Salmon infectious anemia
The infectious salmon anemia virus (engl. Infectious Salmon Anemia , ISA) is a highly contagious viral disease in certain species of salmon . It shows up in a decrease in red blood cells and punctiform bleeding. The disease is a notifiable animal disease in Germany . Affected stocks are killed to prevent further spread.
Pathogen
| Salmon infectious virus | ||||||||||||||||||||
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| Salmon isavirus | ||||||||||||||||||||
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The causative agent is the virus of infectious salmon anemia ( scientifically Salmon isavirus , Infectious Salmon Anemia Virus , ISAV ). The ISAV has been classified as the only species to date in the new monotypic genus Isavirus of the Orthomyxoviridae family . The ISAV has a certain ancestral closeness to the human parainfluenza virus type 2 and a morphology similar to that of influenza viruses .
The genome consists of eight segments of single-stranded RNA with negative polarity ; the entire genome is about 13.5 kb in size. The segments are arranged in individual helical capsids within the virus envelope . The segmentation suggests the possibility of a genetic exchange ( reassortment ) between different variants of the virus and possibly also explains its high variability.
The viral glycoproteins of the virus envelope have hemagglutinin activity (HA) and acetyl esterase activity. However, there is no antigenic similarity to the hemagglutinin of influenza viruses. The host mainly produces antibodies against ISAV-HA and nucleoprotein (NP); only antibodies against HA have a neutralizing effect and serve to eliminate viruses. Currently, all ISAV isolates can be assigned to two serological subtypes on the basis of ISAV-HA.
The ISAV can agglutinate erythrocytes in vitro from a wide variety of fish species, but not avian and mammalian erythrocytes. In cell culture , the virus has an optimum temperature between 15 and 20 ° C; above 20 ° C, reproduction is reduced by 99%, and above 25 ° C it is completely inhibited. Actinomycin D and α-Amanitin can prevent the virus from multiplying in cell culture .
Transmission and occurrence
The transmission occurs through direct contact with virus carriers or through water contaminated with their excretions. Also fish lice ( Caligulus elongatus and Lepeophterius salmonis ) can transmit the disease.
The disease first appeared in Norwegian fish farms in Atlantic salmon ( Salmo salar ) in 1984 and has since been observed in other aquacultures of this fish species in Northern Europe and North America . An outbreak has also been described in the silver salmon ( Oncorhynchus kisutch ) in Chile . The disease has never occurred in Germany.
Other trout fish can be infected experimentally, but they do not develop disease.
Clinical picture
Contagious anemia in salmon is associated with pale gills , swelling of the liver , swelling of the spleen , ascites , petechial bleeding of the stomach appendages, abdominal fat and swim bladder, and severe anemia .
Combat
The fight is done by trying to prevent the disease from spreading. According to current EU law, affected fish stocks must be killed.
literature
- S. Mjaaland, E. Rimstad et al .: Genomic characterization of the virus causing infectious salmon anemia in Atlantic salmon (Salmo salar L.): an orthomyxo-like virus in a teleost. In: Journal of Virology. 71, 1997, pp. 7681-7686.
- CM Fauquet, MA Mayo et al: Eighth Report of the International Committee on Taxonomy of Viruses. London, San Diego, 2004, pp. 691f.
Individual evidence
- ↑ ICTV Master Species List 2018b.v2 . MSL # 34, March 2019
- ↑ a b ICTV: ICTV Taxonomy history: Akabane orthobunyavirus , EC 51, Berlin, Germany, July 2019; Email ratification March 2020 (MSL # 35)
- ↑ Animal Disease Report 2011 by the BMELV . In: Deutsches Tierärzteblatt. (DTBL) Volume 60, May 2012, pp. 714–715.