In vitro antiviral efficacy of two marine algae <i>Sargassum oligocystum</i> and <i>Ulva fasciata</i> against Newcastle Disease Virus

Newcastle Disease Virus (NDV) is a major poultry pathogen, requiring new antiviral agents. This study evaluated the in vitro antiviral activity of Sargassum oligocystum and Ulva fasciata. A total of 60 embryonated chicken eggs were used in an ovo assay. Haemagglutination assays measured NDV antigen titres. Viral titres were assessed using a 96-well plate assay. Data were analysed using 95% exact Clopper–Pearson confidence intervals, Fisher’s Exact Test and bootstrap analysis (10,000 iterations) with significance set at p < 0.05. S. oligocystum (0.32 g ml−1) showed significantly higher antiviral activity, with 100% embryo survival and reduced viral titres (10−4–10−8; p < 0.05). U. fasciata (0.253 g ml−1) showed moderate activity, with 91.9% embryo survival at 10−6 dilution, also significant (p < 0.05) but lower than S. oligocystum. S. oligocystum demonstrates superior antiviral activity against NDV and is a promising natural antiviral source. Further studies are needed to isolate active compounds and confirm efficacy in vivo.