Last month, Food Standard Australia New Zealand (FSANZ) recalled oysters grown in the Coffin Bay area of South Australia due to a Vibrio parahaemolyticus outbreak. At least 36 Vibrio cases after Coffin Bay oyster consumption were reported in South Australia, with many more in other areas of the country.
The recall included fresh and frozen raw Pacific oysters with production dates from September 4, 2021 to November 16, 2021. The oysters were sold in grocery stores, seafood outlets, farms and supermarkets. Citizens were asked to avoid eating raw or undercooked oysters from Coffin Bay, to throw the oysters away or to return them to the place of purchase for a full refund.
Harvesting areas were closed
A harvesting suspension was put in place to allow oyster growers time to put procedures in place to minimise further risk of Vibrio infection.
The Department of Primary Industries and Regions (PIRSA) temporarily closed the Coffin Bay oyster production area, which meant the oysters were restricted from leaving the area to help trace cases of Vibrio poisoning.
While the investigation into the cause of the outbreak was inconclusive, it’s suspected that high temperatures post-harvest contributed to the outbreak.
At the time of closure, Nathan Rhodes, PIRSA’s Executive Director of Biosecurity, said that the department was also working to reduce the likelihood of the Vibrio bacteria being present in oysters by using a program that requires growers to quickly reduce the temperature of oysters after harvesting.
Restrictions lifting progressively
Because of these safety procedures and temperature-reducing efforts, growing areas are being reopened and restrictions affecting oyster production and harvesting are being progressively lifted.
Restrictions on growers will be progressively lifted as individual businesses demonstrate the safety of their systems and processes to SA Health, who will give final approval.
“Growers are implementing procedures to rapidly reduce the temperature of oysters after harvest to further reduce any likelihood of the presence of Vibrio bacteria,” said David Basham, South Australia’s Minister for Primary Industries and Regional Development. “An ongoing surveillance program has been put in place with regular testing of oysters.”
Basham said that the state government has been working closely with 32 accredited growers to be sure that increased controls are in place to safeguard consumers.
South Australians urged to support local
“I am encouraging South Australians to get behind our Coffin Bay oyster growers and support them by purchasing local this Christmas,” said Minister Basham. “We are confident Coffin Bay oyster growers have done everything possible to give confidence to consumers about the safety of their product and we can start seeing South Australia’s famous oysters back on family dining tables in time for Christmas.”
As the risk is reduced, and as grocery stores, markets and other sellers restock the products, consumers should be confident that the oysters they serve at Christmas will be safe as well as tasty.
What is Vibrio parahaemolyticus?
Vibrio parahaemolyticus is a naturally occurring bacterium in sea water. Its numbers can increase to a dangerous level in warm temperatures. People become sick by eating raw or partially cooked oysters — and sometimes fish and other seafood — that have been exposed to the bacterium.
Symptoms of Vibrio infection include nausea, fever, chills, abdominal cramping, headache, muscle aches and watery diarrhoea. The symptoms usually begin within 24 hours after consuming the contaminated food and lasts about three days, but can sometimes last up to 10 days.
Those experiencing symptoms of this food poisoning or who are concerned about their health should seek medical advice.
Vulnerable groups more at risk
Also known as “high-risk groups,” vulnerable persons including pregnant women, children under five, the elderly and those with weakened immune systems should avoid eating raw seafood. These groups are more susceptible to bacterial infection and more likely to experience severe symptoms.
Because shellfish is a high-risk food, extra care needs to be taken during purchasing, storing, preparing and serving. When it comes to raw oysters specifically, if they are pre-shucked, cook them thoroughly before consumption to a minimum internal temperature of 75°C.
Learn more about preventing food-borne illness outbreaks and protecting vulnerable groups through FSF’s comprehensive and nationally-recognised Food Safety Supervisor Course.