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[[Category:To Do - CABI]]
Also Known As – '''''SVC — Swim Bladder Inflammation - SBI'''''
Caused By – ''Spring Viraemia of Carp Virus – SVCV – Rhabdovirus Carpio – RVC''
==Introduction==
Spring Viraemia of Carp is caused by a '''bullet shaped [[Rhabdoviridae|Rhabdovirus]]'''. It is an '''acute, systemic, contagious disease primarily affecting carp'''. The effects of the virus further down the food chain in predators is unknown.
The disease s not zoonotic.
==Distribution==
Europe, North and South America, USSR and Asia.
Spring Viraemia of Carp is passed mainly '''horizontally''', being shed in '''faecal casts, urine and gill mucus'''. It is also transmitted by '''louse, leech, crustacean and annelid vectors'''. It usually enters via the gills and replicates here before dissipating to the swim bladder. Vertical transmission is possible but infrequent.
==Signalment==
Carp are mainly affected, although goldfish and other species have also been found with the disease. . Carp of all four varieties can be infected. There is no age susceptibility, although '''seasonality produces trends at 9-12 and 21-24 months old'''.
'''Feral carp''' are more vulnerable than farmed varieties.
Disease typically occurs in water '''<18⁰C so is predominantly in the Spring'''.
==Clinical Signs==
The virus causes '''haemorrhage and inflammation of the swim bladder leading to abdominal distension, lethargy, imbalance, swimming on their side and sinking'''. Affected fish may also appear pale, with '''darkening of the skin and fins +/- pin point haemorrhages'''. They may congregate in slow moving areas of their habitat.
Mortalities are common.
Where fish can be easily visualised, '''long thick mucoid casts''' will be visible from the vent. Fish are often anaemic due to viral invasion and multiplication within haematopoietic tissues.
==Diagnosis==
Definitive diagnosis can be achieved by '''virus isolation or direct Immunofluorescence''' (IF)<ref> Faisal, M., Ahne, W (1984) '''Spring viraemia of carp virus (SVCV): comparison of immunoperoxidase, fluorescent antibody and cell culture isolation techniques for detection of antigen'''. J Fish Diseases, 7(1):57-64</ref> or '''[[ELISA testing|ELISA]]'''.<ref> Rodák, L., Pospísil, Z., Tománek, J., Vesely, T., Obr, T., Valícek, L (1993) '''Enzyme-linked immunosorbent assay (ELISA) for the detection of spring viraemia of carp virus (SVCV) in tissue homogenates of the carp, Cyprinus carpio L'''. J Fish Diseases, 16(2):101-111</ref> Ideally, IF or ELISA diagnosis should be confirmed by virus isolation (VI). Decomposed carcasses however will seldom produce results. '''Virus Neutralisation''' can be used as an alternative or accompaniment to virus isolation. '''Nested PCR''' and RT-PCR are available of which the former is the more sensitive.
Identification of SVCV is also possible by molecular biology methods such as ribonuclease protection assays, which are more reliable but more advanced and less widely available.
Fish for necropsy should be transported '''under refrigeration or on ice''' but never frozen. All organs and the encephalon should be immediately sent from fish 4-6cm in size or kidney, spleen and encephalon from fish over 6cm. Virus isolation should be performed in under 24 hours.
Necropsy of infected fish reveals '''splenomegaly with reticuloendothelial hyperplasia and enlarged melanomacrophage''' centres. The '''liver is hyperaemic with multifocal necrosis''' and degeneration. '''Kidney tubules are often clogged with casts''' and cells are vacuolated and degenerate due to multiplication of viral cells within them. Pericarditis is also seen. Haemorrhage and organ swelling with '''oedema''' is a cardinal feature and may be present throughout. There may be '''white-grey patches of tissue and organ necrosis'''. Blood vessels throughout show oedematous perivasculitis.
The swim bladder lamina changes into a '''discontinuous monolayer with dilated vasculature''' and lymphocyte infiltration. Electron microscopy reveals '''virus particles in the nuclei''' of the cells.
==Treatment==
There is no treatment once infected.
==Control==
The virus is inactivated by lipid solvents, heating >60⁰ for 15minutes, glycerol, ozone, gamma radiation, UV light, extremes of pH, formalin and both acid and alkaline solvents. Virus infectivity is retained in tap water and mud for 6 weeks.
{{Learning
|flashcards = [[Spring Viraemia of Carp Flashcards]]
}}
==References==
<references/>
Animal Health & Production Compendium, '''Spring Viraemia of Carp Virus datasheet''', accessed 06/07/2011 @ http://www.cabi.org/ahpc/
Animal Health & Production Compendium, '''Spring Viraemia of Carp datasheet''', accessed 06/07/2011 @ http://www.cabi.org/ahpc/
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