Avian polyomavirus infection of a fledgling budgerigar (Melopsittacus undulatus) and differential diagnoses of viral inclusions in psittacine birds--case report and mini-review

A two-week-old budgerigar (Melopsittacus undulatus) of an outdoor aviary died suddenly and was submitted for determination the cause of illness and death. Macroscopically, the sparsely feathered animal was in a poor body condition. Histopathological examination revealed in various mesenchymal and epithelial tissues, numerous up to 15 microm in diameter large intranuclear, amphophilic to basophilic inclusion bodies with a clearing of the centre. Additionally, a feather dysplasia and retention hyperkeratosis of feather follicles was found. Ultrastructurally, viral particles of approximately 35 nm in diameter were detected in the feather follicle epithelium. A PCR for Avian Polyomavirus on fresh skin samples was negative whereas on formalin-fixed kidney samples with a high amount of viral inclusion bodies yielded a positive result. In addition, viral inclusion body diseases, like Avian Poxvirus, Psittacine Beak and Feather disease virus, Avian Adenovirus, Psittacine Herpesvirus and papillomavirus of psittacines are summarized and compared in the present article.