Protection of rainbow trout (Onchorynchus mykiss L.) against Flavobacterium psychrophilum by immersion and injection vaccination using a novel polyvalent vaccine

Abstract

Rainbow Trout Fry Syndrome (RTFS) is a disease caused by the Gram-negative bacterium Flavobacterium psychrophilum, responsible for economic losses in the trout industry worldwide. The diversity of F. psychrophilum strains, inherent difficulties in vaccinating juvenile fish and lack of a reproducible immersion challenge model has hampered the development of a vaccine for this disease. Disease episodes tend to occur between 10-14 oC, with necrotic lesions seen on the skin surrounding the dorsal fin and tail; in small fry often no clinical signs are apparent and death occurs due to septicaemia. At present no commercial vaccines are available, leaving antibiotics as the only course of action to contain disease outbreaks. The development of a vaccine is required, due to the potential risk of resistance developing in the antibiotics presently licensed for use in aquaculture.