Abstract:
Aquaculture has emerged as a key solution to meeting the world’s demand for fish feed over the last few decades. However, the sector faces significant economic challenges due to disease outbreaks. While chemical agents are commonly employed for disease management, their potential ecological impacts raise concerns. Plant extracts, with their inherent pharmacological properties, present a promising alternative. This study investigated the in vitro and in vivo antiviral activity of four plant extracts – Vitis vinifera (grapevine), Rosmarinus officinalis (rosemary), Glycyrrhiza glabra (licorice), and Punica granatum (pomegranate) – against viral hemorrhagic septicemia virus (VHSV) in rainbow trout. These plant species were selected based on existing evidence of their immunostimulatory or antiviral properties, with the aim of identifying novel antiviral compounds for aquaculture applications. The antiviral activity of plant extracts against VHSV was initially evaluated in vitro using the EPC cell line. Cytotoxicity assays established the working concentrations used in subsequent experiments. Then, the antiviral activity of the plant extracts, before or during the course of VHSV infection, were assessed and viral loads were evaluated by means of a focus forming units assay. In vitro results demonstrated that all tested plant extracts exhibited antiviral activity, reducing viral load by over 50% in all cases. Subsequently, an in vivo study was carried out on rainbow trout to evaluate the use of feed supplemented with plant extracts, analysing the immune response by RT-PCR and toxicity by haematological and biochemical techniques. The in vivo antiviral activity was further evaluated by challenging rainbow trout with VHSV and then feeding them with a diet supplemented with plant extracts and monitoring their survival for 20 days. The resulting survival rates exhibited variability depending on the specific plant extract administered, with certain extracts demonstrating superior outcomes. These findings suggest that the use of these plant extracts offers a potential alternative for controlling viral diseases in aquaculture.