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FISH 424: Fish Health Management Virology Lecture:ISAV SVCV WSIV VHSV.

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Presentation on theme: "FISH 424: Fish Health Management Virology Lecture:ISAV SVCV WSIV VHSV."— Presentation transcript:

1 FISH 424: Fish Health Management Virology Lecture:ISAV SVCV WSIV VHSV

2 Infectious Salmon Anemia Virus (ISAV) Hosts and Geographic Range –Highly infectious for Atlantic salmon –potential asymptomatic carriers of the virus Searun brown trout rainbow trout Atlantic herring

3 Infectious Salmon Anemia (ISAV) Viral infection is found in Seawater (Net pens): –Norway (1984) –United Kingdom (1998) –East coast Canada (1998) –East coast United States (2000) –Chile (1999)

4 MAINE CANADA

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6 Infectious Salmon Anemia (ISAV) Etiological agent –1 st described as Hemorrhagic Kidney Syndrome –member of the orthomyxoviridae family. –8 negative strands of RNA enclosed in a lipid envelop –Virions between nm in diameter

7 Infectious Salmon Anemia (ISAV) Transmission Electron Micrographs

8 Infectious Salmon Anemia (ISAV) Virulence and Pathology –lethargic, swim near the water surface –petechial hemorrhage on skin and fins –anemia, exophthalmia, ascites –Pale gills –hepatomegally, splenomegally – petechia in the visceral fat

9 Infectious Salmon Anemia (ISAV)

10 Transmission: –Almost exclusively occurrs during saltwater stages –Horizontal (fish to fish contact) –Coprophagy (feeding on feces) –Sea lice can transmit ISAv from infected to susceptible fish –Transfer by contaminated equipment / People / boat traffic / location near fish processing plants

11 Infectious Salmon Anemia (ISAV) Alexander G. Murray,*† Ronald J. Smith,* and Ronald M. Stagg* *Fisheries Research Services Marine Laboratory, Aberdeen, United Kingdom; and †University of Aberdeen, Aberdeen, United Kingdom Figure 3. Infection status of areas versus number of well-boat visits. Infection status is 0 for no infection, 1 for suspected infection, and 2 for confirmed infection

12 Infectious Salmon Anemia (ISAV) Diagnosis –Isolation through tissue culture SHK-1 and CHSE-214 cells –IFAT (indirect fluorescent antibody test) on tissue imprints –RT-PCR (reverse transcriptase poylmerase chain reaction)

13 Infectious Salmon Anemia (ISAV) Management –Since the virus is readily transmitted in seawater –Shown net pen operations within 5-6 km of an infected site can become contaminated 1.culture sites be spaced no less than 5-6 km apart 2.waste water from slaughter and processing facilities should be thoroughly disinfected 3. control of ship and personnel movements among sites 4.compulsory slaughter of infect stocks (eradication) 5.Attempts to require vaccination

14 Spring Viremia of Carp Virus (SVCV) Hosts and Geographic Range –Natural infections have been recognized in common carp and koi carp (Cyprinus carpio) –Historically only in Europe and Russia –Recently, SVC has been reported in koi in the United States for the first time

15 2. Spring viremia of carp (SVC) was confirmed in ornamental koi carp in Pike County, Missouri on July 13, 2004 Recent News Headlines 1.Spring Viremia of Carp virus (SVCv) was recently identified in a backyard koi and goldfish pond located in Snohomish County, Washington State 3. SVC has previously been reported in Europe, the Middle East and Asia. More recently, it has been reported in North and South America. In the US, SVC outbreaks occurred in North Carolina in 2002 and Washington in June The virus has also been reported in feral common carp populations in Wisconsin and Illinois. SCV is an OIE notifiable disease.

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17 Spring Viremia of Carp Virus Etiological agent –Family Rhabdoviridae –Bullet shaped morphology –single-stranded RNA containing 5 genes

18 Spring Viremia of Carp Virus Virulence and Pathology –Darkening of the skin –Distended abdomen –Exopthalmia –Petechial hemorrhage of the skin, gills, and eyes –Pale gills –Hemorrhage in the swim bladder –Catarrhal enteritis

19 Example of exopthalmia and abdominal distention Clinical signs of disease: Darkening coloration Abdominal distension Exopthalmia

20 Spring Viremia of Carp Virus Virulence and Pathology –virus affects carp at all ages but victims are mostly young fish. –Outbreaks depend on the temperature –High mortality occurs at water temperatures of 10 to 17°C, typically in spring. –At >20 °C, elevated immune response protects carp from infection and re-infection

21 Spring Viremia of Carp Virus Transmission: –Occurs by horizontal transmission –Excretion of SVCV via feces and urine from infected fish –Parasitic transfer of SVCV from diseased to healthy fish –virus could stay infective in the water for more than 4 wks and 6 wks in the mud –source of infection may be contaminated equipment –vertical transmission of SVCV is not an important source of infection

22 Spring Viremia of Carp Virus Diagnosis (Standard Screening Method ) –Isolation of SVCV in cell culture FHM or EPC tissue culture cells –Indirect fluorescent antibody test on infected culture cells or –Enzyme-linked immunosorbent assay (ELISA) or –Neutralization Antibody test or –PCR

23 Spring Viremia of Carp Virus Management –In rearing facilities with a controlled environment, elevation of temperature above 20° C can prevent or stop SVC outbreaks –avoidance of SVCV by using spring or well water –Eradication of diseased fish –Control movement of fish Anglers should not transfer fish or fish parts from one body of water to another –Vaccination provides good protection

24 White sturgeon iridovirus (WSIV) Host and Geographic Range –White Sturgeon –North America

25 WSIV History Recognized as the most prevalent viral pathogen in White Sturgeon. Significant mortality in commercial and conservation aquaculture. Northern California commercial sturgeon farms Lower Columbia River in Oregon and Washington Snake River in Southern Idaho Kootenai River in northern Idaho British Columbia LaPatra et. al. 1994

26 WSIV: Manifestation of Disease Clinical disease can be induced –Overcrowding, transport, handling, etc. Slow chronic wasting syndrome Fry and fingerlings (1 st year) Mortality assumed to be due: –Anorexia –Respiratory function –Osmoregulatory function –Secondary infection

27 WSIV: Clinical Signs of Disease Darkening Pigmentation Emaciated body

28 Manifestation of disease Virus has an affinity for epithelial tissue: Skin Gill Oropharynx Olfactory (barbels) Histology shows: Hypertrophied cells with swollen cytoplasm

29 TEM of WSIV infected cells 5000X

30 WSIV Morphology Icosahedral morphology Size ( nm) Double capsid Dense nucleiod center TEM of WSIV From Kootenai River white sturgeon skin (2004)

31 White sturgeon iridovirus (WSIV) Transmission –Shown to be transmitted from infected fish to healthy individuals –may be endemic in most wild Northwest white sturgeon populations. –Virus may be vertically transmitted from adult to offspring during spawning.

32 White sturgeon iridovirus (WSIV) Diagnosis of infection –Difficult to propagate reliably in tissue culture –Histology for the detection of large hypertrophied cells within the epithelial tissue of the skin, gills, and barbels.

33 White sturgeon iridovirus (WSIV) Management –Ideally, avoidance of WSIV by using spring or well water to rear juvenile sturgeon –Minimize stress of sturgeon during early life stage –Control movement of fish

34 Viral Hemorrhagic Septicemia is 1 of the 7 most important diseases of finfish worldwide and is listed by the OIE as notifiable O.I.E. World Organization for Animal Health Aquatic Animal Health Code 2006 USDA Animal and Plant Health Service Designated at the US Regulatory Authority on Animal Health

35 USDA APHIS Criteria for Diseases/Pathogens of Regulatory Significance Causes significant impact on production, wild resources, or human health Infectious disease and can be spread by commerce Involves host species in interstate or international commerce and be of concern to US trading partners that are free of the disease Reliable diagnostic methods available

36 USDA APHIS Criteria for Diseases/Pathogens of Regulatory Significance Causes significant impact on production, wild resources, or human health Infectious disease and can be spread by commerce Involves host species in interstate or international commerce and be of concern to US trading partners that are free of the disease Reliable diagnostic methods available No human health risk with VHSV No treatment for VHSV VHSV has been found ONLY in wild fish in the Great Lakes Basin

37 Time Line of VHSV described in RBT in Europe (FW) virus isolated and described (FW) saltwater (SW) VHSV hosts in USA 1990 to present- VHSV is found endemic in SW hosts on US East and West Coasts 2003-present- Great Lakes VHSV causes mass mortality in a variety of FW hosts, including sport fish important to Idaho

38 How bad can it get? 2006 Freshwater drum mortality in Lake Erie New virus in naïve hosts becomes epizootic Millions of pounds of FW drum “Windrows of fish” along the beach piled up 10’ wide and 4’ high

39 Herring mortality B.C. Canada

40 HerringRainbow troutWalleye

41 Disease Signs of VHSV Hemorrhagic: Causes leaking of blood from vessels especially under the skin and internal organs Septicemia: Virus in blood and spreads throughout the body in circulation Pop eye: Caused by pressure of hemorrhage pushing beneath the eye

42 Host Range of VHSV 37 host species FW and SW worldwide 28 FW species 19 FW species are important to Idaho including rainbow trout, salmon, bass, bluegill, crappie, and perch Host range is unheard of for other fish viruses!

43 Current VHS Outbreaks:2007 Lake Huron Lake St. Clair Lake Ontario St. Lawrence R. Conesus Lake* Lake Erie Budd Lake* Lake Winnebago* * Not connected by water – baitfish suspected Lake Michigan

44 Current VHS Outbreaks:2007 Lake Huron Lake St. Clair Lake Ontario St. Lawrence R. Conesus Lake* Lake Erie Budd Lake* Lake Winnebago* Summer, 2007 NYDEC Surveillance Lake Michigan

45 3.7%-5% 2.1% Genetic Differences of VHSV Shows an East Coast Origin

46 How did VHSV get into the Great Lakes? Commercial ballast water Natural movement of infected fish Human recreational activities Sport fishing activities (bait minnows, contaminated fishing equipment, illegal fish stocking) Boating Animal activities (mammals, birds) Basically, vectors are unknown!

47 Overview Two genetic types of VHSV correlate West coast and East Coast VHSV in the Great Lakes likely came from an East Coast host Conventional cell culture methods detects Great Lakes VHSV strains VHSV is more stable in freshwater than in sea water. VHSV lasts up to one month when held at 50ºF

48 APHIS Federal Order VHSV Federal Order was issued 10/24/2006 Emergency Action taken to prevent the spread of VHSV Must be followed-up by formal rulemaking

49 Current Provisions Under the Federal Order VHS susceptible species are prohibited from moving out of the 8 States and 2 Canadian Provinces bordering the Great Lakes except under certain conditions –Movement to slaughter with adequate disinfection –Movement to a research or diagnostic lab with adequate disinfection –Movement of live fish testing negative for VHSV by laboratory assays –Movement of salmonids from Canada that meet USFWS inspection requirements Catch-and-Release fishing activities

50 Implications of VHSV for Idaho 20 years surveillance has been negative in cultured and wild fish Sport fishing valued at $ 360 million $ 110 million trout culture industry at risk ESA-listed anadromous salmon and steelhead cultured in Idaho Must prevent VHSV introduction into Idaho

51 What has IDFG done to reduce risk? Live fish for bait prohibited Banned importation of all fish from Great Lakes Basin (GLB) Supported APHIS Federal Order Banned frozen baitfish from GLB Partnering with Idaho Department of Agriculture and trout industry on emergency rule to prevent introduction

52 Future needs: Risk assessment of potential vectors leading to Biosecurity Plan for Idaho  Importations of live fish & eggs  Private ponds  Aquatic nuisance species  Aquatic baits other than fish Education of anglers to reduce risks Support research on VHSV susceptibility of Idaho fish stocks Idaho Fish Health and Sterility Management Policy


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