Method Extracts Noroviruses from Oysters

Several agencies responsible for public health in Canada have recently adopted a technique based on research by the Agricultural Research Service (ARS) to extract and test noroviruses in oysters.

Noroviruses, which cause approximately 23 million illnesses each year, are the leading cause of nonbacterial acute gastroenteritis outbreaks. Oysters, clams and mussels have caused numerous outbreaks of norovirus illness. Symptoms of the illness include potentially severe diarrhea, vomiting or both that develop usually within a day after consuming contaminated food or drink.

The extraction method is based on a procedure published by the ARS in 2001, viral particles are concentrated by homogenization followed by a polyethylene glycol (PEG) precipitation step.

Total RNA is then extracted, most of the total RNA extracted is oyster. Enrichment of viral RNA from total RNA is performed using oligo-dT coated magnetic beads. These magnetic beads bind the polyadenylated (poly-A tail) messenger RNA (mRNA) of Noroviruses. The final extract is then subjected to a reverse-transcriptase PCR procedure which amplifies a specific fragment depending on the primers used (i.e. Norovirus genogroups I / II, and the actin gene target for oysters).

The method effectively separates and purifies norovirus genetic materials from within oyster tissues.

Health Canada recently published this approach as a laboratory method in its "Compendium of Analytical Methods," which provides a ready reference on techniques used by Health Canada, Agriculture and Agri-Food Canada, and the Canadian Food Inspection Agency.

These agencies evaluated the method for effectiveness, as did the FDA, the British Columbia Centre for Disease Control, state and provincial universities, and other agencies. The publication is available online:
Concentration of Norovirus Genogroups I and II from Contaminated Oysters and their Detection Using the Reverse-Transcriptase Polymerase Chain Reaction