On 1 August 2012 Fish Health Inspectors from the Centre for Environment, Fisheries and Aquaculture Science (Cefas) examined stock from a shellfish farm in the River Blackwater Estuary, Essex following reports of high levels of mortality in Pacific (rock) oysters Crassostrea gigas.



Samples taken from the affected site were confirmed as positive for oyster herpesvirus (OsHV-1 var), and a Containment Area has been declared in the River Blackwater Estuary, Essex and the River Colne Estuary, Essex.



In accordance with provisions under the Aquatic Animal Health (England and Wales) Regulations 2009 movements of shellfish out of the Containment Area in the River Blackwater Estuary, and the River Colne Estuary have been restricted, following the confirmation of oyster herpes virus (OsHV-1 var).



Cefas acting on behalf of Defra has issued a confirmed designation prohibiting the movement of Pacific oysters from the Containment Area and applying the following additional control measures:

You must apply to the Fish Health Inspectorate for permission if you wish to move any Pacific oysters out of the area, including movements into purification centres (depuration plants).

You must notify the Fish Health Inspectorate of any increased or unexpected mortality observed in shellfish stocks.

Confirmed Designation number CD Area 03 issued on 27 March 2009 for the control of Bonamiasis in Ostrea edulis (native oysters) remains unaffected by this notice.



OsHV-1 var affects Pacific oysters and can result in high rates of shellfish mortalities.



OsHV-1 var is an emerging disease that has been associated with high levels of mortality in Pacific oysters in France, Jersey and some bays in the Republic of Ireland.



There are no implications for human health.



Any suspicion of the presence of OsHV-1 in Pacific oysters should be immediately reported to the Centre for Environment, Fisheries and Aquaculture Science (Cefas) in Weymouth