Examples of emerging virus diseases in salmonid aquaculture

Aquaculture can offer close to ideal environments for the spread of infectious diseases. Owing to high-density monoculture of hosts, numerous possible routes of transmission and suboptimal protection by available vaccination for several viral diseases, viruses may thrive in modern salmonid aquaculture. Furthermore, infectious diseases do not respect national boundaries and they can have detrimental effects both on the production and on the export of aquaculture products. Effective vaccines are available for only a limited number of serious fish viral diseases, leaving expensive compulsory stamping-out eradication as the official approach. If fish health authorities do not have an efficient risk management procedure, outbreaks may become epizootics. The key to control viral epidemics is to block the transmission of infection. This requires knowledge about reservoirs, susceptibility of infection for the different species of fish, the pattern of shedding of virus and survival of viral infectivity outside the host. The development of highly effective vaccines offers another way of preventing and controlling future risks.