Meta-transcriptomic discovery of a divergent circovirus and a chaphamaparvovirus in captive reptiles with proliferative respiratory syndrome

Viral pathogens are being increasingly described in association with mass morbidity and mortality events in reptiles. However, our knowledge of reptile viruses and their role in population health remains limited. Herein, we describe a meta-transcriptomic investigation of a mass morbidity and mortality event in a colony of central bearded dragons (Pogona vitticeps) in 2014. Severe, extensive proliferation of the respiratory epithelium was consistently found in affected dragons. Similar proliferative lung lesions were identified in bearded dragons from the same colony in 2020 in association with increased intermittent mortality. Total RNA sequencing of bearded dragon tissue identified two divergent DNA viruses: a reptile-infecting circovirus, denoted bearded dragon circovirus (BDCV), and the first exogeneous reptilian chaphamaparvovirus - bearded dragon chaphamaparvovirus (BDchPV). Phylogenetic analysis revealed that BDCV was most closely related to bat-associated circoviruses, exhibiting 70% amino acid sequence identity. In contrast, the newly discovered BDchPV showed approximately 35-40% identity in the non-structural (NS) protein to parvoviruses obtained from tilapia fish and crocodiles in China. Subsequent specific PCR assays detected BDCV exclusively and comprehensively within animals with proliferative pulmonary lesions and respiratory disease. This study expands our understanding of viral diversity in the context of diseased reptiles in captivity.