Relationship to R&D plans and strategies
In the May 2000 Budget, the Federal Government announced its Building a National Approach to Animal and Plant Health program to maintain Australia’s status as a source of high quality agricultural produce with work on aquatic animal health to be funded via AFFA through the FRDC Aquatic Animal Health Subprogram. Following stakeholder consultations, seven projects focusing on the development of improved diagnostic methods for diseases of fish, crustaceans and molluscs were funded under this Subprogram. The Subprogram recently requested advice from aquatic animal health specialists in Australia on priority suggestions for the remaining uncommitted funds. The ‘Maintenance of reagent stocks for diagnosis of important diseases e.g. EHN’ was identified by this forum as one of a number of high priority issues and subsequently forwarded to the Subprogram. The Subprogram’s Steering Committee and Scientific Advisory Committee supported this and other suggestions because of their national significance. This application is made in response to this need.

Pragmatic need
The International Reference Laboratory for EHNV provides research and diagnostic referral services to fish health laboratories in Australia and other countries. Reagents have been supplied upon request for more than 10 years. Research on protocols for improved viral detection and differentiation from related viruses is ongoing, and has been published in high quality journals. These protocols are supplied, together with reference reagents, to any diagnostic laboratory upon request. As many of these original antibody reagents were prepared in 1989-1992, they are deemed likely to be near the end of their shelf life, or stocks of quality-controlled batches are almost exhausted. Furthermore, new protocols have recently been developed using modern tools of molecular biology (Marsh et al 2002 rapid differentiation of Australian, European and American ranaviruses based on variation in major capsid protein gene sequence. Mol.Cell. Probes 16:137-151). For routine use these require development of new reagents, for example standardized DNA solutions.

This project is an operation to replenish stocks of reagents for existing tests and to create stocks for the more newly developed tests and as such is a one-off request. In future we aim to meet costs by charging for supply of reagents, something that OIE Fish Diseases Commission has agreed may be necessary to support reference laboratory activities. Stocks of antibody reagents produced in this project are likely to be viable and sufficient for 15 years assuming freeze drying is successful and current levels of demand, but this will also be dependent on future demand, which is not easily predicted.

This project relates directly to the FRDC VNN Research and Development Plan, to facilitate industry profitability, sustainability, growth and development. There is an overarching need to measure and then reduce the risk to fisheries and aquaculture sectors (including natural resources) associated with transfer of nodaviruses. The aquaculture industry is proactive and responsible (eg triple bottom line reporting) and wishes to manage risks based on sound science. Industry acknowledges a residual risk that cannot be controlled: virus prevalence in the wild and natural fish movements. However, there is an immediate need for industry to conduct business in the face of unknowns with respect to true disease status. While there is a need to ensure that infected, but apparently healthy, stock are not moved to areas that are considered free of the disease/disease agent, it is of fundamental importance for the sustainability of the barramundi aquaculture industry and developing species ventures such as Australian bass that stock are translocated. Current tests for determining disease status are considered inadequate, therefore biosecurity protocols in the short-term are required to address the risk of introduction of disease with water, broodstock and fomites. As new information becomes available through R&D, these protocols will be revised and improved as needed to improve biosecurity. In the meantime, protocols are needed to manage risks with incomplete information and without overburdening industry with uneconomic or unwarranted requirements. There is need for mitigation of impacts on translocation: hatchery to nursery to grow-out; hatchery to wild (eg stocking for recreational fishing); both intra-state and interstate translocations, access to overseas markets; sourcing broodstock from the wild. Financial impacts, environmental impacts and mulitsectorial impacts at level of commercial, recreational and regulatory sectors all need to be addressed.

There is a disturbing pattern of diseases in commercial molluscs nationally. They have required a succession of government/industry responses, with no clear solutions:QX disease, Sydney rock oysters, NSW and QLD; NSW; Pacific oyster mortality syndrome, NSW; Abalone viral ganglioneuritis, VIC; Oyster oedema disease, pearl oysters, WA; Winter mortality, Sydney rock oyster, NSW.

Economic impacts have been substantial or devastating. Wild fisheries and aquaculture have been impacted. In NSW, the primary impact of QX disease led to replacement of Sydney rock oysters by triploid Pacific oysters to reestablish the industry in some estuaries, but this is now threatened by POMS.

In every case the new disease has spread. It has not been possible to devise an intervention strategy that would halt disease spread or ensure the recovery of the industry. Investigating the behaviour of POMS during its predicted recrudescence this summer provides an opportunity to identify factors which may be used to reduce the impact of the infection.

This project seeks to investigate the effect of host, environmental and husbandry factors on POMS prevalence and mortality rate in Pacific oysters during summer 2011-autumn 2012 with the objective of discovering aspects of epidemiology which can be manipulated by oyster growers.

FRDC strategic R&D theme 1 - biosecurity and aquatic animal health, and Aquatic Animal Health Subprogram priority - Nature of disease and host-pathogen interaction - immunology of aquatic invertebrates.