Detection of rabbit haemorrhagic disease virus particles in the rabbit liver tissues

Liver tissues from rabbits experimentally infected with rabbit haemorrhagic disease virus (RHDV) were studied electron microscopically. The earliest change in hepatocytes of the rabbits infected with RHDV was hydropic degeneration. Rough endoplasmic reticulum was dilated with a mild increase in polysomes and cytoplasmic cisternae in degenerated hepatocytes. Characteristic cytopathological changes of necrotic hepatocytes included shrinkage of the cell body, formation of cytoplasmic vesicles, vacuoles or cisternae and karyolysis. A large number of viral particles resembling a calicivirus in size and morphology was demonstrated in the cytoplasm of many necrotic hepatocytes. The particles had accumulated mainly in the membrane-bound cisternae or scattered around the membrane-bound vacuoles of the necrotic hepatocytes. Western blot analysis demonstrated that RHDV antigen was present in the infected hepatocytes. RHDV particles were also detected by immunoelectron microscopy. Replicating patterns of RHDV particles and subsequent cytopathology resembled those in other calicivirus infections.