Filamentous intranuclear inclusion bodies in psittacine birds. A structural and ultrastructural study

This paper concerns a disease affecting a group of African grey parrots, wh ich involves intranuclear inclusion bodies composed of filamentous material . The disease was characterized by either sudden death or death within 2-3 days from onset of non-specific symptoms. At necropsy, gross lesions includ ed enlarged liver, mild hepatic congestion and focal necrosis. Samples from five birds were fixed in 10% formol and routinely processed for light and electron microscopy;. In four birds, numerous hepatocytes displayed an enla rged nucleus, with peripheral margination of chromatin; the nucleus was par tially or wholly filled by a basophilic inclusion body. In the remaining bi rd, inclusion bodies were acidophilic and completely filled the nucleus; nu clear enlargement was less evident than in the other birds. At ultrastructu ral examination, and in both types of IIB, nuclei contained looped filament s but no evidence of viral structures. However, virion-like structures were observed in the cytoplasm of some hepatocytes.