Priority Diseases of Farmed Salmon Flashcards
1
Q
Death of diseased farm salmon
A
(article 2020) deaths at all new high
- suffer from wide range diseases = crowded conditions
- high levels of stress = caused by sea lice infesttation and its treatment, handling and crowding = increasingly susceptable to infection
- Amoebic Gill Disease
~ causes resp problems and death through asphyxiation
~ major mortalities scotland - 50% losses on salmon farms
- 2019 £3 bilion fish farming firm Mowi reported deaths of around 700,000 salmon in just 3 months
diseases/sea lice infestations among top reasons cited for huge no. deaths
- but not clear of exact cause
2
Q
Diseases cause mortality and Non-pathogenic reasons for salmon death
A
- salmon pox virus
- proliferative gill disease
- cardiomyopathy syndrome,
- pancreas disease,
- anaemia,
- fungus
- bacterial challenges
- treatment losses (misuse chemicals, de-licing machines),
- handling errors,
- algal booms,
- jelly fish,
- seals,
- poor water quality
- oxygen shortage
3
Q
Scotlands 10 year farmed fish health framework
A
Areas of action
- information flow and transparancy
- gill health
- sea lice
- cleanerfish
- production cycle and on-farm management
- licencing regime and medicine use
- climate change and ocean acidification
- require commitment and resource from all of its partners
- interaction with no. related activities inc farmed wild fish interactions, help inform future development of framework and working activities
4
Q
Economically important diseases of salmon
A
- Notifiable diseases – e.g. Infectious salmon anaemia, Bacterial kidney disease (BKD) = info from marine scotland website/ceefax
- Sea lice infection – Sea lice infect salmon skin and if not controlled they can cause lesions and secondary infection
- Viral induced cardiomyopathies – Group of diseases, cause similar pathologies. No control measures available except for salmon alphavirus
- Gill health problems – complex disease scenario, contributed by many pathogens. (global warming) bac, virus, parasites cause probs similtaneously. compromise resp system
5
Q
Sea lice infestation
- about
A
- Sea lice are copepods (Crustaceans)
- Occur naturally in coastal and open ocean populations of fish, as well as in freshwater environments
- There are over 300 species of lice, most of which are parasitic on fish
- Natural parasite of wild and farmed sea-caged Atlantic salmon ( Salmo salar)
~ Lepeophtheirus salmonis (common)
~ Caligus elongatus
6
Q
sea lice infestation
- impact
A
- Sea lice infestation is a major issue in many salmon producing countries
- Productivity loss due to lice infestations has cost GBP 1.8 billion in Scotland alone
- In Norway, the total loss caused by sea lice is equivalent to 8.81% of the industry’s total production value
- welfare concern - stress, death, transmit to wild fish
7
Q
sea lice infestation
- life cycle
A
2 main stages - free swimming stage - parasitic stage 2 free swimming stages - noplius stage x2 - copepodid (infective stage) Parasitic stages - chalmus x4 stages (static = parasite attatched to and feed on fish but not mobile) - pre-adult x2 (mobile) - adult (determine if male or female) ~ female = long paired eggstrings at lower end
8
Q
Sea lice regulation
- industry requirements
- industry code of good practice
A
Industry Requirements
- Satisfactory measures – control prevention and reduction
- Legislative requirements – ‘2008 Record Keeping Order’
- Industry Code of Good Practice
Industry Code of Good Practice
- weekly counts 25 fish (5 fish from 5 cages) average no adult female lice exeeds 2 = manditory to report to fish inspectorate
- suggested trigger 0.5 (Feb-June) 1 (July-Jan) Ls adult female
- management agreements
- appropriate training
- good practice in the use of medicinal products
9
Q
economic impact of virus diseases
A
- mortalities
- runting
- post havest condemnation
10
Q
Viruses causing cardiomyopathies
SAV, PMCV, PRV
A
- Salmonid alphavirus (SAV) ~ Salmon pancreas disease (SPD or PD) - Piscine Myocarditis virus (PMCV) ~ Cardiomyopathy syndrome (CMS) ~ inflamation of heart - Piscine Reo virus (PRV) ~ Heart and Skeletal muscle inflammation (HSMI)
11
Q
economic impact of virus diseases
A
- mortalities - range from 5-50% of stock
- runting - poor growth
- post havest condemnation - pale musculature or black colour discolouration
~ muscle inflamation,
~ macrophages gather around lesions,
~ preaching pignemted macrophages = melana macrophages
12
Q
Salmonid alphavirus
- virus
- virus type
- tissue tropism
- age susceptability
- clinical signs
A
- alpha virus
- RNA +ve sense ssRNA (group 4)
- pancreas, heart, skeletal muscle
- post smolts and adults 1st and 2nd year
- lethargy and off food, faecal casts = see large amount of undigested food, white in colour, apear as tails from animal
13
Q
Piscine Reo virus
- virus
- virus type
- tissue tropism
- age susceptability
- clinical signs
A
- Piscine reovirus
- RNA segmented linear dsRNA (group 3)
- heart and skeletal muscle
- post smolt 1st year in sea
- sudden death, ascites in PM = accumulation of fluid in abdominal cavity
14
Q
Piscine Myocarditis virus
- virus
- virus type
- tissue tropism
- age susceptability
- clinical signs
A
- toti virus
- RNA linear dsRNA genome (group 3)
- heart and liver
- sea water - smolts, post smolt and adult
~ when fish handled just before harvest = second heart failure
~ have been reported from hatchery and brood stock very recently - sudden death, flabby hearts in PM, skin haemorrhages
15
Q
Virus disease risk for atlantic salmon during production cycle at sea
A
- sea water transfer and stay in sea for 2 years
- HSMI infection 5-8 months into sea water phase
~ clinical 7-9 months - PD infection 10-12 months
~ PD clinical 11.5-13.5 months - CMS infection 14-17.5 months
~ CMS clinical 16-18 months
(all diseases virus induced cardiomyopathies) - now at seawater transfer, serious infection at early stages in sea water and hatchery (no clinical signs at hatchery) with IPNV infection
- pd also canged as can infect fresh water as well as sea water fish
