Aquaculture Viruses

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

(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 1971-73 Size: Only 65 nM in diam., smallest of fish viruses

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

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

IPN: pathology (what do we see?)

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!

How Bad Can It Be??

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)

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)

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)

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???

(2) Viral Hemorrhagic Septicemia (VHS)

(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

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

Viral Hemorrhagic Septicemia (VHS) Pathogenesis: infection results in viremia, disrupts many organ systems, 200-300g 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

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.

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

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”

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]

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.

(3 ) Infectious Hematopoietic Necrosis (IHN) Who: sockeye, chinook, rainbows; cohos resistant When?: 1950’s in Oregon hatcheries. 100 million mortalities between 1970-1980, 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

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

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

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.

(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.

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

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.

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...

Channel Catfish Virus Disease

Channel Catfish Virus Disease

However, you can always take precautions!