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What is it?
Surra is a chronic wasting disease caused by trypanosomes —single-celled blood parasites related to the organisms that cause sleeping sickness. The disease, which is spread by biting flies, is most severe in horses, donkeys, mules, deer, camels, llamas, dogs and cats, but also occurs in cattle, buffaloes, sheep, goats, pigs and elephants.
Where is it found?
Surra is present in northern Africa, the Middle East, some areas of the former Soviet Union, the Indian subcontinent, China, Southeast Asia (as far east as Timor) and South America. Surveys have shown evidence of infection in Papua Province of Indonesia in cattle imported from other parts of Indonesia.
Surra was diagnosed in a consignment of imported camels at Port Hedland, Western Australia, in 1907. These animals were destroyed and there has been no further evidence of the disease in camels or any other species in Australia.
What are its effects?
Surra is usually fatal in horses, donkeys and mules. The incubation period varies from five to 60 days, depending on the strain of parasite and the degree of stress to the animal.
Clinical signs in horses, donkeys and mules include fever; haemorrhages of the eyelids, nostrils and anus; skin rashes; weight loss; anaemia; and jaundice. There may also be oedema (swelling) of the legs, brisket and abdomen. Death can occur within two weeks in acute cases, but can take up to four months in chronic cases. Acute disease in camels is clinically similar to that in horses but chronic disease is more common, leading to wasting and anaemia.
Surra is frequently chronic in cattle and buffaloes; death may occur up to six months after the onset of signs, but most animals recover and become carriers.
The disease is usually acute and fatal in dogs and cats; dogs sometimes show nervous signs that can be confused with the symptoms of rabies.
What are the risks to Australia?
Surra would be difficult or impossible to eradicate if it were to become established in Australia because it could persist in feral animals such as horses, donkeys, deer, camels, buffaloes, goats and pigs. Control of the disease in livestock could cost cattle, sheep and horse industries millions of dollars.
Recent scientific studies have demonstrated that kangaroos, agile wallabies and pademelons are highly susceptible to infection with surra, which in experimental conditions causes acute clinical signs with high mortality. These findings suggest that surra could also have a significant effect on some native Australian marsupials.
21 Jun 2013