<i>In ovo</i> Antiviral Screening of Four Nigerian Medicinal Plants ( <i>Artemisia absinthium</i> L., <i>Annona senegalensis</i> Pers., <i>Erythrina senegalensis</i> DC., and <i>Jatropha curcas</i> L.) Against Newcastle Disease Virus

Background and aims: Newcastle disease virus (NDV) poses a major threat to global poultry production, driving interest in novel plant-based antiviral agents. This study evaluated the in ovo antiviral potential of methanol extracts from Artemisia absinthium (AA), Annona senegalensis (AS), Erythrina senegalensis (ES), and Jatropha curcas (JC) against NDV. Methods: The extracts were screened for phytochemical content, elemental composition, and cytotoxicity in embryonated chicken eggs. Antiviral activity was assessed through embryo survival, hemagglutination assay, and statistical analysis. NDV infectivity was validated using the Reed-Muench method to determine the 50% egg infectious dose (EID₅₀). Results: All extracts contained flavonoids, saponins, alkaloids, and glycosides. Elemental analysis revealed high levels of calcium, iron, potassium, and zinc. Cytotoxicity studies showed that all extracts were safe at concentrations up to 300 mg/mL. JC demonstrated the strongest antiviral effect, with 0% virus-induced mortality at 200–300 mg/mL (10⁻⁷–10⁻⁸ dilutions), followed by ES. AS represented limited activity, while AA was the least effective. Statistical analysis confirmed significant antiviral actions for JC (P&lt;0.001) and ES (P&lt;0.01), while AS was borderline (P=0.072), and AA was not significant. Finally, a significant overall treatment effect on cytotoxicity was observed as well (P&lt;0.001). Conclusion: JC and ES exhibited promising antiviral activity against NDV in ovo, with JC being the most potent. However, its effectiveness was dose-dependent, and embryotoxicity occurred at higher levels. These findings support further investigation into their use as plant-based antiviral agents for poultry disease management.