Detecting infectious viruses in oyster digestive tissues

The association between shellfish and viral gastroenteritis has been recognized for a long time and the higher frequency of norovirus oyster-related outbreaks compared to food outbreaks caused by person-to-person transmission... [ view full abstract ]

The association between shellfish and viral gastroenteritis has been recognized for a long time and the higher frequency of norovirus oyster-related outbreaks compared to food outbreaks caused by person-to-person transmission has been demonstrated. The first step of the study was to validate the behavior of the Norwalk virus (norovirus GI.1 prototype) and the Tulane virus. After bioaccumulation, tissue distributions were quite similar with most viruses being detected in digestive tissues compared to gills or mantle. Over 8 days the levels of persistence were comparable even in water supplemented with phytoplankton as determined by real-time RT-PCR. Even over longer periods, Norwalk and Tulane virus displayed rather similar persistence. Based on three series of experiments performed in a controlled research farm mimicking normal commercial environmental conditions the calculated half-lives were 7.56 and 4.65 days for Norwalk and Tulane virus respectively. The second step was to adapt the concentration method to detect infectious particles. Using an optimized protocol adapted after poly-ethylene glycol (PEG) concentration some infectious Tulane virus was detected up to 21 days after bioaccumulation. The last step of this study was to apply this protocol to oyster bioaccumulated with a GII.3 cultivable norovirus and to use the recent model to detect infectious particles.