Hemorrhagic enteritis of turkeys: electron microscopy of the causal virus

Spleens of turkey poults inoculated with hemorrhagic enteritis virus were examined by electron microscopy. Negatively stained infectious extracts of spleen tissue contained adenolike virions averaging 75-80 nm in diameter. Intranuclear virions, either scattered or in crystalline arrays, were observed in thin sections of spleen tissue four days after inoculation. The chromatin was condensed and marginated in the nuclei of most cells which contained virions. Some virions in sections appeared as hollow cores with a double-layered capsid. The outer capsid was 75-80 nm in diameter, and the inner capsid 35-40 nm. Virions were not observed in cells or extracts of spleens from uninoculated poults. The detection of intranuclear virions at the time when symptoms appeared and specific antigen titer increased suggests that the adeno-like virions are the causal agent of hemorrhagic enteritis of turkeys.