The Effects of Storage Conditions on the eDNA Recovery rate of Salmon Pathogens.

Environmental DNA, eDNA, is considered today as an essential tool for the efficient detection of pathogens in aquatic environments, providing major benefits for monitoring fish health and controlling diseases in aquaculture. This experiment tests and analyzes the effects of different storage conditions on the eDNA recovery rates of two key salmon pathogens:Yersinia ruckeri, (Y.ruc) and Aeromonas salmonicida, (A.sal). These pathogens are among the common ones found in aquatic environments and are responsible for enteric redmouth disease and furunculosis, respectively. Moreover, they have significant impacts on salmon populations and aquaculture operations. The main goals of this research were to evaluate how different storage temperatures, preservation solutions, and time intervals between filtration and testing the eDNA integrity affect the recovery rates of these two pathogens. Yersinia and Aeromonas were grown and cultured in their respective media in the laboratory. After undergoing filtration, a set of the filter papers containing the different concentrations of the pathogens underwent extraction followed by a quantitative Polymerase Chain (qPCR) and the Cq values obtained are considered as the reference value. The other filter papers were subjected to different storage conditions, including temperatures of 20°C (room temperature of the laboratory) and -20°C, preservation with 80% ethanol and time intervals of 1 day, 3 days, 7 days, 10 days and 14 days for Yersinia and only 7 days, 10 days and 14 days for Aeromonas. This difference in time interval was due to a contamination problem when growing A.sal. After the time interval, eDNA was extracted using established protocols and quantified using qPCR. They are then compared to the reference value and their respective standard series values to evaluate the impact of these variables on eDNA recovery. After experimentation, results showed that the lower storage temperature greatly improved eDNA stability and recovery rates for Yersinia and Aeromonas. Preservation with ethanol also enhanced eDNA integrity, particularly for samples stored at lower temperatures. The study found that the time between sample filtration and processing is also a major factor, with significant eDNA degradation occurring in unpreserved samples stored at room temperature for more than 24 hours. These findings provide important information concerning the optimal storage conditions for eDNA samples, which can increase the efficiency and reliability of eDNA-based pathogen detection techniques. By testing and studying the best techniques and processes for sample preservation, this research supports the effective monitoring and control of fish health in both natural and aquaculture environments.