Currently, Infectious Bursal Disease (IBD) is a highly contagious disease leading to huge economic losses in poultry industry. Our objective was to investigate potential therapeutic effects of the combined extracts of Rhizoma Dryopteridis crassirhizomatis and Fructus mume (RDCFM) against IBDV infection. Seventy-two 4-week-old SPF chickens were randomly divided into six groups and inoculated intranasally with 0.2 ml of 10^2.5 EID₅₀ of IBDV strain CJ801. Twenty-four hours post infection, the birds were orally administered with 400, 200 and 100 mg/kg BW of RDCFM, respectively, 125 mg/kg Astragalus polysaccharide (ASP) and saline water, respectively for 5 days and then monitored daily for 10 days. Finally, the remaining birds were euthanized to collect the sera for detecting antibodies and immune organs for determining the immune organs index as well as virus loads. The herbal extracts improved survival rate and relative body gain rate. Virus loads in bursa of Fabricius in herbal treated groups decreased significantly while higher antibody levels were detected in the three RDCFM groups as compared to those of ASP and infection group. These results implied that chickens administered with 100-200 mg/kg of RDCFM for 5 days could improve protection against IBDV infection and RDCFM may be a promising alternative to ASP and egg yolk antibody.

Key words: Astragalus polysaccharide Crassirhizomatis, Fructus mume, Infectious bursal disease virus, Rhizoma Dryopteridis, Therapeutic efficacy