The rock oyster industry in Australia is currently valued at around $28 million annually. The current output is about half of the industry peak in the late 1970’s. For the industry to survive in the long-term requires the ability to service what may become a premium domestic market demanding a high quality product. The expansion of the industry is likely to be available only from international export, which in turn requires compliance with international regulations on oyster health with a transparent health audit trail. The rock oyster is potentially positioned for re-emerging export success, being a unique product with an extended shelf-life relative to other oyster species (e.g. the Pacific oyster, Crassostrea gigas) and this is an opportunity that should be exploited by the industry.

The techniques of surveillance and diagnosis for molluscan pathogens required by the OIE for imported oyster products are not only stringent and accepted as the worldwide standard, but are also applicable to domestic requirements within Australia. In essence, the regulations state that appropriate diagnostic tests are applied for detecting the presence of pathogens of molluscs (microscopic identification techniques with the potential for specific molecular identification using monoclonal antibodies or DNA probes) which have been collected as part of a surveillance program within delimited coastal zones. The sample size, period and frequency are determined with reference to the cycle of infection of the particular pathogen and its prepatent period. There is an initial 2 year period of surveillance before a zone can be granted a disease-free status, with ongoing surveillance required for this status to be maintained.

The development of a zoning policy framework for marteiliosis will provide a valuable opportunity to implement and field-test Australia’s zoning policy guidelines in a practical context to assist with the development of further zoning policies for diseases of aquatic animals. Considerable interest has already been expressed in the case study by State authorities and it will be discussed at an Aquatic Animal Disease Zoning Workshop in Canberra on 23 January 2001, hosted by the National Offices of Animal and Plant Health. Furthermore, the development of the zoning policy will be of direct benefit to the oyster industry by facilitating domestic and international market access, and through identifying and protecting the remaining disease-free production areas

The potential for poisoning events from biotoxin contamination of shellfish is a growing concern for all shellfish producers, aquaculture managers and the general public in Australia.

Outside of shellfish consumption, the occurrence of marine biotoxins has direct implications for human health for recreational users of the marine and coastal areas in which these blooms occur.

There are also implications for other seafood products which can accumulate biotoxins, as well as for ballast water management and the shipping sector, for general environmental protection / human health, and for sewage processors (as mentioned above, there are strong linkages between algal blooms and sewage output). However, the immediate concern for seafood industries is to assess the need to undertake sampling and monitoring programs in shellfish producing areas and to determine what risks exist for other seafood industries.

There is a genuine and urgent need to update the work undertaken in 1993, and supplement this work with additional information in order to develop a consistent national approach to biotoxin monitoring. The resulting monitoring strategy will be based on an appropriat and targeted sampling strategy, developed through an assessment of need and risk, in order to support the development and implementation of effective management regimes for the shellfish industry.

The NSW oyster industry has suffered severe economic losses during the past 20 years as the result of major outbreaks of gastroenteritis and other oyster-borne diseases. Further outbreaks will cripple the industry from immediate losses and resulting litigation.

There is an urgent need to re-examine the conditions for depuration of NSW oysters harvested in very different geographic and environmental conditions with particular reference to water temperature, salinity and turbidity during depuration. It is important to determine what limitations exist in the current technology and how they might affect purification efficiency and commercial acceptance by oyster farmers. In light of such information, there will be a need to modify the Code of Practice for Oyster Depuration. Equally important is the need to educate and train oyster farmers in proper quality assurance of oyster quality and safety, which will include optimal application of purification technology.

Current safety of oysters is assessed by the presence of E. coli as indicators of bacterial pathogens, yet the majority of oyster-borne disease is of viral origin, principally NV and more recently, HAV. Unfortunately, direct testing for human viruses in oysters is time consuming and very expensive, and will remain so for the foreseeable future. From the perspective of implementing a quality assurance program that will effectively protect public health, it is essential to have more accurate and more reliable indicator tests for the presence of human viruses in oysters. Consequently, there is a clear need to examine the relationship between the presence of bacterial indicators (E. coli), coliphages and human infectious viruses in oysters before, during and after purification. Such a study will not only clarify the behaviour of viruses during purification but could lead to a rapid coliphage assay as a more accurate indicator of human virus presence in oysters.