Abstract
Efforts to advance fish health diagnostics have been highlighted in many studies to improve the detection of pathogens in aquaculture facilities and wild fish populations. Typically, the detection of a pathogen has required sacrificing fish; however, many hatcheries have valuable and sometimes irreplaceable broodstocks, and lethal sampling is undesirable. Therefore, the development of non-lethal detection methods is a high priority. The goal of our study was to compare non-lethal sampling methods with standardized lethal kidney tissue sampling that is used to detect Renibacterium salmoninarum infections in salmonids. We collected anal, buccal, and mucus swabs (non-lethal qPCR) and kidney tissue samples (lethal DFAT) from 72 adult brook trout (Salvelinus fontinalis) reared at the Colorado Parks and Wildlife Pitkin Brood Unit and tested each sample to assess R. salmoninarum infections. Standard kidney tissue detected R. salmoninarum 1.59 times more often than mucus swabs, compared to 10.43 and 13.16 times more often than buccal or anal swabs, respectively, indicating mucus swabs were the most effective and may be a useful non-lethal method. Our study highlights the potential of non-lethal mucus swabs to sample for R. salmoninarum and suggests future studies are needed to refine this technique for use in aquaculture facilities and wild populations of inland salmonids.
Highlights
Disease outbreaks disrupt fish production efforts by reducing the number of fish cultured, the number available for stocking into the wild or delivered for consumption, and the ability to move fish among hatcheries or from the hatchery to wild populations
We evaluated brook trout (Salvelinus fontinalis) collected from the Colorado Parks and Wildlife (CPW) Pitkin Brood Unit (Pitkin, Colorado, USA) to address two primary objectives: (1) determine if non-lethal and standard lethal sampling methods give similar predictions of R. salmoninarum presence, and (2) determine which non-lethal sampling method has the highest rate of predicting infection status when the infection status is known using standard lethal diagnostic techniques
Among the 72 brook trout collected from the CPW Pitkin Brood Unit, 21 were positive with single-round PCR (PCR), 47 were positive with direct fluorescent antibody test (DFAT), and 50 were positive using quantitative PCR
Summary
Disease outbreaks disrupt fish production efforts by reducing the number of fish cultured, the number available for stocking into the wild or delivered for consumption, and the ability to move fish among hatcheries or from the hatchery to wild populations. To reduce disease outbreaks at aquaculture facilities, it is crucial to monitor fish health and to detect the presence of regulated, virulent pathogens. Many of the current American Fisheries Society Fish Health Blue Book (AFS-FHS; [1]) protocols to detect pathogens
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