Unlocking the potential: Cinnamomum cassia (L.) D. Don aqueous extracts as natural defenders against MSRV in largemouth bass aquaculture

Abstract

Aquatic viral diseases pose significant threats to aquaculture, necessitating the exploration of effective preventive measures. In this study, we evaluated the antiviral potential of Cinnamomum cassia (L.) D. Don (CCD) aqueous extracts against Micropterus salmoides rhabdovirus (MSRV) in largemouth bass aquaculture. Initially, twelve plant extracts were screened for antiviral activity against MSRV, revealing that CCD extracts at 100 mg/L concentration significantly inhibited MSRV proliferation in vitro. Further dose-response analysis revealed a concentration-dependent antiviral effect of CCD extracts, with higher concentrations demonstrating increased efficacy against MSRV. Subsequent investigations focused on the protective effects of CCD extracts on MSRV-infected cells. At a concentration of 63 mg/L, CCD extracts significantly reduced MSRV titers, preventing the onset of cytopathic effects (CPE) in cells. Fluorescence and transmission electron microscopy further illustrated the protective effects of CCD extracts on cellular morphology. MSRV-infected cells treated with CCD exhibited preserved cell morphology akin to normal cells, contrasting with the typical apoptotic features observed in untreated infected cells. Additionally, dietary supplementation of CCD extracts in largemouth bass demonstrated notable benefits. Fish fed with CCD extracts exhibited increased survival rates when infected with MSRV, with a 26 % higher survival rate compared to the virus-only group. Furthermore, CCD supplementation enhanced the expression of interferon-gamma (IFNγ), indicating improved immune responses in largemouth bass. Moreover, immersion of CCD extracts in water showed partial inhibition of horizontal MSRV transmission, effectively reducing viral spread and mitigating disease risks in fish populations. These findings highlight the potential of CCD aqueous extracts as feed additives for combating MSRV in aquaculture, showcasing their promising application prospects in disease prevention and control strategies.