Transmission of duck hepatitis B virus from Chinese carrier ducks to Japanese ducklings: a study of viral DNA in serum and tissue.

Human hepatitis B-like viruses have been found in several animal species, including Chinese ducks. Sera from Chinese carrier ducks which were positive for duck hepatitis B virus (DHBV) were inoculated in 33 Japanese one-day-old ducklings. The same sera were inoculated in four 3-week-old ducklings, and three 3-month-old ducks. Ten uninoculated ducklings served as controls. Hepatitis B e-antigen positive human sera and DNA polymerase-positive woodchuck sera were also inoculated into ducklings. DHBV was demonstrated in serum of all ducklings inoculated at one day of age and persisted for more than 6 months in 17 of 20 ducks. In the three ducks in which viremia disappeared, viral DNA was found in liver tissue. Southern hybridization revealed only free viral DNA in infected ducks. Only 1 of 7 ducklings inoculated at 3 weeks or later developed persistent infection. No cross-infectivity by hepatitis B virus or by woodchuck hepatitis virus was demonstrated. By inoculating DHBV-positive sera into 1-day-old ducklings of a virus-free Japanese flock, we were able to transmit DHBV in all of them and established a chronic carrier state in all ducks which were inoculated at 1 day of age.