Polyomavirus Infection in Two Young Parrots: Assessment of Viral Distribution in Organs and Affected Tissues

Avian polyomavirus (APyV) is responsible for diseases in birds belonging to several avian orders, including Psittaciformes, Anseriformes, and other susceptible taxa. APyVs appear to be able to replicate in various organs of susceptible bird species. This study aimed to investigate i) the distribution of APyV in the organs of two parrot chicks belonging to different species, Moluccan eclectus (Eclectus roratus) and blue-winged macaw (Primolius maracana), which died due to APyV infection, and ii) the lesions associated with the infection. By negative-staining electron microscopy, well-defined viral particles morphologically compatible with polyomavirus and polyomavirus-like particles were identified in organs. Detection of APyV was confirmed by real-time PCR, and BLAST analysis of the complete genome revealed 99.96% identity with a budgerigar fledging disease polyomavirus strain. The amount of DNA copy number/ng of DNA ranged from 2.47x10³ found in the myocardium to 3.90x10⁶ found in the feather quills of the eclectus, and from 1.07x10¹ to 1.82x10⁷ detected in the brain and intestine of the blue-winged macaw, respectively. According to the findings of inclusion bodies, viral particles and DNA, the lung appeared as one of the most severely affected tissues. Even if inclusion bodies were not detected, severe lesions were found in the myocardium, bursa of Fabricius and spleen. The results of this study highlight the ability of APyV to spread widely, leading to severe lesions in the organs of infected birds. The most significant amount of viral DNA detected in the gut and feathers highlights the relevance of faeces and feathers as useful samples for the in vivo diagnosis.