A method for the enumeration of poliovirus in selected molluscan shellfish

A virus extraction procedure was developed and evaluated on five commercially important molluscan shellfish species: Crassostrea virginica (Eastern oyster), Mya arenaria (softshell clam), Mytilus edulis (blue mussel), Mercenaria mercenaria (hardshell clam), and Crassostrea gigas, (Pacific oyster). Shellfish tissue homogenates were spiked with poliovirus, extracted, and plaque assayed. Mean virus recoveries were: C. virginica, 63.8%; M. arenaria, 42.1%; M. edulis, 67.3%; M. mercenaria, 48.3%; and C. gigas 10.1%. Shellfish were also allowed to accumulate poliovirus from spiked seawater (10 to 20 PFU/ml of water) over 48 to 72 h. The results indicate that poliovirus could be extracted from four shellfish species exposed to near environmental levels of virus. Virus recoveries per gram of tissue were: M. arenaria, 11.7 PFU; M. mercenaria, 26.0 PFU; M. edulis, 21.5 PFU; and C. virginica, 2.0 PFU. The results of this study indicate that the procedure is effective in extracting ingested viruses from several shellfish species. This procedure may have practical application for enumeration of enteric viruses in environmental samples.