Engineers from the Syndicat mixte du bassin de Thau (SMBT), in Hérault, have developed an innovative tool that could well revolutionize the work of oyster farmers. Supported by the Montpellier company IAGE, a specialist in environmental biological analysis, they have developed a new method for detecting the micro-organisms at the origin of the epidemics that decimate cupped oysters.
This species, which is particularly sensitive to its living environment, filters very large quantities of water every day, and thus captures absolutely everything that lies around in its environment. In particular viruses and bacteria, which bask there.
“It’s truly catastrophic for breeders”
This system, the project of which has been called Pathogens, is currently being tested in the Thau basin. It can detect, in water and shellfish, three supervillains that harm livestock: ostreid Herpes virus and Vibrios of the Splendidus and Aestuarianus species, which cause significant losses of oysters, without represent any danger for consumers who love it.
“There is a natural mortality in cupped oysters, the breeders know it”, explains Romain Pete, trade unionist at SMBT. But these three pathogens are responsible for terrible excess mortality for cupped oyster producers. “Depending on the year, up to 80%, or even more, of the livestock can be decimated”, because of them, points out this researcher in marine biology. “And that is truly catastrophic for breeders. It is also because they are the most destructive that the project carried out in the Thau basin by the SMBT and the company IAGE particularly targeted them.
A phenomenon that appeared “brutally in 2007”
Patrice Lafont, president of the Mediterranean Regional Shellfish Committee (CRCM), expects “a lot from science” to solve this “large-scale” problem. “It’s a phenomenon that appeared suddenly in 2007, in the Mediterranean, then on the Atlantic coast, says the shellfish farmer. And we don’t know how to explain it. »
Until now, it has been difficult to detect the viruses and bacteria that cause disease. Or else too late, once the oysters were touched, and they began to “yawn”, that is to say to open slightly. “This means that the pathogens are present, and that they will begin their funereal work”, confides Romain Pete. The tool developed in the Thau basin makes it possible to flush out these viruses and bacteria well upstream, in the water, thanks to a fairly recent technique, digital PCR, which allows much more sensitive detection of pathogens.
The results collected by this innovative project will be coupled with environmental data, in order to design an epidemiological model intended to preserve the good health of cupped oysters. And make farms more resilient.