Duck hepatitis B virus DNA in liver and serum of Chinese ducks: integration of viral DNA in a hepatocellular carcinoma.

The presence of duck hepatitis B virus (DHBV) DNA in liver and serum and its state (integrated vs. free) were studied in 23 ducks from Chi-tung county in China by spot hybridization and Southern blot hybridization, respectively. In 16 of 23 (70%), DHBV DNA was detected in serum and/or in liver tissue. These infected ducks showed a variety of pathological changes including advanced chronic disease in the liver. In contrast, none of the virus-negative ducks had advanced hepatic changes. One DHBV DNA-seropositive duck had a large hepatocellular carcinoma. Southern blot analysis demonstrated integrated DHBV DNA in neoplastic tissue and abundant episomal DHBV DNA in non-neoplastic tissue of the liver. In one noninfected duck with a small adenoma, no viral DNA was detected in tumor or non-neoplastic tissue. The detection of integrated DHBV DNA in hepatocellular carcinoma suggests that DHBV behaves like human and woodchuck hepatitis viruses in relation to chronic liver disease and hepatocarcinogenesis.