MOLECULAR BIOLOGICAL TOOLS TO DETECT FISH PATHOGENS

Multiple approaches to control viral infections in fish are being empl oyed on an experimental basis in many fish disease laboratories. They include techniques to monitor fish populations for viruses by tissue c ulture infectivity, tagged antibody reagents to detect viral proteins, and nucleic acid probes for in situ hybridization or polymerase chain reaction amplification. The specificity and resolution of these detec tion methods are being constantly improved to increase their ease-of-u se and sensitivity. In addition, scientists are developing prophylacti c treatments in the form of traditional vaccines and subunit, peptide and genetic vaccines using molecular biological techniques. The succes s of all these approaches is obviously dependent on an understanding n ot only of the molecular structure of the virus and its genome but on the pathogenic mechanisms that lead to disease in the host animal as w ell. It is at this level, where there is so little known, that the for mulation of appropriate control strategies has been difficult. For exa mple, molecular techniques have provided evidence that the survivors o f infection with infectious haematopoietic necrosis virus are long-ter m carriers of the virus. This finding raises questions regarding the p olicy of releasing anadromous fish that have survived the disease. Vir al vaccines have been shown to work in preventing virus-induced mortal ities in rainbow trout fry in laboratory trials, but no determination has been made on whether Vaccination also prevents the formation of a virus-carrier state in the survivors. More importantly, is there a vac cine formulation that will prevent carrier formation? (C) 1995 The Fis heries Society of the British Isles