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Aquaculture Viruses

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Aquaculture Viruses How Bad Can It Be?? Fish severely affected by IPNV: Atlantic salmon* (Salmo salar) brook trout* (Salvelinus fontinalis) brown trout* (Salmo trutta ... – PowerPoint PPT presentation

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Title: Aquaculture Viruses


1
Aquaculture Viruses
2
What a Virus Isnt
  • Not a bacterium...
  • Not independent...
  • Cannot survive in absence of a living cell within
    which to replicate...
  • Antibiotics generally dont work on them...

3
What Viruses Are...
  • Infectious agents composed mainly of nucleic acid
    with a protein coat (capsid)
  • Visible with electron microscope (10-200 nM)
  • Carry on normal cell-like function (unless free,
    then infectious)
  • In infectious form no growth no respiration???
  • Can enter living plant, animal or bacterial cell

4
Virus Appearence?
  • Capsid, core and genetic material (DNA/RNA)
  • Capsid outer shell of the virus which encloses
    genetic material (link chemical structure of
    capsid helps determine immune response to virus)
  • capsid is made of many identical individual
    proteins
  • protein core under capsid protecting genetic
    material
  • sometimes an additional covering (lipid bilayer
    w/embedded proteins) on outside known as an
    envelope ( like a baseball)
  • various forms rods, filaments, spheres, cubes,
    crystals

5
Capsid
6
capsomere unit/molecule associated with capsid
structure
7
Typical Virus Shapes
SPHERES
RODS
CUBES
8
More Virus Shapes
9
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10
Composition of T-Even Bacteriophage
  • Capsid brains of virus, tightly-wound protein
    protecting nucleic acids
  • Body attached to capsid head, rod-like
    structure w/retractible sheath, hollow core
  • Tail at end of core is a spiked plate carrying
    6 slender tail fibers, anchor virus to its host

11
How do viruses work?
  • Viruses make use of the host cells chemical
    energy, protein and nucleic acid synthesizing
    ability to replicate themselves...
  • each virus attacks a specific type of cell
  • cold viruses attack cells of the lung
  • the AIDS virus attacks T4 cells of the
  • immune system
  • fish viruses are just as specific

12
Bacteriophage Attack
13
Virusal Mechanism
  • Viruses contain single- or double- stranded DNA
    or RNA
  • Often, the virus alters the intracellular
    environment enough to damage or kill the cell
    (oops!!)
  • If enough cells are destroyed, disease results!

14
Role of RNA/DNA
  • Supplies the codes for building the protein coat
    (capsid) and for producing enzymes needed to
    replicate more viruses
  • Information given so newly-built viruses can lyse
    cells (e.g., bacteriophage)
  • Result cell destroyed.

15
Bottom Line...
  • All viruses only exist to make more viruses
  • Most are harmful
  • Replication host cell death.

16
The Virus Invasion Step by step
  • Phase 1 Attachment of virus to bacteria, etc.
  • Phase 2 injection of DNA or RNA
  • Phase 3 DNA (RNA) enters the host cell
  • Phase 4DNA incorporated (10 minutes) hundreds of
    virions appear causing the cell to rupture,
    releasing hundreds of small viral replicates
  • This is how it can replicate so quickly!

17
The Virus Invasion
18
Whats Infected by a Virus?
  • All living things have some susceptibility to a
    particular virus
  • Virus is specific for the organism
  • Within a species, there may be a 100 or more
    different viruses which can affect that species
    alone
  • Specific for example, a virus that only affects
    one organism (humans and smallpox)
  • Influenza can infect humans and two animals

19
Different Types of Viruses
  • Major classifications animal, plant, bacterial
  • Sub-classified by arrangement and type of nucleic
    acid
  • Animal virus group double-stranded DNA,
    single-stranded DNA, double-stranded RNA,
    single-stranded RNA, retrovirus
  • Influenza SS-RNA

20
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21
Do Viruses ever Change?
  • Mutations do occur.
  • If the mutation is harmful, the new virus
    particle might no longer be functional
    (infectious)
  • However, because a given virus can generate many,
    many copies, a small number of non-functional
    viruses is not important
  • Mutation is not necessarily damaging to the virus
    -- it can lead to a functional but new strain of
    virus

22
Defense Against Viruses
  • First Line skin and mucous membrane, which also
    lines the gastrointestinal and respiratory
    passageways
  • skin is tough and stomach acidity acts as a
    disinfectant
  • Second Line after the virus enters the blood
    and other tissues, white blood cells and related
    cells (phagocytes) consume them
  • accumulation of phagocytes in area of infection
    is known as puss

23
Defense Against Viruses
Antibodies attacking chickenpox virus
24
Defense Against Viruses
  • Antibodies are the best defense against viruses
  • unfortunately, they are specific in their action
  • chickenpox antibody will only attack a chickenpox
    virus
  • a particular virus stimulates the production of a
    particular antibody

25
Defense Against Viral Infection
  • Animals are protected in several ways
  • 1) intracellular if a particular virus attacks
    cells, our bodies produce interferons
  • interferons (alpha, beta or gamma) are proteins
    which interact with adjacent cells and cause them
    to become more resistant to infection by the
    virus
  • if the resistance is not quite good enough, we
    become sick

26
Defense Against Viral Infection
  • 2) immune system (extracellular) kills the
    virus outside the cell
  • also kills the infected cells
  • virus cannot spread
  • eventually the virus is completely removed and we
    get better
  • exception HIV because it infects cells of the
    immune system, itself
  • chemicals/drugs acyclovir, AZT, HIV protease
    inhibitor, several fish vaccines available.

27
Major Fish Viruses
28
Major Viral Infections in Fish
  • Infectious pancreatic necrosis (IPN)
  • Viral hemorrhagic septicemia (VHS)
  • Infectious hematopoetic necrosis (IHN)
  • Channel catfish virus disease (CCVD)

29
(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 1960s, wiped
    out brook trout in Oregon in 1971-73
  • Size Only 65 nM in diam., smallest of fish
    viruses

30
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

31
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

32
IPN pathology (what do we see?)
33
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!

34
How Bad Can It Be??
35
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)

36
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)

37
More
  • halibut (Hippoglossus stenolepis) herrings/sardin
    es (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) whitef
    ish (Coregonidae)carp (Cyprinus
    carpio) goldfish (Carassius auratus)redfin
    perch (Perca fluviatilis) southern flounder (P.
    lethostigma)yellowfin bream (Acanthopagrus
    australis)

38
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???
39
(2) Viral Hemorrhagic Septicemia (VHS)
40
(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

41
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

42
Viral Hemorrhagic Septicemia (VHS)
  • Pathogenesis infection results in viremia,
    disrupts many organ systems, 200-300g fish most
    affected
  • Environmental factors low temp (lt 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

43
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.

44
Viral Hemorrhagic Septicemia (VHS)
External hemorrhages
Liver red in acute stage
45
Viral haemorrhagic septicaemia in rainbow trout.
Note pale color of stomach region, pinpoint
haemorrhages in fatty tissue, and pale gills
Source T HÃ¥stein
Viral haemorrhagic septicaemia in rainbow trout.
Note swollen stomach and pop eye
46
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47
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.

48
(3 ) Infectious Hematopoietic Necrosis (IHN)
  • Who sockeye, chinook, rainbows cohos resistant
  • When? 1950s 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

49
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

50
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

51
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.

52
(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.

53
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

54
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.

55
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...

56
Channel Catfish Virus Disease
57
Channel Catfish Virus Disease
58
However, you can always take precautions!
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