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Diseases of Aquatic Organisms

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DAO 149:109-120 (2022)  -  DOI:

Prevalence and distribution of Renibacterium salmoninarum, causative agent of bacterial kidney disease, in wild trout fisheries in Colorado

Dan A. Kowalski1,*, Rick J. Cordes2, Tawni B. Riepe3, John D. Drennan4, Andrew J. Treble5

1Colorado Parks and Wildlife Aquatic Research Section, Montrose, CO 81401, USA
2U.S. Fish and Wildlife Service Bozeman Fish Health Center, Bozeman, MT 59718, USA
3Colorado Cooperative Fish and Wildlife Research Unit, Colorado State University, Fort Collins, CO 80523, USA
4Colorado Parks and Wildlife Aquatic Animal Health Lab, Brush, CO 80723, USA
5Colorado Parks and Wildlife Aquatic Research Section, Fort Collins, CO 80526, USA
*Corresponding author:

ABSTRACT: Detections of Renibacterium salmoninarum in Colorado USA fish hatcheries have become more frequent in recent years, including one disease outbreak that originated with a wild broodstock. Our objectives were to document the prevalence and distribution of R. salmoninarum in Colorado’s wild trout fisheries, investigate variables that influence that distribution, and evaluate the effectiveness of common testing methods on non-anadromous trout. We sampled wild trout across Colorado and tested kidney tissue with enzyme-linked immunosorbent assay (ELISA), quantitative polymerase chain reaction (qPCR), nested polymerase chain reaction (nPCR), and direct fluorescent antibody test (DFAT). Screening with ELISA showed high prevalence of R. salmoninarum among fish populations, but antigen levels were low. No clinical disease was observed in any of the fish sampled despite the antigen of R. salmoninarum being common. Antigen levels measured by ELISA increased in smaller streams with lower historic fish stocking rates. Brook trout Salvelinus fontinalis had the highest prevalence of the bacterium among fish species and highest ELISA antigen levels. The distribution of brook trout in the smallest streams may help explain the patterns of R. salmoninarum across the landscape. The most effective assays for screening wild trout were qPCR and ELISA; DFAT was inconsistent for bacterial levels encountered in wild trout and generally uninformative. Additionally, qPCR and ELISA can provide quantitative information about bacteria levels. The bacterium R. salmoninarum is ubiquitous in Colorado trout fisheries but is generally found at low levels. Active infections are rare and overt bacterial kidney disease appears more common in Colorado hatcheries than in wild fish.

KEY WORDS: Renibacterium salmoninarum · Bacterial kidney disease · Wild trout · Colorado

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Cite this article as: Kowalski DA, Cordes RJ, Riepe TB, Drennan JD, Treble AJ (2022) Prevalence and distribution of Renibacterium salmoninarum, causative agent of bacterial kidney disease, in wild trout fisheries in Colorado. Dis Aquat Org 149:109-120.

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