Prevalence and molecular characterization of circoviruses, astroviruses and hepadnaviruses in the avifauna of Kopački rit Nature Park, Croatia

Abstract

Wild birds harbour a plethora of viruses but the research into them has mainly focused on those possessing zoonotic potential or causing significant economic losses in poultry, while others, such as astroviruses (AstVs), circoviruses (CV) and hepadnaviruses (HBV), remain neglected. In this study, 35 dead wild birds belonging to at least 21 species from five orders, collected in Kopački rit Nature Park were tested for the presence of AstVs, CV and HBV using PCR with subsequent nucleotide sequencing. A positive result was found in 18 birds. AstVs were found in three passerine birds, CV was detected in 11 birds belonging to Accipitriformes, Anseriformes, Charadriiformes, Passeriformes or Piciformes orders while HBV was found in four birds belonging to either Anseriformes or Passeriformes. More than one virus was found in a single species (AstV and CV) although in two separate birds. Phylogenetic analysis revealed divergent AstVs somewhat similar to different unclassified AstVs detected in undetermined birds. One AstV shared the highest homology with a bat AstV (98.77%). All CV found in the study resemble avian CV, but none of them clusters in the phylogenetic tree with any avian or avian-like CV sequence. All four HBV sequences detected in this study cluster within the duck HBV group, indicating unusual interspecies transmission to cohabitating passerines. The results of this study represent an important contribution to knowledge about the prevalence, ecology and epidemiology of AstVs, CV and HBV in different wild bird species, indicating the need for further studies, including whole genome sequencing of the detected viruses.