What has been done to minimize the use of antibacterial and antiparasitic drugs in Norwegian aquaculture?

Since 1987, the use of antibacterial drugs in Norwegian fish farming has been drastically reduced from about 48 tonnes to approximately 1 tonne annually, varying slightly from year to year. The 649 kg active substance prescribed in 2007 corresponds to approximately 0.03% of the produced biomass being treated once with an antibacterial drug. This is an exceptional figure, particularly when compared with antibacterial drug use in terrestrial animal production or humans. It is therefore highly unlikely that this limited use of antibacterial drugs in farmed fish poses a significant risk to human medicine via the development of antibacterial drug resistance. Among the factors contributing to this favourable situation are: (a) a unique government–industry initiative adopted in the early 1990s to facilitate vaccination against classical furunculosis; (b) development of high-quality vaccines by the pharmaceutical industry; (c) the continuing predominance of vaccination strategies for disease control among fish farmers; (d) adoption of ‘all-in-all-out’ production systems, with mandatory fallowing periods between year classes; and (e) zoning and the spatial re-arrangement of marine production sites to minimize horizontal spread of infections. In Norway, targeted and flexible governance has allowed the rapid implementation of mass vaccination as well as zoo-sanitary measures. The limited use, however, also tends to limit the availability of licensed veterinary drugs in the marketplace. This creates a dilemma that should be addressed as a strategic issue for further long-term development of sustainable industrialized aquaculture.