Psittacine beak and feather disease (PBFD) was diagnosed in an umbrella cockatoo (Cacatua alba) with severe feather dystrophy and loss. Electron microscopically, the intranuclear and intracytoplasmic inclusion bodies observed by light microscopy were composed of viral particles forming paracrystalline arrays, whorls, semicircles or concentric circles. Recovered viral particles from the skin and feather follicle tracts were icosahedral and 15 to 20 nm in diameter.
Sanada, Y., Sanada, N., & Kubo, M. (1999). Electron Microscopical Observations of Psittacine Beak and Feather Disease in an Umbrella Cockatoo (Cacatua alba). Journal of Veterinary Medical Science, 61(9), 1063–1065. https://doi.org/10.1292/jvms.61.1063