Aquaculture Viruses

What a Virus IsntNot a bacterium...Not independent...Cannot survive in absence of a living cell within which to replicate...Antibiotics generally dont work on them...

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 human

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 proteinsprotein core under capsid protecting genetic materialsometimes an additional covering (lipid bilayer w/embedded proteins) on outside known as an envelope ( like a baseball)various forms: rods, filaments, spheres, cubes, crystals

Capsid

capsomere: unit/molecule associated with capsid structure

Typical Virus ShapesRODSSPHERESCUBES

More Virus Shapes

Composition of T-Even BacteriophageCapsid: brains of virus, tightly-wound protein protecting nucleic acidsBody: attached to capsid head, rod-like structure w/retractible sheath, hollow coreTail: at end of core is a spiked plate carrying 6 slender tail fibers, anchor virus to its host

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 lungthe AIDS virus attacks T4 cells of the immune systemfish viruses are just as specific

Bacteriophage Attack

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!

Role of RNA/DNASupplies 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.

Bottom Line...All viruses only exist to make more viruses

Most are harmful

Replication = host cell death.

The Virus Invasion: Step by stepPhase 1: Attachment of virus to bacteria, etc.

Phase 2: injection of DNA or RNA

Phase 3: DNA (RNA) enters the host cell

Phase 4:DNA 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!

The Virus Invasion

Whats Infected by a Virus?All living things have some susceptibility to a particular virusVirus is specific for the organismWithin a species, there may be a 100 or more different viruses which can affect that species aloneSpecific: for example, a virus that only affects one organism (humans and smallpox)Influenza can infect humans and two animals

Different Types of VirusesMajor 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

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 importantMutation is not necessarily damaging to the virus -- it can lead to a functional but new strain of virus

Defense Against VirusesFirst Line: skin and mucous membrane, which also lines the gastrointestinal and respiratory passagewaysskin is tough and stomach acidity acts as a disinfectantSecond Line: after the virus enters the blood and other tissues, white blood cells and related cells (phagocytes) consume themaccumulation of phagocytes in area of infection is known as puss

Defense Against VirusesAntibodies attacking chickenpox virus

Defense Against VirusesAntibodies are the best defense against virusesunfortunately, they are specific in their actionchickenpox antibody will only attack a chickenpox virusa particular virus stimulates the production of a particular antibody

Defense Against Viral InfectionAnimals 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

Defense Against Viral Infection2) immune system (extracellular): kills the virus outside the cellalso kills the infected cellsvirus cannot spreadeventually the virus is completely removed and we get betterexception: HIV because it infects cells of the immune system, itselfchemicals/drugs: acyclovir, AZT, HIV protease inhibitor, several fish vaccines available.

Major Fish Viruses

Major Viral Infections in FishInfectious pancreatic necrosis (IPN)

Viral hemorrhagic septicemia (VHS)

Infectious hematopoetic necrosis (IHN)

Channel catfish virus disease (CCVD)Koi Herpes VirsLymphocytisCacar virusVNN (Viral Nervous Necrosis)Spring Viraemia of Carp (SVC)

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

IPN: general notesSingle 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/urineTransmission (how?): horizontal, by waters via carriers or infected fry; vertical from adults to progeny; experimentally by feeding infected material, IP injectionPathogenesis: entry via gills, digestive tractEnvironmental factors: mortality reduced at lower temps (why?); however, carriers not reduced

IPN: pathology (what do we see?)

IPN: detection, diagnosis and controlIsolation: 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 susceptibleamago 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)

Morehalibut (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 salmonidsWhen?: Recognized in Denmark in 1949, isolated from Pacific Coast in 1989Size: rhabdovirus, bullet-shaped (one rounded end), 185 x 65 nM, lipoprotein envelopenon-segmented SS-RNAConstitution: sensitive to ether and chloroform, heat, acid, resistant to freeze-drying

Viral Hemorrhagic SepticemiaProduces 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 hemorrhagesLiver red in acute stage

Viral haemorrhagic septicaemia in rainbow trout.

Note swollen stomach and pop eye

Viral haemorrhagic septicaemia in rainbow trout.

Note pale color of stomach region, pinpoint haemorrhages in fatty tissue, and pale gills

Source: T Hstein

TypePrevalent host type and location I-aFarmed rainbow trout and a few other freshwater fish in continental Europe[10] I-bMarine fish of the Baltic Sea, Skagerrak, Kattegat, North Sea, Japan[1] I-cFarmed rainbow trout Denmark I-dFarmed rainbow trout in Norway, Finland, Gulf of Bothnia I-eRainbow trout in Georgia, farmed and wild turbot in the Black Sea[11] IIMarine fish of the Baltic Sea IIIMarine fish of the British Isles and northern France, farmed turbot in the UK and Ireland, and Greenland halibut (Reinhardtius hippoglossoides) in Greenland[12] IV-aMarine fish of the Northwest Pacific (North America), North American north Atlantic coast,[13] Japan, and Korea[1][14] IV-bFreshwater fish in North American Great Lakes region[14]

(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

Viral Hemorrhagic SepticemiaPrevention: 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.

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 10C, holding in tanks/handling increase severityExternal pathology: lethargy, whirling, dropsy, exopthalmia, anemia, hemorrhaging of musculature/fins, scoliosisInternal pathology: liver, kidney, spleen pale; stomach/intestines filled with milky fluid; petechial hemorrhagingHistopathology: 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 1968Agent: 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 28-30C, common during warmer months, cooler water = big differenceepizootiology: horizontal, vertical suspectedexternal pathology: spiral swimming; float with head at surface; hemorrhagic fins, abdomen; ascites; pale or hemorrhagic gills; exophthalmiaIpact 95 % ortality ( On Larva and fingerling)Adlt as a carrier

Channel Catfish Virus Disease (CCVD)Internal pathology: hemorrhages of liver, kidney, spleen, gut, musculature; congestion of mesenteries and adiposeHistopathology: necrosis of kidney, other organs; macrophages in sinusoids of liver, etc.; degeneration of brainPresumptive diagnosis: clinical signs, epizootiological evidence

Channel Catfish Virus Disease (CCVD)Prevention: avoid potential carriers (survivors) or infected fry, keep temperature below 27oC (will still produce carriers), anage water qality and sanitation, cleaning the stf with chlorine attenuated vaccine shows some promise

Therapy: none available...

Channel Catfish Virs Disease

Ephitelioma Populasum (cacar virus)

Disebabkan oleh kualitas air yang buruk, padat tebar yang tinggi target : ikan jenis carpGejala : mncl bintik ptih susu berisi nanah yang menyebar sangat cepat mntp selurh permukaan tubuh dgn ketebalan 1-2 mm.

PengobatanLarutan arsenik 1 % dalam senyawa arycil. Penyuntikan pada perut ikan. Lakukan 3 kali penyuntukan selanjutnya dengan 5 % arsin dalam senyawa arycil

LymphocystisDisebabkanoleh iridovirus/ DNADapat menyerang ikan air twar maupun lautGejala: Terdapat penebalan pada sel jaringan ikat sehingga mncl tonjolan atau nodul pada ikan bisa berkelopok ata sendiri. Sasaran uttama kulit atua insang.Tidak ada pengobatan yg efektiv, hanya pencegahan melalui menjaga kualitas air dan peningkatan imunitas ikan. Penularan melalui makanan atapun suntikan dan air.

Koi Herpes Virus (KHV)Disebakan virus DNA dari strain herpes viridaemenyerang ikan mas (Cyprinus)dan koimuncul : temperatur turun dan kualitas air burukGejala : nafsu makan turun, ikan megap megap,terdapat keruskan insang ( bintik putih dan merah pada insang)menyerang insang dan ginjal ikan sehingga terbentuk inflamasi pada ginjal, kllit melepuh,insang membsk, kematian 1-5 hari.Sering diikuti infeksi sekunder oleh bakteri dan jamur ketika luka ada di permukaan tubuh

Pengobatan Segera dipindahkan ikan yang sakit (isolasi) ke suhu air yang lbh tinggi ( 30 C) selama beberapa hari kemudian suhu diturunkansampai 27 C keumdian dikeluarkan. Dilanjtkan pengobatan seknder. Jika sdah mewabah sebaiknya dimusnahkanPencegahan : padat tebar dikurangi, penggunaan benih yang berkalitas dan bebas KHV, mnjaga kualitas air, pemberian pakan yg baik dan sehat, desinfeksi pada semua perslatan dan kolam, mnitoring dan evaluasi ikan dan lingkngan

Viral Nervous Necrosis (VNN)Penyebab : Betanodaviruses family NodoviridaeMenyerang larva ikan sampai dewasa (ikan laut)Target serangan : sistem syaraf dan retinaGejala : Nafsu makan turun, berenang yang tidak teratur, warna tubuh menjadi gelap, posisi terapung dengan perut diatas karena pembengkakan, Kerusakan pada retina mata.Menyebkan kematian 50 %Penyebaran dengan horisontal maupun vertikalVaksinasi diperlukan untuk mencegah VNNPencegahan : manage Kualitas air, benih, pakan dan lingkungan serta sarana budidaya.

However, you can always take precautions!