Retrospective Analysis of Antigen Prevalences ofRenibacterium salmoninarum(Rs) Detected by Enzyme-Linked Immunosorbent Assay in Alaskan Pacific Salmon and Trout from 1988 to 2000 and Management of Rs in Hatchery Chinook and Coho Salmon

Abstract

Five species of anadromous Pacific salmon Oncorhynchus spp. and eight species of nonanadromous fish, including trouts Oncorhynchus and Salvelinus spp., Arctic char S. alpinus, and Arctic grayling Thymallus arcticus (collectively called ''trout''), from Alaskan waters were examined by enzyme-linked immunosorbent assay for annual and total prevalences of Renibacterium salmoninarum (Rs) from 1988 to 2000. The total prevalence of Rs antigen was lower among the Pacific salmon and highest among the nonanadromous salmonid species grouped as ''trout'' that were residents in many of the watersheds. These trout species were likely reservoirs of Rs infection for many of the wild and hatchery stocks of Pacific salmon. Chinook salmon O. tshawytscha and coho salmon O. kisutch comprised 80% of the salmon database, and 45% of these two species were hatchery broodstocks at four facilities where eggs were routinely culled from Rspositive parent fish. The cyclical occurrences of Rs antigen in the coho and Chinook salmon data sets were remarkably similar and, when combined, were opposite from several of the major peaks and declines observed in the next largest data set, that for sockeye salmon O. nerka. Routine culling of eggs from Rs-positive parent fish supplemented with occasional prophylactic erythromycin therapy appeared to provide some success in Rs management for the three Chinook and two coho salmon hatchery stocks examined. The overall Rs prevalences in spawned adult fish were lower than (or at least not amplified above) those for the remaining coho and Chinook salmon stocks in the database, and no significant epizootics of bacterial kidney disease occurred in progeny fish during juvenile rearing.

Interpreting dual ELISA and qPCR data for bacterial kidney disease of salmonids

“…Bacterial kidney disease (BKD) of salmonids is a persistent, often debilitating condition frequently observed among stocks of Chinook salmon, coho salmon, and sockeye salmon of the US Pacific Northwest and Alaska (Meyers et al 2003, Arkoosh et al 2004, Rhodes et al 2006. The enzyme-linked immunosorbent assay (ELISA) has been the diagnostic method of choice in regional hatcheries and captive broodstock programs for nearly 2 decades because of several desirable features.…”

Validation of diagnostic assays to screen broodstock for Flavobacterium psychrophilum infections

“…As previously noted, BCWD outbreaks have occurred at each facility sampled in this study. In general, outbreaks vary in intensity from year to year and facility to facility for F. psychrophilum and for R. salmoninarum (Meyers et al. 2003; Taylor 2004; Madsen et al.…”

“…(2009) have provided a means to evaluate the prevalence of F. psychrophilum in populations of fish and to determine whether there is a relationship between infection levels in broodstock and BCWD outbreaks in progeny. If a relationship exists, it may be possible to set culling thresholds to control vertical transmission as has been carried out to decrease the incidence of bacterial kidney disease (BKD) (Meyers et al. 2003; Munson, Elliott & Johnson 2010).…”

Experimental challenges with Renibacterium salmoninarum in Arctic charr Salvelinus alpinus

“…It is also evident that persistence of antigens in kidney tissue makes it impossible to decide, by ELISA results alone, when the fish in question got infected. Persistent antigens could be one of the explanations for the high percentage of positive ELISA readings in kidney samples from groups of wild salmonids in a number of lakes in Iceland (Jónsdóttir et al 1998) and elsewhere (Meyers et al 1993(Meyers et al , 2003. In a recent paper, reporting on a population of wild brown trout, it was shown that 92.9% of fish with positive ELISA in kidney samples tested positive by PCR in at least 1 organ (kidney, spleen, gills mid-gut and oesophagus), although culture was negative (Guðmunds -dóttir et al 2017).…”

“…It is widespread in wild and cultured stocks of salmonids, in fresh and saline water, and is endemic in many parts of the world (Souter et al 1987, Jónsdóttir et al 1998, Meyers et al 2003, Savas et al 2006, Chambers et al 2008. The bacterium can be transmitted horizontally and vertically via the eggs (Evelyn et al 1986) and survive within mononuclear phagocytes (Gutenberger et al 1997).…”