A cohabitation challenge to compare the efficacies of vaccines for bacterial kidney disease (BKD) in chinook salmon Oncorhynchus tshawytscha

Abstract

The relative efficacies of 1 commercial and 5 experimental vaccines for bacterial kidney disease (BKD) were compared through a cohabitation waterborne challenge. Groups of juvenile chinook salmon Oncorhynchus tshawytscha were vaccinated with one of the following: (1) killed Renibacterium salmoninarum ATCC 33209 (Rs 33209) cells; (2) killed Rs 33209 cells which had been heated to 37°C for 48 h, a process that destroys the p57 protein; (3) killed R. salmoninarum MT239 (Rs MT239) cells; (4) heated Rs MT239 cells; (5) a recombinant version of the p57 protein (r-p57) emulsified in Freund's incomplete adjuvant (FIA); (6) the commercial BKD vaccine Renogen; (7) phosphatebuffered saline (PBS) emulsified with an equal volume of FIA; or (8) PBS alone. Following injection, each fish was marked with a subcutaneous fluorescent latex tag denoting its treatment group and the vaccinated fish were combined into sham and disease challenge tanks. Two weeks after these fish were vaccinated, separate groups of fish were injected with either PBS or live R. salmoninarum GL64 and were placed inside coated-wire mesh cylinders (liveboxes) in the sham and disease challenge tanks, respectively. Mortalities in both tanks were recorded for 285 d. Any mortalities among the livebox fish were replaced with an appropriate cohort (infected with R. salmoninarum or healthy) fish. None of the bacterins evaluated in this study induced protective immunity against the R. salmoninarum shed from the infected livebox fish. The percentage survival within the test groups in the R. salmoninarum challenge tank ranged from 59% (heated Rs MT239 bacterin) to 81% (PBS emulsified with FIA). There were no differences in the percentage survival among the PBS-, PBS/FIA-, r-p57-and Renogen-injected groups. There also were no differences in survival among the bacterin groups, regardless of whether the bacterial cells had been heated or left untreated prior to injection.

Nearshore ecosystem predictors of a bacterial infection in juvenile Chinook salmon

“…Sympatry between infected and susceptible fish provides the opportunity for pathogen transmission, and increased host density elevates the probability of transmission. For bacterial kidney disease, infected fish shed bacteria in water (Austin & Rayment 1985, McKibben & Pascho 1999, and cohabitation of infected and naïve fish is an effective method of experimental challenge (Murray et al 1992, Alcorn et al 2005.…”

Comparison and evaluation of Renibacterium salmoninarum quantitative PCR diagnostic assays using field samples of Chinook and coho salmon

“…Transmission from hatchery to naturally reproducing populations, and vice versa, has been documented (Mitchum & Sherman 1981). As efforts at controlling R. salmoninarum via vaccination have met with limited success in Pacific salmon (Kaattari & Piganelli 1997, Piganelli et al 1999, Alcorn et al 2005, antibiotic treatment and broodstock culling of highly infected egg lots at spawning are the primary methods for mitigating the disease. Thus, efforts to control the spread of the pathogen require the availability of sensitive and reliable detection assays.…”

Both msa Genes in Renibacterium salmoninarum Are Needed for Full Virulence in Bacterial Kidney Disease

“…The infectious agent of BKD, Renibacterium salmoninarum, can be transmitted both horizontally among cohorts and vertically by intraovum inclusion (2,14). Current disease controls include broodstock segregation or culling, antibiotic treatment, and vaccination, but these methods have only moderate efficacy in preventing or treating the disease (1,30,32).R. salmoninarum is a gram-positive diplococcobacillus that grows very slowly and has fastidious nutritional requirements (8,12,39,40).…”