Can shellfish be used to monitor SARS-CoV-2 in the coastal environment?

The emergence and worldwide spread of SARS-CoV-2 raises new concerns and challenges regarding possible environmental contamination by this virus through spillover of human sewage, where it has been detected. The coastal environment, under increasing anthropogenic pressure, is subjected to contamination by a large number of human viruses from sewage, most of them being non-enveloped viruses like norovirus. When reaching coastal waters, they can be bio-accumulated by filter-feeding shellfish species such as oysters. Methods to detect this viral contamination were set up for the detection of non-enveloped enteric viruses, and may need optimization to accommodate enveloped viruses like coronaviruses (CoV).

Here, we aimed at assessing methods for the detection of CoV, including SARS-CoV-2, in the coastal environment and testing the possibility that SARS-CoV-2 can contaminate oysters, to monitor the contamination of French shores by SARS-CoV-2 using both seawater and shellfish.

Using the porcine epidemic diarrhea virus (PEDV), a CoV, as surrogate for SARS-CoV-2, and Tulane virus, as surrogate for non-enveloped viruses such as norovirus, we assessed and selected methods to detect CoV in seawater and shellfish. Seawater-based methods showed variable and low yields for PEDV. In shellfish, the current norm for norovirus detection was applicable to CoV detection. Both PEDV and heat-inactivated SARS-CoV-2 could contaminate oysters in laboratory settings, with a lower efficiency than a calicivirus used as control. Finally, we applied our methods to seawater and shellfish samples collected from April to August 2020 in France, where we could detect the presence of human norovirus, a marker of human fecal contamination, but not SARS-CoV-2.

Together, our results validate methods for the detection of CoV in the coastal environment, including the use of shellfish as sentinels of the microbial quality of their environment, and suggest that SARS-CoV-2 did not contaminate the French shores during the summer season.


SARS-CoV-2, Coastal environment, Seawater, Shellfish, Detection method, Genomic detection

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Desdouits Marion, Piquet Jean-Come, Wacrenier Candice, Le Mennec Cecile, Parnaudeau Sylvain, Jousse Sarah, Rocq Sophie, Bigault Lionel, Contrant Maud, Garry Pascal, Chavanon Fabienne, Gabellec Raoul, Lamort Laure, Lebrun Luc, Le Gall Patrik, Meteigner Claire, Schmitt Anne, Seugnet Jean-Luc, Serais Ophelie, Peltier Cécile, Bressolette-Bodin Céline, Blanchard Yannick, Le Guyader Soizick (2021). Can shellfish be used to monitor SARS-CoV-2 in the coastal environment?. Science Of The Total Environment. 778. 146270 (11p.).,

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