Electron microscopic studies on pathology of experimental hydropericardium syndrome in broiler chicks

Twenty 21-days old chicks were experimentally inoculated with 0.3 ml of 20 per cent suspension of infective liver homogenate derived from natural cases of hydropericardium syndrome (HPS). Clinical signs were non-specific and appeared 36 hours after inoculation. Ultrastructurally numerous large vacuoles, fragmented endoplasmic reticulum and swollen mitochondria were found at 36 hours post inoculation (PI) in the cytoplasm of hepatocytes and myocytes. The infected nuclei were irregularly outlined and contained large intranuclear masses. Virus particles were found attached with these masses. At higher magnification, virus particles appeared isometric and roughly spherical between 75–80 nm in diameter. At 60 hours and 72 hours PI, there was karyorrhexis and complete cellular degeneration characterised by elimination of electron dense materials from the cytoplasm and nucleus. The findings suggested that group I adenovirus were involved in HPS in broilers.