Investigation of F-RNA Bacteriophage as a Tool in Re-Opening Australian Oyster Growing Areas Following Sewage Spills.

Oysters contaminated with human enteric viruses from sewage are implicated in foodborne outbreaks globally. Bacteriophages have been identified as potential indicators for these viruses, but have not been used in shellfish management outside of the USA. This study aimed to determine the background levels of F-RNA phage in five Australian oyster growing areas with a history of sewage spills and closures, over an 18-month period. In addition, oysters from five growing areas impacted by adverse sewage events were investigated for F-RNA phage, Escherichia coli, norovirus (NoV) and hepatitis A virus (HAV). F-RNA phage ≤ 60 pfu/100 gm shellfish flesh were found to represent a conservative background level in the surveyed areas. Following two of the five sewage spills, elevated phage levels were observed in most sample sites less than 4 days post spill. By 7 days, most sites from all events had phage < 30 pfu/100 gm. NoV was detected in day 1 and day 6 samples from one event when all phage were ≤ 30 pfu/100 gm. NoV was also detected in a day 3 sample from another event with < 30 phage pfu/100 gm, however, multiple replicate samples had elevated phage levels. The results of this study add evidence on the potential use of F-RNA phage as a tool in early re-opening of oyster harvest areas post sewage spills. However, it also highlights the need to better understand situations where phage testing may be ineffectual, and the importance of sampling at multiple sites and over multiple time points, to effectively capture evidence of contamination.

Estimating risk associated with human norovirus and hepatitis A virus in fresh Australian leafy greens and berries at retail.

The apparent international rise in foodborne virus outbreaks attributed to fresh produce and the increasing importance of fresh produce in the Australian diet has led to the requirement to gather information to inform the development of risk management strategies. A prevalence survey for norovirus (NoV) and hepatitis A virus (HAV) in fresh Australian produce (leafy greens, strawberries and blueberries) at retail was undertaken during 2013-2014 and data used to develop a risk profile. The prevalence of HAV in berries and leafy greens was estimated to be <2%, with no virus detected in produce during the yearlong survey. The prevalence of NoV in fresh strawberries and blueberries was also estimated to be <2% with no virus detected in berries, whilst for leafy greens the NoV prevalence was 2.2%. Prevalence of a bacterial hygiene indicator, Escherichia coli, was also investigated and found to range from <1% in berries to 10.7% in leafy greens. None of the NoV positive leafy green samples tested positive for E. coli, indicating it is a poor indicator for viral risk. The risk was evaluated using standard codex procedures and the Risk Ranger tool. Taking all data into account, including the hazard dose and severity, probability of exposure, probability of infective dose and available epidemiological data, the risk of HAV and NoV foodborne illness associated with fresh Australian berries (strawberries and blueberries) sold as packaged product was deemed to be low. The risk of foodborne illness from HAV associated with leafy greens was also deemed to be low, but higher than that for fresh berries, due mainly to the potential for recontamination post-processing if sold loose. The risk of foodborne illness from NoV associated with leafy greens was deemed to be low/moderate. Despite the prevalence of NoV in leafy greens being low and the inability to discriminate between infective and non-infective virus using PCR based methodologies, the fact that NoV was detected resulted in a higher risk associated with this pathogen-product pairing; compounded by the higher prevalence of NoV within the community compared to HAV, and the potential for leafy greens to become contaminated following processing if sold loose.

Bacteriophages as enteric viral indicators in bivalve mollusc management.

Human enteric viruses, such as norovirus and hepatitis A virus, are spread by a variety of routes including faecal-oral transmission. Contaminated bivalve shellfish are regularly implicated in foodborne viral disease outbreaks internationally. Traditionally indicator bacteria, the coliforms and Escherichia coli, have been used to detect faecal pollution in growing waters and shellfish. However, studies have established that they are inadequate as indicators of the risk of human enteric viruses. Bacteriophages have been identified as potential indicators or surrogates for human enteric viruses due to their similarities in morphology, behaviour in water environments and resistance to disinfectant treatments. The somatic coliphages, male-specific RNA coliphages (FRNA coliphages) and the bacteriophages of Bacteroides are the groups recognised as most suitable for water and shellfish testing. In this review, we discuss the rationale and supporting evidence for the application of bacteriophages as surrogates for human enteric viruses in shellfish under a variety of conditions. There is some evidence to support the validity of using bacteriophage levels to indicate viral risk in shellfish in highly contaminated sites and following adverse sewage events.