Infectious salmon anemia virus

The Infectious Salmon Anemia ( Infectious Salmon Anemia, ISA) is a highly contagious viral disease of certain species of salmon. The disease is a notifiable disease in Germany.

Pathogen

The causative agent is the virus of infectious salmon anemia ( engl. Infectious Salmon Anemia virus, ISAV ). The ISAV has been classified as so far the only species in the monotypic genus new Isavirus the Orthomyxoviridae family. The ISAV has a certain phylogenetic proximity to the Human parainfluenza virus type 2, and a morphology similar to influenza viruses.

The genome consists of eight segments of single stranded RNA with negative polarity; the entire genome is approximately 13.5 kb in size. The segments are arranged within the virus envelope in each helical capsids. The segmentation suggests the possibility of a genetic exchange ( reassortment ) between different variants of the virus and may also explain its high variability.

The viral glycoproteins of the viral envelope having hemagglutinin activity (HA ), and acetylesterase activity. However, an antigenic similarity to the hemagglutinin of influenza virus does not exist. The host is mainly antibodies against ISAV HA and nucleoprotein (NP ); only antibodies against the HA are neutralizing and serve the viral clearance. Currently, all isolates of ISAV two serological subtypes can be assigned on the basis of the ISAV HA.

The ISAV can agglutinate erythrocytes in vitro a number of fish species, not birds, and mammalian erythrocytes. In cell culture, the virus has a temperature optimum of 15 to 20 ° C, proliferation is reduced by 99 % beyond 20 ° C, above 25 ° C completely inhibited. In cell culture, actinomycin D and α - amanitin can inhibit the replication of the virus.

Transfer and deposits

Transmission is by direct contact with virus carriers or with their excretions contaminated water. Also fish lice ( Caligulus elongatus and Lepeophterius salmonis ) can transmit the disease.

The disease first appeared in 1984 in Norwegian fish farms on Atlantic salmon (Salmo salar ) and has been observed since in other aquaculture of this species in northern Europe and North America. An outbreak is also described in the coho salmon (Oncorhynchus kisutch ) in Chile. In Germany, the disease has never occurred.

Although other trout fish can be infected experimentally, but do not develop disease.

Clinical picture

The Infectious Salmon Anemia is associated with pale gills, liver swelling, splenomegaly, ascites, petechial hemorrhages of the gastric attachments of the abdominal fat and the swim bladder and severe anemia.

Combat

The control is done by attempting to stop the spread of the disease. Under current EU law affected fish stocks are to kill.

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