After the holidays, oyster farmers face new contamination of their production by noroviruses, the gastroenteritis virus. The Charente-Maritime prefecture issued an order on Tuesday evening banning the collection and marketing of clear oysters in two areas of the Marennes-Oléron basin. Already last week, several shellfish production basins were closed in Morbihan and Mont-Saint-Michel bay, after contamination with the virus. Little reminder of the questions that arise.
Can we still eat oysters?
There is no danger, assure the authorities. "The oysters sold come from virus-free areas", specifies Jean-Baptiste Milcamps, departmental director of territories and the sea of Charente-Maritime, contacted by "Le Parisien". And to insist: "We have not had any suspicion or declaration of contamination in other areas".
This "temporary crisis" is not unusual but seems more significant than in previous years, he said, given the peak of gastroenteritis that occurred in December.
What measures have the authorities taken?
The contaminated shellfish production basins in Morbihan, Mont-Saint-Michel Bay and in Charente-Maritime have been closed, after several prefectural orders. All shellfish have thus been "prohibited from fishing, collection, dispatch and marketing", until further notice.
In Charente, the ban will be lifted on January 15. "It is estimated that from this date, there is no longer any risk of the virus spreading," explains Jean-Baptiste Milcamps.
As a precautionary measure, product recalls have also been decided in the Morbihan on products that were not yet on sale. Finally, the neighboring basins "are subject to careful monitoring", underlines the prefecture of Charente-Maritime.
How is the virus transmitted?
"Oysters are never at the origin of the virus, they only transmit it to humans," explains Laurent Champeau, director of the Regional Shellfish Culture Committee (CRC) of Poitou-Charentes, whom we reached by phone.
According to him, this contamination is explained both by the peak of gastroenteritis which affects France since December but also by the discharges of treatment plants saturated by heavy rains. "Filtration systems are not always optimal," he says. The virus will then proliferate in the water, which itself will contaminate the flesh of the shell. The oyster then becomes a vector for the transmission of the virus ”.
Another possible factor is boats that dump their droppings in the water.
How is a basin decontaminated?
"The virus has a limited lifespan in water," notes Jean-Baptiste Milcamps, from the Charente-Maritime prefecture. The decontamination then takes place naturally: "The basin is usually closed 28 days after the identification of the virus, while waiting for it to die".
What impact for oyster farmers?
"It is still too early to measure the impact this will have on our turnover," notes Laurent Champeau. The two closed basins in Charente-Maritime concern only a "geographically limited" area. "If the collection ban only concerns two small basins, the publicity made around this crisis could however affect sales".
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The situation is more worrying in Morbihan. The prefecture took four arrests in seven areas between December 18 and January 2, reporting "grouped human cases" of disease in the department. In all, 150 oyster businesses would be affected out of a total of 330, according to the Regional Shellfish Farming Committee of South Brittany.
In a petition launched on January 1, the "Oyster Alliance" of Morbihan demands "substantial compensation for all oyster farmers", questioning the state, which it accuses of being "incapable of protecting the coastline". "The elected officials of Morbihan gargle to welcome more and more locals and tourists, signing building permits without hesitation while forgetting to take care of the management of human waste and sanitation", denounce the oyster farmers.
For its part, the prefecture of Morbihan, which sees it as a "temporary crisis", expects a "rapid return to the quality of oysters".
What solutions are envisaged?
A meeting is planned soon at the Ministry of Agriculture to discuss possible new methods of rapid decontamination of oysters. The question of possible compensation for oyster farmers will also be studied.
Finally, an inventory of all the purification systems in Morbihan is planned to review the priority of the work to be carried out. " It's urgent. We are asking that sewage treatment plants quickly go upmarket to protect our marine environments, ”concludes Laurent Champeau from CRC.