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.