One year after norovirus contamination, oyster farmers decide to break a taboo

It’s not easy to open oysters, a few hours before Christmas Eve. Jean-Pierre, veterinarian in Chabanais, in Limousin, nevertheless tackles it every year. “I have to open six dozen because there are often ten of us at the table,” he says. It can easily take half an hour! » Around the table, the mollusk always provokes contrasting reactions. While Bernard, the oldest member of the family, discreetly throws himself on them, Amandine, the young cousin, swallows them one after the other and Nikki, originally from England, grimaces at the strange customs of the French. Despite this frenzied consumption, Jean-Pierre’s family was not affected by the psychosis that set in last year in the middle of the end-of-year holidays. Remember. From December 21, 2023, collective foodborne illness (Tiac) hit thousands of consumers, contaminated by the gastroenteritis virus, called norovirus. The authorities quickly announced a ban on sales of oysters from the Arcachon basin, and recalls followed in Morbihan, Manche, Loire-Atlantique and Vendée.

A year later, Thierry Lafon, oyster farmer in Gujan-Mestras (Gironde) and president of the Arcachon Basin Water Defense Association, still remembers this dark series: “All eyes were turned to us then that we were victims of an injustice Until last year, we did not dare to denounce the origin of the contamination, for fear of revealing the extent of the problem. But our sales have fallen so much that the situation. has become untenable.” So now it’s all up in arms. Thierry Lafon decided to break the taboo and file a complaint against his own community. He criticizes the Arcachon Basin Intercommunal Union for not properly maintaining its sanitation network. Result: in the event of heavy rain, the wastewater from this aging circuit contaminates its oysters, raised at sea. Other oyster farmers have followed suit. Since then, environmental investigations have been launched and have confirmed their fears.

“When norovirus pollutes oysters, it is systematically because of our wastewater,” says Soizick Le Guyader, biologist at Ifremer, an institute specializing in oceans. In the event of a gastroenteritis epidemic, it goes into our toilets and spreads through the sanitation system in our towns. However, most of these networks are difficult to maintain and tend to overflow during heavy rains. » The very resistant norovirus then spreads at sea, before contaminating the oysters, sometimes for several weeks.

Strong media impact

An unsavory situation, which threatens the entire economy of the precious shellfish. Because if norovirus contamination only affected 2% of national production, the media coverage which accompanied the poisonings was devastating. “Most oyster farmers saw their sales drop by 40 to 60% after this crisis,” notes Philippe Le Gal, president of the National Shellfish Farming Committee and oyster farmer in Surzur (Morbihan). However, the mollusk is far from being the only vector of gastroenteritis. Very contagious, it can be transmitted through a sick person or through poorly washed salad. But it is the oyster, a fresh and living product, which crystallizes consumer distrust. Raised in a marine environment, it is dependent on its environment. “Oyster farmers have always had to adapt to climatic and health threats,” continues Philippe Le Gal, who launched his operation in the 1990s. At the time, it was bacteria E.coli which affected his oysters. “Now it’s norovirus. And the threat is increasing with climate change. The more abundant the rains, the more wastewater can overflow into the sea,” he recalls.

Monitoring and renovations

The end of the silence around wastewater allows solutions to be put in place. Since December 2024, oyster producers have been experimenting, in 70 areas of the French coast, with a monitoring system in partnership with local authorities and the Veolia water management service. It aims to identify the presence of norovirus through weekly laboratory checks. The complaints of breeders are also starting to bear fruit. Many communities are launching large projects to renovate their sanitation networks. Like the intercommunality of Auray Quiberon Terre Atlantique, in Morbihan, where elected officials put 50 million euros on the table to improve the circuit. Enough to reassure breeders and consumers. And so far, no outbreaks of gastroenteritis have been reported.