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

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

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.

Identification and diagnosis

Testicles should be firm and springy on palpation with no abnormal lumps and with scrotal circumference above 28cm. 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

An integrated approach to prevent ovine brucellosis should consider the following:

• only purchasing sires with an animal health statement from studs accredited as OB-free

developing and implementing a farm biosecurity plan

• if not purchasing from accredited studs, keep newly purchased rams separate and test prior to mixing with your flock

• keeping rams in small groups with the younger and older rams separated

• isolating rams from ewes until their disease status is established as ewes can spread OB

• palpating ram testicles to check for lumps prior to purchasing and before joining

• seeking veterinary advice if you notice lower lambing percentages, longer lambing periods or abnormal lumps in the testes

• establishing the OB status of your flock before introducing OB-free sires and maintaining ram-proof fences to avoid visits from your neighbours’ rams.

 

Ovine Brucellosis Testing

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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.

Most States have a voluntary accreditation scheme for ram breeders, which is also recommended by the ASSBA. OB-free accreditation requires two successive negative blood tests of all rams over the age of six months, at an interval of not less than 60 days and not more than 180 days, and then routine testing of the ram flock.

The first phase of the Brucellosis Accreditation Scheme is to have your property inspected by a Department of Agriculture Animal Health Officer, which includes a check of the boundary fences and waterways of the paddocks where the rams are housed. Once that is approved, testing of every ram over the age of six months, on the property is performed by an accredited Vet. This includes a blood test and a check of the rams’ scrotums. A negative test result is followed up with a second test at not less than 60 days and not more than 180 days from the first test. A second negative test gives the farm its accreditation. The next test is required within twelve months of the second test, and tests all rams, over the age of six months, on the property, that have been used or will be used at any time in the future. After three annual negative tests, testing is undertaken every two years. Further information can be obtained from your Dept. of Ag. Animal Health Officer.