Background
Results and discussion
Clinical presentation and gross pathology of HSMI cases in Atlantic salmon and HSMI-like cases in coho salmon
Gross pathology findings | Frequency1 (%) | |
---|---|---|
Atlantic salmon | Coho salmon | |
Yellow liver | 60.3 % | 55.3 % |
Hemopericardium | 28.6 % | 55.3 % |
Pale gill | 19.0 % | 56.5 % |
Nutmeg liver | 19.0 % | - |
Pale heart | 19.0 % | 43.5 % |
Splenomegally | 17.5 % | 29.4 % |
Visceral melanosis | 15.9 % | - |
Petechiae in visceral fat | 15.9 % | 7.1 % |
Liver pseudomembrane | 12.7 % | - |
Ascites | 12.7 % | 20.0 % |
Congestion in intestines | 11.1 % | - |
Hemorrhagic eye | 11.1 % | - |
Hepatomegally | 9.5 % | - |
Renomegally | 4.8 % | 10.6 % |
Fluid content in stomach | 3.2 % | 14.1 % |
Congestion in pyloric caeca | 3.2 % | - |
Clotted blood in the abdominal cavity | 3.2 % | 17.6 % |
Jaundice | 1.6 % | 24.7 % |
Biliary cholestasis | - | 31.8 % |
Spinal fracture | - | 22.4 % |
Kidney rupture | - | 11.8 % |
Lipid cysts in visceral fat | - | 7.1 % |
Accumulation of feed oil in the stomach | - | 5.9 % |
Exophthalmia | - | 2.4 % |
Hydropericardium | - | 2.4 % |
Gastric dilatation (bloat) | - | 2.4 % |
Tissue | Atlantic salmon | Coho salmon | ||||||
---|---|---|---|---|---|---|---|---|
Histopathological description | Diagnosis | Frequency | Histopathological description | Diagnosis | Frequency | |||
Heart | Epicardium | Multifocal to diffuse infiltration of mononuclear cells. | Mononuclear epicarditis, subacute, multifocal to diffuse, moderate to severe. | 33/36 | Multifocal to diffuse infiltration of mononuclear cells. | Mononuclear epicarditis, subacute, multifocal to diffuse, moderate to severe. | 18/18 | |
Myocardium | Spongy layer | Multifocal to diffuse infiltration of mononuclear cells of spongy layer and compact layer. Multifocal to diffuse myocardial degeneration & necrosis. | Mononuclear myocarditis, degenerative, necrotic, subacute to chronic, multifocal to diffuse, moderate to severe. | 33/36 | Multifocal to diffuse infiltration of mononuclear cells of spongy layer. Some mononuclear cells are present in the compact layer. Focal to multifocal myocardial degeneration & necrosis. | Mononuclear myocarditis, degenerative, necrotic, subacute to chronic, multifocal to diffuse, moderate to severe. | 15/18 | |
Compact layer | Not significant findings | |||||||
Red muscle | Multifocal to diffuse infiltration of mononuclear cells in red muscle. Multifocal to diffuse myocytic degeneration & necrosis. | Mononuclear myocarditis, degenerative, necrotic, subacute to chronic, Multifocal to diffuse, moderate to severe. | 30/36 | Multifocal to diffuse infiltration of mononuclear cells in red muscle. | Mononuclear myocarditis, Multifocal to diffuse, mild to moderate. | 12/18 | ||
Liver | Blood vessels surrounded by a mononuclear cell infiltrate. Degeneration, necrotic, hemorrhagic, acute to subacute, focal to multifocal, moderate to severe. | Mononuclear hepatitis, necrotic, hemorrhagic, acute to subacute, focal to multifocal, moderate to severe. | 16/36 | Blood vessels surrounded by a mononuclear cell infiltrate. Degeneration, necrotic, acute to subacute, focal to multifocal, mild to moderate. | Mononuclear perivascular hepatitis, necrotic, acute to subacute, focal to multifocal, mild to moderate. | 14/18 | ||
Tissue | Atlantic salmon | Coho salmon | ||||||
Histopathological description | Diagnosis | Frequency | Histopathological description | Diagnosis | Frequency | |||
Spleen | Diffuse infiltration of mononuclear cells, interstitial. Diffuse congestion with evidence of increase in circulating granulocytes & intravascular erythrophagia. | Splenitis, subacute, diffuse, moderate. | 11/36 | Diffuse infiltration of mononuclear cells, interstitial. Diffuse congestion with evidence of increase in circulating granulocytes & intravascular erythrophagia. | Splenitis, subacute, diffuse, moderate. | 10/18 | ||
Kidney | Diffuse infiltration of mononuclear cells, interstitial. | Interstitial nephritis, subacute, diffuse, moderate. | 4/36 | Diffuse infiltration of mononuclear cells, interstitial. | Interstitial nephritis, subacute, diffuse, moderate. | 11/18 | ||
Pyloric caeca | Extensive proliferation of fibroblasts-like cells, mononuclear, eosinophilic cells with eccentric nucleus & macrophage-like cells. Large empty vacuoles adjacent to the pancreatic area observed in some cases. | Vaccine induced peritonitis | 11/36 | No significant findings. | No significant findings. | 18/18 | ||
Gill | Lamellar fusion across multiple filaments. | Branchiosis multifocal, moderate. | 3/36 | Lamellar fusion across multiple filaments. Numerous interlamellar vesicle formation. Neoparamoeba perurans showing nucleus & “parasome". Granular eosinophilic intracytoplasmic inclusions in hypertrophied epithelial cells. | Focal to multifocal bacterial & parasitic hyperplasia, subacute to chronic, moderate to severe, with Paramoeba perurans & epitheliocystis-like inclusions. | 16/18 | ||
Posterior gut | Multifocal to diffuse infiltration of mononuclear cells in lamina propria & sub mucosa. | Mononuclear enteritis, multifocal to diffuse, moderate. | 5/36 | Multifocal to diffuse infiltration of mononuclear cells in lamina propria & sub mucosa. | Mononuclear enteritis, multifocal to diffuse, moderate. | 4/18 |
Histopathology of HSMI cases in Atlantic salmon and HSMI-like cases in coho salmon
Field variation of susceptibility to PRV by host species
Screening for PRV by RT-qPCR
Phylogenetic analysis and sequence diversity of PRV genomic segment S1
Genomic segment S1 of PRV Genotype II
Genotype | Ia | Ib | II | ||||||||||||||||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
PRV isolate
2
| 1 |
2
|
3
| 4 |
5
| 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 |
16
| 17 |
18
| 19 |
20
| 21 |
22
|
23
|
24
|
25
| 26 |
Ia
|
KT456503 | - |
99.9
|
99.8
| 99.8 |
99.6
| 99.6 | 99.6 | 99.6 | 99.6 | 99.5 | 99.3 | 99.3 | 99.2 | 99.0 | 98.7 |
96.0
| 96.0 |
96.0
| 96.0 |
96.0
| 96.0 |
95.9
|
95.8
|
80.7
|
80.5
| nd | |
KU131593
a
|
100
|
-
|
99.6
|
99.6
|
99.5
|
99.5
|
99.5
|
99.5
|
99.5
|
99.4
|
99.2
|
99.2
|
99.0
|
98.9
|
98.6
|
95.9
|
95.9
|
95.9
|
95.9
|
95.9
|
95.9
|
95.8
|
95.7
|
80.9
|
80.3
|
nd
| |
KU131594
a
|
100
|
100
|
-
|
99.5
|
99.6
|
99.4
|
99.4
|
99.4
|
99.4
|
99.3
|
99.0
|
99.0
|
98.9
|
98.9
|
98.4
|
95.8
|
95.8
|
95.8
|
95.8
|
95.8
|
95.8
|
95.7
|
95.5
|
80.6
|
80.4
|
nd
| |
KC473454 | 99.3 |
99.3
|
99.3
| - |
99.4
| 99.4 | 99.4 | 99.4 | 99.4 | 99.3 | 99.0 | 99.0 | 98.9 | 98.8 | 98.4 |
95.8
| 95.8 |
95.8
| 95.8 |
95.8
| 95.8 |
95.7
|
95.5
|
80.5
|
80.3
|
nd
| |
KU131591
a
|
100
|
100
|
100
|
99.3
|
-
|
99.3
|
99.3
|
99.3
|
99.3
|
99.2
|
98.9
|
98.9
|
98.8
|
98.8
|
98.3
|
95.7
|
95.7
|
95.7
|
95.7
|
95.7
|
95.7
|
95.5
|
95.4
|
80.7
|
80.5
|
nd
| |
KR872636 | 99.6 |
99.6
|
99.6
| 98.9 |
99.6
| - | 99.3 | 99.5 | 99.5 | 99.6 | 99.4 | 99.4 | 99.0 | 99.2 | 98.6 |
95.9
| 95.9 |
95.9
| 95.9 |
95.9
| 95.9 |
95.8
|
95.7
|
80.6
|
80.4
| nd | |
KT456500b
| 98.9 |
98.9
|
98.9
| 98.2 |
98.9
| 98.6 | - | 99.3 | 99.3 | 99.2 | 98.9 | 99.2 | 98.8 | 98.7 | 98.3 |
95.7
| 95.7 |
95.7
| 95.7 |
95.7
| 95.7 |
95.5
|
95.4
|
80.4
|
80.2
| nd | |
JN991006 | 100 |
100
|
100
| 99.3 |
100
| 99.6 | 98.9 | - | 99.8 | 99.4 | 99.2 | 99.2 | 99.3 | 98.9 | 98.8 |
96.3
| 96.3 |
96.3
| 96.3 |
96.3
| 96.3 |
96.1
|
96.0
|
80.6
|
80.4
| nd | |
HG329868 | 100 |
100
|
100
| 99.3 |
100
| 99.6 | 98.9 | 100 | - | 99.4 | 99.2 | 99.2 | 99.5 | 98.9 | 99.0 |
96.4
| 96.4 |
96.4
| 96.4 |
96.4
| 96.4 |
96.3
|
96.1
|
80.9
|
80.6
| nd | |
KU160514 | 99.6 |
99.6
|
99.6
| 98.9 |
99.6
| 99.3 | 98.6 | 99.6 | 99.6 | - | 99.3 | 99.5 | 98.9 | 99.3 | 98.4 |
95.8
| 95.8 |
95.8
| 95.8 |
95.8
| 95.8 |
95.7
|
95.5
|
80.2
|
80.3
| nd | |
KT456501 | 98.6 |
98.6
|
98.6
| 97.8 |
98.6
| 98.2 | 97.5 | 98.6 | 98.6 | 98.2 | - | 99.0 | 98.7 | 98.9 | 98.2 |
95.5
| 95.5 |
95.5
| 95.5 |
95.5
| 95.5 |
95.4
|
95.3
|
80.5
|
80.3
| nd | |
KC473453 | 99.6 |
99.6
|
99.6
| 98.9 |
99.6
| 99.3 | 99.3 | 99.6 | 99.6 | 99.3 | 99.3 | - | 98.7 | 99.0 | 98.2 |
95.5
| 95.5 |
95.5
| 95.5 |
95.5
| 95.5 |
95.4
|
95.3
|
80.3
|
80.0
| nd | |
KT456505 | 98.6 |
98.6
|
98.6
| 97.8 |
98.6
| 98.2 | 97.5 | 98.6 | 98.6 | 98.2 | 97.1 | 98.2 | - | 98.4 | 98.6 |
96.1
| 96.1 |
96.1
| 96.1 |
96.1
| 96.1 |
96.0
|
95.9
|
80.9
|
80.7
| nd | |
KU160513 | 98.9 |
98.9
|
98.9
| 98.2 |
98.9
| 98.6 | 97.8 | 98.9 | 98.9 | 98.6 | 97.5 | 98.6 | 97.5 | - | 98.0 |
95.3
| 95.3 |
95.3
| 95.3 |
95.3
| 95.3 |
95.2
|
95.1
|
80.2
|
79.9
| nd | |
HG329848 | 100 |
100
|
100
| 99.3 |
100
| 99.6 | 98.9 | 100 | 100 | 99.6 | 98.6 | 99.6 | 98.6 | 98.9 | - |
96.4
| 96.4 |
96.4
| 96.4 |
96.4
| 96.4 |
96.3
|
96.1
|
80.9
|
80.7
| nd | |
KU131597
|
96.4
|
96.4
|
96.4
|
95.7
|
96.4
|
96.0
|
95.3
|
96.4
|
96.4
|
96.0
|
95.3
|
96.0
|
95.3
|
95.3
|
96.4
|
-
|
100
|
100
|
100
|
100
|
100
|
99.9
|
99.8
|
79.2
|
79.0
|
nd
|
Ib
|
HG329897c
| 96.4 |
96.4
|
96.4
| 95.7 |
96.4
| 96.0 | 95.3 | 96.4 | 96.4 | 96.0 | 95.3 | 96.0 | 95.3 | 95.3 | 96.4 |
100
| - |
100
| 100 |
100
| 100 |
99.9
|
99.8
|
79.2
|
79.0
| nd | |
KU131602
|
96.4
|
96.4
|
96.4
|
95.7
|
96.4
|
96.0
|
95.3
|
96.4
|
96.4
|
96.0
|
95.3
|
96.0
|
95.3
|
95.3
|
96.4
|
100
|
100
|
-
|
100
|
100
|
100
|
99.9
|
99.8
|
79.2
|
79.0
|
nd
| |
KC795571 | 96.4 |
96.4
|
96.4
| 95.7 |
96.4
| 96.0 | 95.3 | 96.4 | 96.4 | 96.0 | 95.3 | 96.0 | 95.3 | 95.3 | 96.4 |
100
| 100 |
100
| - |
100
| 100 |
99.9
|
99.8
|
79.2
|
79.0
| nd | |
KU131604
a
|
96.4
|
96.4
|
96.4
|
95.7
|
96.4
|
96.0
|
95.3
|
96.4
|
96.4
|
96.0
|
95.3
|
96.0
|
95.3
|
95.3
|
96.4
|
100
|
100
|
100
|
100
|
-
|
100
|
99.9
|
99.8
|
79.2
|
79.0
|
nd
| |
GU994022 | 96.4 |
96.4
|
96.4
| 95.7 |
96.4
| 96.0 | 95.3 | 96.4 | 96.4 | 96.0 | 95.3 | 96.0 | 95.3 | 95.3 | 96.4 |
100
| 100 |
100
| 100 |
100
| - |
99.9
|
99.8
|
79.2
|
79.0
| nd | |
KU131603
|
96.0
|
96.0
|
96.0
|
95.3
|
96.0
|
95.7
|
94.9
|
96.0
|
96.0
|
95.7
|
94.9
|
95.7
|
94.9
|
94.9
|
96.0
|
99.6
|
99.6
|
99.6
|
99.6
|
99.6
|
99.6
|
-
|
99.6
|
79.1
|
78.8
|
nd
| |
KU131598
a
|
95.7
|
95.7
|
95.7
|
94.9
|
95.7
|
95.3
|
94.6
|
95.7
|
95.7
|
95.3
|
94.6
|
95.3
|
94.6
|
94.6
|
95.7
|
99.3
|
99.3
|
99.3
|
99.3
|
99.3
|
99.3
|
98.9
|
-
|
79.0
|
78.7
|
nd
| |
KU131595
a
|
79.0
|
79.0
|
79.0
|
78.3
|
79.0
|
79.0
|
78.3
|
79.0
|
79.0
|
79.0
|
78.3
|
79.0
|
79.0
|
78.3
|
79.0
|
78.3
|
78.3
|
78.3
|
78.3
|
78.3
|
78.3
|
77.9
|
77.5
|
-
|
99.5
|
nd
|
II
|
KU131596
a
|
78.6
|
78.6
|
78.6
|
77.9
|
78.6
|
78.6
|
77.9
|
78.6
|
78.6
|
78.6
|
77.9
|
78.6
|
78.6
|
77.9
|
78.6
|
77.9
|
77.9
|
77.9
|
77.9
|
77.9
|
77.9
|
77.5
|
77.2
|
99.3
|
-
|
nd
| |
LN680851d
| nd |
nd
|
Nd
| nd |
nd
| Nd | nd | nd | nd | Nd | nd | nd | nd | nd | nd |
nd
| nd |
nd
| nd |
nd
| nd |
nd
|
nd
|
nd
|
nd
| - |
Genotype | Ia | Ib | II | ||||||||||||||||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
PRV isolate
2
| 1 |
2
|
3
| 4 |
5
| 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 |
16
| 17 |
18
| 19 | 20 | 21 |
22
|
23
|
24
|
25
| 26 |
Ia
|
KT456503 | - | ||||||||||||||||||||||||||
KU131593
a
|
99.2
|
-
| |||||||||||||||||||||||||
KU131594
a
|
100
|
99.2
|
-
| ||||||||||||||||||||||||
KC473454 | 100 |
99.2
|
100
| - | |||||||||||||||||||||||
KU131591
a
|
98.4
|
97.6
|
98.4
|
96.8
|
-
| ||||||||||||||||||||||
KR872636 | 98.4 |
97.6
|
98.4
| 96.8 |
96.8
| - | |||||||||||||||||||||
KT456500b
| 100 |
99.2
|
100
| 98.4 |
98.4
| 98.4 | - | ||||||||||||||||||||
JN991006 | 98.4 |
97.6
|
98.4
| 96.8 |
98.4
| 98.4 | 98.4 | - | |||||||||||||||||||
HG329868 | 99.2 |
98.4
|
99.2
| 97.6 |
99.2
| 99.2 | 99.2 | 99.2 | - | ||||||||||||||||||
KU160514 | 97.6 |
96.8
|
97.6
| 96.0 |
99.2
| 99.2 | 97.6 | 97.6 | 98.4 | - | |||||||||||||||||
KT456501 | 96.8 |
96.0
|
96.8
| 95.2 |
98.4
| 98.4 | 96.8 | 96.8 | 97.6 | 97.6 | - | ||||||||||||||||
KC473453 | 97.6 |
96.8
|
97.6
| 96.0 |
99.2
| 99.2 | 97.6 | 97.6 | 98.4 | 100 | 97.6 | - | |||||||||||||||
KT456505 | 97.6 |
96.8
|
97.6
| 96.0 |
97.6
| 97.6 | 97.6 | 97.6 | 98.4 | 96.8 | 96.0 | 96.8 | - | ||||||||||||||
KU160513 | 96.8 |
96.0
|
96.8
| 95.2 |
98.4
| 98.4 | 96.8 | 96.8 | 97.6 | 99.2 | 96.8 | 99.2 | 96.0 | - | |||||||||||||
HG329848 | 99.2 |
98.4
|
99.2
| 97.6 |
99.2
| 99.2 | 99.2 | 99.2 | 100 | 98.4 | 97.6 | 98.4 | 98.4 | 97.6 | - | ||||||||||||
KU131597
|
92.7
|
91.9
|
92.7
|
91.9
|
92.7
|
92.7
|
92.7
|
93.5
|
93.5
|
91.9
|
91.1
|
91.9
|
91.9
|
91.1
|
93.5
|
-
|
Ib
| ||||||||||
HG329897c
| 92.7 |
91.9
|
92.7
| 91.9 |
92.7
| 92.7 | 92.7 | 93.5 | 93.5 | 91.9 | 91.1 | 91.9 | 91.9 | 91.1 | 93.5 |
100
| - | ||||||||||
KU131602
|
92.7
|
91.9
|
92.7
|
91.9
|
92.7
|
92.7
|
92.7
|
93.5
|
93.5
|
91.9
|
91.1
|
91.9
|
91.9
|
91.1
|
93.5
|
100
|
100
|
-
| |||||||||
KC795571 | 92.7 |
91.9
|
92.7
| 91.9 |
92.7
| 92.7 | 92.7 | 93.5 | 93.5 | 91.9 | 91.1 | 91.9 | 91.9 | 91.1 | 93.5 |
100
| 100 |
100
| - | ||||||||
KU131604
a
|
92.7
|
91.9
|
92.7
|
91.9
|
92.7
|
92.7
|
92.7
|
93.5
|
93.5
|
91.9
|
91.1
|
91.9
|
91.9
|
91.1
|
93.5
|
100
|
100
|
100
|
100
|
-
| |||||||
GU994022 | 92.7 |
91.9
|
92.7
| 91.9 |
92.7
| 92.7 | 92.7 | 93.5 | 93.5 | 91.9 | 91.1 | 91.9 | 91.9 | 91.1 | 93.5 |
100
| 100 |
100
| 100 | 100 | - | ||||||
KU131603
|
92.7
|
91.9
|
92.7
|
91.9
|
92.7
|
92.7
|
92.7
|
93.5
|
93.5
|
91.9
|
91.1
|
91.9
|
91.9
|
91.1
|
93.5
|
100
|
100
|
100
|
100
|
100
|
100
|
-
| |||||
KU131598
a
|
91.9
|
91.1
|
91.9
|
91.9
|
91.1
|
91.9
|
91.9
|
92.7
|
92.7
|
91.1
|
90.3
|
91.1
|
91.1
|
90.3
|
92.7
|
99.2
|
99.2
|
99.2
|
99.2
|
99.2
|
99.2
|
99.2
|
-
| ||||
KU131595
a
|
79.8
|
80.6
|
79.8
|
80.6
|
79.8
|
79.8
|
79.8
|
79.8
|
80.6
|
79.0
|
78.2
|
79.0
|
79.8
|
78.2
|
80.6
|
78.2
|
78.2
|
78.2
|
78.2
|
78.2
|
78.2
|
78.2
|
77.4
|
-
|
II
| ||
KU131596
a
|
79.8
|
80.6
|
79.8
|
79.8
|
80.6
|
79.8
|
79.8
|
79.8
|
80.6
|
79.0
|
78.2
|
79.0
|
79.8
|
78.2
|
80.6
|
78.2
|
78.2
|
78.2
|
78.2
|
78.2
|
78.2
|
78.2
|
77.4
|
100
|
-
| ||
LN680851d
| 79.8 |
80.6
|
79.8
| 79.8 |
80.6
| 79.8 | 79.8 | 79.8 | 80.6 | 79.0 | 78.2 | 79.0 | 80.6 | 78.2 | 78.2 |
78.2
| 78.2 |
78.2
| 78.2 | 78.2 | 78.2 |
78.2
|
77.4
|
97.6
|
97.6
| - |