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Development of procedures for improved viral reduction in oysters during commercial depuration

Project Code: B04002

06/05/2010

Centre for Environment, Fisheries & Agriculture Science (CEFAS) Weymouth
Dore, W

The most frequent cause of gastroenteritis associated with the consumption of oysters is from Norovirus (NV) as they tend to be eaten raw or lightly cooked. Bivalve molluscan shellfish accumulate human pathogenic micro-organisms when grown in sewage-polluted waters. To reduce the risk associated with such oysters, they are purified prior to consumption, by a process called depuration. Depuration involves submerging the oysters in a tank of clean seawater, which removes sewage contaminants. Despite worldwide use of depuration, outbreaks of illness following the consumption of purified oysters continue to occur.

Male-specific RNA (FRNA) bacteriophages have similar physical and genomic characteristics to the NVs and their ease of enumeration makes them an attractive indicator for modelling the removal of these viruses during depuration. FRNA bacteriophage has therefore been proposed as an index of virus removal during depuration. It is considered that the use of depuration procedures, which produce oysters free from FRNA bacteriophage, would be likely to remove NVs and other human viruses.

The overall objective of this study was to develop procedures involving the use of elevated temperature for extended periods that would allow increased viral reduction during commercial depuration of oysters.

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