Dar seafood ppp standard

4. Discussion of relative risk rankings

The relative risk rankings for those commodity/hazard pairings ranked as medium or high are summarised in Table 12. The factors impacting upon the rankings are discussed below, and a comparison is made with the findings of other relevant risk assessments or ranking exercises.

High relative risk rankings

Oysters and other bivalve molluscs – polluted and/or unmonitored waters

Oysters and other bivalve molluscs (except when the consumed product is only the adductor muscle, for example, roe-off scallops) harvested from growing environments likely to be exposed to faecal contamination and/or not under a shellfish safety management scheme were found to present a relatively high risk to public health. The risk is mainly due to the likelihood of illness caused by contamination with the hepatitis A virus and algal biotoxins (particularly amnesic shellfish poison and paralytic shellfish poison). These hazards are introduced in the pre-harvest phase of bivalve production.

The incidence of food-borne illness from eating oysters and other bivalve molluscs in Australia is characterised by a number of small outbreaks and sporadic cases due to Vibrio species and a few large outbreaks due to enteric viruses in oysters harvested from polluted and inadequately controlled waters. While adoption of risk management strategies has improved the safety of bivalve shellfish in Australia, residual risks remain. Monitoring of harvest waters for indicators of sewage pollution (for example, faecal or total coliforms) helps manage the risks from enteric pathogens, bacterial and viral, but cannot predict levels of Vibrio species in oysters. Monitoring for potentially toxic species of algae only partly reduces the risks due to algal biotoxins, as concentrations of toxin in oysters do not necessarily always correlate with levels of algae in the water.
Based on these considerations, for oysters and bivalves harvested from waters managed by a comprehensive shellfish safety scheme, such as the ASQAP, the relative risk ranking reduces to medium.

The risk ranking for cooked oysters and other bivalves is the same as the ranking for product to be eaten raw, as the hazards leading to the risk ranking are not greatly affected by the light cooking normally applied to these products.