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Companion animals such as cats and dogs harbor diverse microbial communities that can potentially impact human health due to close and frequent contact. To better characterize their total infectomes and assess zoonotic risks, we characterized the overall infectomes of companion animals (cats and dogs) and evaluated their potential zoonotic risks. Meta-transcriptomic analyses were performed on 239 samples from cats and dogs collected across China, identifying 24 viral species, 270 bacterial genera, and two fungal genera. Differences in the overall microbiome and infectome composition were compared across different animal species (cats or dogs), sampling sites (rectal or oropharyngeal), and health status (healthy or diseased). Diversity analyses revealed that viral abundance was generally higher in diseased animals compared to healthy ones, while differences in microbial composition were mainly driven by sampling site, followed by animal species and health status. Disease association analyses validated the pathogenicity of known pathogens and suggested potential pathogenic roles of previously undescribed bacteria and newly discovered viruses. Cross-species transmission analyses identified seven pathogens shared between cats and dogs, such as alphacoronavirus 1, which was detected in both oropharyngeal and rectal swabs albeit with differential pathogenicity. Further analyses showed that some viruses, like alphacoronavirus 1, harbored multiple lineages exhibiting distinct pathogenicity, tissue, or host preferences. Ultimately, a systematic evolutionary screening identified 27 potential zoonotic pathogens in this sample set, with far more bacterial than viral species, implying potential health threats to humans. Overall, our meta-transcriptomic analysis reveals a landscape of actively transcribing microorganisms in major companion animals, highlighting key pathogens, those with the potential for cross-species transmission, and possible zoonotic threats., Importance: This study provides a comprehensive characterization of the entire community of infectious microbes (viruses, bacteria, and fungi) in companion animals like cats and dogs, termed the "infectome." By analyzing hundreds of samples from across China, the researchers identified numerous known and novel pathogens, including 27 potential zoonotic agents that could pose health risks to both animals and humans. Notably, some of these zoonotic pathogens were detected even in apparently healthy pets, highlighting the importance of surveillance. The study also revealed key microbial factors associated with respiratory and gastrointestinal diseases in pets, as well as potential cross-species transmission events between cats and dogs. Overall, this work sheds light on the complex microbial landscapes of companion animals and their potential impacts on animal and human health, underscoring the need for monitoring and management of these infectious agents., Competing Interests: The authors declare no conflict of interest.

Mites are notorious for being vectors transmitting infectious pathogens and source of allergens causing allergic conditions in animals and humans. However, despite their huge impact on public health, the virome of mites remains unknown. Here we characterized the virus diversity and abundance of 14 species of medically important mites based on total RNA sequencing data sets generated in this study as well as those deposited in the Sequence Read Archive (SRA) database. A total of 47 genetically distinct viruses were identified and classified into 17 virus families or virus super-groups, and the viral sequences accounted for as much as 29.67% of total non-rRNA transcriptome in one mite library. The most commonly identified viruses are members of Picornavirales , among which we revealed more than one type of viruses that are evolutionarily related to dicistronic viruses but contain a single open reading frame, thus likely representing a recent example of host (i.e., mite)-related parallel evolution from dicistronic to monocistronic genomic form within the family Dicistroviridae To our best knowledge, this is the first time to perform comprehensive and systematic screening of RNA virome in medically important mites including house dust mites (HDM). Overall, the RNA virome identified here provides not only significant insights into the diversity and evolution of RNA viruses in mites, but also a solid knowledge base for studying their roles in human diseases. IMPORTANCE Mites are important group of arthropods that are associated with a variety of human diseases including scrub typhus and asthma. However, it remains unclear whether or not mites carry viruses that might play a role in human infections or allergic disease. In this study, we used a total transcriptomics approach to characterize and compare the complete RNA virome within mites that are relevant to human health and diseases. Specifically, our data revealed a large diversity, a high abundance, and a flexible genomic evolution for these viruses. Although most of the viruses identified here are unknown to associate with human infectious disease, the abundant presence of viral RNAs may play an immunomodulatory role in the development of allergic reactions such as asthma during environmental exposure to mite allergens, and therefore provide important insights into the mite-induced allergy and preparation of mite allergen vaccines., (Copyright © 2020 American Society for Microbiology.)

Unlabelled: Viruses of the family Flaviviridae are important pathogens of humans and other animals and are currently classified into four genera. To better understand their diversity, evolutionary history, and genomic flexibility, we used transcriptome sequencing (RNA-seq) to search for the viruses related to the Flaviviridae in a range of potential invertebrate and vertebrate hosts. Accordingly, we recovered the full genomes of five segmented jingmenviruses and 12 distant relatives of the known Flaviviridae ("flavi-like" viruses) from a range of arthropod species. Although these viruses are highly divergent, they share a similar genomic plan and common ancestry with the Flaviviridae in the NS3 and NS5 regions. Remarkably, although these viruses fill in major gaps in the phylogenetic diversity of the Flaviviridae, genomic comparisons reveal important changes in genome structure, genome size, and replication/gene regulation strategy during evolutionary history. In addition, the wide diversity of flavi-like viruses found in invertebrates, as well as their deep phylogenetic positions, suggests that they may represent the ancestral forms from which the vertebrate-infecting viruses evolved. For the vertebrate viruses, we expanded the previously mammal-only pegivirus-hepacivirus group to include a virus from the graceful catshark (Proscyllium habereri), which in turn implies that these viruses possess a larger host range than is currently known. In sum, our data show that the Flaviviridae infect a far wider range of hosts and exhibit greater diversity in genome structure than previously anticipated., Importance: The family Flaviviridae of RNA viruses contains several notorious human pathogens, including dengue virus, West Nile virus, and hepatitis C virus. To date, however, our understanding of the biodiversity and evolution of the Flaviviridae has largely been directed toward vertebrate hosts and their blood-feeding arthropod vectors. Therefore, we investigated an expanded group of potential arthropod and vertebrate host species that have generally been ignored by surveillance programs. Remarkably, these species contained diverse flaviviruses and related viruses that are characterized by major changes in genome size and genome structure, such that these traits are more flexible than previously thought. More generally, these data suggest that arthropods may be the ultimate reservoir of the Flaviviridae and related viruses, harboring considerable genetic and phenotypic diversity. In sum, this study revises the traditional view on the evolutionary history, host range, and genomic structures of a major group of RNA viruses., (Copyright © 2015, American Society for Microbiology. All Rights Reserved.)