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)
Viral infection is almost exclusively found in fish in seawater although one incident in Norway occurred in par in freshwater.

4. CANADA
MAINE

6. Infectious Salmon Anemia (ISAV)
Etiological agent
1st 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
Fish infected with ISA become lethargic, have erratic swimming and tend to swim near the water surface.
Disease of infected fish tend to produce pectechial hemorrhage on the skin and fins

9. Infectious Salmon Anemia (ISAV)

10. Infectious Salmon Anemia (ISAV)
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)
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
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

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)
                                                                                                                                
Remember doing a tissue imprint

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
culture sites be spaced no less than 5-6 km apart
waste water from slaughter and processing facilities should be thoroughly disinfected
control of ship and personnel movements among sites
compulsory slaughter of infect stocks (eradication)
Attempts to require vaccination
There is no theraputic measure to reduce outbeaks and infection and since the virus is readily transmitted in seawater and studies have shown

14. Spring Viremia of Carp Virus (SVCV)
                                                                                                                                                                                                                                                                                                          
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. Recent News Headlines
Spring Viremia of Carp virus (SVCv) was recently identified in a backyard koi and goldfish pond located in Snohomish County, Washington State
2. Spring viremia of carp (SVC) was confirmed in ornamental koi carp in Pike County, Missouri on July 13, 2004
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.

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
inflammation of the intestines
inflammation of a mucous membrane

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
The optimum temperature for viral replication in vitro is 20-22°C (68-72°F), however, this is also an optimum temperature range for immune function of susceptible species (Fijan 1999). Clinical and experimental data indicate that maximum mortality can be expected at water temperatures below 18°C (64°F) (Fijan 1999; McAllister 1993).
These findings have led experts (Wolf 1988; Ahne 1980; Fijan 1999) to suggest that outbreaks of SVC can be prevented or stopped in mature fish by raising water temperatures above 20°C (68°F); however, the results of such attempts have not been well documented. Because of the potential severity of the disease, depopulation is recommended.

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
PCR 
Spring viremia of carp can be diagnosed by clinical signs,

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
For the past 16 years, WSIV has been recognized as the most prevalent viral pathogen in White sturgeon.
This virus has caused significant mortality in both commercial and conservation aquaculture.
It was first detected in 1988 in commercial farms in northern California where annual losses were common. since the 1990’s the virus has been detected in cultured sturgeon in the lower columbia river in Oregon and Washington, the Snake river in southern Idaho, the Kootenai river in northern Idaho. The virus has also been isolated in a commercial rearing facility in 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 (1st year)
Mortality assumed to be due:
Anorexia
Respiratory function
Osmoregulatory function
Secondary infection
Clinical disease can be triggered by subjecting sturgeon harboring the virus to stressful condtions such as…over crowding, transport, handling, etc.
Is characterized as a slow chronic wasting syndrome that primarily affects fry and fingerlings of the first year of growth and mortality is assumed to be due to anorexia. Respiratory disfunction, and failure to control osmoregulation. And secondary infections

27. WSIV: Clinical Signs of Disease
Some of the clinical signs are a darkeniing coloration along with this emaiated body appearance
Darkening Pigmentation Emaciated body

28. Manifestation of disease
Virus has an affinity for epithelial tissue:
Skin
Gill
Oropharynx
Olfactory (barbels)
This virus is characterized as being epitheliotrophic, meaning that it has an affinity for epithelial tissue.
Primarily the skin, gills, oropharynx, and olfactory organs, such as the barbells.
Because this virus is difficult to grow in tissue culture, The most common diagnostic method used for detecting a WSIV infection is by histology where you can see these large hypertrophied cells within the epithelial tissue of these preferred organs.
skin and gill.
Histology shows:
Hypertrophied cells with swollen cytoplasm

29. TEM of WSIV infected cells
5000X
A closer look at these infected cells by electron microscopy shows numerous virus particles within the cytoplasm which supports previous findings that approx 70% of the virus remains cell associated.

30. TEM of WSIV From Kootenai River white sturgeon skin (2004)
WSIV Morphology
Icosahedral morphology
Size ( nm)
Double capsid
Dense nucleiod center
The virus particles have an icosahedral morphology typical of other iridoviruses that are approximately nm in size, have a characteristic double capsid formation and a dense nucleoid center where, presumably, the genetic information is stored
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.
Because this virus is difficult to grow in tissue culture, The most common diagnostic method used for detecting a WSIV infection is by histology where you can see these large hypertrophied cells within the epithelial tissue of these preferred organs.

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 1938- described in RBT in Europe (FW)
1963- virus isolated and described (FW)
1988- 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. Herring
Rainbow trout
Walleye

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

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