Vibrios (excluding toxigenic V. cholerae O1/O139): V. parahaemolyticus, V. vulnificus, non-O1/non-O139 V. cholerae and non-toxigenic V. cholerae O1 are found in estuarine and marine environments in Australia and have been isolated from oysters [31,33,34]. These endogenous pathogens are not efficiently removed by depuration [33–35] and levels do not necessarily always correlate with counts of coliform indicator organisms [9,34]. Monitoring of water quality may not be adequate to control the food safety risks due to these pathogens, and post-harvest measures, such as suitable temperature control to prevent outgrowth, is necessary. Several studies have demonstrated the presence of vibrios in Australian molluscan shellfish and there have been a number of outbreaks and sporadic cases of food-borne illness documented (Appendix 2; [9,19]).
Algal biotoxins: Potentially toxic algae are found throughout Australian shellfish growing waters [4]. However, not all isolates of the causative organisms produce toxin, and concentrations of the toxins in shellfish will not necessarily always correlate with levels of algae in the water [4].
Algal biotoxins are not quickly removed by depuration or relaying. Monitoring of water quality may not entirely control the food safety risks due to these hazards. Levels of algal biotoxins are not affected by processing or consumer food handling practices.
There is some evidence of food-borne illness caused by algal biotoxins in molluscan shellfish in Australia, limited to two outbreaks of diarrhoeic shellfish poisoning due to consumption of pipis harvested from waters that were not subject to the requirements of a shellfish safety program, but a significant number of outbreaks occur worldwide [4].
There have been no failures in imported foods tested for domoic acid (amnesic shellfish poison) or paralytic shellfish poison since 1998, and only one FSANZ-coordinated food recall due to domoic acid in the period 1990–2003. Analytical data demonstrate the occasional presence of paralytic shellfish poison, amnesic shellfish poison and neurotoxic shellfish poison in Australian bivalve molluscs [4,16].