SPECTRUM OF LIVER-DISEASE AND DUCK HEPATITIS-B VIRUS-INFECTION IN A LARGE SERIES OF CHINESE DUCKS WITH HEPATOCELLULAR-CARCINOMA

The striking difference in the geographical distribution of liver canc er in ducks raised the question of whether duck hepatitis B virus (DHB V), like mammalian hepadnaviruses, could be an oncogenic agent, Hepato cellular carcinomas (HCCs) have been found only in domestic ducks in Q idong, China, where hepatitis B virus infection and aflatoxin B-1 (AFB (1)) are both risk factors and where a high frequency of human HCCs ha s been reported, To date, the study of liver pathology occurring in Ch inese ducks has been hampered by the small number of samples available . We describe here a series of 59 Chinese brown duck livers that were collected in Qidong more than 20 years ago and formalin fixed, Thirty- six HCCs, which ranged from well-differentiated trabecular to highly a naplastic type, were identified in relatively young ducks (average age , 3.3 years), Several unique features not previously reported, such as tumor giant cells, tumor necrosis, tumor thrombi in blood vessels, an d inactive cirrhosis, were observed. Bile ductule proliferation, known to be a prominent feature of AFB(1) exposure in ducks, was present in 86% of livers. Using polymerase chain reaction (PCR) and two primer p airs, located within conserved portions of the DHBV S and C genes, we demonstrated the presence of DHBV DNA in 23 of 34 HCCs analyzed (68%). The spectrum of liver pathology that we report in brown ducks from Qi dong was never observed in Pekin ducks of the same age chronically inf ected with DHBV and followed under controlled conditions outside China , suggesting that causative factors other than virus infection may be involved in duck liver carcinogenesis observed in this area. However, because DHBV DNA was present in most HCCs, and given the lower sensiti vity of PCR in formalin-fixed tissue, we cannot rule out the importanc e of DHBV infection in the liver disease of ducks from this study. The specific role of Chinese DHBV isolates and brown duck breed in Liver pathology and oncogenesis observed in Qidong ducks should be further i nvestigated in controlled experimental transmission studies with long term follow-up in the absence of external carcinogens.