GovWire

Contents

1. How to spot Marteilia refringens
2. How Marteilia refringens is spread
3. Preventing and controlling Marteilia refringens
4. Further information on Marteilia refringens
5. Legislation relating to Marteilia refringens
6. Who to contact if you suspect Marteilia refringens

Marteilia refringens is a protozoan parasite infecting molluscan shellfish including the native (or flat) oyster (Ostrea edulis) and blue mussel (Mytilus edulis).

Information on susceptible and vector species can be found here: GB Lists of susceptible and vector species.

Great Britain is free from Marteilia refringens expect for an infected zone (or Confirmed designation area) in the river Tamar which is 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 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 Marteilia refringens

Outbreaks are most likely to occur in late summer and autumn when water temperatures are at their highest.

Signs of the disease can include:

• Increase of dead / empty shells
• Gaping shells which dont close when touched or when exposed to air
• Weak

How Marteilia refringens is spread

Marteilia refringens is spread through movements of and contact with infected shellfish and contact with contaminated equipment or water.

Preventing and controlling Marteilia refringens

There is no treatment for Marteilia refringens.

Prevention is the best approach to disease control. You can protect your shellfish by being aware of the signs of Marteilia refringens 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 are Marteilia refringens 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 Marteilia refringens, particularly increased mortality and gaping shells. The FHI will investigate and if required will apply disease control measures.

Further information on Marteilia refringens

World Organisation for Animal Health (WOAH) Aquatic Manual chapter Marteilia refringens.

Legislation relating to Marteilia refringens

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 Marteilia refringens

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 Marteilia refringens 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 Marteilia refringens.

• 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