title: Intramuscular challenge of rainbow trout (Oncorhynchus mykiss) with two Norwegian field strains of Flavobacterium psychrophilum.
abstract: In recent years there has been an increasing occurrence of Flavobacterium psychrophilum infections in farmed salmonids in Norway. The current study describes two field isolates of F. psychrophilum collected from farmed rainbow trout (Oncorhynchus mykiss) fingerlings and post smolts in Norway. Virulence of the two isolates was tested in vivo by intramuscular (IM) and/or intraperitoneal (IP) challenge of disease free, un-vaccinated rainbow trout. The isolates were concluded to be highly virulent compared to a reference isolate as they yielded high mortality after IM challenge even at low challenge doses. The more virulent of the two isolates was further used to establish a challenge model to evaluate the efficacy of vaccines against infections with F. psychrophilum. Three groups were included in the vaccination-challenge study; a vaccinated group given a 6 antigen (Ag) component vaccine containing F. psychrophilum antigens (6 Ag/F.psy(+)), a control vaccinated group administered a similar 5 antigen component vaccine without F. psychrophilum antigens (5 Ag/F.psy(-)), and a non-injected negative control group. Results from the IM challenge demonstrated that 1) our challenge model is able to discriminate between protected and unprotected experimental groups and 2) that the vaccine induced protection is specific against F. psychrophilum as mortality in the 5 Ag/F.psy(-) group was equally high as in the negative control, while the 6 Ag/F.psy(+) induced a high level of protection (RPS60 = 86.7%). The present study is one of the first to describe protection against F. psychrophilum infections induced by a multicomponent injection vaccine.
authors.affiliation: PHARMAQ AS, Harbitzalléen 2A, 0275 Oslo, P.O. Box 267 Skøyen, N-0213 Oslo, Norway. borge.nilsen-fredriksen@pharmaq.no
authors.forename: Børge N
authors.initials: BN
authors.lastname: Fredriksen
authors.forename: Anette
authors.initials: A
authors.lastname: Furevik
authors.forename: David
authors.initials: D
authors.lastname: Gauthier
authors.forename: Marie
authors.initials: M
authors.lastname: Egenberg
authors.forename: Erik D
authors.initials: ED
authors.lastname: Paulsen
authors.forename: Bjørn
authors.initials: B
authors.lastname: Brudeseth
mesh_terms: D000818:Animals; D001428:Bacterial Vaccines / Q000008:administration & dosage / Q000276:immunology*; D004797:Enzyme-Linked Immunosorbent Assay / Q000662:veterinary; D005393:Fish Diseases / Q000276:immunology* / Q000382:microbiology; D045826:Flavobacteriaceae Infections / Q000276:immunology / Q000382:microbiology / Q000662:veterinary*; D005417:Flavobacterium / Q000276:immunology* / Q000302:isolation & purification / Q000472:pathogenicity*; D007273:Injections, Intramuscular / Q000662:veterinary; D007274:Injections, Intraperitoneal / Q000662:veterinary; D009664:Norway; D017686:Oncorhynchus mykiss; D016133:Polymerase Chain Reaction / Q000662:veterinary
chemical_list: D001428:Bacterial Vaccines
keywords: Flavobacterium psychrophilum; Intramuscular challenge; Norwegian field isolates; Rainbow trout; Vaccination