Whilst 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).
Brucellosis in Cattle
Bovine brucellosis or contagious abortion causes mass abortion in cattle herds. Most affected cows remain carriers and suffer continuing reproductive problems.
In Australia, Tasmania led the way in the eradication of bovine brucellosis with a rigorous test and slaughter scheme and strict biosecurity measures. Other States followed Tasmania's example and Australia as a whole is now declared free of the disease. This status is recognised internationally.
Eradication of bovine brucellosis has enhanced Australia's reputation in expanding export markets for cattle and beef products. To protect this reputation and to ensure that Tasmania remains free of this disease, any abortions in cattle should be investigated by a veterinary practitioner and serious outbreaks can be referred to the NRE Tas all hours Emergency Animal Disease Hotline 1800 675 888.
Other Forms of Brucellosis
None of the three forms of the disease as listed below occurs 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 to 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.