Ali Mohammadi
Najmeh Mosleh
Tahoora Shomali
Maryam Ahmadi
Sara Sabetghadam

Introduction: The study aimed to investigate the antiviral activity of Zataria multiflora (ZM) essential oil against Newcastle disease virus (NDV) on Vero cells. Methods: The cytotoxicity of ZM essential oil was evaluated by MTT assay. Cells were infected with ۱۰۰ TCID۵۰ of a field isolate of virulent NDV (JF۸۲۰۲۹۴.۱). ZM essential oil at concentrations of ۱/۵۰۰۰, ۱/۲۵ ۰۰۰, ۱/۱۲۵ ۰۰۰ or ۱/۶۲۵ ۰۰۰ was added at different times of infection: ۶۰ minutes pre infection, simultaneously and ۶۰ minutes post infection. Cells were evaluated morphologically. The TCID۵۰, neutralizing index (NI) and HA titer were determined. Results: Cells treated with ZM essential oil in all concentrations ۱ hour before or after infection, showed CPE similar to control virus cells. In simultaneous use, cells treated with ۱/۵۰۰۰ concentration of the essential oil, remained morphologically normal. TCID۵۰ values of all treatments were very close to that of control virus except for simultaneous administration at concentration of ۱/۵۰۰۰ which was about ۱۰۰۰ folds lower. Virus titer in different treatments was exactly the same as control virus titer in Haemagglutination (HA) test. Conclusion: ZM essential oil has some antiviral activity on NDV in vitro, which is possibly by destruction of virus infectivity or inhibition of early phases of viral proliferation cycle.