Oyster virus reaches Great Britain

The same herpes virus that devastated France’s oyster industry has struck Pacific oyster stocks in Great Britain for the first time.

Inspectors with the country’s Centre for Environment, Fisheries and Aquaculture Science (Cefas) have confirmed that oyster samples taken from a shellfish farm in Whitstable, Kent, have tested positive for the OsHV-1 virus. Cefas inspectors visited Seasalter Shellfish after the firm noticed a high mortality rate among its Pacific oyster stocks.
A ban on the movement of oysters in certain parts of Kent, including The Swale, Thames and North Kent Coast, has been implemented to prevent the spread of the outbreak. The ban “will continue until tests in the containment area prove there is no longer a threat of transfer of the herpes virus,” a Cefas spokesperson told SeafoodSource.

The OsHV-1 virus has been linked to high mortality levels in Jersey and some bays in Ireland. But the most severe impact has been in France, where the disease has killed juvenile oysters in most of the country’s key oyster-producing areas. France is Europe’s biggest oyster producer, yielding about 120,000 metric tons annually.

The extent of mortality from the virus is so harsh that France’s oyster production is expected to fall 40 percent this year. The decline is likely to continue over the next two years, largely because oysters require three years to reach maturity.

According to France’s shellfish organization, Comite National de La Conchyliculture, the virus is threatening about one-quarter of France’s 4,200 shellfish firms, but the specific cause of the virus still remains a mystery. In a bid to shed light on the phenomenon, three scientific programs are under way in France to study oyster juveniles, all coordinated by the country’s Institut français de recherche pour l’exploitation de la mer (Ifremer).

In the United Kingdom, the current containment zone also incorporates wild Pacific oysters and native oysters, which means “it’s not enough that farmed oysters are OK,” added the spokesperson, referring to the ban.

According to Cefas, the disease may have entered the affected area through the movement of live oysters through contaminated equipment. A warm summer isn’t helping, either — officials suggest that the disease is temperature dependent and occurs when water temperatures exceed 16 degrees C.

Around 1,000 metric tons of Pacific oysters are produced in the UK each year, in addition to some 250 metric tons from wild fisheries. This compares to a total of 444 metric tons of native oysters, both wild and farmed.

The Shellfish Association of Great Britain and Association of Scottish Shellfish Growers warned two weeks ago that the virus in France may create major oyster supply shortages in the UK. At the time, the disease has not been reported yet in the UK.



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