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

Abstract

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.

Monitoring SARS-CoV-2 as a Microbiological Risk in Shellfish Aquaculture

“…A recent monitoring study made in several sites along the coast of France reported the absence of SARS-CoV-2 in oysters (Desdouits et al, 2021). The authors, nonetheless, do not exclude shellfish as potential agents of transmission, but highlight the need for more monitoring studies before reaching such conclusion.…”

First evidence of SARS-CoV-2 genome detection in zebra mussel (Dreissena polymorpha)

“…Indeed, the possible toxicity of raw wastewater, causing an advanced dissection of organisms exposed to the most concentrated raw sewage conditions (18% of samples during the exposure at the end of September and 26% of samples during the last exposure, in November), did not allow mussels to be exposed any longer. To dispense with the toxicity of raw wastewater, a longer exposure of the mussels (from 14 to 21 days) in the laboratory to a noninfectious SARS-CoV-2 or to low pathogenic CoV strains could improve characterization of virus accumulation within mussels (Desdouits et al, 2021;Wurtzer et al, 2020b).…”

“…or in countries whose water treatment structures are still underdeveloped. As announced by several recent studies, the bivalve taxon represents a complementarity, even a more than plausible alternative for the detection of viruses in the environment (Capizzi-Banas et al, 2021;Desdouits et al, 2021;La Rosa et al, 2021;Polo et al, 2021). Various fields of application can therefore be envisaged, such as 486 environmental biomonitoring for health purposes.…”

“…In fact, these organisms can bioaccumulate biological and chemical pollutants for several days or even weeks, allowing pollution to be monitored over time, and filter a significant volume of water that is better representative of the mass of water (Bervoets et al, 2005;Palos Ladeiro et al, 2018;Wiesner et al, 2001). Concerning the SARS-CoV-2 genome, oysters have already proven their effectiveness by accumulating this virus during laboratory exposures (Desdouits et al, 2021).…”

“…However, there is still little knowledge concerning the survival of infectious SARS-CoV-2 in this aquatic environment. At a laboratory scale, Desdouits et al (2021) demonstrated the accumulation of inactivated SARS-CoV-2 genome in different shellfish tissues of oysters (Crassostrea gigas). Wurtzer et al (2021) have shown the presence of numerous forms of SARS-Cov-2 genomes in wastewaters including a small part of infectious and encapsidated particles using RT-qPCR and infectivity assays.…”