Infectious Salmon Anemia - ISA. Dagfinn Ulriksen, M.Sc Special Adviser Aquaculture Aon Grieg Norway

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Clementine Barnett
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1 Infectious Salmon Anemia - ISA Dagfinn Ulriksen, M.Sc Special Adviser Aquaculture Aon Grieg Norway 1

Initial comments Since the first confirmed outbreak of ISA in Norway in 1984, ISA has been associated with fear and sleepless nights for both farmers and Insurers.

2 Initial comments Since the first confirmed outbreak of ISA in Norway in 1984, ISA has been associated with fear and sleepless nights for both farmers and Insurers. ISA impose a serious threat to the sites suffering an outbreak. However, has it received a reputation of being the number one threat to the salmon farming industry unjustified??? The following presentation will present a summary of the scientific knowledge and a brief status of the disease in Norway and Chile in particular. Source: University of Bergen, Norway 2

3 ISA facts ISA is a viral disease caused by a Orthomyxoviridae virus (same family as the influenza virus) ISAV (ISA virus) affects Atlantic salmon and trout ISAV can replicate in other salmonoid species, but do not cause a disease outbreak (Rainbow trout etc.) ISAV is believed to be a natural occurring virus in North Atlantic salmon and trout populations ISAV spread through horizontal and vertical transmission ISAV have a limited lifetime in seawater (less than 48 hours) ISAV possess no threat to human health Affected fish is safe to handle and to consume 3

4 ISA facts ISAV affect the blood system causing damage to blood vessels and blood cells, causing anemia and subsequent death (clinical outbreak) Mortality 2-50% in affected cages IMPORTANT: presence of ISAV is NOT synonyms to ISA (disease) Annual site probability of an ISA outbreak in Norway is between 1-2,5% Transfer of ISAV to Chile through ISAV positive eggs from countries with natural occurring ISAV infected salmon populations ISA outbreaks has been confirmed in Norway (>1984), Canada east coast (>1996) Scotland (>1999), Chile (>1999*), US east coast (>2000), Faroe Islands (>2001) 4

5 History of ISA in Norway ISA outbreaks Norway Number of outbreaks : Regulations on wastewater disinfection from processing, regulation on disinfection of seawater/freshwater to hatcheries, regulation on dead fish control and removal/deposit. 1992: Introduction of combat zones and observation zones at and around outbreaks : Mandatory green certificate, ban on using seawater at hatcheries, movement of fish at seawater prohibited : Stop ISA campaign, regulation on transits/well 2005 boats, split generations (not mandatory) Source: Mattilsynet 5

6 History of ISA in Norway ISA has been detected along the entire Norwegian coast Most outbreaks in seawater Initially outbreaks were associated with high mortalities and classical symptoms ISA outbreaks today show a more complex picture with often less mortalities etc. Legislative impact has been positive in the development of ISA combat If ISA is confirmed, the official legislation is stamping out However, lately we have seen some adaptations (single cage culling) Legislation aim to reduce impact of outbreaks not to eradicate ISAV Normally an ISA outbreak in Norway result in low insurance claims, if any, compared to PD, IPN, salmon lice etc. 6

7 How is fish contaminated and how does ISAV spread Like most disease agens in aquaculture, ISAV originates from wild populations Trout and salmon believed to be the natural reservoir of ISAV Natural trout and salmon populations in both Norway and Scotland ISAV positive ISAV show distinct geographical characteristics (genotypes) Led to the hypothesis that the main route for ISAV is through vertical transmission Horizontal transmission important in hatcheries and during outbreaks in seawater Statistics and experiments have indicated that very few numbers of fry initially are contaminated (through vertical transmission). Numbers increase through production cycle before smoltification. 7

8 Why is ISA not a bigger problem in Norway? Annual site probability of outbreak: 1-2,5% Studies have shown that 22 out of 24 Norwegian hatcheries contain ISAV positive individuals. Unpublished studies from seawater indicate high prevalence here also. Why then the low numbers of clinical ISA outbreaks? Legislation on farming operations as imposed around 1990 has been important Biology of the ISAV also important 8

9 Biology of ISAV short version RNA virus: continuous replication Believed to be two different types occurring in farming operations: - Non virulent - Virulent Non virulent type believed to be very common Non virulent ISAV spread mainly through vertical transmission but also through horizontal transmission mainly in hatcheries Virulent ISAV a result of a mutation. Mechanism still unknown, but associated with stress factors. Virulent ISAV associated with clinical outbreaks Virulent ISAV spread through horizontal transmission Legislative discussions in the future will have to focus on these issues 9

10 What about the ISA situation in Chile ISA outbreaks in Chile Number of outbreaks Q3-07 Q4-07 Q1-08 Q2-08 Q3-08 Q4-08 Source: SERNAPESCA 10

11 What about the ISA situation in Chile ISA outbreaks Norway Number of outbreaks Present situation in Chile????? 2005 Source: Mattilsynet 11

12 ISA situation in Chile First detection in 1999 on Coho salmon Unclear weather this was a true outbreak or detection of a carrier virus Virus later genotyped to be of Canadian origin (Canada East Coast) No detections until July 2007 (no testing either) Virus probably present for a long time in Chilean farmed salmon populations Outbreaks prior to 2007 probably camouflaged as SRS outbreaks SRS outbreaks and losses stable from 2001 through fold increase in SRS outbreaks and losses in late 2005 and ISA???? In addition, Chile suffered heavy Caligus infections 2005 and Caligus could be an important vector for horizontal transmission and maintaining a strong virus infection within a farming area. ISAV from Chilean outbreaks (2007/2008) to be of Norwegian origin (vertical transmission) 12

13 ISA situation in Chile ISA were able to develop into an uncontrolled epidemic as a consequence off certain factors in farming operations like: - High densities/high number of fish at many sites - Carrying capacity breached at many areas/sites - More than one company and multiple generations in a small area - Deterioration in the general biological status - Increasing levels of Caligus Horizontal transmission between single sites in seawater as a consequence of the above factors nourish a wide spread epidemic 13

14 What is the Chilean aquaculture industry doing to mitigate ISA? Stop in, or reduced import of eggs Sernapesca to impose new regulations on farming operations - New zone plan - Each zone to contain management areas - Areas to contain one generation and one species (all in/all out) - Zones to contain strickt biosecurity barriers etc. Some farming companies have already imposed strict internal regulations: - Screening of brood fish for presence of ISAV - Screening of fry/pre-smolts for ISAV - Main goal is to produce ISAV free smolts and subsequent ISAV free broodstock (break the cycle) New seawater production and husbandry models introduced 14

15 Prognosis for ISA in Chile Provided a joint effort by all operators in Chile, a situation comparable to the situation in Norway should be possible to obtain (1-2% per site outbreak probability, or even less) within the next 2-3 years. By strict screening of brood fish + fry/pre-smolt, introduction of ISAV free smolt, or low prevalence ISAV smolts should be possible. This, combined with no natural reservoirs of ISAV (apart from present affected farms), should over time make it possible to control this disease. Introduction of new production and husbandry models will have positive effect on the total disease situation in Chile (as it had in Norway) 15

16 Concluding remarks Knowledge of the virus and how it spread are continuously evolving Provided we have an industry and a legislative body that use available knowledge and expertise, ISA could possess a very low problem and risk to both farmers and Insurers However, all parties involved must move in the same direction 16

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18 ISA outbreaks Time period in seawater before outbreaks No. of outbreaks No. of months Source: National Veterinary Institute, Norway 18

19 Seasonal distribution of ISA outbreaks in the period Season Number of outbreaks January March 5 April June 12 July September 7 October - December 8 Source: National Veterinary Institute, Norway 19

20 Site proximity in Chile Source: Google Earth 20

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The surveillance program for infectious salmon anaemia (ISA) and bacterial kidney disease (BKD) in Norway 2016

Annual Report The surveillance program for infectious salmon anaemia (ISA) and bacterial kidney disease (BKD) in Norway 2016 Norwegian Veterinary Institute The surveillance program for infectious salmon