Evaluation of the Antiviral Activity of a Natural Product, Schisandrin B, Against Rhabdovirus Infection in Chinese Rice Field Eels

Chinese rice-field eel rhabdovirus (CrERV), an emerging viral pathogen, causes massive death in rice-field eels (<i>Monopterus albus</i>), thus threatening the industry's development. There is currently no established treatment strategy for CrERV. This study evaluated the anti-CrERV effects of schisandrin B (Sch B) in vitro and in vivo. The results indicated that Sch B at 20 mg/L could inhibit the expression of the CrERV G protein, with a maximum inhibition rate of 69.5%. Additionally, Sch B mitigated the nuclear damage and mitochondrial membrane potential decline induced by CrERV, thereby preserving cellular morphology. A time-of-addition study suggested that Sch B might exert its antiviral effects during the mid-stage of viral replication. In vivo, Sch B exhibited promising preventive and therapeutic effects against CrERV infection in rice-field eels, enhancing their survival rate by 57% and 51%, when added at 0.075% and 0.025%, respectively. Overall, the natural product Sch B was proven to have excellent anti-CrERV activity, with broad prospects for application in aquaculture.