The method could be a boon to food suppliers andprocessors who use molluscs in their products, and whorisk damage to reputation and huge costs arising fromcontamination and product recalls caused by noroviruses.
Oysters, clams and mussels are the source of numerousoutbreaks of norovirus illness and can lead to severediarrhea and vomiting after consuming contaminatedfood or drink. Symptoms typically last for about 48hours.
Canada's health regulator, which helped develop thetechnique in conjunction with US counterparts, hasapproved the laboratory method and published detailsof the procedure online.
It provides a detailed step-by-step reference for food technologists and plant testers who want to use the technique.
The method effectively separates and purifiesnorovirus genetic materials from within oyster tissuesusing reverse-transcriptase polymerase chain reaction(PCR), a technique increasingly used in laboratory foodtesting.
PCR generates large quantities of DNA from tinysamples. It can be used to detect very smallquantities of pathogens.
The extraction method is based on a procedure published in 2001 by microbiologist David Kingsley and lead scientist Gary Richards at the US agriculture department's research service at Delaware State University in Dover.
In 2002 the research service published an article on its successful use to detect both hepatitis A virus and norovirus in Asian clams implicated in an outbreak of illness in New York state.
Canadian scientists first contacted Richards in 2004 about a suspected outbreak of oyster-associated norovirus illness in British Columbia, which led to an evaluation of the method.
Noroviruses cause approximately 23 million illnesseseach year, according to the research unit of the USagriculture department. They are the leading cause ofnon-bacterial acute gastroenteritis outbreaks.They are associated with food poisoning outbreaks inschools and nursing homes, on cruise ships and withthe consumption of contaminated water and food.