Anti Marek’s Disease Virus Activity of Scurrula oortiana (Tea Mistletoe) Stem Extract in Embryonated Chicken Eggs*

S. oortiana extract has been previously shown to have anti-tumour and antiviral activity in vitro. This study was carried out to investigate an antiviral effect of S. oortiana stem extract against Marek’s Disease Virus (MDV) in ovo. The antiviral effect was studied in embryonated chicken eggs (n = 5 per treatment) by inoculating 0, 0.1, 0.2, or 0.4 mg extract/egg before or after infection with MDV. In the “before” treatment, the extract was administered on day 9 with MDV infection on day 12. In the “after” treatment, the extract was administered on day 12 after infection with MDV on day 9. Histopathological examinations were performed on day 20 to determine the number of inclusion bodies, pock formation, macrophage infiltration and immunohistochemistry was used to determine the frequency and intensity of viral antigen expression. Inoculation of the extract before MDV infection significantly (p<0.05) reduced the frequency and intensity of viral antigen expression. There was also a significantly lower level of epithelial destruction on chorioallantoic membrane of the groups given 0.2 and 0.4 mg extract/egg than the control group given no extract. This study provides the first evidence of anti MDV viral activity of S. oortiana extract in vivo and may provide an alternative method to prevent or alleviate Marek’s disease.