<正>Objective:To evaluate the antiviral activity of the alcohol extract of Styela plicata on DHBV （duck hepatitis B virus） in vivo. Methods: Guangzhou-Sheldrake ducklings congenitally infected with DHBV were assigned to receive the alcohol extract of Styela plicata or lamivudine for 30 consecutive days. The DHBV DNA of sera was detected by RT-PCR. and the histological analysis of duckling liver was evaluated. Results:Thirty days after therapy

histological analysis of duckling liver showed that the ducklings receiving the alcohol extract of Styela plicata or lamivudine exhibited catabatic status in the degree of liver cell degeneration and inflammation compared with the ducklings receiving normal diet. DHBV DNA of sera from alcohol extract of Styela plicata-treated ducklings and lamivudine-treated ducklings all produced significantly lower levels compared with ducklings receiving normal diet （P<0. 01 ）. Although these treatment groups all exhibited a rebound phenomenon 10 d after withdrawal of medication

they still exhibited a significant lower level of serum DHBV DNA compared with the control group responded to normal diet （P<0. 05

P<0. 01）. Conclusion:Styela plicata may be an effective antiviral medicine in treating chronic hepatitis B. The data of this experiment will be valuable in studying the therapeutic role and the potential therapeutic mechanism of Styela plicata.