“RT-qPCR at ¨points-of-need¨ for rapid and reliable detection of Atlantic salmon (Salmo salar) cardiac viral infections (7103)”

RT-qPCR at ¨points-of-need¨ for rapid and reliable detection of Atlantic salmon (Salmo salar) cardiac viral infections

Myocardial infection in salmon with Piscine Myocarditis virus (PMCV), Piscine Orthoreovirus (PRV) and Salmonid alphavirus (SAV), pose challenges for the fish health and welfare and may have significant economic implications. Rapid and reliable viral detection is essential for timely and informed management decisions. Currently, detection relies on molecular methods (RT-qPCR) conducted in centralized laboratories. During the Covid-19 pandemic, compact equipment and user-friendly kits for the detection of the SARS-CoV-2 at ¨points-of-need¨ were developed. This study evaluates RT-qPCR assays based on similar technology for detecting PMCV, PRV and SAV by the local fish health services. The assays utilize robotic extraction and kits, developed by Schweitzer Biotech Company (SBC, Taiwan) and can yield results within two hours post-sampling, while minimizing contamination risks. Heart tissue samples collected by the local veterinary services were analyzed in parallel by using SBC kits at Aquamedic’s lab and standard protocols by central labs. Additionally, positive archive samples and reference test results were also included. We assessed the quality agreement (positive/negative results) between the SBC kits and the central lab. The agreement was almost excellent for SAV and PMCV and moderate for PRV according to Cohen’s kappa analysis. The samples for SAV come mainly from experimentally infected fish or from salmon farms outside the SAV-zone, thus further SAV-positive field samples will be recruited. The PMCV and PRV SBC kit detected a higher rate of positive results. Of note, the observed differences are mostly in specimens with low viral loads (Ct-values >32) originating from fish groups with no clinical signs of disease. We believe that these differences can be explained by methodological variations e.g. extraction method, equipment etc. among the labs. Additional data from tests performed directly by the local veterinary services will be incorporated into the results in the future. Nevertheless, the results so far support the local use of small-sized equipment and SBC kits for rapid detection and flexible monitoring of cardiac viruses in farmed Atlantic salmon. Adoption of such ¨point-of-need¨ diagnostics could reduce response time and drive targeted farming management in salmon aquaculture which may subsequently improve salmon health monitoring.

1. Spanos, Georgios, Aquamedic, Presenter
2. Midtlyng, Paul J., Aquamedic, Author