Ostreid herpesvirus-1 microvariant (oyster herpesvirus)
How to spot oyster herpesvirus, what to do if you suspect it and measures to prevent its spread.
Applies to England and Wales
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Details
Contents
- How to spot oyster herpesvirus
- How oyster herpesvirus is spread
- Preventing and controlling oyster herpesvirus
- Legislation relating to oyster herpesvirus
- Who to contact if you suspect oyster herpesvirus
Oyster herpesvirus is a viral disease affecting Pacific oysters (Magallana [Syn. Crassostrea] gigas). It is caused by Ostreid herpesvirus-1 microvariant, which is a disease causing (or pathogenic) form of the virus Ostreid herpesvirus-1. It can affect juvenile and adult Pacific oysters, although mortalities are usually highest in juveniles and can be up to 100%.
Information on susceptible and vector species can be found here: GB Lists of susceptible and vector species.
Great Britain is free from oyster herpesvirus except in infected zones known as Confirmed designation areas), and which are under disease controls to contain and prevent further spread, more information can be found here: Listed diseases of fish, molluscs and crustacea and their status - GOV.UK (www.gov.uk). It was first detected in GB in 2010, in a population of Pacific oysters on the north Kent coast.
The pathogenic microvariant of oyster herpes virus-1 is a ‘listed’ (also referred to as ‘notifiable’) disease which you are legally obligated to report immediately to the Fish Health Inspectorate (FHI), Cefas Fish Health Inspectorate - GOV.UK (www.gov.uk)
It does not affect humans.
How to spot oyster herpesvirus
Outbreaks are most likely to occur when seawater temperatures are above 16°C, late summer to mid-autumn when sea temperature is at its highest.
Signs of the disease can include:
- Increase of dead / empty shells
- Gaping shells which don’t close when touched or when exposed to air
- Weak
How oyster herpesvirus is spread
Oyster herpesvirus is spread through movements of and contact with infected shellfish and contact with contaminated equipment or water.
Preventing and controlling oyster herpesvirus
There is no treatment for oyster herpesvirus.
Prevention is the best approach to disease control. You can protect your shellfish by being aware of Oyster herpesvirus and other serious diseases and checking stock health regularly. Implement good husbandry and biosecurity practises.
Further information on biosecurity measures plans, guidance and templates can be found here: Biosecurity Measure Plans - Information and Templates - GOV.UK (www.gov.uk)
You must be sure any shellfish introduced into disease free areas are oyster herpesvirus-1 microvariant free. Do not buy shellfish of unknown origin. Follow the rules on moving aquatic animals: Aquatic animal health and movements guides - GOV.UK (www.gov.uk)
You must report it to the FHI immediately if you notice or become aware of shellfish showing any of the signs of oyster herpesvirus, particularly increased mortality and gaping shells. The FHI will investigate and if required will apply disease control measures.
Legislation relating to oyster herpesvirus
The Aquatic Animal Health (England and Wales) Regulations 2009
The listed diseases are in Regulation 1251/2008 as amended by the Animals, Aquatic Animal Health, Invasive Alien Species, Plant Propagating Material and Seeds (Amendment) (EU Exit) Regulations 2020, at Chapter 2, Annex 1A and Schedule 1 of The Aquatic Animal Health (England and Wales) Regulations 2009.
Who to contact if you suspect Oyster herpesvirus
If you suspect or know of a listed disease of fish and shellfish in England and Wales, you must report it immediately to the Fish Health Inspectorate (FHI), Cefas. You must also tell the FHI immediately if you know or suspect that increased mortality has occurred.
Under the Aquatic Animal Health (England and Wales) Regulations 2009 it is a legal obligation to report suspicion of oyster herpesvirus in any farmed or wild shellfish to the FHI. It is an offence under the Regulations to fail to inform the FHI of suspicion of oyster herpesvirus.
- Email: fhi@cefas.gov.uk
- Telephone: 01305 206700 - Monday to Thursday - 9:00 am to 5:00 pm, Friday 9:00 am to 4:30 pm
- For emergencies out of hours telephone: 01305 206630
Fish Health Inspectorate
Centre for Environment, Fisheries and Aquaculture Science (Cefas)
Barrack Road, The Nothe
Weymouth
Dorset
DT4 8UB