Characterization of the genomic sequence of a novel CRESS DNA virus identified in Eurasian jay (Garrulus glandarius)

Unveiling the Virome of Wild Birds: Exploring CRESS-DNA Viral Dark Matter

Amid global health concerns and the constant threat of zoonotic diseases, this study delves into the diversity of circular replicase-encoding single-stranded DNA (CRESS-DNA) viruses within Chinese wild bird populations. Employing viral metagenomics to tackle the challenge of "viral dark matter," the research collected and analyzed 3,404 cloacal swab specimens across 26 bird families. Metagenomic analysis uncovered a rich viral landscape, with 67.48% of reads classified as viral dark matter, spanning multiple taxonomic levels. Notably, certain viral families exhibited host-specific abundance patterns, with Galliformes displaying the highest diversity. Diversity analysis categorized samples into distinct groups, revealing significant differences in viral community structure, particularly noting higher diversity in terrestrial birds compared to songbirds and unique diversity in migratory birds versus perching birds. The identification of ten novel Circoviridae viruses, seven Smacoviridae viruses, and 167 Genomoviridae viruses, along with 100 unclassified CRESS-DNA viruses, underscores the expansion of knowledge on avian-associated circular DNA viruses. Phylogenetic and structural analyses of Rep proteins offered insights into evolutionary relationships and potential functional variations among CRESS-DNA viruses. In conclusion, this study significantly enhances our understanding of the avian virome, shedding light on the intricate relationships between viral communities and host characteristics in Chinese wild bird populations. The diverse array of CRESS-DNA viruses discovered opens avenues for future research into viral evolution, spread factors, and potential ecosystem impacts.

Multiple novel smaco-like viruses identified in chicken cloaca swabs

Viral metagenomics has been used in numerous animal virus discoveries. Recently, an unprecedented diversity of CRESS DNA viruses was identified using this method, and this has expanded our understanding of the environmental distribution and host range of CRESS DNA viruses. In this study, using an unbiased viral metagenomics approach, we investigated the fecal virome of chickens collected from two farms of Anhui Province, China. Five novel CRESS DNA viruses were obtained and characterized. The genome of the five viruses is 2,401-2,742 bp in length, containing two ORFs in the same orientation. Phylogenetic analysis indicated that all five viruses have a closer genetic relationship to smacoviruses than to other viruses in the order Cremevirales. Pairwise comparison of Rep amino acid sequences showed that these five viruses had only low amino acid sequence identity (8.9%-30.6%) to members of the family Smacoviridae, and the sequence identity among the five smaco-like viruses and other unclassified smacovirus strains was 70.3-95.8%. These findings broaden our knowledge of the genetic diversity of CRESS DNA viruses and provide a basis for classification of unclassified smacoviruses.

Novel Circoviruses from Birds Share Common Evolutionary Roots with Fish Origin Circoviruses

Circoviruses occur in a variety of animal species and are common pathogens of mammalian and avian hosts. In our study internal organ samples of wild birds were processed for screening of circoviral sequences. Two novel viruses were identified and characterized in specimens of a little bittern and a European bee-eater that suffered from wing injuries, were weakened, had liver or kidney failures, and finally succumbed at a rescue station. The 1935 nt and 1960 nt long viral DNA genomes exhibited a genomic structure typical for circoviruses and were predicted to encode replication-associated protein in the viral strand, and a capsid protein in the complementary strand of the replicative intermediate DNA form. The genome of the newly described viruses showed 37.6% pairwise identity with each other and ≤41.5% identity with circovirus sequences, and shared a common branch with fish, human and Weddel seal circoviruses in the phylogenetic tree, implying evolutionary relationship among the ancestors of these viruses. Based on the results the little bittern and European bee-eater circoviruses represent two distinct species of the Circovirus genus, Circoviridae family.

Genomic Diversity of CRESS DNA Viruses in the Eukaryotic Virome of Swine Feces

Replication-associated protein (Rep)-encoding single-stranded DNA (CRESS DNA) viruses are a diverse group of viruses, and their persistence in the environment has been studied for over a decade. However, the persistence of CRESS DNA viruses in herds of domestic animals has, in some cases, serious economic consequence. In this study, we describe the diversity of CRESS DNA viruses identified during the metagenomics analysis of fecal samples collected from a single swine herd with apparently healthy animals. A total of nine genome sequences were assembled and classified into two different groups (CRESSV1 and CRESSV2) of the Cirlivirales order (Cressdnaviricota phylum). The novel CRESS DNA viral sequences shared 85.8–96.8% and 38.1–94.3% amino acid sequence identities for the Rep and putative capsid protein sequences compared to their respective counterparts with extant GenBank record. Data presented here show evidence for simultaneous infection of swine herds with multiple novel CRESS DNA viruses, including po-circo-like viruses and fur seal feces-associated circular DNA viruses. Given that viral genomes with similar sequence and structure have been detected in swine fecal viromes from independent studies, investigation of the association between presence of CRESS DNA viruses and swine health conditions seems to be justified.

Fur Seal Feces-Associated Circular DNA Virus Identified in Pigs in Anhui, China

Fur seal feces-associated circular DNA virus (FSfaCV) is an unclassified circular replication-associated protein (Rep)-encoding single-stranded (CRESS) DNA virus that has been detected in mammals (fur seals and pigs). The biology and epidemiology of the virus remain largely unknown. To investigate the virus diversity among pigs in Anhui Province, China, we pooled 600 nasal samples in 2017 and detected viruses using viral metagenomic methods. From the assembled contigs, 12 showed notably high nucleotide acid sequence similarities to the genome sequences of FSfaCVs. Based on these sequences, a full-length genome sequence of the virus was then obtained using overlapping PCR and sequencing, and the virus was designated as FSfaCV-CHN (GenBank No. MK462122). This virus shared 91.3% and 90.9% genome-wide nucleotide sequence similarities with the New Zealand fur seal strain FSfaCV-as50 and the Japanese pig strain FSfaCV-JPN1, respectively. It also clustered with the two previously identified FSfaCVs in a unique branch in the phylogenetic tree based on the open reading frame 2 (ORF2), Rep-coding gene, and the genome of the reference CRESS DNA viruses. Further epidemiological investigation using samples collected in 2018 showed that the overall positive rate for the virus was 56.4% (111/197) in Anhui Province. This is the first report of FSfaCVs identified in pigs in China, and further epidemiological studies are warranted to evaluate the influence of the virus on pigs.

Occurrence and genetic diversity of CRESS DNA viruses in wild birds: a Hungarian study

Circoviruses, cycloviruses and other circular, replication-associated protein-encoding single stranded (CRESS) DNA viruses have been detected in a variety of animal taxa. In this study, cloacal swab samples (n = 90) were examined for CRESS DNA viruses from 31 wild bird species living at various aquatic sites in Hungary to identify possible reservoirs of viruses pathogenic to domestic poultry. A total of 30 (33.3%) specimens tested positive with pan-CRESS DNA virus specific PCR. Goose circovirus (GoCV), Duck associated cyclovirus 1 (DuACyV-1) and Garrulus glandarius associated circular virus 1 (GgaCV-1) were detected in nine, three and two different bird species, respectively. Selected specimens were subjected to whole genome sequencing. The obtained sequence data revealed conserved gene structure within the identified virus species and detected homologous (within GoCV) and possible heterologous recombination (within DuACyV-1) events. Results presented here provide new information on the genomic diversity and evolution of selected CRESS DNA viruses.

Eukaryotic Circular Rep-Encoding Single-Stranded DNA (CRESS DNA) Viruses: Ubiquitous Viruses With Small Genomes and a Diverse Host Range

While single-stranded DNA (ssDNA) was once thought to be a relatively rare genomic architecture for viruses, modern metagenomics sequencing has revealed circular ssDNA viruses in most environments and in association with diverse hosts. In particular, circular ssDNA viruses encoding a homologous replication-associated protein (Rep) have been identified in the majority of eukaryotic supergroups, generating interest in the ecological effects and evolutionary history of circular Rep-encoding ssDNA viruses (CRESS DNA) viruses. This review surveys the explosion of sequence diversity and expansion of eukaryotic CRESS DNA taxonomic groups over the last decade, highlights similarities between the well-studied geminiviruses and circoviruses with newly identified groups known only through their genome sequences, discusses the ecology and evolution of eukaryotic CRESS DNA viruses, and speculates on future research horizons.

Novel single-stranded, circular DNA virus identified in cats in Japan

We detected a novel feline stool-associated circular DNA virus (FeSCV) in fecal samples from cats with diarrhea using consensus primers matching those of circovirus and cyclovirus. FeSCV is a circular DNA virus containing a genome with a total length of 2,046 nt encoding 2 open reading frames. Phylogenetic analyses indicated that FeSCV is classified into a clade different from that of circovirus and cyclovirus. Since the FeSCVs detected in several cats in the same household had genetically similar genomes, these viruses are most likely derived from the same origin.