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| Brucellosis in SheepWhilst most farmers know brucellosis means trouble, many are unsure of the exact nature of the disease. Brucellosis is the name given to the disease caused by the Brucella family of bacteria.
There are five Brucella bacteria each causing a different form of the disease.- Brucella abortus - affects cattle, causing bovine brucellosis (contagious abortion) - sometimes affects horses, causing fistulous withers.
- Brucella ovis - affects sheep, causing ovine brucellosis.
- Brucella melintensis - mainly affects female goats, causing caprine brucellosis - can also affect female sheep.
- Brucella suis - affects pigs, causing swine brucellosis - it has also been isolated from horses.
- Brucella canis - affects dogs, causing canine brucellosis.
The Brucella diseases occur throughout the world and, excepting ovine brucellosis, are zoonotic, that is they can be spread from animals to humans.
Brucellosis in humans caused by Brucella abortus was known as undulant fever in Australia, before this disease was eradicated. It is an occupational disease of people who work with animals, such as veterinarians, farmers and abattoir personnel.
In animals the Brucella bacteria localise and multiply in the reproductive organs. In males this often results in reduced fertility. Pregnant females can suffer abortion, stillbirth or early death of the offspring when the uterus becomes infected.
The disease can spread to other animals if they eat infected afterbirth, fluids or any contaminated feed.
Brucella bacteria can also localise in mammary glands, (infecting milk) and in limb joints (causing arthritis).
Ovine brucellosis mainly affects rams, causing lesions in their reproductive organs.
Affected rams develop hard, abscess-like swellings in the epididymis, which is closely attached to the testicles, particularly at the lower end. These lesions are most noticeable because they are so much harder than the rest of the epididymis and also because the swellings are irregular in size making one epididymis feel quite different in shape from the other. Normally, there is no significant difference in shape between a pair of epididymii. Rams may become permanently infertile.
The disease is transmitted at joining when a clean ram serves a ewe that has recently been served by an infected ram in the same cycle. Rams can also transmit the disease between themselves through homosexual activities. Ewes although fairly resistant to the disease, can be carriers of the infection for extended periods, resulting in abortions and discharge of the organism in the placenta, vaginal discharges and the milk.
Ovine brucellosis is not known to cause disease in humans.
The Department of Primary Industries and Water in conjunction with veterinary practitioners and industry, has developed a voluntary ovine brucellosis accreditation scheme to control the disease in Tasmanian flocks. Accredited private veterinary practitioners carry out the work and the Department keeps the records.
Before the flock can be accredited as being ‘free of ovine brucellosis’ all rams and teasers over six months of age must be blood tested twice and found negative on both occasions. The interval between the two tests must be between two and five months and with a third test twelve months later. For a flock to maintain an ‘ovine brucellosis free’ status, all rams eligible for testing must be reassessed every two years once the flock has had three clean initial tests. Rams introduced from non-accredited flocks must be isolated for six weeks and then pass a blood test before joining the rest of the flock.
A print friendly PDF version of the Ovine brucellosis Accreditation Scheme Schedule is attached below for downloading. This document contains information on accreditation requirements and application forms.
This is a Portable Document Format (PDF) file and requires the use of Adobe Acrobat Reader. The Reader is easy to download and is free of charge.
Further information about the scheme is available from the Department of Primary Industries and Water on 1300 368 550 or private veterinary practitioners.
None of the three forms below of the disease occur in Tasmania.
Swine brucellosis is a disease that affects reproduction in pigs. Although abortions are unusual, stillbirths are common and young piglets born with the infection have a high mortality. The disease appears to be confined o the north of Australia, occurring mainly in Queensland.
Canine brucellosis causes abortions and infertility in dogs. It does not occur in Australia but has been reported in all the other continents except Africa. Dogs from the UK must be tested for canine brucellosis and found negative before they can be imported into Australia.
Caprine brucellosis causes abortion and udder infection in goats and sheep. The disease does not occur in Australia but it is common in the Mediterranean region, Asia and Latin America. The bacterium responsible can also infect humans, causing Malta Fever. Human infection usually occurs from consuming contaminated milk, milk products or uncooked meat.
Horses occasionally become infected with Brucella abortus, and Brucella suis, and the problem is then called fistulous withers. Chronic draining abscesses occur, usually in the withers region (above the shoulder), and surgery may be necessary to completely clean up the infection. Because Brucella abortus is involved there is an added risk that the infection can be transferred to humans or other animals, especially cattle. In Australia, however, horses are free of Brucella abortus bacterium because of the eradication program for bovine brucellosis.
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