Immunity in pekin ducks experimentally and naturally infected with duck hepatitis b virus

The immune response to duck hepatitis B virus (DHBV) had not been elucidated. An assay was therefore established to detect the presence of antibody to DHB surface antigen (anti‐DHBs) in serum of experimentally inoculated and naturally infected ducks. Anti‐DHBs in serum was detected by indirect RIA from the percentage inhibition of binding of rabbit anti‐DHBs to purified DHBsAg. Specificity was confirmed by positive and negative controls, infected and noninfected sera, and a mouse monoclonal antibody to DHB core antigen (anti‐DHBc). Serum and liver samples were tested for DHBV DNA by dot‐blot hybridization assay. Adult ducks repeatedly inoculated with DHBV remained non‐viraemic but developed anti‐ DHBs. This antibody activity neutralized the infectivity of DHBV, which was experimentally inoculated into 1‐day‐old ducklings. In naturally infected flocks anti‐DHBs was detected in a proportion of noninfected adult ducks as well as 1‐ day‐old hatchlings. Anti‐DHBs activity in hatchlings neutralized the infectivity of experimentally inoculated DHBV. Pekin ducks can therefore mount a neutralizing antibody response to DHBV, and immunity may be transferred in ovo from dam to offspring.