Pancreas Disease (PD)

Physical Signs:

• Development of poor growing and emaciated fish ("runts") 10
• Increased mortality 10
• There are usually few gross findings at necropsy. Occasionally, small haemorrhages (petechiae) can be seen in the visceral fat between the pyloric caeca, and over time this fat is reduced. Affected fish often have an empty gastrointestinal tract 14

Behavioral Changes:

• Sudden loss of appetite 10
• Lethargic fish that tend to stand close together near the water surface and against the direction of the currents 10
• Abnormal swimming patterns 10
• Difficulties maintaining correct position in water due to muscle damage 10

Early Stages: A sudden stop of eating, followed by lethargy and abnormal swimming (for example difficulty maintaining normal posisition in the water or fish gathering against the current) 310.

Advanced Stages: Mortality usually begins 2–3 weeks after the first signs 10. High levels of mortality may occur, together with reduced growth, visibly stunted runts with poor body condition, and downgraded fillet quality at slaughter 3.

• Different SAV subtypes (genotypes) are associated with PD in Atlantic salmon and rainbow trout in marine farms. There are seven sybtypes of SAV (SAV1- SAV7) that have been described with distinct geographical distributions:

• Horizontal transmission between fish: The virus spreads mainly by horizontal transmission through water, from infected to susceptible fish within and between cages 310.
• Seawater currents: Virus particles can be carried by seawater currents, enabling spread from infected sites to neighbouring farms 10.
• Human activities: Movements of live fish (including smolts), well‑boat transport, equipment and work boats that are not properly disinfected can contribute to spread between sites and regions 10.
• Insufficient biosecurity: Lack of preventive measures between sites (for example poor fallowing, inadequate separation of risk zones, or insufficient cleaning and disinfection) increases the risk of transmission and establishment of PD in new areas 110.

Clinical Examination: Observation of physical and behavioral symptoms like reduced feed intake, lethargy, abnormal swimming and stunted runts 210. Clinical findings alone are not specific for PD and must be confirmed by laboratory testing.

Laboratory Tests:

• RT-PCR (Real-time Polymerase Chain Reaction): Primary method for detection of viral RNA. In Norway, genotyping of positive samples (SAV2 vs SAV3) is mandatory when PD is suspected or detected, to support surveillance and control measures 10.
• Histopathology: Tissue samples (typically pancreas, heart and skeletal muscle) are examined for characteristic lesions associated with PD, including degeneration and inflammation in exocrine pancreas, heart and red skeletal muscle. Histopathology is central for differentiating PD from other cardiac and muscular diseases 25 10.
• Additional methods: Virus isolation in cell culture, immunohistochemistry to detect viral antigen in tissues, and analyzing bloodserum/plasma can be peformed in selected cases 10.

Biosecurity Protocols:

• Strict quarantine measures for new stock to prevent the introduction of SAV 2.
• Regular disinfection of well‑boats, equipment and slaughter/processing facilities, treatment of transport water, and careful control of seawater intake for post‑smolt production in PD‑affected zones are key measures to prevent spread with water and equipment 810..
• Government regulation and surveillance programmes, like the PD regulation in Norway, enable early detection of PD and help to limit spread between sites and regions. Such strategies, based on zoning, movement restrictions, surveillance and fallowing, have also been implemented in several European salmon‑producing regions 610.

Vaccination Strategies:

• Several commercial vaccines against PD are available and have shown effectiveness in reducing infection levels, mortality rates, and viral shedding 1 7.
• A monovalent vaccine was made commercially available in 2007, and a multivalent vaccine capable of immunizing fish against multiple SPDV strains was introduced in 2015 1.
• Conventional inactivated virus vaccines have shown variable effects in mitigating the disease, whereas a DNA vaccine used over the last 7–8 years is thought to have contributed to the recent reduction in reported PD cases in Norway 21.
• In Norway, the conventional oil‑adjuvanted inactivated virus PD vaccine commercially available is ALPHA JECT® micro 1 PD (Pharmaq), and the DNA PD vaccine is Clynav® (MSD Animal Health). The latter one only offers protection against SAV3. 22[23](https://www.felleskatalogen.no/medisin-vet/clynav-msd-animal-health-645975[felleskatalogen](https://www.felleskatalogen.no/medisin-vet/dyreeier/pil-clynav-msd-animal-health-646224).
• In the UK and Ireland, AQUAVAC® PD3 (MSD Animal Health) is available as a trivalent oil‑adjuvanted inactivated virus vaccine that induces active immunity against pancreas disease, infectious pancreatic necrosis (IPN) and furunculosis 24

Farm Management Practices:

• Reduced stocking densities to decrease the risk of virus transmission 1.
• Regular health monitoring and early detection programs to identify and manage outbreaks promptly 19.
• Implementing all-in/all-out stocking practices to reduce the risk of spreading infections 1.
• Avoiding unnecessary stressful operations during high‑risk periods can help reduce the impact of PD 13.

Supportive measures:

• Functional feeds can be used as a supportive measure during PD risk periods and outbreaks to help maintain digestion, condition and survival, but they do not eliminate infection 14 15

Notable Outbreaks:

• Norway (2010): Economic losses were estimated to be 0.72 € per kg in Norwegian salmon production due to high mortality rates, reduced growth, and reduced quality of the finished product 16

Response Strategies and Outcomes:

• Norway: PD is a listed fish disease in Norway (category F), and any suspicion or detection of PD must be reported immediately to the Norwegian Food Safety Authority (Mattilsynet) 10.
• PD has been regulated in Norway through specific regulations since 2007, with an intensive surveillance programme in 2012–2017 followed by a national PD regulation introduced in 2017 with the goal of reducing disease impact, preventing establishment in surveillance zones and limiting spread of SAV2 and SAV3 1710.
• All sites with farmed salmonids in raw seawater are subject to monthly PCR testing for SAV, with positive results notified to Norwegian Food Safety Authority 1710.
• In 2008, Norway divided its coastline into two administrative zones, with one zone defined as an endemic PD zone from Jæren to Skjemta (Flatanger), and two surrounding surveillance zones along the rest of the coast 10.
• Key control measures include movement control, coordinated operation and fallowing over larger areas, treatment of transport water, control of seawater intake for post‑smolt production, and rapid slaughter of infected populations outside the endemic zone 1710.
• Overall, these measures have helped to contain PD mainly within the endemic zone and to prevent wider establishment in the national surveillance zones.

Lessons Learned: The importance of early detection, robust biosecurity, and coordinated response efforts in controlling PD outbreaks has become clear. Overall, these measures have helped to keep PD largely confined to the endemic zone and to prevent wider establishment in the national surveillance zones. National statistics from Norway also indicate an overall gradual reduction in the number of PD cases caused by both SAV2 and SAV3 since 2018 18.

PD Incidence in Chile:

• Chile has also faced challenges with PD, impacting both farmed and wild salmon populations.
• The incidence of PD in Chile has been influenced by factors such as water temperature and farming practices.

Geographical Spread:

• PD outbreaks in Chile have been reported across various regions, with some areas experiencing higher rates due to environmental conditions and farm density.

Economic Impact:

• The economic impact in Chile includes significant losses from fish mortality and decreased productivity.
• The Chilean salmon farming industry has incurred substantial costs related to PD management and control measures.

Treatment & Management:

• Chile has adopted similar strategies to Norway and Scotland, including vaccination, biosecurity measures, and health monitoring.
• Efforts to control PD in Chile also involve environmental management practices to reduce the risk of outbreaks.

PD Incidence in Norway:

• At present, two PD epizootics caused by different SAV genotypes are recognised in Norway: most PD cases are due to SAV3 and occur south of Stadt, whereas nearly all PD cases caused by SAV2 are found north of Hustadvika 10.
• Between 2009 and 2011, there were 75 to 89 outbreaks per year 20
  • In 2018, 134 confirmed PD cases were registered, and the number has decreased gradually since then: 77 cases in 2022, 58 in 2023, 43 in 2024, and 37 in 2025 19.

Economic Impact:

• In 2010, the economic loss was estimated to be 0.72 € per kg in Norwegian salmon production 16

Treatment & Management:

• Vaccination in endemic areas, PD regulations, strong biosecurity, movement control and coordinated fallowing (see “Response strategies and outcomes – Norway” for details).
• Publicly available disease maps and official reports (via BarentsWatch and Mattilsynet) allow geographical monitoring of PD outbreaks and support rapid response.