DHBV manipulation and prediction of the outcome of infection

Background/Aims: The immunological response of ducks to acute infection with duck hepatitis B virus (DHBV) has not been fully characterised. In this study the relationship between viral dose and the outcome of infection in immune competent 26-day-old ducks was examined. Methods: Indirect ELISA assays were developed to detect the presence of antibody to DHB surface antigen and DHB core antigen. A DHBV serum pool was titrated in 1-day-old and 26-day-old ducklings. Results: The ID₅₀ dose of the ducks injected at 26 days of age was found to be 1000 times that of the ducks injected on day of hatch. The antibody responses and serum DHBV DNA were followed in eight ducks inoculated with DHBV positive serum when 26 days of age and in three ducks infected with DHBV on day of hatch. The three ducks infected on day of hatch were viraemic by day 7 and remained highly viraemic throughout the experimental period. In the older ducks, inoculation with 1000ID₅₀ resulted in the development of chronic carriage, while inoculation with either 100 or 10ID₅₀ doses resulted in acute infection with or without viraemia. These ducks were able to clear the infection from their circulation, but only 50% cleared DHBV from the liver within the experimental period. All infected ducks developed anti-core activity. Only non-viraemic ducks developed anti-surface activity. Conclusions: DHBV infection can be established in immune competent adolescent ducks, with variable disease outcomes comparable to HBV infection in humans.