Ovine Brucellosis

10th August 2018

In recent months we have diagnosed Ovine Brucellosis within a number of local flocks. This increase in brucellosis has been reported to be occurring across a wide area of NSW in the past 6-12 months.

Ovine Brucellosis is a bacterial infection (Brucella ovis) which typically localizes in the testes of infected rams. The disease is generally maintained within a flock by infected rams and is spread from ram to ram either directly or via ewes served by multiple rams. Once a ram has become infected he will remain infected for life and within a few months the infection will start causing testicular abnormalities and will start to reduce the ability to produce sperm.

The serving of a ewe by an infected ram will cause a transient uterine infection that is generally cleared by the ewe’s immune system after a period of time. However it is thought that a small percentage of infected ewes may not be able to completely clear the infection and may act as carriers for a much longer time frame.

Brucellosis typically results in reduced conception rates due to a combination of ram infertility (when large numbers of rams become infected) and poor embryo attachment in ewes with a transient endometritis (inflammation of the uterine lining). On rare occasions it has also been implicated in late term abortion outbreaks. This highlights another benefit of scanning ewes for pregnancy – being able to differentiate between poor conception rates (low scanning percentage) and late term abortions/poor lamb survival (adequate scanning rates but low marking rates).

The properties on which we have diagnosed the disease have typically been well run operations with reasonable biosecurity measures whom only buy rams from Ovine Brucellosis Accredited studs. Where the disease has entered some of these flocks has been difficult to determine but the most likely sources of introduction include stray infected rams/ewes or buying infected rams or teasers (particularly from sale yards).

In some instances, producers have been alerted to a potential problem through poor scanning rates and investigations have revealed brucellosis in their ram flocks. However there have been several occasions on properties with no noted issues where routine palpation has discovered rams with testicular lesions which have then been confirmed to have brucellosis with blood testing – emphasizing the importance of regular screening of ram flocks to catch any outbreaks early before fertility issue arise.

Screening of ram flocks typically involves scrotal palpation of all rams to identify any with testicular lesions which may be very subtle in the early stages of disease. Any rams with lesions are then bled and tested for brucellosis for confirmation/exclusion of the disease. In smaller ram flocks (<15-20 rams) it may be easier to bleed all rams whether lesions are present or not.

Please do not hesitate to call the clinic on (02) 6377 1258 if you would like to palpate your ram flocks or if you want to discuss brucellosis in general.