Enhancing viral detection in aquaculture water through virus-microplankton associations and plankton net concentration

Abstract

Despite the growing emphasis on aquatic disease monitoring via environmental DNA (eDNA) in water samples, detecting low concentrations of viruses in aquatic environments remains challenging. Prior studies demonstrated that plankton act as mechanical vectors for several aquatic viral pathogens but not for the viral hemorrhagic septicemia virus (VHSV). In this study, we aimed to identify the potential interaction between VHSV and microplankton and further assess the effectiveness of the water concentration method using a plankton net for VHSV detection in water. Briefly, VHSV was co-cultured with Chlorella, rotifer, and microcosms generated using plankton nets with sieve sizes of 20, 40, and 70 μm. A close interaction between VHSV and rotifer and microplankton collected with the 70 μm-plankton net with an abundant zooplankton population was found, likely influenced by the filter-feeding behaviors of zooplankton. We also found that VHSV could adsorb to fish feces at concentrations 25–88 times higher than that in the equivalent volume of seawater. Subsequently, we evaluated the efficiency of a 70 μm-plankton net for VHSV concentration in rearing water containing infected fish compared to the iron flocculation method. Notably, the plankton net outperformed the iron flocculation method in terms of sensitivity (∼10 to 20-fold), possibly due to its ability to capture fish-derived organic materials, such as feces, shed from infected fish. Our overall findings advocate for the plankton net concentration approach, not only for its pronounced sensitivity but also its operational simplicity, identifying it as a promising avenue for efficient VHSV detection in aquaculture water monitoring. © 2024