Fish diseases caused by bacterial, viral and parasitic pathogens represent some of the major obstacles for expansion of freshwater aquaculture. Therefore research and development should focus on sustainable control strategies of these infectious diseases. Classical methods for control are medication (antibiotics, anthelmintics), zoo-sanitary measures and vaccination. In addition, breeding for disease resistance has recently been focus for considerable research efforts and may prove important in the future. However, it may be worth expanding the list of strategies to provide aquaculture with flexible tools for control.

Biosecurity strategies. Basic information obtained from disease surveillance and monitoring is necessary for an effective health control to be fulfilled. Regulation of movements of live fish and eggs in addition to firm management of production sites and hygienic measures may then create basis for healthy stocks. Establishment of pathogen free aquaculture systems is a realistic way to secure disease free production animals. This, however, must be based on species of which the total life cycle can be controlled and where disinfected eggs and fry are stocked in decontaminated facilities (e.g. trout and salmon hatcheries). In systems based on introduction of wild caught fry (e.g. eel farming) additional methods may be applied. In this context it is recommended to strengthen research on use of mechanical and biological (including probiotic) methods for elimination or inhibition of infective parasitic and bacterial organisms.

Immuno-stimulation. Basic and applied research on the teleost immune system has shown that fish are able to respond with adaptive and innate mechanisms against various pathogens. Thus, vaccination against specific pathogens is widely applied. Further, recent work has shown that stimulation with products from natural sources may stimulate and upregulate innate immune mechanisms and result in improved survival of fish when exposed to parasitic, bacterial and viral pathogens. In this context it is recommended to focus research on the immune mechanisms involved in this protection.

Kurt Buchmann (D. V. Sc., Ph.D., M. Sc.) is research professor (Veterinary Fish Parasitology) employed at the Royal Veterinary and Agricultural University in Denmark. He is leader of the research network and research school SCOFDA (Sustainable Control of Fish Diseases in Aquaculture) involving Danish research institutions working in the field of Fish Diseases. SCOFDA is suppoted by the Danish Agricultural and Veterinary Research Council and the Ministry of Food, Agriculture and Fisheries. Kurt Buchmann’s main research fields are fish immunology, vaccinology and fish parasitology but is currently in charge of or associated with projects concerning fish bacteriology and virology.

Contact Details: Section of Fish Diseases, Department of Veterinary Microbiology, Royal Veterinary and Agricultural University, Stigbøjlen 4, DK-1870 Frederiksberg C. Denmark. E-mail: kub@kvl.dk