is no treatment for brucellosis and flocks diagnosed with brucellosis are encouraged to undertake an eradication program to reduce economic impacts and risk to neighbouring flocks.

Infected rams become carriers for life and are a constant source of infection while ewes are only transiently infected and generally clear the infection after two cycles (~ 35 days). As such eradication is designed around culling infected rams and allowing adequate time for the ewe to clear the infection before joining. Practically this looks like ensuring the ewes don’t encounter rams for 4 months post lambing (because ewes don’t begin cycling as soon as they lamb) and isolating any purchased stock ewes for at least 35 days before introducing rams.

Consider performing a reproductive examination

While winter is not a time people tend to think about their rams, it is the perfect time to perform a reproductive examination which should include the four T’s – teeth, tossle, toes, testes. The most important part of this examination in winter is examination of the testes for lesions as this allows enough time for abnormalities to be detected and an investigation and eradication program to be undertaken before the next joining.

While brucellosis lesions can occur anywhere, the most common site of lesions is the tail of the epididymis. Both testicles should be pulled down and the cord running between the testicle and the body of the ram should be palpated between the thumb and forefinger. Palpation in normal years is just as important as this helps you to differentiate between normal and abnormal structures, in order to address them appropriately.

Preventative measures

Measures that can be taken to prevent the introduction of brucellosis into your flock include:

• Only buying in rams from studs that are accredited with the NSW Ovine Brucellosis Accreditation Scheme. Do not assume that all studs are accredited, always request to see their accreditation.
• Prevent strays and ensure all boundary fences are sound.
• Avoid purchasing rams from the saleyards
• If buying rams that are not accredited, quarantine rams on arrival and have them blood tested to exclude brucellosis after 60 days.
• Examine rams at least three months before joining every year to ensure they are sound.

For more information contact Central West Local Land Services Animal Health team on 1300 795 299.