A bulletin for the Australian Food Industry June 1997
Contents: Food poisoning and the regulatory response | Cutting boards - is plastic better than wood? | Hygiene monitoring by ATP luminometry | AQIS Director defends food inspection system | Cheese from unpasteurised milk banned | Oysters and Hepatitis A | Farmers seek compensation over chemical residue in meat | Australian Smallgoods Food Safety Guidelines
Oysters and Hepatitis A
The original source of all foodborne human viruses is the human intestine. Contamination of food occurs either during its preparation by infected food handlers, or from contact with polluted water.
Control of foodborne viruses therefore depends on educating food handlers to maintain hygienic standards of food preparation. It also requires the use of clean water, free from pollution or sewage sludge, for the irrigation of crops that are to be consumed raw and for the cultivation of shellfish.
The main food associated with foodborne viruses is molluscan shellfish, especially oysters, which are usually found in shallow coastal or estuarine waters. These shellfish are filter feeders that can concentrate virus particles from the surrounding water. Oysters are eaten raw or after a mild heat process, which is poorly controlled and may not inactivate the virus. Depuration can not be relied upon to remove viruses and outbreaks of viral disease have been attributed to depurated shellfish.
In January and February of this year Wallis Lake, NSW was identified as the site of an outbreak of hepatitis A associated with the consumption of oysters. Viral hepatitis has a long incubation period and it is now unlikely that the source of the outbreak, or the contaminated sewage that carried it, will be identified. As a result of the outbreak, a class action against various parties, by more than 300 people is likely to proceed.
The State Government is currently implementing a program to upgrade sewage systems around Wallis Lake.
Food Science Australia
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