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UNE leads world in practical control of chicken virus

June 01, 2005

Walkden-Brown thumb.jpgMost of the one million chickens that Australians eat every day are vaccinated against the virulent Marek’s disease virus. This “blanket” vaccination strategy could be about to change.

Research at The University of New England has paved the way for “tactical” rather than “blanket” vaccination against the disease, a development that would enable Australian producers to save millions of dollars a year in vaccination costs. This saving by producers should lead, then, to reductions for consumers in the price of chicken.

The research team led by UNE’s Associate Professor Steve Walkden-Brown has developed a simple and inexpensive test that can detect the presence of the Marek’s disease virus in a poultry-farmer’s shed, identify the strain, and indicate the severity of the problem by measuring the number of copies of the virus in the sample. The beauty of the test is that it can do all this simply by analysing a sample of dust from the shed.

The ability of the test to quantify the presence of the virus in poultry shed dust is the researchers’ most recent and, according to Dr Walkden-Brown, most groundbreaking achievement. “Now you can collect a dust sample from your shed, send it in the mail to UNE, and we’ll tell you how many copies of the virus there are in it,” he said. Two Australian poultry companies are already using the test which, when fully commercialised, will probably cost between $50 and $80.

Previously, the only way to test for the presence of Marek’s disease involved the killing of a number of chickens from each shed, rapid transport to a laboratory, and very complicated and expensive virus isolation procedures based on cell culture. “Because of the cost and difficulties associated with such testing, it was not done at all,” Dr Walkden-Brown said. “In the absence of information about the presence and abundance of the virus, producers have often resorted to a conservative approach of blanket vaccination to control the disease. While vaccination is, generally speaking, an excellent way to control disease, in the case of Marek’s disease there is good evidence that the virus has evolved towards greater virulence in response to blanket vaccination.”

Marek’s disease, a viral infection that eventually causes tumours in chickens, is a disease of major concern to the international poultry industry, costing the industry between $US1 billion and $US2 billion a year, mostly in vaccination costs. “Blanket” vaccination of broiler chickens in Australia began about a decade ago, following the large-scale introduction of new poultry strains from abroad that proved to be highly susceptible to the disease and that were not protected by the available Australian vaccines.

Dr Walkden-Brown (pictured here in the Chicken Isolation Unit at UNE) arrived at UNE at the end of 1995, at the height of the Marek’s disease epidemic. In 1996 he began collaborative research with Dr Peter Groves of Baiada Poultry Pty Ltd. This developed into a three-year project (1998-2000), funded by the Australian Research Council (ARC), that succeeded in improving the diagnosis and control of the disease. The diagnostic tests developed during that project have been successfully transferred to the poultry industry.

“We found that we could extract DNA and test for the virus in samples of dust from poultry sheds,” Dr Walkden-Brown said. “The problem with those tests, however, was that they provided simply a yes/no answer. They gave no indication of the quantity of the virus present. A further ARC-funded project (once again in collaboration with Baiada Poultry) has resulted in the new test that can quantify the viral presence in a dust sample. “This has enabled DNA testing for Marek’s disease on an industrial scale,” Dr Walkden-Brown explained.

The availability of this test, and research by Dr Walkden-Brown and his colleagues indicating that some regions of Australia are free of Marek’s disease, allows a new approach to managing the disease. “The industry can now move away from a strategy of suppressing Marek’s disease by vaccinating every bird in the major poultry-producing regions of Australia,” he said. “It could, instead, monitor for the disease on a farm or regional basis, and vaccinate only where necessary. We’ve developed a routine monitoring system that will allow managers to make decisions from a position of knowledge rather than a position of ignorance.

“Our research group, with its combination of veterinarians, virologists and molecular microbiologists, appears to be the only group in the world to develop this approach to managing Marek’s disease to the point of practical application. I firmly believe this is the way the disease will be managed world-wide in two or three years’ time.”


Media contact: Associate Professor Steve Walkden-Brown, School of Rural Science and Agriculture, UNE (02) 6773 5152 or Jim Scanlan, Public Relations, UNE (02) 6773 3049.

Posted by Jim Scanlan at June 1, 2005 11:34 AM