Safety of medical feed additives in the food chain

Fish and other organisms in aquaculture may be subjected to a wide range of diseases, some of which are mediated by viruses, fungi, and bacteria, or by internal and external parasites. For infectious diseases where a treatment is available, veterinary drugs may be administered by baths or by inclusion of the therapeutic agent in the feed. This chapter gives an outline of medical feed additives in aquaculture, with a main focus on the situation in Norway. The use of antibacterial agents included in aquaculture feeds remains largely unrestricted in several countries with high and growing aquaculture production, even though in recent years nations with export of such products increasingly need to put efforts to comply with the demands from the importer. A range of external and internal parasites pose a challenge in the aquaculture of fish and other organisms. The main ectoparasite problem in the farming of Atlantic salmon is the salmon lice. Before registration of veterinary products, evaluation of safety data on the target species must be performed. To protect public health, maximum limits, residue of a pharmacologically active substance that may be present in food without presenting harm to the consumer, must be established. To ensure that residue level after a treatment is below the established limit, withdrawal periods before slaughtering have been determined. Veterinary drugs used in the aquaculture production may enter the environment around the farming site. The use of antisea lice agents can negatively affect nontarget crustaceans.