Viral Diseases in Cold water Fish

Infectious pancreatic necrosis (IPN) virus

-\> family of the Birnaviridae (60nm, non-enveloped)
-\> two serotypes (A and B)
-\> different genotypes

Infectious pancreatic necrosis (IPN) virus

-\> erratic swimming, darkening of the skin, abdominal swelling, exophtalmia, pale gills, petechial haemorrhages on the ventral surface, white/yellow casts from the anal orifice
-\> lack of food in the digestive tract, milky mucous substance, petechial haemorrhages and visceral ascites

Infectious pancreatic necrosis (IPN) virus

-\> mortality in fry, no disease in older fish
-\> pancreatic necrosis, acute sloughing of the mucosal epithelium, congestion and necrosis of liver

Aquabirnavirus-related diseases

Diagnosis:
• symptoms
• macroscopic lesions: abdominal swelling
• histopathology: pancreatic necrosis/sloughing of intestinal epithelial cells
• virus isolation BF-2 and CHSE-214 (+ serological identification) • immunofluorescence
• qRT-PCR
• serology

Vaccination:
• inactivated vaccines (ip), rVP2 (ip or oral), DNA vaccine (ip or oral)

Infectious haematopoietic necrosis virus (IHNV) virus

-\> belongs to the rhabdoviridae
-\> sudden increase in fish mortality (mainly young animals)

Infectious haematopoietic necrosis virus (IHNV) virus

-\> swim rotating about the long axis or whirling violently
-\> dark coloration, distended abdomen, exophthalmia, pale gills, mucoid, opaque faecal casts, petechial haemorrhages at the base of the fins and vent and sometimes behind the head

Infectious haematopoietic necrosis virus (IHNV) virus

-\> viral entry through gills, skin, fin base, oral region, oesophagus, stomach
-\> secondary replication in haematopoietic tissues of kidneys and spleen (2-4days)
-\> necrosis in haematopoietic tissues, porsterior kidney, spleen, liver, pancreas, digestive tract

Infectious haematopoietic necrosis virus (IHNV) virus

Immunity:
• early antiviral response: interferon
• specific antiviral response: temperature-dependent induction of neutralizing antibodies (\>3-4 weeks) -\> clears the virus (\>54days)
• long term antiviral respons: memory stage (\>6 weeks)

Rhabdovirus-related diseases

Diagnosis:
• symptoms
• macroscopic lesions: dark coloration, distended abdomen and haemorrhages
• histopathology: necrosis of the granular cells of the alimentary tact
• virus isolation EPC + BF-2 (+ serological identification)
• immunofluorescence
• qRT-PCR
• serology

Vaccination:
• DNA vaccine expressing the G protein (ip or oral)

Viral haemorrhagic septicemia (VHS)

-\> belongs to the rhabdoviridae
-\> three serotypes
-\> 60°-30° latitude north (not in the southern hemisphere)
-\> 4-14°C: disease / 15-18°C: less problems

Viral haemorrhagic septicemia (VHS)

-\> flashing, leaping, corkscrewing motion, surface swimming
-\> mortality
-\> pale gills, accumulation of ascitic fluid, swollen abdomen, iris eye haemorrhage and exophtalmia, faecal casts
-\> haemorrhages over the liver, in adipose tissue & muscles

Viral haemorrhagic septicemia (VHS)

-\> first replication in the gills, then endothelial cells 2d head kidney (haematopoietic cells, macrophages) 4d liver (hepatocytes) 6d pancreatic acinar cells
-\> shedding in the urine (\> 3d)
-\> acute (0-30d)(moribund), chronic (persistence-no disease), nervous form (certain strains with brain tropism)

Viral haemorrhagic septicemia (VHS)

-\> Innate immunity: IFN and antiviral cytotoxic cells (NK, NCC, antibody dependent cytotoxicity)
-\> Adaptive immunity humoral/antibodies (4weeks)

Rhabdovirus-related diseases

Diagnosis:
• symptoms
• macroscopic lesions: haemorrhages
• histopathology:
• virus isolation RTG-2 + BF-2 (+ serological identification)
• immunofluorescence
• qRT-PCR
• serology

Vaccination:
• inactivated (ip), subunit baculo-expressed G protein (ip), attenuated (ip, immersion or oral), DNA vaccine expressing the G protein (ip or oral)

Infectious Salmon Anaemia (ISA)

-\> belongs to the orthomyxovirus (genus Isavirus)
-\> agglutinates erythrocytes of ≠ fish species HE envelope protein
-\> segmented (n\=8) RNA genome
-\> other fish can be infected without disease (reservoir

Infectious Salmon Anaemia (ISA)

-\> normal nutritional condition, swim sluggishly at the water surface
-\> anemia (Hct

Infectious Salmon Anaemia (ISA)

-\> portal of entry: gills
-\> generalized replication in endothelial cells and macrophages (5-10d)
-\> peak replication at 15d, then decrease of viral load and \>25d second rise in viral load

Orthomyxovirus-related diseases

Diagnosis:
• symptoms
• macroscopic lesions: haemorrhages
• histopathology:
• virus isolation on salmon cell lines (+ serological identification)
• immunofluorescence
• qRT-PCR
• serology

Vaccination:
• inactivated (ip)

Alphavirus-related diseases

1. Salmon pancreas disease (SPD)(SAV1, 4, 5, 6)(atlantic salmon)(seawater)
2. Sleeping disease (SD) & Haemorrhagic smolt syndrome (HSS) (SAV2)(rainbow trout, atlantic salmon)(fresh & marine water)
3. (NSAV)(SAV3)(Norvegian salmon, rainbow trout)(fresh & marine water)

(NSAV)(SAV3)

-\> belongs to the togaviridae (genus alphavirus); RNA, envelope (E1, E2)
-\> grower fish
-\> SPD-virus; outcome influenced by fish strain, T°, acute outbreaks (8-15°C) - chronic outbreaks at low temperatures (

(NSAV)(SAV3)

-\> SD-virus; mortality up to 22%
-\> sudden inappetence, lethargy, motility problems, secondary mechanical damages of the skin, increased faecal casts, spitting out pellets, increased mortality (sometimes sudden death (SD syndrome))

(NSAV)(SAV3)

-\> main pathological features: no feed in intestines, yellow casts, haemorrhages in caecal fat
-\> histopathological lesions: extensive loss of pancreatic acinar cells (necrosis), cardiomyocyte degeneration and inflammation, skeletal muscle degeneration, general fibrosis

Alphavirus-related diseases

Diagnosis:
• symptoms
• macroscopic lesions: motility problems, sudden death
• histopathology: pancreas necrosis, muscle necrosis/fibrosis
• virus isolation on salmon cell line - Chinook Salmon Embryo ChSE-214 and trout cell line Rainbow Trout Gonad RTG-2 (+ serological identification)
• immunofluorescence
• qRT-PCR
• serology

Vaccination:
• inactivated vaccine (ip)