The establishment of a new native oyster and/or western rock oyster aquaculture sectors in SA and the former in Tasmania will not only diversify the business risk of the existing Pacific oyster sector, but has the potential to become a multi-million dollar industry itself. As native oysters would be more suited to subtidal or low intertidal culture while western rock oysters are an ideal alternative species to mitigate POMS, the successful development of these aquaculture sectors will strengthen the confidence of existing/new growers and investors in Pacific, western rock and native oysters; thereby encouraging further expansion of the industry. In addition, supporting species diversification is one of the high strategic priorities in the Oysters Australia Strategic Plan 2014-2019.

This is the first time that an illness associated with Vibrio has been traced-back to Tasmanian oysters. Regrettably, this incident occurred in the only major harvesting area in Tasmania that has not been impacted by the current Pacific oyster mortality event.

In Australia the control of Vibrio is currently limited to temperature controls during storage or transport. Pre-harvest controls used by the shellfish quality assurance programs are predicated on controlling risk posed by faecal contamination and biotoxins and are not suitable for controlling risk from these naturally occurring bacteria. Although the recent implementation of the Codex Standard for pathogenic marine vibrios suggests risk in bivalve growing areas should be assessed to ascertain the risk to public health, there has been limited research undertaken in Australia. The studies undertaken to date have generally been short in nature with no comprehensive longitudinal studies being undertaken and methodologies have now progressed significantly, whereas New Zealand has been undertaking a long-term survey to understand the risk posed by these pathogens (Cruz, Hedderley & Fletcher 2015). This issue may become a risk in accessing key markets that are active in monitoring or who regulate for these pathogens.

There is an immediate need to collect information on prevalence for the remainder of the summer period to understand the risk and evaluate if there is a relationship to salinity, temperature and toxic strains. This information will be immediately useful for developing appropriate management plans in this growing region.

This illness outbreak will likely result in Tasmanian Shellfish Quality Assurance Program and the other state programs having to consider how to manage risk in the growing areas and establish what is an acceptable level. The work proposed here could be used as a framework for future work that assesses risk across the bivalve industry Australia-wide.

Norovirus (NoV) is the leading cause of gastroenteritis outbreaks worldwide, and is commonly associated with shellfish. Between 2001-2010 seventeen Australian cases of suspected shellfish related NoV outbreaks were reported in OzFoodNet (Knope, 2011). More recently (March 2013) 400 people were reportedly affected by NoV following consumption of contaminated oysters from Tasmania.
Virus contamination in food poses major concerns for consumers and can impact export trade. The WHO/FAO working group (2008) on food-borne viruses, and European Food Safety Authority’s (EFSA) opinion (2011) ranked bivalves among the highest risk food groups in terms of NoV and hepatitis A virus (HAV). In 2011 the Codex Committee on Food Hygiene ratified a draft guideline on viruses in foods, with a specific annex on bivalves. It recommends that countries monitor for NoV and HAV in bivalves following high risk pollution events. Additionally, in early 2012 EFSA recommended the introduction of an acceptable NoV limit in oysters and the EU Community Reference Laboratory (2012) recommended an ‘absence’ criterion be applied for HAV in bivalves. Because of these impending international regulations (noting that some importing nations already require NoV testing), the Australian oyster industry members have indicated that they would like a more comprehensive evaluation of the prevalence of viruses in Australian oysters. There is little information on the baseline levels of NoV in Australian oysters. Although, a small pilot survey in oysters was conducted in production areas, more information is needed.
Recent developments made at SARDI in the use of molecular biology techniques for virus detection in foods would enable the occurrence of these viruses in bivalves to be determined through a virus prevalence survey. Similar surveys have been undertaken worldwide, including in the USA, UK, France and China, and might contribute to the development of market access strategies at the international level.