Common Name: Viral Hemorrhagic Septicemia (VHS). Also known as 'Egtved virus' in Europe.
Taxonomy: Available through ITIS.
Identification: VHS is an RNA virus with a bullet-shaped morphology typical of rhabdoviruses and a 11–12 kb nucleotide genome encoding five structural proteins. Viral particles are 170-180 nm in length and 60-70 nm in width (Skall et al. 2005; Elsayad et al. 2006). A classification based on sequences of N- and G-genes reveals four major genotypic groups that correspond to the geographical distribution of the virus: one group includes isolates from European inland waters and northern marine coastal areas, a second group is composed of marine isolates from the Baltic Sea, a third group comprises isolates from the North Sea, and a fourth group comprises North American isolates. Thus far, the virus has been found in Europe, North America, Japan and Korea (Nishizawa et al. 2002; Skall et al. 2005). Based on a comparison of the gene sequences of all North American VHS isolates, Elsayad et al. (2006) propose that the VHS isolate obtained from a muskellunge in Lake St. Clair constitutes a distinct sublineage of the North American genotype that likely originated on the east coast of North America.
The clinical signs of VHS differ depending on the course of infection. In the latent manifestation of the disease, some mortality may occur and fish become hyperactive, sometimes displaying nervous symptoms such as twisting of the body and behavior that involves swimming erratically in circles or in a corkscrew pattern (CFSPH 2003). Conversely, some carriers of the virus may show no symptoms at all (Dopazo et al. 2002). Histopathological changes occur in the liver, kidneys, spleen and skeletal muscle (McAllister 1990); the kidney and spleen appear to be the organs most often targeted by VHS virus (Brudeseth et al. 2002). In the acute form of the disease, fish become lethargic, dark and anemic, with bulging eyes, congested kidneys, mottled liver, and with hemorrhage in the eyes, skin, gills, fin bases, skeletal muscle and viscera (McAllister 1990). Mortality is very high and the disease is short-lived (CFSPH 2003). In the chronic form of the disease, mortality is low and all the symptoms are similar to the acute form, except that hemorrhaging is not common; instead, the liver, spleen and kidneys experience an accumulation of fluid such that the body becomes bloated and the liver and kidneys become very light in color (McAllister 1990). Survivors of infection can be carriers of the virus throughout the rest of their lives.
Size: The VHS virus is approximately 170–180 nm long and 60–70 nm wide (Elsayad et al. 2006; McAllister 1990). Native Range: VHS is indigenous to eastern and western Europe, Japan, and the Pacific coast (from California to Alaska) and Atlantic coast of North America. Some evidence suggests that the European strains of VHS are native to the Atlantic Ocean. It is generally believed that all strains of VHS are derived from a common marine ancestor (Skall et al. 2005).
Nonindigenous Occurrences: VHS virus has been present in the Great Lakes since at least 2003. The North American strain of the virus was first isolated from muskellunge Esox masquinongy caught in the northwest part of Lake St. Clair, Michigan (Elsayad et al. 2006). In 2005, infected freshwater drum Aplodinotus grunniens and round goby Neogobius melanostomus were captured in the Bay of Quinte, Lake Ontario (Wren and Lee 2006). In the spring and summer of 2006, VHS was detected in fishes in the Thousands Islands area of the St. Lawrence River (Wren and Lee 2006) and in Lake St. Clair, Lake Erie and Lake Ontario (USDA 2006). All isolates from these areas belong to the same sublineage of the North American genotype (M. Faisal, personal communication, November 2006).
Means of Introduction: It is not known how VHS was initially introduced to the Great Lakes–St. Lawrence River system; however, genetic evidence suggests that the virus originated from the Atlantic coast of North America, possibly via transport in ballast water or infected migratory fishes (Elsayad et al. 2006). Aquaculture activities are implicated in the spread of the virus (Skall et al. 2005; Fisheries Research Services 2006). The potential for transport with bait fish (reviewed by Goodwin et al. 2004) is demonstrated by the virus' recovery in cell culture from frozen Pacific herring Clupea pallasi after two freeze/thaw cycles in a conventional freezer (Meyers et al. 1994). Waterfowl might also play a role in transmitting the virus (Peters & Neukirch 1986).
Status: The North American strain of VHS virus is present in Lake St. Clair, Lake Erie, Lake Ontario, and the St. Lawrence River (Elsayad et al. 2006; USDA 2006).
Ecology: VHS occurs in both marine and freshwater environments. It requires an incubation period of approximately 7 to 15 days, depending on water temperature (CFSPH 2003). It becomes inactivated in ether, chloroform, glycerol, formalin, sodium hypochlorite, sodium hydroxide, iodophors, UV radiation, or by desiccation, or exposure to pH levels lower than 2.4 or higher than 12.2 (CFSPH 2003; McAllister 1990). VHS is still stable at a pH of 5.0, while the optimum replication pH is 7.4–7.8. The optimum replication temperature is 14–15ºC, whereas replication is low at 6ºC and almost non-existent at 20ºC (De Kinkelin et al. 1980; Bernard et al. 1983; McAllister 1990). The virus becomes inactive after 24 hours at 20ºC in water, but can persist for five days at 4ºC in water (CFSPH 2003). Consequently, fish mortality from VHS is greatest at 3–12ºC and is very rare above 15ºC (McAllister 1990).
Fishes are susceptible to infection at any age. VHS is transmitted to juvenile and adult fish most often via urine and sex products that enter a fish through secondary gill lamellae, or possibly through fin bases or via wounds; it cannot enter eggs and infect fish before hatching (McAllister 1990; Brudeseth et al. 2002; CFSPH 2003; Harmache et al. 2006). Juvenile fish are generally more susceptible than adults. Experiments have recorded infection after contact with infected fish and after immersion in infected water; the virus can remain activated in water for several days (McAllister 1990). The VHS virus can persist for long periods of time in the bottom of culture ponds, potentially in invertebrates (CFSPH 2003). There is evidence of infections transferred between farmed and free-living fishes in European inland waters and coastal areas (Stone et al. 1997; Skall et al. 2005). The mortality rate for infected fish varies between 20% and 80%, depending on environmental conditions, and has reached 100% in trout fry (CFSPH 2003).
Impact of Introduction: A) Realised: The North American VHS strain is less virulent to salmon and trout than the European strain (Follett et al. 1997) and has not caused large fish kills of these species in the Great Lakes to date (USDA 2006). However, mortality of other species has been documented. In 2005, VHS apparently caused large die-offs of freshwater drum Aplodinotus grunniens and round goby Neogobius melanostomus in eastern Lake Ontario and muskellunge Esox masquinongy in Lake St. Clair (Wren and Lee 2006). In the spring and summer of 2006, VHS was implicated as a cause of large die-offs of round goby and muskellunge in the Thousands Islands area of the St. Lawrence River (Wren and Lee 2006) and die-offs of muskellunge, northern pike Esox lucius, gizzard shad Dorosoma cepedianum, smallmouth bass Micropterus dolomieui, walleye Sander vitreus and yellow perch Perca flavescens in Lake St. Clair, Lake Erie and Lake Ontario (USDA 2006). B) Potential: Nearly 50 species of fish are known to be susceptible to VHS. The virus was first isolated from most of these species only within the past two decades (Skall et al. 2005). Susceptible fishes include several species of commercial importance (e.g. lake trout Salvelinus namaycush, rainbow trout Oncorhynchus mykiss, brook trout Salvelinus fontinalis, and coregonids Coregonus spp.) that have not yet been killed by the virus in the Great Lakes basin. European freshwater-strain VHS infections usually manifest themselves in salmonids, particularly rainbow trout, which suffer high mortality rates. Although the North American strain appears to be of low pathogenicity to salmonids, it has caused mass mortality in a variety of other marine fishes (Kocan et al. 2003; Meyers and Winton 1995; Skall et al. 2005).
Remarks: A U.S. Federal Order aims to prevent the spread of VHS into aquaculture facilities by restricting the interstate movement and importation of live fish of VHS-susceptible species: http://www.aphis.usda.gov/vs/aqua/pdf/vhs-fed-order_ogc-changes.pdf
References: Bernard, J., P. de Kinkelin and M. Bearzotti-Le Berre. 1983. Viral Hemorrhagic Septicemia of rainbow trout: relation between the G polypeptide and antibody production in protection of the fish after infection with the F25 attenuated variant. Infection and Immunity 39: 7– 14. Brudeseth, B.E., R.S. Raynard, J.A. King and Ǿ. Evensen. 2005. Sequential pathology after experimental infection with marine viral hemorrhagic septicemia isolates of low and high virulence in turbot (Scophthalmus maximus L). Veterinary Pathology 42: 9–18. Center for Food Security and Public Health (CFSPH). 2003. Viral Hemorrhagic Septicemia. Institute for International Cooperation in Animal Biologics and College of Veterinary Medicine, Iowa State University, Ames, Iowa. 3 pp. <http://www.cfsph.iastate. edu/Factsheets/pdfs/viral_hemorrhagic_septicemia.pdf> Revision date: 08/08/2005 de Kinkelin, P., M. Bearzotti-Le Berre and J. Bernard. 1980. Viral Hemorrhagic Septicemia of rainbow trout: selection of a thermoresistant virus variant and comparison of polypeptide synthesis with the wild-type virus strain. Journal of Virology 36: 652–658. Dopazo, C.P., I. Bandin, C. López-Vasquez, J. Lamas, M. Noya and J.L. Barja. 2002. Isolation of viral hemorrhagic septicaemia virus from Greenland halibut Reinhardtius hippoglossoides caught at the Flemish Cap. Diseases of Aquatic Organisms 50: 171–179. Elsayed, E., M. Faisal, M. Thomas, G. Whelan, W. Batts and J. Winton. 2006. Isolation of viral haemorrhagic septicaemia virus from muskellunge, Esox masquinongy (Mitchill), in Lake St. Clair, Michigan, USA reveals a new sublineage of the North American genotype. Journal of Fish Diseases 29: 611–619. Fisheries Research Services. 2006. Risks to wild freshwater fisheries from viral hemorrhagic septicaemia (VHS) disease. Scottish Executive Environment and Rural Affairs Department. <http://www.marlab.ac.uk/FRS.Web/Uploads/Documents/VHSVRisksV3.pdf> Revision date: 31/05/2006 Follett, J.E., T.R. Meyers, T.O. Burton and J.L. Geesin. 1997. Comparative susceptibilities of salmonid species in Alaska to infectious hematopoietic virus (IHNV) and North American viral hemorrhagic septicemia virus (VHSV). Journal of Aquatic Animal Health 9: 34–40. Goodwin, A.E., J.E. Peterson, T.R. Meyers and D.J. Money. 2004. Transmission of exotic fish viruses: the relative risks of wild and cultured bait. Fisheries 29(5): 19
Summary • There is a risk of transfer of VHSV from farmed to wild freshwater fish species and vice versa. • There is evidence that a reservoir of infection may be created in wild freshwater fish species. This may pose a risk of re-infection of farms (eg rainbow trout). • There are no reports of VHSV infection leading to significant disease outbreaks in wild freshwater fish stocks. • Based on evidence from outbreaks in farms and experimental evidence, free living rainbow trout, brown trout, whitefish, grayling and pike may be at risk of disease. • Available evidence suggests a high infection pressure would be required to initiate a disease outbreak in wild fish (eg shedding of virus from an infected farm).
Evidence There is a risk of transfer of VHSV from farmed to wild freshwater fish species and vice versa The transfer of infection between free-living and farmed fish in the freshwater environment has been suspected in many cases during the 40-year history of VHS control in both Denmark and Germany (Skall, pers comm). Indeed, VHSV-infected free-living, mainly feral fish including brown and rainbow trout, have been identified on several occasions (Ahne & Jørgensen 1993, Enzmann et al. 1987, 1992, 1993; Jørgensen 1982; Meier et al. 1986; Olesen & Jørgensen 1983). Furthermore a correlation between infection status of nearby fish farms and evidence of infection in free living rainbow trout has been established in Denmark (Skall, pers comm.). While the direction of viral transmission (ie farm to wild or wild to farmed fish) is often difficult to ascertain, VHSV which causes disease in rainbow trout is widely believed to have been introduced to rainbow trout aquaculture from a marine source (Snow et al., 2004). Since isolates from wild freshwater fish are genetically similar to those causing disease outbreaks in farms (Einer-Jensen et al., 2004), these viruses therefore probably originated in association with aquaculture. Evidence from Denmark and Germany indicates that once VHSV is established in a water catchment system as a result of disease in farms, the virus may become enzootic and wild carrier fish may present a risk of re-infection of farmed fish. Such re-infection of farms is likely linked to the presence of a large number of highly susceptible host species and the artificial conditions under which they are cultured.
Mechanisms of Transmission of VHS VHS is believed to be primarily spread through transport of live infected fish (Skall, 2005) though it can also be transmitted via contaminated water (Jorgensen, 1973). In the latter case, such incidences are usually correlated with the presence of clinical disease on rainbow trout farms which have the potential to create a large infection pressure via the shedding large quantities of virus. There are no reports of VHS having been spread via angling activities or angling equipment.
Free living freshwater fish species which might be at risk of infection with VHSV in Europe The freshwater host range for VHSV was recently reviewed by Skall et al. (2005). Evidence of VHS infection has been demonstrated in a range of wild-caught freshwater species including brown trout (Salmo trutta), white fish (Corgonus sp), grayling (Thymallus thymallus) pike (Esox lucius) and European eel (Anguilla anguilla) (Castric et al., 1992; Enzmann et al. 1987, 1992, 1993; Thiery et al, 2002). Free living rainbow trout can also be infected and are believed to be a primary risk factor in the transmission of VHS disease from wild to farmed fish in Denmark (Skall pers comm.). Other species which have been demonstrated to replicate virus experimentally include Brook trout (Salvelinus fontinalis) (Rasmussen, 1965), Golden trout (Oncorhynchus aguabonita) (Ahne et al, 1976) and Rainbow trout x coho salmon (Ord et al., 1976). VHSV has never been isolated from Atlantic salmon in freshwater despite extensive routine monitoring. Infection of a small proportion of carrier individuals has been demonstrated following water-borne infection (de Kinkelin & Castric , 1982; King et al., 2002) but such experiments involved artificially high levels of infection pressure which most likely would not be encountered in the wild fish environment.
Evidence for disease occurrence in wild freshwater fish Outbreaks of disease have never been reported in wild fish, although disease outbreaks are often difficult to identify in wild stocks. Losses in farmed rainbow trout and brown trout aquaculture (Jørgensen, 1980; de Kinkelin and le Berre, 1977) suggest that these species of wild fish could be at risk of disease. Fluctuations in the prevalence of antibodies over a period of four years have also been interpreted as suggesting the maintenance of an epidemic within wild populations of brown trout (Enzmann et al., 1992). VHSV has also been reported to induce mortality in pike (Esox lucius) in experimental studies and in a hatchery situation (Meier and Jørgensen, 1980; Enzmann et al., 1993). Infections of whitefish with VHSV were reported in Germany and Switzerland (Ahne & Thomsen 1985; Meier et al., 1986) with fish showing typical VHS clinical signs. Whitefish nave also been shown to be susceptible to VHS is experimental trials (Skall et al., 2004). VHS disease has been demonstrated in Atlantic salmon following injection with VHSV but not by water-borne transmission (de Kinkelin & Castric, 1982). 31 May 2006
References Ahne W. & Jørgensen P.E.V. (1993) Prevalence of neutralising antibodies to IHNV and VHSV in freeliving and cultured rainbow trout in Germany. Bulletin of the European Association of Fish Pathologists 13, 7–9. Ahne, W., Negele, R.D. & Ollenschlager B. (1976) Verleichende Infektionsversuche mit Egtved-Viren (Stamm F1) bei Regenbogenforellen (Salmo gairdneri) und Goldforellen (Salmo aguabonita). Berliner und Munchener Tierarzliche Wochenschrift 89, 161-164. Ahne W. & Thomsen I. (1985) Occurrence of VHS virus in wild white fish (Coregonus sp.) Zentralblatt für Veterinarmedizin 32, 73-75 Castric J., Jeffroy J., Bearzotti M. & de Kinkelin P. (1992) Isolation of viral haemorrhagic septicaemia virus (VHSV) from wild elvers Anguilla anguilla. Bulletin of the European Association of Fish Pathologists 12, 21–23. De Kinkelin P. & le Berre M. (1977) Isolement d'un Rhabdovirus pathogéne de la Truite Fario (Salmo trutta L., 1766). C.R.Acad.Sc.Paris 284, 101-104 De Kinkelin, P, & Castric, J. (1982) An experimental study of the susceptibility of Atlantic salmon fry, Salmo salar L., to viral haemorrhagic septicaemia. J. Fish Dis 5, 57-65. Einer-Jensen K., Ahrens P., Forsberg R. & Lorenzen N. (2004) Evolution of the fish rhabdovirus viral haemorrhagic septicaemia virus. Journal of General Virology 85, 1167–1179. Enzmann P.-J., Konrad M., Parey K. & Wetzlar H. (1987) Natürliches wirtsspektrum des virus der viralen hämorrhagischen septikämie der regenbogenforelle. Tierarztliche Umschau 42, 228–230. Enzmann P.J., Konrad M. & Rapp J. (1992) Epizootiological studies on viral haemorrhagic septicaemia in brown trout Salmo trutta fario. Diseases of Aquatic Organisms 12, 143–146. Enzmann P.-J., Konrad M. & Parey K. (1993) VHS in wild living fish and experimental transmission of the virus. Fisheries Research 17, 153–161. Jørgensen P.E.V. (1982) Egtved virus: occurrence of inapparent infections with virulent virus in free-living rainbow trout, Salmo gairdneri Richardson, at low temperature. Journal of Fish Diseases 5, 251–255. Jørgensen P.E.V.(1980). Egtved virus: the susceptibility of brown trout and rainbow trout to eight virus isolates and the significance of the findings for the VHS control. In Ahne W (Ed.): Fish Diseases. Springer-Verlag. Berlin 1980; Pages 3-7. Jorgensen, P.E.V. (1973) Artificial transmission of viral haemorrhagic septicaemia (VHS) of rainbow trout. Rivista Italiana di Piscicoltura e ittiopatologia 8, 101-102 King J.A., Snow M., Skall H.F. & Raynard R.S. (2001) Experimental susceptibility of Atlantic salmon Salmo salar and turbot Scopththalmus maximus to European freshwater and marine isolates of viral haemorrhagic septicaemia virus. Diseases of Aquatic Organisms 47, 25–31. Meier W., Ahne W. & Jørgensen P.E.V. (1986) Fish viruses: viral haemorrhagic septicaemia in white fish (Coregonus sp.). Journal of Applied Ichthyology 2, 181–186 Meier W. & Jørgensen P.E.V. (1986) Isolation of VHS virus form pike fry (Esox lucius) with haemorrhagic symptoms. Pages 8-17 in W. Ahne (Ed.) Fish Diseases. Spinger-Verlag. Berlin. Meier W, Jørgensen PEV. Isolation of VHS virus from pike (Esox lucius L.) with hemorrhagic symptoms. In Ahne W (Ed.): Fish Diseases. Springer-Verlag. Berlin 1980; pages 8-17 Olesen N.J. & Jørgensen P.E.V. (1983) Egtvedsyge (VHS) i fritlevende regnbueørreder. Ferskvandsfiskeribladet 81, 130–132. Ord, W.M., Le Berre, M. & de Kinkelin, P. (1976) Viral haemorrhagic septicaemia; Comparative susceptibility of rainbow trout (Salmo gairdneri) and hybrids (S. gairdneri x Oncorhynchus kisutch) to experimental infection. Journal of the Fisheries Research Board of Canada 33, 1205-1208 Rasmussen C.J. (1965) A biological study of the Egtved disease (INUL). Annals of the New York Academy of Sciences 126, 427–460. Skall, H. F., Olesen, N. J. & Mellergaard, S. (2005) Viral haemorrhagic septicaemia virus in marine fish and its implications for fish farming – a review. Journal of Fish Diseases 28, 509-529. Skall H.F., Slierendrecht W.J., King J.A. & Olesen N.J. (2004) Experimental infection of rainbow trout Oncorhynchus mykiss with viral haemorrhagic septicaemia virus isolates from European marine and farmed fishes. Diseases of Aquatic Organisms 58, 99–110. Snow M., Bain N., Black J., Taupin V., Cunningham C.O., King J.A., Skall H.F. & Raynard R.S. (2004) Genetic population structure of marine viral haemorrhagic septicaemia virus (VHSV). Diseases of Aquatic Organisms 61, 11–21. Thiéry R., de Boisséson C., Jeffroy J., Castric J., de Kinkelin P. & Benmansour A. (2002) Phylogenetic analysis of viral haemorrhagic septicaemia virus (VHSV) isolates from France (1971–1999). Diseases of Aquatic Organisms 52, 29–37.
Viral Hemorrhagic Septicemia Egtved Disease, Infectious Nephrotic Swelling and Liver Degeneration, Abdominal Ascites of Trout, Infectious Anemia of Trout, Pernicious Anemia of Trout Last Updated: Aug. 8, 2005
Importance: Viral hemorrhagic septicemia is economically important in rainbow trout and turbot farming. Significant mortality has also been seen in Pacific herring and pilchard along the Pacific coast of North America.
Etiology: Viral hemorrhagic septicemia (VHS) is caused by the viral hemorrhagic septicemia virus (VHSV or Egtved virus). This virus is a member of the genus Novirhabdovirus and family Rhabdoviridae. Both marine and freshwater isolates occur.
Species affected: Viral hemorrhagic septicemia affects rainbow trout, brown trout, brook trout, gray¬ling, white fish (Coregonus sp.), pike, and turbot. A number of marine species are also susceptible, including Pacific herring, Pacific salmon (Oncorhynchus spp.), Pacific cod, Pacific sandlance, and pilchard. In the Atlantic Ocean, susceptible species include Atlantic Cod, haddock, poor cod, rockling, sprat, herring, whiting, blue whiting, lesser argentine, Norway pout, shiner perch, Dab, English sole, flounder, and plaice. Most warm–water fish are resistant to this disease.
Geographic distribution: Viral hemorrhagic septicemia affects farmed rainbow trout and a few other freshwa¬ter species in continental Europe and Japan. VHSV has also been isolated from a variety of wild marine fish in North Atlantic, the Baltic sea, and the North American part of the Pacific Ocean.
Transmission: VHSV is shed in the urine, feces, and sexual fluids. Reservoirs include clinically ill fish and asymptomatic carriers. Transmission can occur through the water or by contact. The virus is thought to enter the body through the gills or possibly through wounds. Oral infection probably does not occur. Virus maintenance in invertebrates or transmission by parasitic flagellates may be possible but is unproven. The virus is unstable in pond water, particularly when it is warm. Infectivity is lost after 24 hours at 20° C but can persist for five days at 4° C.
Incubation period: The incubation period varies with water temperature, but is usually 7 to 15 days.
Clinical signs: Viral hemorrhagic septicemia has been divided into acute, chronic, and nervous forms of the disease. These syndromes overlap and characteristics of all three forms may be seen during outbreaks. In the acute form, clinical signs include darkening of the body, anemia, and protru¬sion of the eyes. Hemorrhages may be seen in the gills and eyes, and sometimes at the base of the pectoral fins and the body surface. The course of acute disease is brief and mortality is high. In the chronic form, infected fish blacken and the gills lose color. Protrusion of the eyes, anemia, and fluid accumulations in the abdomen are often seen. Hemorrhages are less common than in the acute form and mortality is usually low. In the nervous form, the body becomes twisted and fish swim in circles or on their sides, but few other symptoms are typically present.
Post mortem lesions: Scattered hemorrhages may be seen in the skeletal muscles, perivisceral adipose tissue in the abdomen, air bladder, intestines, and other organs. In chronic disease, the body cavity may be filled with fluid. The spleen may be enlarged and in some forms is very dark red. The liver is usually dark red in the acute form; in the chronic form, it often contains petechiae. The kidneys are reddened in the acute form and rarely swollen; in the chronic form, they are often grayish, swollen, and undulating. Fish with the nervous form may have no significant gross lesions. In some cases, muscle degeneration may occur with few other signs.
Morbidity and Mortality: Viral hemorrhagic septicemia can occur at any age, but younger fish appear to be most susceptible. Water tempera¬ture influences the likelihood of infection; this disease usually develops at temperatures between 4°C and 14°C. Outbreaks occur most often in the spring, when the temperature of the water is either rising or fluctuating. The mortality rate varies from 20% to 80% and is influ¬enced by environmental conditions. Mortality of up to 100% has been seen in trout fry.
Diagnosis: Clinical: Viral hemorrhagic septicemia should be suspected in trout, a few other freshwater fish, and marine species with hemorrhages or nervous signs.
Laboratory tests: Viral hemorrhagic septicemia can be diagnosed by virus isolation in cell cultures; appropriate cell lines include BF–2 (Bluegill fry) and RTG–2 (Rainbow trout gonad) cells. EPC (Epithelioma papulosum cyprini) cells can also be used, but are less susceptible to infection. Virus identity is confirmed by virus neutralization, immunofluorescence, an enzyme–linked immunosorbent assay, immunoperoxidase staining, or a polymerase chain reaction (PCR)–based assay. Viral antigens can also be identified directly in tissues by immunofluorescence, immunohistochemistry, or ELISA. A PCR technique is in development. Serology by virus neutralization or ELISA may be effec¬tive in detecting carriers, but has not yet been validated for routine diagnosis.
Samples to collect: The samples to collect depend on the size of the fish. Small fish (less than or equal to 4 cm) should be sent whole. The viscera including the kidney should be collected from fish that are 4 to 6 cm long. The kidney, spleen, heart, and encephalon should be sent from larger fish. Samples of ovar¬ian fluid should also be collected from broodfish at spawn¬ing. Samples should be taken from ten diseased fish and combined to form pools with approximately 1.5 g of mate¬rial (no more than five fish per pool). The pools of organs or ovarian fluids should be placed in sterile vials. The samples may also be sent in cell culture medium or Hanks’ basal salt solution with antibiotics. They should be kept cold (4°C) but not frozen. If the shipping time is expected to be longer than 12 hours, serum or albumen (5–10%) may be added to stabilize the virus. Ideally, virus isola¬tion should be done within 24 hours after fish sampling.
Recommended actions if viral hemorrhagic septicemia is suspected: Notification of authorities: Viral hemorrhagic septicemia should be reported to state or federal authorities immediately upon diagnosis or suspi¬cion of the disease. Federal: Area Veterinarians in Charge (AVICS) http://www.aphis.usda.gov/vs/area_offices.htm State vets: http://www.aphis.usda.gov/vs/sregs/official.html Quarantine and Disinfection: Viral hemorrhagic septicemia is a highly contagious dis¬ease; quarantines are necessary to control outbreaks. VHSV can survive for long periods in the bottom of farm ponds, possibly in protozoans or metazoans, if the ponds are not dried and disinfected. VHSV can be inactivated by formalin, drying, iodophor disinfectants, sodium hydroxide, sodium hypochlorite, and pH 2.5 or 12.2. The virus is also highly thermolabile. The effec¬tiveness of lime disinfection is suspect. Public health: There is no indication that this disease is a threat to human health.
For More Information: World Organization for Animal Health (OIE) http://www.oie.int OIE Diagnostic Manual for Aquatic Animal Diseases (2000) http://www.oie.int/eng/normes/fmanual/A_summry.htm OIE International Aquatic Animal Health Code (2001) http://www.oie.int/eng/normes/fcode/a_summry.htm
The purpose of this Federal Order is to prevent the spread of viral hemorrhagic septicemia (VHS) into aquaculture facilities. This Order amends and replaces the Order for VHS issued on October 24, 2006, by allowing the importation or interstate movement of VHS-susceptible live species of fish (as specified below) under certain conditions, while continuing to prevent the spread of VHS.
This Order is issued pursuant to the Animal Health Protection Act (AHPA). The AHPA authorizes the Secretary of Agriculture to prohibit or restrict the importation or movement in interstate commerce of any animal, article, or means of conveyance if the Secretary determines that the prohibition or restriction is necessary to prevent the introduction or dissemination of any pest or disease of livestock into or within the United States.
Due to outbreaks of VHS, the Administrator of the Animal and Plant Health Inspection Service (APHIS) has determined that it is necessary, in order to prevent the spread of VHS into aquaculture facilities, to prohibit or restrict the importation of VHS-susceptible species of live fish from two Canadian Provinces into the United States and to prohibit or restrict the interstate movement of the same species of live fish from VHS-affected or at-risk States.
All international and interstate movement of VHS-susceptible species of live fish from affected or at-risk Provinces or States that is not specified as permissible by this Order is prohibited.
1. Affected or At-Risk Regions U.S. States: Illinois, Indiana, Michigan, Minnesota, New York, Ohio, Pennsylvania, and Wisconsin. Canadian Provinces: Ontario, Quebec
2. VHS-Susceptible Species of Live Fish The current list of species of VHS-susceptible live fish affected by this Order is located on the APHIS Web site at www.aphis.usda.gov/vs/aqua/. A paper copy of this list may also be received by calling 301-734-6188.
3. Permissible International Movement of VHS-Susceptible Species of Live Fish VHS-susceptible species of live salmonid fish from affected Canadian provinces may be imported into the United States only if the shipment meets the requirements set forth in title 50, Code of Federal Regulations, Sections 16.13 (a) (3) and 16.13 (b).
4. Permissible Movement of VHS-Susceptible Species of Live Fish from VHS-affected or at-risk States
(a) Movement to slaughter facilities: VHS-susceptible species of live fish may be moved interstate from any VHS-affected or at-risk State to any other State if all of the following conditions are met: (1) The fish are for human consumption. (2) The fish, if not tested for VHS, are accompanied by a valid form VS 1-27 (Permit for Movement of Restricted Animals) issued by an APHIS area office. (3) The fish are transported to a State-inspected slaughter facility. The slaughter facility must discharge waste water to a municipal sewage system that includes waste water disinfection. Alternately, the slaughter facility may discharge to either a non-discharging settling pond or a settling pond that disinfects according to all applicable EPA and State regulatory criteria. Offal, including carcasses, from the slaughter facility must be either rendered or composted.
(b) Movement to research and diagnostic laboratories VHS-susceptible species of live fish may be moved interstate from VHS-affected or at-risk States to research or diagnostic laboratories in any State if all of the following conditions are met: (1) The fish are transported to an approved research or diagnostic laboratory. Laboratory approval to work with VHS shall be authorized by the State, Tribal or Federal competent authority for aquatic animal health. (2) The fish are accompanied by a valid form VS 1-27 (Permit for Movement of Restricted Animals) issued by an APHIS area office. (3) Effluent and carcasses shall be considered medical waste and shall be disposed of at the receiving research or diagnostic facility according to all applicable EPA and State regulatory criteria.
(c) Other movement VHS-susceptible species of live fish from VHS-affected or at-risk States may be moved interstate to any State if the following conditions are met: The fish are transported with documentation from the appropriate State, Tribal, or Federal competent authority(s) for aquatic animal health stating that the fish have tested negative for VHS virus according to (i) the USFWS/AFS-FHS Standard Procedures for Aquatic Animal Health Inspections section of the Suggested Procedures for the Detection and Identification of Certain Finfish and Shellfish Pathogens 2005 Edition, American Fisheries Society, Fish Health Section, Bethesda, Maryland (commonly referred to as the AFS Blue Book); or (ii) the World Organization for Animal Health (OIE) Manual of Diagnostic Tests for Aquatic Animals, Fifth Edition (2006), Chapter 2.1.5, OIE, Paris, France.
5. Permissible Movement of VHS-Susceptible Species of Live Fish through VHS-affected or at-risk States For live fish originating from non-restricted areas, permission to transit through a State to another State of destination is not required under this Order.
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