Cross‐protection of a live‐attenuated Flavobacterium psychrophilum immersion vaccine against novel Flavobacterium spp. and Chryseobacterium spp. strains

Abstract

For salmonid producers, a common threat is Flavobacterium psychrophilum . Recent advancements in bacterial coldwater disease (BCWD) management include the development of a live‐attenuated immersion vaccine that cross‐protects against an array of F. psychrophilum strains. Emerging family Flavobacteriaceae cases associated with clinical disease have been increasing, including pathogenic isolates of Flavobacterium spp. and Chryseobacterium spp. The cross‐protective ability of a live‐attenuated F. psychrophilum vaccine was determined against three virulent Flavobacteriaceae isolates. Juvenile rainbow trout were vaccinated, developed high F. psychrophilum ‐specific antibody titres and were challenged with Chryseobacterium spp. isolates (S25 and T28), a Flavobacterium sp. (S21) isolate, a mixed combination of S21:S25:T28, and a standard virulent F. psychrophilum CSF259‐93 strain. Results demonstrated strong protection in the CSF259‐93 vaccinated group (relative per cent survival (RPS)=94.44%) when compared to the relevant CSF259‐93 controls ( p p

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