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Exotic disease research in Australia
Br. vet. J . (1989) . 145, 1
PERSONAL VIEWPOINT EXOTIC DISEASE RESEARCH IN AUSTRALIA Australia enjoys a freedom from many major exotic diseases, which permits it to retain a competitive position internationally (about 10% of Australia's export earnings come from livestock products) . However, this freedom is under constant threat with the increasing volume of all forms of international traffic . The Australian government has built a laboratory .a t Geelong in Victoria, for carrying out work on exotic diseases, including diagnosis, research, training and vaccine development and testing . The laboratory incorporates sophisticated facilities for microbiological containment . Since the commencement of activities in 1984, programmes of research have been developed which are directed at improving diagnosis and developing vaccines, appropriate for use under Australian conditions . One area of disease diagnosis that requires particular attention in the Australian context is the differentiation of exotic viruses from related endemic agents . This includes distinguishing endemic, non-pathogenic bluetongue and Newcastle disease virus isolates from exotic, virulent strains and the differentiation of antibodies induced by swine fever and mucosal disease viruses in pigs . There may be other viruses with cross-reactions to important exotic agents, as yet unidentified or incompletely characterized . A number of rhabdoviruses isolated from arthropod vectors collected in northern Australia could fall into this category . At least eight types of bluetongue virus are represented in Australia . These are not associated with clinical disease and are not present in the southernmost parts of the country . Export of live sheep and goats to some countries is conditional upon their freedom from antibody to bluetongue and the related epizootic haemorrhagic disease of deer (EHD) viruses . Improved serological procedures are being developed, using enzyme-linked immunosorbent assay (ELISA) to increase the sensitivity and specificity of antibody assays used to ensure the serologically negative status of such livestock . With the prospect of exotic bluetongue viruses being introduced and perhaps not readily recognized as such, new isolates undergo serotype identification and pathogenicity testing, often over a prolonged period of time . Rapid identification procedures are being developed, using monoclonal antibodies and nucleic acid probes, to differentiate exotic from endemic strains of bluetongue virus . The use of gene probes and RNA sequence analysis has suggested the existence of 'topotypes', being groups of isolates, geographically related and with particular genomic similarities . Recently, bluetongue virus type 15 was isolated for the first time in Australia . It is only distantly related to North American, South African and other Australian isolates, suggesting that it has a different geographical origin and was introduced into the country at a different time . Two other bluetongue virus isolates from sentinel animals were serologically identified as new serotypes in Australia (3 and 16) but the use of topotyping gene probes indicated that they were related to previous isolates of different serotypes and were therefore not new incursions .
2
BRITISH
VETERINARY'
JOURNAL,
145 . I
While foot-and-mouth disease represents the greatest exotic disease threat to Australia, adverse community reaction has prevented its importation into the Australian Animal Health Laboratory, for research into improved methods of diagnosis . This has made it necessary for staff to carry out work overseas and to direct their efforts to developing procedures that do not require the use of live virus . Working initially at the Animal Virus Research Institute at Pirbright, UK, and now in research laboratories in Thailand, antigen detection procedures using ELISA have been applied to the diagnosis of the disease . Attempts are being made to use synthetic viral peptides, or antisera raised against them, as reagents for improved diagnostic tests, which would have the particular appeal of enabling the production of reagents to be carried out without the use of live virus . A wide interest has been shown in research directed toward constructing recombinant viruses, to express immunizing antigens . Vaccinia virus has been the most widely used vector although there are many other candidates which may have greater application in vaccine production . Having successfully developed methods for constructing recombinant vaccinia viruses and carrying out immunological studies with them, a group at Geelong is now engaged in constructing recombinant fowlpox viruses and determining their potential for immunizing poultry against a range of endemic and exotic agents . Such vaccines would be cheap to produce, could be multivalent (sufficient coding capacity can be inserted into the poxvirus genome to represent several unrelated viral antigens) and would obviate the risk of live, virulent virus being present in the preparation . The overall philosophy of research at Geelong embodies a multidisciplinary approach to areas of work identified as priorities through consultation with livestock sector representatives and scientists in appropriate fields of activity . While a broad range of disciplines is represented at Geelong, collaboration with other laboratories in Australia and overseas is actively pursued and encouraged . A . J . FORNIAN, Geelong, Australia
PERSONAL VIEWPOINT EXOTIC DISEASE RESEARCH IN AUSTRALIA Australia enjoys a freedom from many major exotic diseases, which permits it to retain a competitive position internationally (about 10% of Australia's export earnings come from livestock products) . However, this freedom is under constant threat with the increasing volume of all forms of international traffic . The Australian government has built a laboratory .a t Geelong in Victoria, for carrying out work on exotic diseases, including diagnosis, research, training and vaccine development and testing . The laboratory incorporates sophisticated facilities for microbiological containment . Since the commencement of activities in 1984, programmes of research have been developed which are directed at improving diagnosis and developing vaccines, appropriate for use under Australian conditions . One area of disease diagnosis that requires particular attention in the Australian context is the differentiation of exotic viruses from related endemic agents . This includes distinguishing endemic, non-pathogenic bluetongue and Newcastle disease virus isolates from exotic, virulent strains and the differentiation of antibodies induced by swine fever and mucosal disease viruses in pigs . There may be other viruses with cross-reactions to important exotic agents, as yet unidentified or incompletely characterized . A number of rhabdoviruses isolated from arthropod vectors collected in northern Australia could fall into this category . At least eight types of bluetongue virus are represented in Australia . These are not associated with clinical disease and are not present in the southernmost parts of the country . Export of live sheep and goats to some countries is conditional upon their freedom from antibody to bluetongue and the related epizootic haemorrhagic disease of deer (EHD) viruses . Improved serological procedures are being developed, using enzyme-linked immunosorbent assay (ELISA) to increase the sensitivity and specificity of antibody assays used to ensure the serologically negative status of such livestock . With the prospect of exotic bluetongue viruses being introduced and perhaps not readily recognized as such, new isolates undergo serotype identification and pathogenicity testing, often over a prolonged period of time . Rapid identification procedures are being developed, using monoclonal antibodies and nucleic acid probes, to differentiate exotic from endemic strains of bluetongue virus . The use of gene probes and RNA sequence analysis has suggested the existence of 'topotypes', being groups of isolates, geographically related and with particular genomic similarities . Recently, bluetongue virus type 15 was isolated for the first time in Australia . It is only distantly related to North American, South African and other Australian isolates, suggesting that it has a different geographical origin and was introduced into the country at a different time . Two other bluetongue virus isolates from sentinel animals were serologically identified as new serotypes in Australia (3 and 16) but the use of topotyping gene probes indicated that they were related to previous isolates of different serotypes and were therefore not new incursions .
2
BRITISH
VETERINARY'
JOURNAL,
145 . I
While foot-and-mouth disease represents the greatest exotic disease threat to Australia, adverse community reaction has prevented its importation into the Australian Animal Health Laboratory, for research into improved methods of diagnosis . This has made it necessary for staff to carry out work overseas and to direct their efforts to developing procedures that do not require the use of live virus . Working initially at the Animal Virus Research Institute at Pirbright, UK, and now in research laboratories in Thailand, antigen detection procedures using ELISA have been applied to the diagnosis of the disease . Attempts are being made to use synthetic viral peptides, or antisera raised against them, as reagents for improved diagnostic tests, which would have the particular appeal of enabling the production of reagents to be carried out without the use of live virus . A wide interest has been shown in research directed toward constructing recombinant viruses, to express immunizing antigens . Vaccinia virus has been the most widely used vector although there are many other candidates which may have greater application in vaccine production . Having successfully developed methods for constructing recombinant vaccinia viruses and carrying out immunological studies with them, a group at Geelong is now engaged in constructing recombinant fowlpox viruses and determining their potential for immunizing poultry against a range of endemic and exotic agents . Such vaccines would be cheap to produce, could be multivalent (sufficient coding capacity can be inserted into the poxvirus genome to represent several unrelated viral antigens) and would obviate the risk of live, virulent virus being present in the preparation . The overall philosophy of research at Geelong embodies a multidisciplinary approach to areas of work identified as priorities through consultation with livestock sector representatives and scientists in appropriate fields of activity . While a broad range of disciplines is represented at Geelong, collaboration with other laboratories in Australia and overseas is actively pursued and encouraged . A . J . FORNIAN, Geelong, Australia