Unveiling the diversity of avastroviruses in tropical wild birds from the Atlantic Forest, Brazil

Astroviruses are widespread RNA viruses that infect a broad range of animal hosts, with avastroviruses (AAstVs) primarily infecting avian species. While AAstVs are well-documented in domestic birds, their presence in wild birds, particularly in tropical ecosystems like Brazil’s Atlantic Forest, has been underexplored. This study investigated the prevalence and genetic diversity of AAstVs in wild birds from the Serra do Mar State Park, São Paulo. A total of 417 fecal samples were collected from birds representing 89 species between 2022 and 2023. During a parallel investigation of Reovirales -related viruses, NGS unexpectedly revealed a potential novel AAstV strain in one sample, here named Passerine Avastrovirus (PasAstV M1580). Conventional RT-PCR, targeting the conserved RdRp gene, detected AAstV in 7.67% (32/417) of the samples. AAstV was repeatedly detected in recaptured individuals of Troglodytes musculus and Hylophilus poicilotis at multiple time points. Immune status was not assessed, limiting interpretation of shedding versus natural infection. Complete genome analysis of PasAstV M1580 revealed typical AAstV genomic features and suggests that it may represent a putative novel species within the Avastrovirus genus, displaying amino acid identity ranging from 25.18% to 33.23% in the ORF2 region compared to prototype strains. The genomic characterization of PasAstV M1580 expands the known diversity within the genus Avastrovirus and provides new insights into ecology of AAstVs in tropical wild bird populations of the Brazilian Atlantic Forest.