Experimental accumulation and persistence of norovirus, feline calicivirus and rotavirus in blue musseis (Mytilus edulis)

Outbreaks of viral gastrointestinal diseases due to the consumption of contaminated shellfish have been repeatedly reported. Human pathogenic viruses may accumulate in shellfish after faecal contamination of the growing area and thereafter persist tor several weeks. Here, blue mussels (Mytilus edulis) were contaminated with noroviruses and rotaviruses for 24 hours in a recirculation artificial seawater system. Noroviruses were found to be enriched 100 to 1000fold within the mussels and persisted therein for at least 4 weeks as assessed by semiquantitative real-time RT-PCR. In contrast, rotaviruses were not efficiently enriched in shellfish and they were only detectable tor approximately one week using realtime RT-PCR and cell culture. Feline calicivirus, used as surrogate for norovirus infectivity testing, was also only detectable in shellfish for approximately oneweek. For rotavirus, the inactivation kinetics in shellfish and contaminated seawater were largely similar. In contrast, norovirus was highly stable in shellfish for at least 4 weeks, but the amount declined in seawater and was no longer detectable therein at 3 weeks after contamination. The results indicate a unique mechanism of norovirus enrichment and persistence in shellfish. For improvement of microbial safety, surveillance may be focused on detection of noroviruses in shellfish samples.