More to keep them busy.
In health surveillance, essentially PCR methodology is used to detect virus genetic material. This methodology gives a snapshot of infection status in the population. An important prerequisite for detecting viruses with this methodology is that virus RNA / DNA is present at the time the sample is taken. Infections with short duration will therefore often be challenging to capture. Short duration in this context is either that the fish gets rid of the virus by becoming immune or that the fish dies as a result of the developing disease. In other words, it is a prerequisite that infected fish survives until the sample is taken. The absence of virus-positive wild fish can therefore be caused by wild fish not infected (function of time and susceptibility to infection) that infected wild fish are not caught because the infection is short-lived or wild fish infected,
Thus, in the absence of virus-positive wild fish it becomes too easy to conclude that wild fish is not infected (of farmed fish). Furthermore, it would maintain the monitoring of the same agent based on the expectation that increased infection pressure will reflect in several virus-positive fish of little value. The Veterinary Institute therefore changed its health monitoring plan and has focused on generating new knowledge about wild fish and wildlife interaction, including investigating infectious tissue in freshwater, family surveys to detect infection, mapping the incidence of new agents, etc. The results may Read on the websites of the Norwegian Food Safety Authority, the Veterinary Institute and the Institute of Marine Research.
Complex interaction
As described, there is a major focus on virus diseases in the aquaculture industry and in research and monitoring in wild fish health. Viral diseases, however, are only one of several groups of infectious diseases, and it is important to make sure that there is a total load of infectious diseases in the aquaculture that poses a threat to the wild fish. It is also important to make sure that this influence is unlikely to occur in the form of outbreaks of mass deaths. Wild fish that are impaired by disease will disappear without drama because they are an easy exchange for different predators because they lose the fight for food or because illness interacts with other factors of influence. Probably there is a complex interaction where disease interacts with other factors and affects life history, productivity and reproductive capacity.
It is said that when someone recognizes a problem, someone can do something about it. It has taken decades to come where we are today in terms of knowledge about salmon lice and interaction wild-farming. We must acknowledge that research on the effects of other infectious diseases in fish farming today is hardly the starting point. Thus, it may take many years before we make real progress in this field of research. The major challenges lie in adapting and developing methods for studying wild fish health in general, the complex interaction and the factors that influence this.
Meanwhile, the shortage of knowledge will in itself pose a threat to wild salmonids.
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