Duck hepatitis B virus infection and duck hepatocellular carcinoma.

To study the relationship between duck hepatitis B virus (DHBV) infection and duck hepatocellular carcinoma (DHCC), histological examination and DHBV DNA hybridization were performed in 875 ducks from three flocks in Qidong County. Among them, 34 suffered from hepatoma, including 23 hepatocellular carcinoma, 8 cholangiocarcinoma and 3 hepatocellular-cholangiocarcinoma. Of the 34 ducks with hepatoma 27 were positive for DHBV DNA in the liver and/or serum. DHBV DNA was demonstrated in neoplastic nodules of 22 ducks. Southern blot analysis showed that 13 cases were of the integrated pattern of DHBV DNA in neoplastic nodules. The paratumor tissues of 14 ducks with massive tumor were analysed at the same time. Five cases showed integrated pattern, 4 cases free pattern and the other 4 cases both integration and free pattern of DHBV DNA. The hybridization pattern of DHBV DNA in tumor nodule was different from that in paratumor regions in 11 cases and identical in 3 cases. DHBV antigen was positive in 13 tumor nodules and 21 paratumor tissues in the 34 ducks with hepatic tumor by both victoria blue and orcein stain methods. Advanced liver diseases were found in 30 out of the 34 ducks with hepatoma, including 12 cirrhosis and 18 chronic active hepatitis. In southern blot analysis of 122 DHBV DNA positive Qidong ducks without hepatoma, only free pattern of DHBV was seen, while 44 control ducks from Changchun were negative for DHBV DNA. Neither hepatic tumor nor liver diseases were seen in the control ducks. The results suggest that hepatocellular carcinoma in ducks is similar to that in human HCC. They have a high frequency of viral DNA integrated into the host genome and a liver disease background.

Liver orcein stain and viral DNA in duck hepatitis B virus infection in Chinese ducks and experimentally infected Japanese ducklings.

Liver sections were stained with orcein, and duck hepatitis B virus was identified in sera and livers by the hybridization technique in 106 ducks (44 Chinese ducks, 15 Japanese ducks and 47 Japanese ducklings). Orcein-positive hepatocytes were found in 18 of 38 (47%) duck hepatitis B virus DNA seropositive ducks, and only in 3 of 68 (4%) seronegative ducks. The three ducks were all from a heavily infected flock in southern China. Serial analyses of viral DNA by Southern blot and spot hybridizations in experimentally infected Japanese ducklings revealed a dissociation or a time gap between the amount of viral DNA in serum and the emergence of orcein positive hepatocytes. Orcein-positive hepatocytes were generally associated with prolonged presence of viral infection for at least 4 to 6 months. These findings support the clinical hypothesis that the presence of orcein-positive hepatocytes indicates persistent rather than acute infection. Since orcein-positive hepatocytes have been seen in infection with hepatitis B, woodchuck hepatitis, ground squirrel and duck hepatitis B viruses, accumulation of orcein-positive material in liver cells may be one of the common properties these viruses share. This stain may be utilized for screening new hepatitis B virus-like viruses.