1. Aquaculture Viruses

2. Major Viral Infections in Fish
Infectious pancreatic necrosis (IPN)
Viral hemorrhagic septicemia (VHS)
Infectious hematopoetic necrosis (IHN)
Channel catfish virus disease (CCVD)

3. (1) Infectious Pancreatic Necrosis (IPN)
What?: viral infection of salmonids (trout and char)
Time: Acute
Result: high mortality (fry and fingerlings)
Rare in larger fish (good thing!)
History: Isolated in Pacific NW in 1960’s, wiped out brook trout in Oregon in
Size: Only 65 nM in diam., smallest of fish viruses

4. IPN: general notes
Single capsid shell, icosohedral symmetry, no envelope
Contains two segments of DS-RNA
Fairly stable and resistant to chemicals (acid, ether, etc.), variable resistance to freezing
Remains infectious for 3 months in water (uh oh!)
Targets pancreas and hematopoietic tissues of kidney and spleen

5. IPN: epizootiology (disease process)
Who?: All salmonids, brook trout most susceptible, marine fish (flounder?)
Reservoirs (where)?: carriers, once a carrier always a carrier, virus particles shed in feces/urine
Transmission (how?): horizontal, by waters via carriers or infected fry; vertical from adults to progeny; experimentally by feeding infected material, IP injection
Pathogenesis: entry via gills, digestive tract
Environmental factors: mortality reduced at lower temps (why?); however, carriers not reduced

6. IPN: pathology (what do we see?)

7. IPN: detection, diagnosis and control
Isolation: whole fry, kidney, spleen, pyloric cecae, sex fluids are all good sources, .i.e. check these!!!
Presumptive tests: epizootiological evidence and/or typical PCR in infected cells
Definitive tests: serology (fluorescent antibody test (FAT))
Control: avoid virus in water, virus-free stock, destruction of infected stock, vaccine exists now!

8. How Bad Can It Be??

9. Fish severely affected by IPNV:
Atlantic salmon* (Salmo salar) brook trout* (Salvelinus fontinalis) brown trout* (Salmo trutta) danio zebrafish* (Brachydanio rerio) rainbow trout* (Oncorhynchus mykiss) yellowtail* (Seriola lalandi)

10. Other species known to be susceptible…
amago salmon (Oncorhynchus rhodurus) Arctic char (Salvelinus alpinus) Atlantic menhadden (Brevoortia tyrannus) carangids (Carangidae) chinook salmon (Oncorhynchus tshawytscha) chum salmon (Oncorhynchus keta) cichlids (Cichlidae) coho salmon (Oncorhynchus kisutch) common scallop (Pecten maximus) cutthroat trout (Salmo clarki) cyprinids (Cyprinidae) Danube salmon (Salmo hucho) drums/croakers (Sciaenidae) eels (Anguilla spp) grayling (Thymallus thymallus)

11. More…
halibut (Hippoglossus stenolepis) herrings/sardines (Clupidae) Jap. amberjack (Seriola quinqueradiata) lake trout (Salvelinus namaycush) lampreys (Petromyzontyidae) left-eye flounders (Bothidae) loach (Misgurnus anguillicaudatus) loaches (Cobitidae) masou salmon (Oncorhynchus masou) Pacific salmon (Oncorhynchus spp) perches (Percidae) pikes (Esocidae) silversides (Atherinidae) sockeye salmon (Oncorhynchus nerka) soles (Soleidae) Southwest European nase (C. toxostoma)
striped snakehead (Channa striatus) suckers (Cotostomidae)
summer flounder (Paralichthys dentatus) turbot (Psetta maxima) white seabass (Moronidae) whitefish (Coregonidae) carp (Cyprinus carpio) goldfish (Carassius auratus) redfin perch (Perca fluviatilis) southern flounder (P. lethostigma) yellowfin bream (Acanthopagrus australis)

12. Asymptomatic carriers...
coalfish (Pollachius virens) common carp (Cyprinus carpio) discus fish (Symphysodon discus) goldfish (Carrasius auratus) heron (Ardea cinerea) loach (Cobitidae) minnow (Phoxinus phoxinus) noble crayfish (Astacus astacus) pike (Esox lucius) river lamprey (Lampetra fluviatalis) shore crab (Carcinus maenas) Spanish barbel (Barbus graellsi) white suckers (Catostomas commersoni)
Infectious pancreatic necrosis in Atlantic salmon.
Note swollen stomach and 'pop eye'
Source: Australian Animal Health Laboratory
...what now???

13. (2) Viral Hemorrhagic Septicemia (VHS)

14. (2) Viral Hemorrhagic Septicemia (VHS)
What?: Viral disease of European salmonids
When?: Recognized in Denmark in 1949, isolated
from Pacific Coast in 1989
Size: rhabdovirus, bullet-shaped (one rounded end), 185 x 65 nM, lipoprotein envelope
non-segmented SS-RNA
Constitution: sensitive to ether and chloroform, heat, acid, resistant to freeze-drying

15. Viral Hemorrhagic Septicemia
Produces a general viremia, tissue and organ damage, liver necrosis, spleen, kidney
Epizootiology: cultured rainbow trout, also brown trout, steelhead, chinook, coho (most cases in WA state)
Reservoirs: again...survivors are life-long carriers, usually rainbow trout, brown in Europe
Transmission: horizontal through water, virus can occur on eggs spawned by carriers, IP injection, birds, hatchery equip

16. Viral Hemorrhagic Septicemia (VHS)
Pathogenesis: infection results in viremia, disrupts many organ systems, g fish most affected
Environmental factors: low temp (< 8oC, 46oF)
External pathology: lethargy, hanging downward in water (dropsy), swimming in circles, exopthalmia, dark discoloration, hemorrhages in roof of mouth, pale gills w/focal hemorrhages

17. Viral Hemorrhagic Septicemia (VHS)
Internal pathology: gut devoid of food, liver pale, hemorrhages in connective tissue, kidney gray and swollen (chronic), red and thin (acute)
Histopathology: necrosis of liver, kidney nephrons, spleen, pancreas, melanin in kidneys and spleen (OUCH!)
Isolation/tests: isolated from kidney/spleen, epizootiological evidence, definitive test is serum neutralization, or FAT.

18. Viral Hemorrhagic Septicemia (VHS)
External hemorrhages
Liver red in acute stage

19. Viral haemorrhagic septicaemia in rainbow trout.
Note pale color of stomach region, pinpoint haemorrhages in fatty tissue, and pale gills
Source: T Håstein
Viral haemorrhagic septicaemia in rainbow trout.
Note swollen stomach and “pop eye”

20. Type
Prevalent host type and location
  I-a
Farmed rainbow trout and a few other freshwater fish in continental Europe[10]
  I-b
Marine fish of the Baltic Sea, Skagerrak, Kattegat, North Sea, Japan[1]
  I-c
Farmed rainbow trout Denmark
  I-d
Farmed rainbow trout in Norway, Finland, Gulf of Bothnia
  I-e
Rainbow trout in Georgia, farmed and wild turbot in the Black Sea[11]
  II
Marine fish of the Baltic Sea
  III
Marine fish of the British Isles and northern France, farmed turbot in the UK and Ireland, and Greenland halibut (Reinhardtius hippoglossoides) in Greenland[12]
  IV-a
Marine fish of the Northwest Pacific (North America), North American north Atlantic coast,[13] Japan, and Korea[1][14]
  IV-b
Freshwater fish in North American Great Lakes region[14]

21. Viral Hemorrhagic Septicemia
Prevention: clean broodstock, water = fish, avoid infected broodstock, test and slaughter
Can spread very quickly from farm to farm: avoid close proximity to other farms
Vaccines are under development.
One EPA-approved disinfectant: Virkon® AQUATIC (made by Dupont). Bleach kills the VHS virus.

22. (3 ) Infectious Hematopoietic Necrosis (IHN)
Who: sockeye, chinook, rainbows; cohos resistant
When?: 1950’s in Oregon hatcheries million mortalities between , if infected, 70% mortality likely, esp. in young fish (fry: 90-95% mort. possible)
What?: bullet shaped rhabdovirus, non- segmented SS-RNA, sensitive to heat and pH, glycoprotein is spiked on surface of virus

23. Infectious Hematopoietic Necrosis (IHN)
Reservoirs: survivors life-long carriers, adults shed virus at spawning
Transmission: horizontal, primary mode is vertical via ovarian fluid (virus hitches ride on sperm into egg); however, feces, urine, and external mucus possible. Also, feeding and inoculation have worked experimentally
Pathogenesis: gills suspected; incubation period depends on temp, route, dose, age; extensive hemorrhaging, necrosis of many tissues; death usually due to kidney failure

24. Infectious Hematopoietic Necrosis (IHN)
Environmental factors: temp. very important, slows below 10◦C, holding in tanks/handling increase severity
External pathology: lethargy, whirling, dropsy, exopthalmia, anemia, hemorrhaging of musculature/fins, scoliosis
Internal pathology: liver, kidney, spleen pale; stomach/intestines filled with milky fluid; petechial hemorrhaging
Histopathology: extensive necrosis of hematopoetic tissue of kidney/spleen

25. Infectious Hematopoietic Necrosis (IHN)
Definitive diagnosis: serum neutralization, FAT, ELISA
Prevention: avoidance, quarantine, clean water with UV, ozone, virus-free stock; test, slaughter, disinfect; disinfect eggs; vaccines under development; elevated water temp
No vaccines as of June 2007.

26. (4) Channel Catfish Virus Disease (CCVD)
Contagious herpes virus affecting only channel catfish less than four months old
Occurs in SE United States, California, Honduras
Acute hemorrhagia, high mortality, first discovered in 1968
Agent: enveloped capsid, icosohedral nucleocapsid with 162 capsomeres
Physio/chemical properties: easy to kill, sensitive to freeze-thaw, acid, ether, etc.

27. Channel Catfish Virus Disease (CCVD)
Environmental factors: optimal temperature 28-30◦C, common during warmer months, cooler water = big difference
epizootiology: horizontal, vertical suspected
external pathology: spiral swimming; float with head at surface; hemorrhagic fins, abdomen; ascites; pale or hemorrhagic gills; exophthalmia

28. Channel Catfish Virus Disease (CCVD)
Internal pathology: hemorrhages of liver, kidney, spleen, gut, musculature; congestion of mesenteries and adipose
Histopathology: necrosis of kidney, other organs; macrophages in sinusoids of liver, etc.; degeneration of brain
Presumptive diagnosis: clinical signs, epizootiological evidence
Definitive diagnosis: SN or FAT.

29. Channel Catfish Virus Disease (CCVD)
Prevention: avoid potential carriers (survivors) or infected fry, keep temperature below 27oC (will still produce carriers), attenuated vaccine shows some promise
Therapy: none available...

30. Channel Catfish Virus Disease

31. Channel Catfish Virus Disease

32. However, you can always take precautions!