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Beyond the Bale : Dec - Jan 08
By Dr Gio Braidotti Efforts to stop an incursion of sheep pox into Australia have received a timely boost with the development of a suite of advanced new diagnostic tests. The highly contagious sheep pox virus, which belongs to the capripox group that also causes disease in goats and cattle, can cause stock losses and prolonged eradication costs, and an incursion would be expected to disrupt Australia's wool trade for months. The economic consequences are considered second only to foot-and-mouth disease. The biosecurity project was prompted by a worldwide shift towards using vaccination as the prime control strategy: an approach that neglects the diagnostics and eradication techniques needed by Australia. To counter antiquated tests and a growing research vacuum, AWI inter vened to ensure that Australia's wool and livestock industries were adequately protected. Over three years to early 2007, CSIRO researchers at Livestock Industries and the Australian Animal Health Laboratory joined forces with the National Centre for Foreign Animal Diseases (NCFAD) in Winnipeg, Canada. Together the scientists developed new and quicker outbreak diagnostics and post-outbreak eradication technologies. "The stark reality was that existing tests for capripox disease were cumbersome, time-consuming, dated and deficient relative to the trade restrictions associated with an outbreak," says Dr David Boyle, CSIRO's project leader for molecular diagnostics and head of the project. "Australia really needed to enhance its diagnostic and surveillance capabilities." Capripox viruses cause serious disease in sheep, goats and cattle associated with high morbidity and mortality, especially in animal breeds with no prior exposure to the viruses. Health impacts are equivalent to smallpox in humans, causing fever, enlarged lymph nodes, skin nodules and lesions in the lungs and guts, followed by death. For Australian sheep, studies have estimated that mortality rates could reach as high as 80 per cent, with the highest death rate in young animals. Animals that recover face a prolonged convalescence resulting in the loss of at least one season's production of wool and meat. Disease transmission occurs primarily through inhalation of aerosols, although physical contact and biting insects have also been implicated in spreading disease. Since the virus persists for several months in dried scab material sloughed into wool, importing countries are expected to place bans on greasy wool from infected regions. The socioeconomic consequences associated with an outbreak saw the AWI-funded researchers keen to boost disease diagnostic capabilities, but from the outset the project faced a daunting challenge: "Although we could access the complete genome sequence of several capripox viruses, regulatory constraints in Australia prevented us from working with either the live virus or infected animals in our own laboratories," Dr Boyle says. To obtain the biomaterials needed, Dr Boyle and his colleague Dr Tim Bowden set out for Canada, where live virus and diseased animals were available at the NCFAD. The Canadian collaborators not only held a strain of sheep pox, but were able to import additional strains for laboratory studies. Over three years, the international team used the infected material they generated to create fast virus- detection systems. Requiring just three to four hours to process upon receipt of samples, the new diagnostic test is based on DNA technology and the polymerase chain reaction (PCR) technique. Confirmation of test results is achieved using electron microscopy to examine virus morphology and virus cultivation in cell culture. For ongoing surveillance and the re-establishment of Australia's disease-free status, serological tests using antigen specific for capripox viruses have been developed. Each technique is less cumbersome and more precise than previously available tests. "We are now in a far better position to respond to a suspect case of capripox diseases in sheep, goats and cattle," Dr Boyle says. That means the ability to respond to an incursion without resorting to using the vaccine, a tactic that would confound efforts to eradicate the virus. ú More information: Dr David Boyle, firstname.lastname@example.org New tests strengthen biosecurity fence Biotechnology has been successfully applied to improve defence against a virus capable of severely disrupting trade in Australian wool Internet joins fight against lice 8ANIMAL HEALTH BEYOND THE BALE Feedback from growers has helped a team of pest- management experts from across Australia to compile best- practice information about lice treatments into a decision- support tool that is accessible through the internet. Called LiceBoss, the computer tool aims to help with tricky lice-management issues while providing cost-benefit and chemical residue estimates that are associated with different treatment strategies. Heading the development team on the AWI-funded project is Dr Peter James from the Queensland Department of Primary Industries and Fisheries (QDPI&F).The multi-state project also saw the involvement of Dr Brian Horton from the Tasmanian Department of Primary Industries and Water, Dr Di Evans from the Department of Agriculture and Food, Western Australia, and Dr Noel Campbell, formerly of the Victorian DPI. The scientists have pulled off a tremendous feat, integrating information across the spectrum of lice-control issues and producing a set of queries that guide the user through a minefield of inter-related risks, costs and benefits.To facilitate access, the database is divided into modules dealing with lice eradication in short wool, treatment in long wool, and strategies for pregnant ewes or ewes with lambs. Throughout the development process, programmers never lost sight of on-farm realities, so that a support module is available covering the spectrum of registered lice-control products. A further tool is included that monitors the chemical residue impacts of various treatments, which is particularly valuable when aiming for residue-sensitive wool markets. Choices made when working through LiceBoss can be further tested with the Treatment Assessment module. This checks the probability of achieving eradication from an on-farm treatment and provides suggestions for improving treatment technique and efficacy. There is also a Rubbing Assessment tool, to determine whether rubbing is likely to be due to lice or other causes, which feeds into a way of estimating lice numbers by simply considering the amount of rubbing and fleece biting. Complementing the tools is the Lice Info area containing the latest information about the economic impact of lice, chemical resistance and residues, in addition to on-farm biosecurity measures to prevent lice infestations. (Top) a sheep infected with a capripox virus. (Above) CSIRO researcher Dr David Boyle has headed a project that has created fast-detection systems for capripox diseases. PHOTOS: CSIRO
Oct 07 - Nov 07
Feb - Mar 08 Supplement