Comparative pathogenicity of two subtypes (hepatitis-type and pancreatitis-type) of duck hepatitis A virus type 1 in experimentally infected Muscovy ducklings

Duck hepatitis A virus type 1 (DHAV-1) causes acute hepatitis with high morbidity and mortality in ducklings of the genera Cairina and Anas and is characterized by ecchymotic haemorrhage and necrosis of the liver surface. Since September 2011, a new subtype of DHAV-1 (named pancreatitis-type DHAV-1) has been isolated. This new subtype is characterized by yellowish or haemorrhagic pancreatitis, but with no significant pathological changes in the liver. To further investigate the difference in pathogenicity between hepatitis-type DHAV-1 and pancreatitis-type DHAV-1, we infected Muscovy ducklings with a hepatitis-type DHAV-1 strain, FZ86, or a pancreatitis-type DHAV-1 strain, MPZJ1206, and then compared the resulting gross lesions, histopathological changes, viral distribution and cellular apoptosis in the liver and pancreas of Muscovy ducklings. The results suggested that FZ86 induced a more efficient viral propagation in the liver than MPZJ1206, and the gross and histopathological lesions were also limited to the liver. However, MPZJ1206 induced more effective viral replication in the pancreas than FZ86. The MPZJ1206-infected Muscovy ducklings showed an obviously yellowed and haemorrhagic pancreas, but with no significant pathological changes in the liver. Furthermore, FZ86 induced notable hepatocyte apoptosis and increased the expression of caspase-3 in the liver, whereas MPZJ1206 caused apoptosis in a large number of acinar epithelial cells and elevated the expression of caspase-3 in the pancreas. Taken together, these results demonstrated that pancreatitis-type DHAV-1 has many new pathogenic features which distinguish it from the hepatitis-type DHAV-1. RESEARCH HIGHLIGHTS Pancreatitis-type DHAV-1 (MPZJ1206) was characterized by pancreatic haemorrhage and yellow discolouration, but with no obvious haemorrhage and necrosis in the liver. Pancreatitis-type DHAV-1 (MPZJ1206) exhibits many new pathogenic features which distinguish it from the hepatitis-type DHAV-1 (FZ86).