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Fish diseases – treatment and prevention
Fish diseases are categorized as infectious and non-infectious diseases. The infectious diseases have the greatest impact. All farmed salmon in Norway are now vaccinated. Bacterial infections in salmons are no longer a problem. The consumption of antibiotics is extremely low.
In the early days of Norwegian aquaculture, the incidence of bacterial infections such as classic fibrosis, coldwater fibrosis and furunculosis in salmon caused the biggest problems. These infections were treated with antibiotics, high doses in some cases. Highly effective vaccines have now been developed to combat these bacterial infections in fish. These were first used in 1994. All farmed salmon in Norway are now vaccinated. Bacterial infections in salmon are no longer a problem. The consumption of antibiotics is extremely low.
Important to develop effective vaccines against viral infections in fish
Infectious diseases among salmon today are viral infections or infections with ricetcii. Infectious pancreal necrosis virus (IPNV) and infectious salmon anaemia (ISA) are particularly important, but so too are pancreal disease (PD) and cardio-skeletal myopathy (CSM). In addition, there is pisciricetsii and proliferative gill disease, where ricetsii alone or in combination with a virus represent the agents in question. There is no antiviral treatment or medicines designed to combat viral infections in fish. It is therefore important to develop effective vaccines against viral infections in fish.
The incidence and impact of salmon lice is considerably reduced
The salmon parasite Gyrodactylus salaris may pose a great threat to wild salmon in freshwater. Of the parasites, salmon lice, Lepeotheirus salaris, is the biggest problem. By means of national plans to monitor and combat fish disease, including synchronised regional pharmaceutical delousing regimes, the incidence and impact of salmon lice has been considerably reduced in recent years. Salmon lice can pose a threat to stocks of wild salmon. Control of salmon lice among farmed salmon also results in reduced infection among wild salmon in fjords and along the coast.
Non-infectious diseases
Among non-infectious diseases, developmental anomalies, deformities, cataracts and vaccine damage have so far been the most important. As far as these non-infectious diseases are concerned, research has uncovered new and important data concerning their causes and development. By understanding the actual processes of these diseases, one has been able to reduce their incidence by means of targeted measures in respect of operating conditions, operating parameters and feed composition.
The range of diseases found among farmed marine coldwater species is very similar to that found among salmon, albeit with differences and variations specific to each species. Among viral infections, one has registered problems related to nodavirus. The most prevalent diseases found in particular in cod but also in halibut and turbot are bacterial infections. Pathogenic bacteria found in marine fish are variants of those found in salmon. Vibrosis in cod is a problem. The development of vaccines for marine fish is not yet at the same stage as it is for salmon with similar diseases.
From: http://www.fisheries.no/aquaculture/health_welfare/fish_health_disease_treatment/