Characterization of a new virus from cockatoos with psittacine beak and feather disease

A novel virus isolated from the feather follicles of cockatoos diagnosed as having psittacine beak and feather disease was characterized by electron microscopy, nucleic acid content, and polypeptide composition. Purified virions displayed an icosahedral symmetry, were nonenveloped, and had a mean diameter of 14 to 16 nm negatively stained. Three major viral proteins were identified, with approximate molecular weights of 26.3, 23.7, and 15.9 kDa. The viral nucleic acid was found to be single-stranded DNA based on acridine orange staining, resistance to alkali and ribonuclease, and sensitivity to both DNAse 1 and S1 nuclease. The size of the DNA was estimated to be between 1.7 and 2.0 kb by agarose gel electrophoresis. This size and its circular conformation were confirmed by electron microscopy. A preliminary transmission study using purified virus induced pathological lesions characteristic of those observed in the natural disease. On the basis of the extremely small size of the virions and the single-stranded circular viral DNA, we propose that the etiologic agent of psittacine beak and feather disease represents a previously undescribed viral pathogen.