Dar seafood ppp standard

Scientific issues

Introduction

The hazards of concern with pearl oyster meat and offshore scallops are algal biotoxins. Hazards derived from faecal pollution and agricultural run-offs, such as enteric bacterial and viral pathogens, are not currently a significant issue because harvesting currently occurs at relatively remote offshore locations. It is generally recognised that very little toxin migrates from the viscera into the adductor muscle in scallops.

Public health data

There is no evidence of illness from algal biotoxins in scallops or pearl oysters in Australian epidemiological datasets. Unfortunately, outbreak datasets are usually incomplete and capture information on only a fraction of the total food-borne illness in Australia. Furthermore, sporadic cases of food-borne illness (where illness is scattered; occurring singly and not as an outbreak) are not included in these datasets (unless a death results and the food vehicle is identified). Low levels of reporting, even of quite severe food-borne illnesses, are a major data gap and introduce uncertainty into the scientific evaluation. For this reason, FSANZ does not rely solely on outbreak data in evaluating the public health risks due to food safety hazards.

Accumulation of toxins in bivalves

There are no reports in the scientific literature relating to prevalence, concentration or distribution of algal biotoxins in pearl oysters (Pinctada spp.). A proposed study on the accumulation of algal toxins in pearl oyster meat by the pearl oyster industry has yet to get underway.
Given the large inter-species variation in the ability of bivalves to accumulate and detoxify algal biotoxins (see, for example, Bricelj and Shumway, 1998), it is not sound to extrapolate from the findings of low accumulation in scallop adductor to assume a similar low level of accumulation in pearl oyster meat. Assumptions made about toxin uptake being similar between different species might turn out to be incorrect once data is available.
There is evidence that bivalves harvested from areas of fast currents and/or deep waters are still able to accumulate toxins. Paralytic shellfish poisoning (PSP) toxin has been found at high levels in sea scallops (Placopecten magellanicus) harvested at a depth of 180 metres in the Gulf of Maine, USA (Cembella et al., 1993), and from areas subject to 14 metre tidal flows in the Bay of Fundy, Canada (Watson-Wright et al., 1990).
Campbell et al. (2001) report that in king scallop (Pecten maximus) samples taken from a closed harvest area in north west Scotland, the level of algal biotoxin (ASP) accumulating in adductor muscle was very low, and they did not find levels exceeding the regulatory limit. However, while the level of toxin in roe was much lower than in other tissues (except adductor muscle), 22% of individual roe samples still exceeded the regulatory limit (20 mg/kg).
New Zealand applies a scheme of flesh testing of scallops from its commercial scallop fisheries (including offshore-remote fisheries). Roe samples are tested (usually weekly) for the four major classes of algal biotoxins, and ‘muscle & roe’ samples are tested if the roe toxin level exceeds a trigger level⁶⁵. Combined results from ten years of commercial and non-commercial testing programmes have been recently reviewed (NZFSA, 2003). Some samples of scallop roe and ‘muscle & roe’ were found to have levels of ASP higher than the maximum limit allowed in the Code.

Summary of scientific issues

FSANZ concludes that there is significant variability in interspecies accumulation of algal biotoxins such that it is not appropriate to extrapolate from scallops to pearl oysters, given the severity of the health impact of algal biotoxins and the absence of specific data from Pinctada species.
Although scallop adductor muscle does not accumulate significant levels of algal biotoxins, available data implies that the roe may accumulate toxins to levels that might pose a significant public health and safety risk following consumption of roe-on scallops sourced from offshore harvest areas.