Localization of norovirus and poliovirus in Pacific oysters

To examine the uptake and tissue distribution of norovirus (NoV) and poliovirus (PV) experimentally bioaccumulated in feeding Pacific oysters (Crassostrea gigas). Pacific oysters were allowed to bioaccumulated either PV or NoV under tidally synchronized feeding conditions in laboratory tanks. Oysters were then either fixed and paraffin wax embedded prior to localizing virus within tissues by immunohistochemistry (IHC), or they were dissected into digestive tract (stomach, intestine and digestive diverticula), gill and labial palp tissues, and the viral load determined by quantitative RT-PCR. Both PV and NoV immunoreactivities were predominantly found in the lumen and within cells of the digestive tract tissues; however, PV was also found within cells of nondigestive tract tissues, and in the gills and labial palp. Quantitative RT-PCR of tissue extracts corroborate the immunohistochemical data in that the major site for virus localization is the gut, but significant amounts of viral RNA were identified in the gills and labial palp. The human enteric viruses, PV and NoV, are readily bioaccumulated by feeding Pacific oysters and that some of the virus is internalized within cells of both digestive and nondigestive tissues. Oysters that have been virally contaminated even after depuration (cleaning) in uncontaminated seawater could pose a human health risk if consumed.