Waiting game

Published on
August 8, 2010

For the last six years, the UK oyster industry has anxiously watched while disease has obliterated France’s Pacific oyster (Crassostrea gigas) production. Then, UK producers’ worst fears were realized a few weeks ago when that same disease — the recently discovered OsHV-1 (oyster herpesvirus type 1) — was found on the Kent coast, in southern England.

According to reports, OsHV-1 wiped out between 8 and 10 million oysters at the Seasalter Shellfish site in Whitstable. Since the outbreak, the shellfish sector has been on tenterhooks, taking some comfort from the fact the virus has still only been found at that one location.

David Jarrad, assistant director of the Shellfish Association of Great Britain (SAGB), explained that OsHV-1 is a new variant strain of a virus that had been around for many years. The initial virus had never created any mortality, but then eight years ago mortalities started to be reported in France.

Five years ago, keen to prevent similar problems in the UK, the SAGB advised its members not to import French oysters for “re-watering” in the UK. Jarrad told SeafoodSource that the move was purely on the basis that no one knew what the problem was, but it was widely agreed there was indeed a problem.

Only last year the OsHV-1 was discovered and linked to the large scale mortalities in France — every area in the country that had mortality was identified as having the variant herpes virus. Yet the French still argue today that it wasn’t the main cause of the problem and that another, as yet unknown factor, was to blame.

However, the SAGB pushed authorities last year to implement new European legislation that would prohibit the off-site movement of shellfish infected with the herpes virus. That law was put in place for a one-year period, starting January 2010. Up to the start of July, OsHV-1 had not been found around the UK coast, but then sadly there was the significant mortality off the north Kent coast. Seasalter’s shore site was tested and diagnosed positive for the virus. Incidentally, its hatchery tested negative.

As per the European legislation, a containment zone has been set up and no shellfish are allowed to be moved out of that area except for direct human consumption. Saying that, the mortalities were so extreme there was little left for human consumption.

It should be highlighted that there’s absolutely no concern about the consumption of oysters even if they are highly infected with the herpes virus. “The legislation is you can take oysters from a containment area and put them on the market and it wouldn’t say that if there was an issue,” said Jarrad.

The obvious question is what’s the chance of OsHV-1 spreading to other UK fisheries? The problem is it’s not yet known how the disease came to be in the Kent area in the first place. It could have been transmitted in many ways, such as in the ballast water of ships or via shellfish attached to the underside of vessels. The SAGB said it’s doubtful whether the true passage of the disease’s arrival will ever be ascertained.

All the UK industry can really do is wait and hope that the decimation of French stocks is not repeated on its side of the English Channel. Five or six years ago, there were mortality events in only one or two sites in France. Today, it’s prevalent in almost every oyster-growing area in the country, said Jarrad.

The virus outbreak in France has meant that the availability of oysters has significantly fallen, and prices have subsequently increased. So in the short- and medium-term, irrespective of the outbreak in Kent, the industry is looking at elevated prices. And the likelihood is there will be a shortage in the autumn, so both buyers and consumers can expect prices to creep up further. In the short-term, Jarrad said the industry will benefit from the prices in the market. However, it will have to counter that with inflated prices for oysters from hatcheries because the demands put upon hatcheries from the UK and overseas have been enormous.

To date there has been no consumer reaction to the herpes outbreak. But buyers are expected to remain loyal to UK oysters for the time being. As one foodservice supplier told SeafoodSource, “Britain may only produce a tiny fraction of the oysters of countries like France, but they’re regarded as among Europe’s finest oysters.”

The long-term effects remain anyone’s guess. But if the UK virus escalates, it’s feasible this situation, combined with the much more serious problem across the Channel in France, will widen the market door to other oyster-producing countries.

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Contributing Editor reporting from London, UK

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