Infectious Salmon Anemia
The disease in question was first reported in the 1980s. To date, infectious salmon anemia has produced a mortality rate of close to 90% in some breeding farms. In this article we are going to give you more details about the responsible organism, its symptoms and its diagnosis.
History of infectious salmon anemia
In the mid-1980s, the first cases of a hitherto unknown disease were detected in Norway. The affected animals all belonged to the same species: Salmo salar , the so-called Atlantic salmon.
At first, and due to the symptoms it caused, this disease was baptized as hemorrhagic kidney syndrome. As more cases were diagnosed and the causative agent was discovered, it was renamed ISA, which stands for Infectious Salmon Anemia.
Over time, outbreaks of this disease have been reported in other countries: Canada, Scotland, the United States or the Faroe Islands. A common denominator in all these cases is that the affected subjects were specimens grown in saltwater farms, which in many cases represented a considerable economic loss.
What are the causes?
The cause of this disease is a virus. Colloquially, it is known by the name of infectious salmon anemia virus or ISAV, for its acronym in English. At the biological level, it belongs to the Orthomyxoviridae family . This group of viruses, where we can also find the viruses that cause influenza, affects only vertebrate organisms.
The mortality caused by ISAV in salmon is extremely high if it is not detected in time. At first, mortality rates may be as low as 1%, but left unchecked, some farms have reported mortality close to 90% in a matter of months.
Apart from Atlantic salmon, there are reported cases of this disease in other aquatic species, such as silver salmon ( Oncorhynchus kisutch ) or rainbow trout ( Oncorhynchus mykiss ). In the case of humans, this virus is harmless.
Symptoms and transmission of infectious salmon anemia
There are a number of symptoms that can indicate the presence of ISAV. The most common are usually:
- Darkening of the skin
- Lethargy.
- Localized hemorrhages in the eyes.
- Severe anemia, which causes the gills to appear pale in color.
- In some specimens, the spleen and liver are abnormally large.
One of the most important challenges in this disease is controlling its transmission. And it is that, when the virus is inside a tank, it spreads very quickly among all the fish. Transmission can also occur between different tanks, but more slowly.
Is there an effective treatment?
When dealing with a virus, pharmacological or veterinary measures are more limited. For this reason, the best treatments involve a series of biocontrol measures, combined with very strict hygiene and disinfection of the farms. What is sought by applying these measures is that the incidence of the virus is lower.
For this, special sanitary products must be applied to tanks, machinery and personnel in contact with salmon. If the disease is detected, the affected animals must be quickly removed. Therefore, one of the best preventive techniques is to separate both farms and tanks far enough so that the virus cannot spread.
Despite all this, some fish farms have suffered millions in losses, which is why infectious salmon anemia has raised the alarm in the salmon industry in recent years.
