Improving risk management of enteric viruses in Australia oysters

Enteric viral illnesses associated with shellfish are relatively rare in Australia, and national guidance for regulatory control on this issue has been scarce. The advent of Codex guidelines for the control of viruses in food... [ view full abstract ]

Enteric viral illnesses associated with shellfish are relatively rare in Australia, and national guidance for regulatory control on this issue has been scarce. The advent of Codex guidelines for the control of viruses in food and the recommendation by the EU that criteria for pathogenic viruses in live bivalve molluscs be established prompted an examination of the issue in Australia. A national prevalence survey for Norovirus (NoV) and Hepatitis A virus (HAV) in market-ready Australian grown oysters was conducted during 2014-15. The survey was designed to reflect national oyster production levels. NoV GI, NoV GII and HAV were determined by quantitative RT-PCR (ISO/TS 15216-1). The estimated prevalence for NoV and HAV in Australian oysters as a result of the survey was <2% with a 95% confidence interval. This result was supported by epidemiological evidence, with no confirmed oyster-related foodborne illness reported during the survey period.

Never-the-less, Australian shellfish are impacted by occasional sewage overflows, particularly related to weather events. New risk management guidelines were added to the Australian Operations’ Manual, and a review was undertaken on the potential use of bacteriophage to ameliorate the impact of conservative risk management. The review determined that there is supporting evidence from published data justifying the use FRNA phage as indicators for contaminated sites and post adverse events, although the evidence was not universal. An investigation currently underway aims to determine background bacteriophage levels and changes in phage and viral levels during adverse events, to improve viral risk management in the Australian context.