Survival of poliovirus in New Zealand green-lipped mussels, Perna canaliculus, on refrigerated and frozen storage

Poliovirus survival in live and frozen mussels during storage was assessed by both viral culture and molecular methods. Live New Zealand green-lipped mussels were incubated overnight at 20 degreesC in an aerated tank of filtered seawater seeded with the poliovirus 2 (PV2) vaccine strain. An extraction and concentration method that preserved viral infectivity was used to recover PV2 taken up by the mussels at day 0, at day 2 after storage at 4 degreesC, and at days 7, 14, and 28 after storage at -20 degreesC. This method allowed both culture and molecular analysis to be carried out. Presence of intact PV2 in each batch of mussels was determined by a pan-enterovirus specific reverse transcription-polymerase chain reaction (RT-PCR) and confirmed by dot-blot hybridization, Survival of infectious PV2 was determined by the monolayer plaque assay. After 48 h at 4 degreesC, infectious PV2 levels were 81% of the original level detected in the mussels. Infective virus levels then declined to 66, 53, and 44% after storage at -20 degreesC for 7, 14, and 28 days, respectively. Generic RT-PCR methods were 10 times more sensitive than cell culture techniques for virus detection but did not give information on virus infectivity. The survival of infectious pathogenic viruses in fresh and frozen mussels on storage constitutes a potential health risk and so is a major concern for public health authorities.