Infectious salmon anaemia (ISA)
How to spot infectious salmon anaemia (ISA), what to do if you suspect it and measures to prevent its spread.
Applies to England and Wales
Documents
Details
Contents
- How to spot ISA
- How ISA is spread
- Preventing and controlling ISA
- Further information on ISA
- Legislation relating to ISA
- Who to contact if you suspect ISA
Infectious salmon anaemia (ISA) is a viral disease mainly affecting farmed Atlantic salmon in seawater, although some cases have been reported in freshwater. Other susceptible species include rainbow trout and brown trout.
More information on susceptible and vector species can be found here: Lists of possible Susceptible and vector species (publishing.service.gov.uk)
Great Britain is free from ISA and it is a ‘listed’ (also referred to as ‘notifiable’) disease which you are legally obligated to report immediately to the Fish Health Inspectorate - GOV.UK (www.gov.uk).
ISA was first detected in Norway in the early 1980’s. It has since been found in Canada, Scotland Faroe islands, USA and Chile. The UK has had 3 outbreaks between 1998 and 2009.
It does not affect humans.
How to spot ISA
ISA can occur all year round, but generally in early summer and winter. Infected fish may be lethargic, lack appetite and hang at the margins.
Signs of the disease can include:
- Lethargy
- Pale gills
- Swollen abdomen
- Bulging eyes
- Dark and swollen spleen
- Dark liver
How ISA is spread
ISA is spread through contact with infected fish. Infected fish may release virus from their skin and mucous, and from their urine, faeces, ovarian fluid and ova.
ISA can be spread through movements of infected fish, contaminated water, and contaminated equipment such as husbandry, angling and fish transport equipment and boats.
Infected fish do not have to be sick or diseased to spread the virus.
Preventing and controlling ISA
There is no effective treatment for ISA.
Prevention is the best approach to disease control. You can protect your fish by being aware of the signs of ISA and other serious diseases and checking stock health regularly. Implement good husbandry and biosecurity practises including surface disinfection of newly fertilised and eyed salmonid eggs using an appropriate method.
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 fish introduced are ISA free. Do not buy fish of unknown origin. Follow the rules on importing, exporting and moving fish.
You must report it to the FHI immediately if you notice or become aware of fish showing any of the signs of ISA. The FHI will investigate and apply disease control measures if required.
Further information on ISA
World Organisation for Animal Health (WOAH) Aquatic Manual chapter ISA.
Legislation relating to ISA
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 ISA
If you suspect or know of a listed disease of fish or 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 ISA in any farmed or wild fish to the FHI. It is an offence under the Regulations to fail to inform the FHI of suspicion of ISA.
- 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