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22 September 1998 |
Ref 98/224 |
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An innovative test developed by CSIRO scientists at the Australian Animal Health Laboratory (AAHL) has allowed the speedy diagnosis of the recent Newcastle disease outbreak at two NSW poultry farms.
The tests also showed that the Sydney outbreak is due to an unusually virulent strain of virus.
According to CSIRO's Dr Peter Daniels, researchers at AAHL use a number of techniques to complement the standard international test, which gives greater confidence in the diagnosis and yields more information about the virus strain.
Newcastle disease viruses are present in most countries including Australia, but serious disease causing strains have not occurred in the country since 1932, says Dr Daniels. A fast and accurate diagnosis is critical to the control of any disease outbreak.
A test to show the strength (or virulence) of the Newcastle disease virus, developed by AAHL scientists in the early 1990s, involves examining the membrane surrounding an egg under a microscope.
"The first step involves infecting an egg in the laboratory with the suspect samples from the outbreak," says Dr Daniels. "After the virus has multiplied in the egg, the egg membrane is washed with a special fluorescent chemical that attaches itself only to the Newcastle disease virus. A mild form of the virus will only be seen in the top surface of the membrane. However the more virulent strains will penetrate all levels of the membrane."
Another test involves reading the unique genetic fingerprint (or genetic sequence) of the virus to determine whether it is a virulent strain, or the usual, milder (non-virulent) strain usually seen in Australia. Results of this test also show the disease strain is more virulent than the strains normally found in Australia.
Dr Daniels explains that the primary role of AAHL is to support State animal health laboratories in the diagnosis of foreign (exotic) or emergency animal diseases.
"A great deal of effort and resources goes into ensuring we are prepared for animal disease outbreaks. Our strategy has been to develop a suite of fast and accurate tests for each of the most important animal diseases, such as Newcastle disease," Dr Daniels says.
AAHL has isolated virulent Newcastle disease virus from two separate properties in NSW. Further test results to confirm the degree of virulence will be provided to NSW Agriculture this week. At this stage there is no evidence that the disease is spreading.
Media information:
For information about the response to the Newcastle
disease outbreak in NSW,
contact Col Begg on 02 6391 3312.
For information about the diagnostic capability of CSIRO's
Australian Animal Health Laboratory (AAHL) and a fact sheet,
contact Emma Homes on 03 5227 5123 or
Dr Peter Daniels on 03 5227 5272.
(Australia's largest scientific research organisation)
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