- The Ifremer Health Environment and Microbiology laboratory in Nantes is tracking the possible presence of the new coronavirus on the French coast.
- He will have an increased surveillance on the shells which are real sponges.
"It is not because we have found nothing that we should not ask questions!" At the Ifremer Health Environment and Microbiology laboratory in Nantes, Soizick Le Guyader and his team are tracking the possible presence of the new coronavirus on the French coast. “During the confinement, we knew about the big foci of the epidemic. And the coastline was little affected. But with the deconfinement and the holidays, people are going to move, and therefore we have to keep an eye on it, ”summarizes the researcher.
A first series of tests, the results of which were announced in mid-May, had detected no trace of SARS-CoV-2 in samples of seawater and molluscs. Since then, more than a hundred samples in total have been analyzed, without showing any evidence of the virus responsible for Covid-19 either.
Around the world, traces of the virus have been found in wastewater, the monitoring of which, scientists say, can prevent the epidemic from evolving. However, "when there is pollution on land, it will reach the sea," sums up Philippe Riou, director of the Oceanography and ecosystem dynamics department of the French Research Institute for Exploitation of the Sea.
And the Ifremer teams have solid experience in the search for viruses in the marine environment. They have been tracking, for example, for years the noroviruses, responsible for gastroenteritis, which can in particular nest in oysters.
Seashells are sponges
"The shells are sponges, they filter large quantities of water" to feed themselves by drawing nutrients from them, explains Jean-Côme Piquet, head of microbiological surveillance and the network of control of shellfish production zones (oysters and mussels in particular) at the Nantes laboratory. However, the remains of human waste, even after treatment in a treatment plant, "are good food for shellfish", notes Soizick Le Guyader. As a result, molluscs also behave as "contamination integrators".
And if the coronavirus were to spread on the coast, for example thanks to the arrival of vacationers, their study could allow “to be able to anticipate a minimum”. The researchers have therefore set up a network of twenty monitoring points, where samples will be taken for analysis every two weeks. "It may not seem like much, but we are used to monitoring the coastline and we have selected the points known to be the most affected by human faeces," explains Jean-Côme Piquet.
The shells will be dissected and analyzed
Teams will also be able to respond urgently to other points in the event of an alert, for example a failure of a wastewater system. The shellfish collected are dissected and the virus will, for example, be sought in the digestive system of oysters, where researchers are used to tracking noroviruses.
"We do cultures, then sequencing", which makes it possible to duplicate a large number of DNA series, explains Marion Desdouits, one of the researchers. "We are going to target the known sequences (of the virus), that is, those that look like it and could alert us" to its presence.
Still a lot of strangers
So far, nothing to report, but the entire lab is on the alert. With the unknowns inherent in emerging diseases: what is the exact infectious dose? How long would the virus remain active in this environment?
"The viral emergence poses a real challenge in an environment subjected to strong pressures from all sides," warns Soizick Le Guyader. "There is climate change [which is gradually warming the seas] and the human population too, which is increasing on the coast." The researcher does not expect a respite: "It will become more and more dense, with all the activities around and their consequences".
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