Growing Futures

Protecting consumers from seafood-borne illness

Protecting consumers from seafood-borne illness

Monitoring Pacific oyster populations reduces risk of bacterial illness

New Zealand exports about 1,500 tonnes of Pacific oysters each year with a value of $15 million, mainly to consumers in Australia and Asia. Vibrio bacteria, such as Vibrio paraheamolyticus and Vibrio vulnificus, present in seawater can be ingested by oysters, and can cause gastroenteritis and other diseases if these are then consumed by humans, potentially affecting the perceived safety of all New Zealand seafood exports.

Research, designed to determine the potential effects of climate change on Vibrio bacteria, analysed oysters during the summer harvests of 2009 to 2012 and compared results with data collected in the 1980s. The research showed that Vibrio vulnificus numbers were higher than expected in the key Pacific oyster harvest areas of Northland, Auckland and Coromandel, and occasionally reached critical levels during times of high seawater temperature.

As a result, a new monitoring programme was put in place by the Ministry for Primary Industries (MPI) for the 2014/15 summer season. Under the programme, when Vibrio vulnificus population numbers reach a critical threshold, harvesting must cease or Pacific oysters harvested from affected areas are required to undergo strict postharvest treatments to reduce the potential effects of Vibrio bacteria when consumed. In addition, Plant & Food Research initiated a new research programme to develop a protocol for frozen storage of Pacific oysters that reduces Vibrio numbers to safe concentrations.

The Vibrio research programme was funded by the Ministry of Business, Innovation & Employment through the Cawthron Institute's Safe New Zealamd Seafood programme.

Created: September 2015

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