Induction of mitochondrial damage via the CREB3L1/miR-34c/COX1 axis by porcine epidemic diarrhea virus infection facilitates pathogenicity

Porcine epidemic diarrhea virus (PEDV) is a primary cause of viral diarrhea in neonatal piglets, leading to substantial economic losses in the swine industry globally. It primarily targets epithelial cells of the small intestine, compromising intestinal function and resulting in the death of affected animals. As mitochondria are essential for maintaining gut health, this study investigates the effects of PEDV infection on mitochondrial function in small intestinal epithelial cells and its subsequent impacts. Using small RNA sequencing, fluorescence in situ hybridization, dual luciferase reporter assay, gene overexpression, and silencing experiments, we investigated the mitochondrial structural and functional impairments induced by PEDV infection in jejunum epithelial cells of piglets and characterized the regulatory pattern of miRNAs in mitochondria of jejunum epithelial cells during PEDV infection. The results indicate that PEDV infection leads to the upregulation and mitochondrial localization of the nuclear-encoded microRNA, miR-34c, which in turn suppresses COX1 expression. The activation of the miR-34c/COX1 axis diminishes mitochondrial complex III, IV, and V activities, depletes ATP, lowers mitochondrial oxygen consumption, induces mitochondrial depolarization, increases the accumulation of mitochondrial reactive oxygen species (mtROS), and stimulates mitophagy. Furthermore, we confirm that CREB3L1 acts as an upstream transcription factor regulating the miR-34c/COX1 axis during PEDV infection, modulating mitochondrial damage in the epithelial cells of the jejunum. These findings demonstrate for the first time that PEDV infection activates the miR-34c/COX1 axis via the transcription factor CREB3L1 and regulates the nuclear-mitochondrial communication and mitochondrial fate, providing a new perspective on the pathogenesis of PEDV.IMPORTANCEThis study reveals the mechanism by which the porcine epidemic diarrhea virus (PEDV) disrupts mitochondrial function in piglets, enhancing viral pathogenicity. By demonstrating how PEDV infection upregulates miR-34c, leading to COX1 suppression and subsequent mitochondrial dysfunction, the research highlights a novel aspect of viral manipulation of host cellular mechanisms. These findings provide a deeper understanding of the PEDV pathogenesis and identify potential targets for therapeutic intervention, advancing efforts to mitigate the economic impact of PEDV on the swine industry.

Relevancy Prediction of the Emerging Pathogens with Porcine Diarrhea by Logistic Regression Model

Porcine viral diarrhea has always been one of the main obstacles to the healthy development of the pig industry in China with its variety of pathogens and complexity of co-infections. Analysis of the dominant mixed-infection model is a fundamental step in boosting the prevention and control of porcine diarrhea. In this study, 3256 porcine fecal samples were collected from 17 pig herds in Shanghai, China, from 2015 to 2023 to identify novel pathogenic infection patterns. The results confirmed that porcine astrovirus (PAstV), porcine sapelovirus (PSV), and porcine epidemic diarrhea virus (PEDV) were the top three agents with positive rates of 28.47%, 20.71%, and 20.23%, respectively. Porcine rotavirus (PoRV) and transmissible gastroenteritis virus (TGEV) accounted for only 8.12% and 1.12%, respectively. Importantly, mixed infection rates were high and complicated. The double infection rate was higher than that of a single infection. Next, the mixed-infection model of PEDV and emerging diarrheal pathogens was explored. The predominant dual-infection models were PEDV/PKoV (porcine kobuvirus) (14.18%), PEDV/PAstV (10.02%), and PEDV/PSV (9.29%). The predominant triple infection models were PEDV/PKoV/PAstV (18.93%), PEDV/PSV/PAstV (10.65%), and PEDV/PKoV/PSV (7.10%). The dominant quadruple-infection model was PEDV/PAstV/PSV/PKoV (46.82%). In conclusion, PEDV is mainly mix-infected with PAstV, PSV, and PKoV in clinical settings. Furthermore, multiple-factor logistic regression analysis confirmed that PAstV, PKoV, bovine viral diarrhea virus (BVDV), and PEDV were closely related to porcine diarrhea. PEDV/PKoV, PEDV/porcine sapovirus (PoSaV), PKoV/BVDV, PoSaV/BVDV, and porcine deltacoronavirus (PDCoV)/PoSaV had great co-infection dominance, which will be helpful for porcine co-infection research.

Development and Immunogenicity Study of Subunit Vaccines Based on Spike Proteins of Porcine Epidemic Diarrhea Virus and Porcine Transmissible Gastroenteritis Virus

Porcine epidemic diarrhea virus (PEDV) and transmissible gastroenteritis virus (TGEV) are responsible for significant economic losses in the swine industry. The S1 proteins of these viruses serve as key targets for vaccine development. In this study, prokaryotic expression vectors for pCZN1-PEDV S1, pCZN1-TGEV S1, and pCZN1-PEDV S1-TGEV S1 were constructed. The corresponding proteins were expressed, purified, and used to prepare monovalent, bivalent, and mixed (PEDV S1 + TGEV S1) vaccines. Kunming (KM) mice were immunized with subunit vaccines, with PBS as the negative control (NC) and a commercial inactivated vaccine as the positive control (PC). Immune responses, including specific antibody (IgG, IgG1, IgG2a) levels, virus neutralization, and IFN-γ production, were evaluated. All vaccines induced high levels of specific IgG, IgG1, and IgG2a antibodies. At weeks 2 and 8, the PEDV S1 + TGEV S1 vaccine induced significantly higher levels of specific IgG and IgG1 compared to the PC (p < 0.001). The PEDV S1 vaccine also induced significantly higher specific IgG2a levels than the PC at week 4 (p < 0.0001). Virus neutralization assays demonstrated that the subunit vaccines induced neutralizing antibody levels comparable to or exceeding those of the PC. Furthermore, IFN-γ levels were significantly elevated in all vaccinated groups compared to the NC (p < 0.0001), indicating a robust immune response. These results suggest that the subunit vaccines are promising candidates for the safe and effective control of both PEDV and TGEV infections.

First Detection of a Novel Posavirus 2 Strain Identified from Pigs in China

Porcine stool-associated RNA virus (Posavirus) is an unclassified virus with sequence similarity to viruses in the order of Picornaviridae. In China, lineage 1 Posavirus (Posavirus 1) has been circulating in the field since its initial emergence in 2014 however no other lineages have been reported. To investigate the genetic diversity of Posavirus in China, 1200 diarrheic samples were collected from pigs in China. Following high-throughput and Sanger sequencing, one complete genome sequence of a Posavirus (designated SC01) strain was obtained. The genome of SC01 strain was 10217 nucleotides in length and encoded a polyprotein of 3346 amino acids. Genome comparative analysis revealed that SC01 shared 85.6% nucleotide similarity to Posavirus 2 strains, but only 35.2-58.0% sequence identity with Posavirus 1 and 3-12 strains. Phylogenetic analysis showed that the SC01 was classified in Posavirus 2 and clustered into a separate branch with the American Posavirus 2 isolates, indicating that the SC01 is a Posavirus 2 strain. Notably, a novel 1-amino acid deletion was observed in polyprotein at amino acid position 147. This is the first report of the presence of Posavirus 2 in China, and the genomic data of SC01 provides insights into the genetic diversity and evolution of Posavirus in the region.

The prevalence and shedding of porcine epidemic diarrhea virus in intensive swine farms of China from 2022 to 2023

Porcine epidemic diarrhea has emerged as a significant threat to the global swine industry. The shedding and exposure status of porcine epidemic diarrhea virus (PEDV) in intensive farms is not completely understood. In this study, a total of 56,598 clinical samples collected from 256 intensive pig farms in 20 provinces in China from 2022 to 2023, were evaluated for PEDV using quantitative real-time PCR. The overall PEDV prevalence was 11.78 % and 28.45 % at the sample and farm levels, respectively, which are relatively high in Northern China and the fourth and first quarter of the year. The PEDV-positive rates and viral loads in suckling piglet herds were higher than those in growing-finishing pigs and multiparous sows. Meanwhile, 15.61 % of pig pens, 9.51 % of corridors, 9.4 % of office areas, 9.23 % of production personnel, and 8.33 % of pig cart driver samples were positive for PEDV, indicating potential biosafety gaps in intensive pig farms. In addition, 93.41 % of inguinal lymph node tissue samples contained viral nucleic acids, revealing a possible persistent infection of PEDV in pig herds. Our study presents the first report of the large-scale detection of PEDV in intensive pig farms, which constitutes indirect evidence of virus circulation in pig herds. This study provides valuable data for preventing and controlling PEDV infection in the future.

Investigation of Transmission and Evolution of PEDV Variants and Co-Infections in Northeast China from 2011 to 2022

Porcine epidemic diarrhea virus (PEDV) is a rapidly evolving virus that causes outbreaks in pig herds worldwide. Mutations in the S protein of PEDV have led to the emergence of new viral variants, which can reduce vaccine immunity against prevalent strains. To understand the infection and variation pattern of PEDV in China, an extensive epidemiological survey was conducted in northeast China from 2015 to 2022. The genetic diversity of enteroviruses co-infected with PEDV and the PEDV S gene was analyzed, common mutation patterns that may have led to changes in PEDV virulence and infectivity in recent years were identified, and structural changes in the surface of the S protein resulting from mutations in the PEDV S gene from 2011 to 2022 were reviewed. Of note, two distinct mutations in the emerging 2022 HEB strain were identified. These findings provide a basis for a better understanding of PEDV co-infection and genetic evolution in northeast China.

PoRVA G9P[23] and G5P[7] infections differentially promote PEDV replication by reprogramming glutamine metabolism

PoRVA and PEDV coinfections are extremely common in clinical practice. Although coinfections of PoRVA and PEDV are known to result in increased mortality, the underlying mechanism remains unknown. Here, we found that PoRVA infection promoted PEDV infection in vivo and in vitro and that PoRVA G9P[23] (RVA-HNNY strain) enhanced PEDV replication more significantly than did PoRVA G5P[7] (RVA-SXXA strain). Metabolomic analysis revealed that RVA-HNNY more efficiently induced an increase in the intracellular glutamine content in porcine small intestinal epithelial cells than did RVA-SXXA, which more markedly promoted ATP production to facilitate PEDV replication, whereas glutamine deprivation abrogated the effect of PoRVA infection on promoting PEDV replication. Further studies showed that PoRVA infection promoted glutamine uptake by upregulating the expression of the glutamine transporter protein SLC1A5. In SLC1A5 knockout cells, PoRVA infection neither elevated intracellular glutamine nor promoted PEDV replication. During PoRVA infection, the activity and protein expression levels of glutamine catabolism-related enzymes (GLS1 and GLUD1) were also significantly increased promoting ATP production through glutamine anaplerosis into the TCA cycle. Consistent with that, siRNAs or inhibitors of GLS1 and GLUD1 significantly inhibited the promotion of PEDV replication by PoRVA. Notably, RVA-HNNY infection more markedly promoted SLC1A5, GLS1 and GLUD1 expression to more significantly increase the uptake and catabolism of glutamine than RVA-SXXA infection. Collectively, our findings illuminate a novel mechanism by which PoRVA infection promotes PEDV infection and reveal that the modulation of glutamine uptake is key for the different efficiencies of PoRVA G9P[23] and PoRVA G5P[7] in promoting PEDV replication.

Metagenomics to Identify Viral Communities Associated with Porcine Respiratory Disease Complex in Tibetan Pigs in the Tibetan Plateau, China

Tibetan pig is a unique pig breed native to the Qinghai-Tibet Plateau. To investigate viral communities associated with porcine respiratory disease complex (PRDC), 167 respiratory samples were collected from Tibetan pigs in the Ganzi Tibetan autonomous prefecture of Sichuan province. Following library construction and Illunima Novaseq sequencing, 18 distinct viruses belonging to 15 viral taxonomic families were identified in Tibetan pigs with PRDC. Among the 18 detected viruses, 3 viruses were associated with PRDC, including porcine circovirus type 2 (PCV-2), Torque teno sus virus (TTSuV), and porcine cytomegalovirus (PCMV). The genomic sequences of two PCV-2 strains, three TTSuV strains, and one novel Porprismacovirus strain were assembled by SOAPdenovo software (v2). Sequence alignment and phylogenetic analysis showed that both PCV-2 strains belonged to PCV-2d, three TTSuVs were classified to TTSuV2a and TTSuV2b genotypes, and the Porprismacovirus strain PPMV-SCgz-2022 showed a close genetic relationship with a virus of human origin. Recombination analysis indicated that PPMV-SCgz-2022 may have originated from recombination events between Human 16,806 × 66-213 strain and Porcine 17,668 × 82-593 strain. Furthermore, the high proportion of single infection or co-infection of PCV2/TTSuV2 provides insight into PRDC infection in Tibetan pigs. This is the first report of the viral communities in PRDC-affected Tibetan pigs in this region, and the results provides reference for the prevention and control of respiratory diseases in these animals.

Screening for Viruses in Indigenous Greek Black Pigs

The successful advancement of xenotransplantation has led to the development of highly sensitive detection systems for the screening of potentially zoonotic viruses in donor pigs and preventing their transmission to the recipient. To validate these methods, genetically modified pigs generated for xenotransplantation, numerous minipigs and other pig breeds have been tested, thereby increasing our knowledge concerning the pig virome and the distribution of pig viruses. Of particular importance are the porcine cytomegalovirus, a porcine roseolovirus (PCMV/PRV) and the hepatitis E virus genotype 3 (HEV3). PCMV/PRV has been shown to reduce the survival time of pig transplants in non-human primates and was also transmitted in the first pig heart transplantation to a human patient. The main aim of this study was to determine the sensitivities of our methods to detect PCMV/PRV, HEV3, porcine lymphotropic herpesvirus-1 (PLHV-1), PLHV-2, PLHV-3, porcine circovirus 2 (PCV2), PCV3, PCV4 and porcine parvovirus 1 (PPV1) and to apply the methods to screen indigenous Greek black pigs. The high number of viruses found in these animals allowed for the evaluation of numerous detection methods. Since porcine endogenous retroviruses (PERVs) type A and B are integrated in the genome of all pigs, but PERV-C is not, the animals were screened for PERV-C and PERV-A/C. Our detection methods were sensitive and detected PCMV/PRV, PLHV-1, PLHV-1, PLHV-3, PVC3 and PERV-C in most animals. PPV1, HEV3, PCV4 and PERV-A/C were not detected. These data are of great interest since the animals are healthy and resistant to diseases.

High Prevalence, Genetic Diversity, and Recombination of Porcine Sapelovirus in Pig Farms in Fujian, Southern China

Porcine sapelovirus (PSV) is a ubiquitous virus in farmed pigs that is associated with SMEDI syndrome, polioencephalomyelitis, and diarrhea. However, there are few reports on the prevalence and molecular characterization of PSV in Fujian Province, Southern China. In this study, the prevalence of PSV and a poetical combinative strain PSV2020 were characterized using real-time PCR, sequencing, and bioinformatics analysis. As a result, an overall sample prevalence of 30.8% was detected in 260 fecal samples, and a farm prevalence of 76.7% was observed in 30 Fujian pig farms, from 2020 to 2022. Noteably, a high rate of PSV was found in sucking pigs. Bioinformatics analysis showed that the full-length genome of PSV2020 was 7550 bp, and the genetic evolution of its ORF region was closest to the G1 subgroup, which was isolated from Asia and America; the similarity of nucleotides and amino acids to other PSVs was 59.5~88.7% and 51.7~97.0%, respectively. However, VP1 genetic evolution analysis showed a distinct phylogenetic topology from the ORF region; PSV2020 VP1 was closer to the DIAPD5469-10 strain isolated from Italy than strains isolated from Asia and America, which comprise the G1 subgroup based on the ORF region. Amino acid discrepancy analysis illustrated that the PSV2020 VP1 gene inserted twelve additional nucleotides, corresponding to four additional amino acids (STAE) at positions 898-902 AAs. Moreover, a potential recombination signal was observed in the 2A coding region, near the 3' end of VP1, owing to recombination analysis. Additionally, 3D genetic evolutionary analysis showed that all reference strains demonstrated, to some degree, regional conservation. These results suggested that PSV was highly prevalent in Fujian pig farms, and PSV2020, a PSV-1 genotype strain, showed gene diversity and recombination in evolutionary progress. This study also laid a scientific foundation for the investigation of PSV epidemiology, molecular genetic characteristics, and vaccine development.

Triplex-Loop-Mediated Isothermal Amplification Combined with a Lateral Flow Immunoassay for the Simultaneous Detection of Three Pathogens of Porcine Viral Diarrhea Syndrome in Swine

Porcine epidemic diarrhea virus (PEDV), porcine bocavirus (PBoV), and porcine rotavirus (PoRV) are associated with porcine viral diarrhea. In this study, triplex loop-mediated isothermal amplification (LAMP) combined with a lateral flow dipstick (LFD) was established for the simultaneous detection of PEDV, PoRV, and PBoV. The PEDV-gp6, PoRV-vp6, and PBoV-vp1 genes were selected to design LAMP primers. The amplification could be carried out at 64 °C using a miniature metal bath within 30 min. The triplex LAMP-LFD assay exhibited no cross-reactions with other porcine pathogens. The limits of detection (LODs) of PEDV, PoRV, and PBoV were 2.40 × 10¹ copies/μL, 2.89 × 10¹ copies/μL, and 2.52 × 10¹ copies/μL, respectively. The consistency between rt-qPCR and the triplex LAMP-LFD was over 99% in field samples testing. In general, the triplex LAMP-LFD assay was suitable for the rapid and simultaneous detection of the three viruses in the field.

The discovery of novel papillomaviruses in cats in Southwest China

Feline viral diarrhea is a significant cause of death in kittens. In this study, 12 mammalian viruses were identified by metagenomic sequencing in diarrheal feces in 2019, 2020, and 2021, respectively. Interestingly, a novel of felis catus papillomavirus (FcaPV) was identified for the first time in China. Subsequently, we investigated the prevalence of FcaPV in 252 feline samples, including 168 diarrheal feces and 84 oral swabs, with a total of 57 (22.62%, 57/252) samples detected positive. Of the 57 positive samples, FcaPV genotype 3 (FcaPV-3) was detected at high prevalence rate (68.42%, 39/57), followed by FcaPV-4 (22.8%, 13/57), FcaPV-2 (17.54%, 10/57), and FcaPV-1 (1.75%, 1/55), while no FcaPV-5 and FcaPV-6. In addition, two novel putative FcaPVs were identified, which were the highest similarity to Lambdapillomavirus from Leopardus wiedii or canis familiaris, respectively. Therefore, this study was the first characterization of the viral diversity in feline diarrheal feces and the prevalence of FcaPV in Southwest China.

Genetic characterization of four strains porcine circovirus-like viruses in pigs with diarrhea in Hunan Province of China

In this study, we detected a circular replication-associated protein (Rep)-encoding single-stranded (CRESS) DNA virus [named Po-Circo-like (PCL) virus] in intestinal tissue and fecal samples of pigs. PCL virus contains a single-stranded DNA genome, and ORF1 encodes the Rep and not the typical capsid protein encoded in PCV. The Rep protein may be responsible for viral genome replication. In addition, PCL virus may be one of the pathogens causing diarrhea symptoms in pigs. We identified four strains of PCL virus in two different pig farms with severe diarrhea outbreaks in Hunan Province, China. The strains in this study share 85.7-99.7% nucleic acid identity and 84.7-100% amino acid identity with Rep of the reference strains. A multiple sequence alignment of these PCL viruses and Bo-Circo-like CH showed a identity of 93.2% for the Rep protein, and the nucleotide identity was 86.7-89.3%. Moreover, Bo-Circo-like CH and HN75, HN39-01, HN39-02 had similar stem-loop sequences. In conclusion, the present study is the first detailed report of the PCL virus in Hunan provinces, which is a potential new virus in pigs that might be involved in cross-species transmission. Further investigation is needed to determine the pathogenesis of this virus and its epidemiologic impact.

Novel Virus Identification through Metagenomics: A Systematic Review

Metagenomic Next Generation Sequencing (mNGS) allows the evaluation of complex microbial communities, avoiding isolation and cultivation of each microbial species, and does not require prior knowledge of the microbial sequences present in the sample. Applications of mNGS include virome characterization, new virus discovery and full-length viral genome reconstruction, either from virus preparations enriched in culture or directly from clinical and environmental specimens. Here, we systematically reviewed studies that describe novel virus identification through mNGS from samples of different origin (plant, animal and environment). Without imposing time limits to the search, 379 publications were identified that met the search parameters. Sample types, geographical origin, enrichment and nucleic acid extraction methods, sequencing platforms, bioinformatic analytical steps and identified viral families were described. The review highlights mNGS as a feasible method for novel virus discovery from samples of different origins, describes which kind of heterogeneous experimental and analytical protocols are currently used and provides useful information such as the different commercial kits used for the purification of nucleic acids and bioinformatics analytical pipelines.

Porcine sapelovirus 2A protein induces mitochondrial-dependent apoptosis

Porcine sapelovirus (PSV) is an emerging pathogen associated with symptoms of enteritis, pneumonia, polioencephalomyelitis and reproductive disorders in swine, resulting in significant economic losses. Although PSV is reported to trigger cell apoptosis, its specific molecular mechanism is unclear. In this research, the cell apoptosis induced by PSV infection and its underlying mechanisms were investigated. The morphologic features of apoptosis include nuclear condensation and fragmentation, were observed after PSV infection. The cell apoptosis was confirmed by analyzing the apoptotic rates, caspase activation, and PARP1 cleavage. Caspase inhibitors inhibited the PSV-induced intrinsic apoptosis pathway and reduced viral replication. Among the proteins encoded by PSV, 2A is an important factor in inducing the mitochondrial apoptotic pathway. The conserved residues H48, D91, and C164 related to protease activity in PSV 2A were crucial for 2A-induced apoptosis. In conclusion, our results provide insights into how PSV induces host cell apoptosis.

Viral Metagenomics Reveals Diverse Viruses in Tissue Samples of Diseased Pigs

The swine industry plays an essential role in agricultural production in China. Diseases, especially viral diseases, affect the development of the pig industry and threaten human health. However, at present, the tissue virome of diseased pigs has rarely been studied. Using the unbiased viral metagenomic approach, we investigated the tissue virome in sick pigs (respiratory symptoms, reproductive disorders, high fever, diarrhea, weight loss, acute death and neurological symptoms) collected from farms of Anhui, Jiangsu and Sichuan Province, China. The eukaryotic viruses identified belonged to the families Anelloviridae, Arteriviridae, Astroviridae, Flaviviridae, Circoviridae and Parvoviridae; prokaryotic virus families including Siphoviridae, Myoviridae and Podoviridae occupied a large proportion in some samples. This study provides valuable information for understanding the tissue virome in sick pigs and for the monitoring, preventing, and treating of viral diseases in pigs.

A total infectome approach to understand the etiology of infectious disease in pigs

BACKGROUND

The global pork industry is continuously affected by infectious diseases that can result in large-scale mortality, trade restrictions, and major reductions in production. Nevertheless, the cause of many infectious diseases in pigs remains unclear, largely because commonly used diagnostic tools fail to capture the full diversity of potential pathogens and because pathogen co-infection is common.

RESULTS

We used a meta-transcriptomic approach to systematically characterize the pathogens in 136 clinical cases representing different disease syndromes in pigs, as well as in 12 non-diseased controls. This enabled us to simultaneously determine the diversity, abundance, genomic information, and detailed epidemiological history of a wide range of potential pathogens. We identified 34 species of RNA viruses, nine species of DNA viruses, seven species of bacteria, and three species of fungi, including two novel divergent members of the genus Pneumocystis. While most of these pathogens were only apparent in diseased animals or were at higher abundance in diseased animals than in healthy animals, others were present in healthy controls, suggesting opportunistic infections. Importantly, most of the cases examined here were characterized by co-infection with more than two species of viral, bacterial, or fungal pathogens, some with highly correlated occurrence and abundance levels. Examination of clinical signs and necropsy results in the context of relevant pathogens revealed that a multiple-pathogen model was better associated with the data than a single-pathogen model was.

CONCLUSIONS

Our data demonstrate that most of the pig diseases examined were better explained by the presence of multiple rather than single pathogens and that infection with one pathogen can facilitate infection or increase the prevalence/abundance of another. Consequently, it is generally preferable to consider the cause of a disease based on a panel of co-infecting pathogens rather than on individual infectious agents. Video abstract.

The Prevalence of Porcine Circovirus-like Viruses in China Presents New Challenges to the Diagnosis of Diarrhea-Associated Viruses. Comment on Yang et al. Epidemiology and Evolution of Emerging Porcine Circovirus-like Viruses in Pigs with Hemorrhagic Dysentery and Diarrhea Symptoms in Central China from 2018 to 2021. Viruses 2021, 13, 2282

Recently, a report in Viruses has highlighted the problem of porcine circovirus-like (PCL) virus [...]

Genetic characterization of upper respiratory tract virome from nonvaccinated Egyptian cow-calf operations

Bovine respiratory disease (BRD) is the costliest complex disease affecting the cattle industry worldwide, with significant economic losses. BRD pathogenesis involves several interactions between microorganisms, such as bacteria and viruses, and management factors. The present study aimed to characterize the nasal virome from 43 pooled nasal swab samples collected from Egyptian nonvaccinated cow-calf operations with acute BRD from January to February 2020 using metagenomic sequencing. Bovine herpesvirus-1 (BHV-1), first detection of bovine herpesvirus-5 (BHV-5), and first detection of bovine parvovirus-3 (BPV-3) were the most commonly identified in Egyptian cattle. Moreover, phylogenetic analysis of glycoprotein B revealed that the BHV-1 isolate is closely related to the Cooper reference strain (genotype 1.1), whereas the BHV-5 isolate is closely related to the reference virus GenBank NP_954920.1. In addition, the whole-genome sequence of BPV-3 showed 93.02% nucleotide identity with the reference virus GenBank AF406967.1. In this study, several DNA viruses, such as BHV-1 and first detection BHV-5, and BPV-3, were detected and may have an association with the BRD in Egyptian cattle. Therefore, further research, including investigating more samples from different locations to determine the prevalence of detected viruses and their contributions to BRD in cattle in Egypt, is needed.

The Complexity of Swine Caliciviruses. A Mini Review on Genomic Diversity, Infection Diagnostics, World Prevalence and Pathogenicity

Caliciviruses are single stranded RNA viruses, non-enveloped structurally, that are implicated in the non-bacterial gastroenteritis in various mammal species. Particularly in swine, viral gastroenteritis represents a major problem worldwide, responsible for significant economic losses for the pig industry. Among the wide range of viruses that are the proven or suspected etiological agents of gastroenteritis, the pathogenicity of the members of Caliciviridae family is among the less well understood. In this context, the present review presents and discusses the current knowledge of two genera belonging to this family, namely the Norovirus and the Sapovirus, in relation to swine. Aspects such as pathogenicity, clinical evidence, symptoms, epidemiology and worldwide prevalence, genomic diversity, identification tools as well as interchanging hosts are not only reviewed but also critically evaluated. Generally, although often asymptomatic in pigs, the prevalence of those microbes in pig farms exhibits a worldwide substantial increasing trend. It should be mentioned, however, that the factors influencing the symptomatology of these viruses are still far from well established. Interestingly, both these viruses are also characterized by high genetic diversity. These high levels of molecular diversity in Caliciviridae family are more likely a result of recombination rather than evolutionary or selective adaptation via mutational steps. Thus, molecular markers for their detection are mostly based on conserved regions such as the RdRp region. Finally, it should be emphasized that Norovirus and the Sapovirus may also infect other domestic, farm and wild animals, including humans, and therefore their surveillance and clarification role in diseases such as diarrhea is a matter of public health importance as well.

Isolation, Characterization, and Molecular Detection of Porcine Sapelovirus

Porcine sapelovirus (PSV) is an important emerging pathogen associated with a wide variety of diseases in swine, including acute diarrhoea, respiratory distress, skin lesions, severe neurological disorders, and reproductive failure. Although PSV is widespread, serological assays for field-based epidemiological studies are not yet available. Here, four PSV strains were recovered from diarrheic piglets, and electron microscopy revealed virus particles with a diameter of ~32 nm. Analysis of the entire genome sequence revealed that the genomes of PSV isolates ranged 7569–7572 nucleotides in length. Phylogenetic analysis showed that the isolated viruses were classified together with strains from China. Additionally, monoclonal antibodies for the recombinant PSV-VP1 protein were developed to specifically detect PSV infection in cells, and we demonstrated that isolated PSVs could only replicate in cells of porcine origin. Using recombinant PSV-VP1 protein as the coating antigen, we developed an indirect ELISA for the first time for the detection of PSV antibodies in serum. A total of 516 swine serum samples were tested, and PSV positive rate was 79.3%. The virus isolates, monoclonal antibodies and indirect ELISA developed would be useful for further understanding the pathophysiology of PSV, developing new diagnostic assays, and investigating the epidemiology of the PSV.

Torque Teno Sus Virus (TTSuV) Prevalence in Wild Fauna of Northern Italy

Torque teno sus virus (TTSuV) is a non-enveloped circular ssDNA virus which frequently infects swine and has been associated with hepatic, respiratory, and autoimmune disorders. TTSuV’s pathogenic role is still uncertain, and clear data in the literature on virus reservoirs are lacking. The aims of this study were to investigate the presence of potentially zoonotic TTSuV in wild animals in Northern Italy and to evaluate their role as reservoirs. Liver samples were collected between 2016 and 2020 during four hunting seasons from wild boars (Sus scrofa), red deer (Cervus elaphus), roe deer (Capreolus capreolus), and chamois (Rupicapra rupicapra). Samples originated from areas in Northern Italy characterized by different traits, i.e., mountains and flatland with, respectively low and high farm density and anthropization. Viral identification was carried out by end-point PCR with specific primers for TTSuV1a and TTSuVk2a species. TTSuV prevalence in wild boars was higher in the mountains than in the flatland (prevalence of 6.2% and 2.3%, respectively). In wild ruminants only TTSuVk2a was detected (with a prevalence of 9.4%). Our findings shed light on the occurrence and distribution of TTSuV in some wild animal species, investigating their possible role as reservoirs.

Detection of porcine enteric viruses (Kobuvirus, Mamastrovirus and Sapelovirus) in domestic pigs in Corsica, France

Many enteric viruses are found in pig farms around the world and can cause death of animals or important production losses for breeders. Among the wide spectrum of enteric viral species, porcine Sapelovirus (PSV), porcine Kobuvirus (PKoV) and porcine Astrovirus (PAstV) are frequently found in pig feces. In this study we investigated sixteen pig farms in Corsica, France, to evaluate the circulation of three enteric viruses (PKoV, PAstV-1 and PSV). In addition to the three viruses studied by RT-qPCR (908 pig feces samples), 26 stool samples were tested using the Next Generation Sequencing method (NGS). Our results showed viral RNA detection rates (i) of 62.0% [58.7-65.1] (n = 563/908) for PSV, (ii) of 44.8% [41.5-48.1] (n = 407/908) for PKoV and (iii) of 8.6% [6.8-10.6] (n = 78/908) for PAstV-1. Significant differences were observed for all three viruses according to age (P-value = 2.4e-13 for PAstV-1; 2.4e-12 for PKoV and 0.005 for PSV). The type of breeding was significantly associated with RNA detection only for PAstV-1 (P-value = 9.6e-6). Among the 26 samples tested with NGS method, consensus sequences corresponding to 10 different species of virus were detected. This study provides first insight on the presence of three common porcine enteric viruses in France. We also showed that they are frequently encountered in pigs born and bred in Corsica, which demonstrates endemic local circulation.

Dynamics of the Enteric Virome in a Swine Herd Affected by Non-PCV2/PRRSV Postweaning Wasting Syndrome

A commercial pig farm with no history of porcine circovirus 2 (PCV2) or porcine reproductive and respiratory syndrome virus (PRRSV) repeatedly reported a significant reduction in body weight gain and wasting symptoms in approximately 20–30% of the pigs in the period between three and six weeks after weaning. As standard clinical interventions failed to tackle symptomatology, viral metagenomics were used to describe and monitor the enteric virome at birth, 3 weeks, 4 weeks, 6 weeks, and 9 weeks of age. The latter four sampling points were 7 days, 3 weeks, and 6 weeks post weaning, respectively. Fourteen distinct enteric viruses were identified within the herd, which all have previously been linked to enteric diseases. Here we show that wasting is associated with alterations in the enteric virome of the pigs, characterized by: (1) the presence of enterovirus G at 3 weeks of age, followed by a higher prevalence of the virus in wasting pigs at 6 weeks after weaning; (2) rotaviruses at 3 weeks of age; and (3) porcine sapovirus one week after weaning. However, the data do not provide a causal link between specific viral infections and the postweaning clinical problems on the farm. Together, our results offer evidence that disturbances in the enteric virome at the preweaning stage and early after weaning have a determining role in the development of intestinal barrier dysfunctions and nutrient uptake in the postweaning growth phase. Moreover, we show that the enteric viral load sharply increases in the week after weaning in both healthy and wasting pigs. This study is also the first to report the dynamics and co-infection of porcine rotavirus species and porcine astrovirus genetic lineages during the first 9 weeks of the life of domestic pigs.

An emerging orthopneumovirus detected from dogs with canine infectious respiratory disease in China

Canine infectious respiratory disease (CIRD) is a major cause of morbidity in dogs and is associated with several viral pathogens. The viral diversity associated with CIRD was investigated by analyzing the viral communities from nine CIRD-affected dogs using metagenomics. The results identified 10 mammalian viruses, including canine parvovirus, canid alphaherpesvirus 1, canine kobuvirus, Felis catus papillomavirus 3, canine respiratory coronavirus, canine adenovirus 2, Canis familiaris polyomavirus (DogPyV), canine coronavirus, human papillomavirus and canine pneumovirus (CPnV). Interestingly, CPnV and DogPyV were first discovered in China. Further investigation in 107 samples in China using specific PCR found only two CPnV positive strains in 51 CIRD samples and none in 56 healthy samples. Furthermore, a complete nucleotide sequence of CPnV strain SMU-2020-CB19 and a partial nucleotide sequence of strain SMU-2020-CB14 were obtained. Sequence comparisons and phylogenetic analysis showed that both novel CPnV strains were a close match to the detected swine orthopneumovirus strain in USA, but distantly related to other CPnV strains. Here, the first discovery and characterization of orthopneumovirus in dogs with CIRD in China were reported, highlighting the need for further research on pathogenicity and transmission in China.

Distribution and genetic diversity of Enterovirus G (EV-G) on pig farms in Thailand

Background

Enterovirus G (EV-G) causes subclinical infections and is occasionally associated with diarrhea in pigs. In this study, we conducted a cross-sectional survey of EV-G in pigs from 73 pig farms in 20 provinces of Thailand from December 2014 to January 2018.

Results

Our results showed a high occurrence of EV-Gs which 71.6 % of fecal and intestinal samples (556/777) and 71.2 % of pig farms (52/73) were positive for EV-G by RT-PCR specific to the 5’UTR. EV-Gs could be detected in all age pig groups, and the percentage positivity was highest in the fattening group (89.7 %), followed by the nursery group (89.4 %). To characterize the viruses, 34 EV-G representatives were characterized by VP1 gene sequencing. Pairwise sequence comparison and phylogenetic analysis showed that Thai-EV-Gs belonged to the EV-G1, EV-G3, EV-G4, EV-G8, EV-G9 and EV-G10 genotypes, among which the EV-G3 was the predominant genotype in Thailand. Co-infection with different EV-G genotypes or with EV-Gs and porcine epidemic diarrhea virus (PEDV) or porcine deltacoronavirus (PDCoV) on the same pig farms was observed.

Conclusions

Our results confirmed that EV-G infection is endemic in Thailand, with a high genetic diversity of different genotypes. This study constitutes the first report of the genetic characterization of EV-GS in pigs in Thailand.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12917-021-02988-6.

Molecular characterization of a porcine sapelovirus strain isolated in China

Porcine sapelovirus (PSV) infections have been associated with a wide spectrum of symptoms, ranging from asymptomatic infection to clinical signs including diarrhoea, pneumonia, reproductive disorders, and polioencephalomyelitis. Although it has a global distribution, there have been relatively few studies on PSV in domestic animals. We isolated a PSV strain, SHCM2019, from faecal specimens from swine, using PK-15 cells. To investigate its molecular characteristics and pathogenicity, the genomic sequence of strain SHCM2019 was analysed, and clinical manifestations and pathological changes occurring after inoculation of neonatal piglets were observed. The virus isolated using PK-15 cells was identified as PSV using RT-PCR, transmission electron microscopy (TEM), and immunofluorescence assay (IFA). Sequencing results showed that the full-length genome of the SHCM2019 strain was 7,567 nucleotides (nt) in length, including a 27-nucleotide poly(A) tail. Phylogenetic analysis demonstrated that this virus was a PSV isolate belonging to the Chinese strain cluster. Recombination analysis indicated that there might be a recombination breakpoint upstream of the 3D region of the genome. Pathogenicity experiments demonstrated that the virus isolate could cause diarrhoea and pneumonia in piglets. In breif, a recombinant PSV strain, SHCM2019, was isolated and shown to be pathogenic. Our results may provide a reference for future research on the pathogenic mechanism and evolutionary characteristics of PSV.

Monsavirus in monkey rectal swab and throat swab specimens in China: Proposal for Posaliviridae as a new family in Picornavirales

Posa-like viruses have been detected in the fecal samples of several host species and are considered unclassified members of Picornavirales. Here, we identified genomic fragments of novel posa-like viruses (monsaviruses) in monkey specimens through next generation sequencing and obtained 11 full-length genomes. This monsavirus shared 88.5-89.2% nucleotide similarity with the Tottori-HG1 strain (GenBank accession LC123275). In total, 713 nucleotide polymorphism sites were identified, indicating their persistent evolution during circulation. The genomic organization and phylogenetic relationship of monsavirus were determined. Subsequent phylogenetic analysis of the conserved replication block of Hel-Pro-RdRp and core RNA-dependent RNA polymerase domain-based analysis of posa-like viruses showed significant separation compared with other known families. Further, posa-like virus genomes possessed the classical replication block of picornavirus in the 5' part of genome and picorna-like capsid domains at the structural coding region of 3' part of genome. Based on these results, we proposed the new family Posaliviridae, within Picornavirales. Four genera, which showed 68.6-75.5% amino acid distances but similar genomic organization including the conserved replication block of Hel-Pro-RdRp, the same order of the genomic coding region, and picorna-like capsid domains, were identified. The flexible genomic organization strategy and a large evolutionary scale of Posaliviridae was explicit. This study provides novel information on monsaviruses and important taxonomic data for the family Posaliviridae.

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.

Viral Metagenome-Based Precision Surveillance of Pig Population at Large Scale Reveals Viromic Signatures of Sample Types and Influence of Farming Management on Pig Virome

Pigs are a major meat source worldwide and a pillar of Chinese animal husbandry; hence, their health and safety are a prioritized concern of the national economy. Although pig viruses have been continuously investigated, the full extent of the pig virome has remained unknown and emerging viruses are still a major threat to the pig industry. Here, we report a comprehensive study to delineate the pig virome of 1,841 healthy weaned pigs from 45 commercial farms collected from 25 major pig-producing regions across China. A viromic sequence data set, named Pigs_VIRES, which matched 96,586 viral genes from at least 249 genera within 66 families and which almost tripled the number of previously published pig viromic genes, was established. The majority of the mammalian viruses were closely related to currently known ones. A comparison with previously published viromes of bovines, avians, and humans has revealed the distinct composition of Pigs_VIRES, which has provided characteristic viromic signatures of serum, pharyngeal, and anal samples that were significantly influenced by farming management and disease control measures. Taken together, Pigs_VIRES has revealed the most complete viromic data set of healthy pigs to date. The compiled data also provide useful guidance to pig viral disease control and prevention and the biosafety management of pig farms. Especially, the established viromic protocol has created a precision surveillance strategy to potentially innovate currently used surveillance methods of animal infectious diseases, particularly by making precision surveillance available to other animal species on a large scale or even during a nationwide surveillance campaign.

IMPORTANCE Pigs are deeply involved in human lives; hence, their viruses are associated with public health. Here, we established the most comprehensive virome of healthy piglets to date, which provides a viromic baseline of weaned pigs for disease prevention and control, highlighting that longitudinal viromic monitoring is needed to better understand the dynamics of the virome in pig development and disease occurrence. The present study also shows how high standards of animal farm management with strict biosafety measures can significantly minimize the risk of introduction of pathogenic viruses into pig farms. Particularly, the viromic strategy established, i.e., high-throughput detection and analyses of various known and unknown pathogenic viruses in a single test at large scale, has completely innovated current surveillance measures in provision of timely and precise detection of all potentially existing pathogenic viruses and can be widely applied in other animal species.

Avian leukosis virus subgroup J infection alters viral composition in the chicken gut

Chicken is one of the economically important poultry species. Avian leucosis virus subgroup J (ALV-J) has emerged as a serious cause of mortality and suboptimal performance of domestic chickens. Changes in virome may contribute to pathogenesis. Thus, it is important to investigate the effects of ALV-J infection on the composition of the virome in chicken. In the study metagenomic sequencing was used to characterize the virome of feces collected from the AVL-J infected chickens and the controls. Our results indicated that the chicken gut virome contained a diverse range of viruses that can be found in mammal, reptile, fish, and frogs. Furthermore, at the order, family and genus levels, AVL-J infection significantly altered the chicken gut virome composition. The predominant order was Herpesvirales, accounting for more than 96% of the chicken gut virome. Furthermore, the relative abundance of Caudovirales in the controls was higher than that in the AVL-J-infected chickens. At the family level, the relative abundance of Herpesviridae, Myoviridae, Alloherpesviridae, and Genomoviridae was significantly altered in the AVL-J-infected chickens compared with that in the controls. Additionally, the relative abundance of 15 genera showed a significant difference between the AVL-J-infected chickens and controls. These results will increase our understanding of the viral diversity and changes in the virome of chicken gut, with implications in chicken health.

Identification and genomic characterization of emerging CRESS DNA viruses in thoroughbred horses in China

Multiple novel circular replication-associated protein (Rep)-encoding single stranded (CRESS) DNA viruses have been extensively identified in the feces of humans and animals. Here, we first detected CRESS DNA virus (named Horse-CRESS DNA-like virus, HCLV) in two fecal samples from 10 imported thoroughbred (TB) horses in the customs quarantine station in North Xinjiang province, China. Additionally, we found that this virus was not detected in local breeds (LBs) (0/41) and was found only in imported TB horses (2/73). We obtained the whole-genome sequences of four viruses (HCLV ALSK-3-4, ALSK-13-10, CJ-1-2, and CJ-13-1). Unlike Circovirus and Cyclovirus, whose genome sequences have 1700 to 2100 nucleotides (nt), these HCLVs have circular genome with 3503, 3504, 3485, 3491 nt, respectively and five major ORFs. The ORF1 gene encodes the Rep protein in HCLVs. Furthermore, the Rep protein of the four HCLVs share 23.3-84.8%, 21.6-27.4%, 23.7-27.2% amino acid identity with the corresponding reference viruses of Kirkoviruses, genus Circovirus, and genus Cyclovirus, respectively. Moreover, RCR domain, P-loop NTPase domains, and nonanucleotide motif (TAGTATTAC) of the HCLVs are similar to Circovirus and Cyclovirus. Phylogenetic analysis showed that the virus was grouped together with members in Kirkoviruses. These results suggest the HCLV probably entered Xinjiang province via the international trade of horses.

The Complex Co-infections of Multiple Porcine Diarrhea Viruses in Local Area Based on the Luminex xTAG Multiplex Detection Method

The large-scale outbreaks of severe diarrhea caused by viruses have occurred in pigs since 2010, resulting in great damage to the pig industry. However, multiple infections have contributed to the outbreak of the disease and also resulted in great difficulties in diagnosis and control of the disease. Thus, a Luminex xTAG multiplex detection method, which was more sensitive and specific than general multiplex PCR method, was developed for the detection of 11 viral diarrhea pathogens, including PKoV, PAstV, PEDV, PSaV, PSV, PTV, PDCoV, TGEV, BVDV, PoRV, and PToV. To investigate the prevalence of diarrhea-associated viruses responsible for the outbreaks, a total of 753 porcine stool specimens collected from 9 pig farms in Shanghai during 2015-2018 were tested and the pathogen spectrums and co-infections were analyzed. As a result, PKoV, PAstV and PEDV were most commonly detected viruses in diarrheal pigs with the rate of 38.65% (291/753), 20.32% (153/753), and 15.54% (117/753), respectively. Furthermore, multiple infections were commonly seen, with positive rate of 28.42%. Infection pattern of the viral diarrhea pathogens in a specific farm was changing, and different farms had the various diarrhea infection patterns. A longitudinal investigation showed that PEDV was the key pathogen which was closely related to the death of diarrhea piglets. Other pathogens might play synergistic roles in the pathogenesis of diarrhea disease. Furthermore, the surveillance confirmed that variant enteropathogenic viruses were leading etiologic agents of porcine diarrhea, either mono-infection or co-infections of PKoV were common in pigs in Shanghai, but PEDV was still the key pathogen and multiple pathogens synergistically complicated the infection status, suggesting that controlling porcine diarrhea might be more complex than previously thought. The study provides a better understanding of diarrhea viruses in piglets, which will aid in better preventing and controlling epidemics of viral porcine diarrhea.

Detection and genetic characteristics of porcine bocavirus in central China

To investigate the epidemic profile and genetic diversity of porcine bocavirus (PBoV), 281 clinical samples, including 236 intestinal tissue samples and 45 fecal samples were collected from diarrheic piglets on 37 different pig farms in central China, and two SYBR Green I-based quantitative PCR assays were developed to detect PBoV1/2 and PBoV3/4/5, respectively. One hundred forty-eight (52.67%) of the 281 clinical samples were positive for PBoV1/2, 117 (41.63%) were positive for PBoV3/4/5, 55 (19.57%) were positive for both PBoV1/2 and PBoV3/4/5, and 86.49% (32/37) of the pig farms were positive for PBoV. Overall, the prevalence of PBoV was 74.73% (210/281) in central China. Subsequently, nearly full-length genomic sequences of two PBoV strains (designated CH/HNZM and PBoV-TY) from two different farms were determined. Phylogenetic analysis demonstrated that the two PBoV strains obtained in this study belonged to the PBoV G2 group and had a close relationship to 10 other PBoV G2 strains but differed genetically from PBoV G1, PBoV G3, and seven other bocaviruses. CH/HNZM and PBoV-TY were closely related to the PBoV strain GD18 (KJ755666), which may be derived from the PBoV strains 0912/2012 (MH558677) and 57AT-HU (KF206160) through recombination. Compared with reference strain ZJD (HM053694)-China, more amino acid variation was found in the NS1 proteins of CH/HNZM and PBoV-TY. These data extend our understanding of the molecular epidemiology and evolution of PBoV.

Swine virome on rural backyard farms in Mexico: communities with different abundances of animal viruses and phages

Domestic swine have been introduced by humans into a wide diversity of environments and have been bred in different production systems. This has resulted in an increased risk for the occurrence and spread of diseases. Although viromes of swine in intensive farms have been described, little is known about the virus communities in backyard production systems around the world. The aim of this study was to describe the viral diversity of 23 healthy domestic swine maintained in rural backyards in Morelos, Mexico, through collection and analysis of nasal and rectal samples. Next-generation sequencing was used to identify viruses that are present in swine. Through homology search and bioinformatic analysis of reads and their assemblies, we found that rural backyard swine have a high degree of viral diversity, different from those reported in intensive production systems or under experimental conditions. There was a higher frequency of bacteriophages and lower diversity of animal viruses than reported previously. In addition, sapoviruses, bocaparvoviruses, and mamastroviruses that had not been reported previously in our country were identified. These findings were correlated with the health status of animals, their social interactions, and the breeding/rearing environment (which differed from intensive systems), providing baseline information about viral communities in backyard swine.

Viral communities associated with porcine diarrhoeal disease and genetic characterization of a bufavirus in Tibetan pigs in China

To investigate the viral communities in diarrhoeal faeces of Tibetan pigs, 146 diarrhoeic samples were collected from 16 pigs farms on the Tibetan plateau. Nineteen viruses belonging to eleven viral taxonomic families were identified in a pooled library. Metagenomics analysis revealed that the viruses were mainly small linear and circular DNA viruses. Furthermore, sequences of 10 NS1 genes and two complete genomes of PBuVs were obtained by PCR amplification. Sequence comparisons and phylogenetic analysis showed that the PBuVs from Tibetan pigs displayed more abundant genetic diversity than those from domestic pigs. This is the first description of the faecal viral community in Tibetan pigs associated with diarrhoea.

A plate of viruses: Viral metagenomics of supermarket chicken, pork and beef from Brazil

A viral metagenomics study was conducted in beef, pork, and chicken sold in supermarkets from Southern Brazil. From chicken, six distinct gyroviruses (GyV) were detected, including GyV3 and GyV6, which for the first time were detected in samples from avian species, plus a novel smacovirus species and two highly divergent circular Rep-encoding ssDNA (CRESS-DNA) viruses. From pork, genomes of numerous anelloviruses, porcine parvovirus 5 (PPV5) and 6 (PPV6), two new genomoviruses and two new CRESS-DNA viruses were found. Finally, two new CRESS-DNA genomes were recovered from beef. Although none of these viruses have history of transmission to humans, the findings reported here reveal that such agents are inevitably consumed in diets that include these types of meat.

Treatments of porcine fecal samples affect high-throughput virome sequencing results

The porcine enteric microbiota is currently extensively studied, taking advantage of developments in high-throughput sequencing technologies. However, the viral part of the microbiota, the virome, is being lightly explored, and the impact of the pretreatments used before sequencing the viruses is barely considered. In this study, the impacts of filtration, RNase and DNase treatments on virus reads recovery and diversity after sequencing on a MiSeq platform were assessed on fecal samples individually taken at <3, 5, 12 and 20 weeks from two piglets. None of the four pretreatment series affected the virus read averages or influenced diversity, but the samples with the higher proportion of reads corresponding to an entry in the "nt" database were those receiving the least number of pretreatments. The enzymatic pretreatments affected the detection of the single-stranded RNA viruses of Aichivirus C, porcine astrovirus, Sapovirus and posavirus, which is worrisome, as these viruses can be involved in swine diarrhea. If enzymatic pretreatments are used when sequencing using a high-throughput method, it may impact single-stranded RNA virus recovery, but not the overall virome diversity. Therefore, filtrated samples may be the better option, reducing the amount of bacterial genetic material while preserving the virus reads.

Genotypic Characteristics and Correlation of Epidemiology of Staphylococcus aureus in Healthy Pigs, Diseased Pigs, and Environment

China is one of the largest producers of pigs and pork in the world. However, large-scale studies on pig-associated Staphylococcus aureus in relation to healthy pigs, diseased pigs and environment are scarce. The objective of the present study was to characterize and compare S. aureus isolates from healthy pigs, diseased pigs and environment through antimicrobial susceptibility testing, multiple locus sequence typing, spa typing, and antimicrobial resistance gene screening. Results showed all isolates were susceptible to linezolid and vancomycin. However, 66.7% (104/156) isolates were multidrug-resistant by displaying resistance to three or more antibiotics and high rates of resistance to penicillin, tetracycline, clindamycin, and clarithromycin were observed. Of the 20 multilocus sequence types (STs) identified among the isolates, ST9, ST188, and ST7 were most commonly isolated from healthy pigs and environment, while ST1 was most commonly isolated from diseased pigs. In total, 17 spa types were represented among the isolates, while t4792 was most commonly isolated from diseased pigs and t899, t189 were most commonly isolated from healthy pigs and environment. In conclusion, the genotypic and epidemiology characteristics observed among the isolates suggest pigs and pork could be important players in S. aureus dissemination.

Picobirnaviruses: prevalence, genetic diversity, detection methods

This article presents a general overview of the prevalence, genetic diversity and detection methods of picobirnaviruses (PBVs), which are small, non-enveloped icosahedral viruses with a segmented double-stranded RNA genome consisting of two segments taxonomically related to the genus Picobirnavirus of the family Picobirnaviridae. This review of scientific papers published in 1988-2019 provides data on the PBV distribution in the nature and a broad host range. PBV infection is characterized as opportunistic, the lack of understanding of the etiological role of PBVs in diarrhea is emphasized, since these viruses are detected both in symptomatic and asymptomatic cases. The concept of PBV infection as a chronic disease caused by a long-lasting persistence of the virus in the host is considered. Such factors as stress syndrome, physiological conditions, immune status and host age at the time of primary PBV infection influence the virus detection rate in humans and animals. The possible zoonotic nature of human PBV infection is noted due to the capacity for interspecies PBV transmission acquired during evolution as a result of the reassortment of the genome segments of different viruses infecting the same host. Data providing evidence that PBVs belong to eukaryotes and a challenging hypothesis stating that PBVs are bacterial viruses are presented. The need to intensify work on PBV detection because of their wide distribution, despite the complexity due to the lack of the cultivation system, is emphasized. Two strategies of RT-PCR as main PBV detection methods are considered. The genomes of individual representatives of the genus isolated from different hosts are characterized. Emphasis is placed on the feasibility of developing primers with broader specificity for expanding the range of identifiable representatives of the genus PBV due to a huge variety of their genotypes. The importance of effective monitoring of PBV prevalence for studying the zoonotic and anthroponotic potential using metagenomic analysis is highlighted, and so is the possibility of using PBV as a marker for environmental monitoring.

Co-infection status of novel parvovirus's (PPV2 to 4) with porcine circovirus 2 in porcine respiratory disease complex and porcine circovirus-associated disease from 1997 to 2012

As global pig health diseases, porcine respiratory disease complex (PRDC) and porcine circovirus-associated disease (PCVAD) generate substantial economic losses despite pigs been vaccinated against the primary causative virus, highlighting the importance of understanding virome interactions and specifically co-factor infections. Established primary endemic pathogens for PRDC include porcine circovirus 2 (PCV2), porcine reproductive and respiratory syndrome virus (PRRSv) and swine influenza virus (SIV), and PCV2 aetiology in interaction with other co-infecting viruses can result in PCVAD. Porcine parvovirus (PPV) 1 is a well-characterized virus with an available vaccine preventing reproductive failure in sows. However, whilst novel PPV 2 to 7 viruses have been identified since 2001, their viral pathogenic potential in clinical and subclinical disease remains to be determined. Therefore, this study has sought to develop a better understanding of their potential role as associated co-infections in PRDC and PCVAD by examining archival samples for the presence of PCV2 and the novel parvoviruses PPV2-4 from clinically diseased pigs across production age stages. Epidemiologically, the novel PPV2 was found to be the most prevalent within the fattener age group with PPV2-4 statistically associated with pig respiratory disease and enteric ulcers. Additionally, statistical modelling by latent class analysis (LCA) on veterinary pathology scored pigs found a clustering co-factor association between PPV2 and PCV2, suggesting the novel PPV may be involved in PRDC and PCVAD. Phylogenetic analysis of novel PPVs revealed the PPV2 capsid evolution to be diverged from the original strains with a low nucleotide homology of 88%-96% between two distinct clades. These findings determine that novel PPV 2-4 viruses are statistically associated as co-infectors in a diseased pig population, and significantly detected PPV2 clustering co-infection frequency with PCV2 in PRDC and PCVAD diseased pigs through LCA analysis.

The Husavirus Posa-Like Viruses in China, and a New Group of Picornavirales

Novel posa-like viral genomes were first identified in swine fecal samples using metagenomics and were designated as unclassified viruses in the order Picornavirales. In the present study, nine husavirus strains were identified in China. Their genomes share 94.1–99.9% similarity, and alignment of these nine husavirus strains identified 697 nucleotide polymorphism sites across their full-length genomes. These nine strains were directly clustered with the Husavirus 1 lineage, and their genomic arrangement showed similar characteristics. These posa-like viruses have undergone a complex evolutionary process, and have a wide geographic distribution, complex host spectrum, deep phylogenetic divergence, and diverse genomic organizations. The clade of posa-like viruses forms a single group, which is evolutionarily distinct from other known families and could represent a distinct family within the Picornavirales. The genomic arrangement of Picornavirales and the new posa-like viruses are different, whereas the posa-like viruses have genomic modules similar to the families Dicistroviridae and Marnaviridae. The present study provides valuable genetic evidence of husaviruses in China, and clarifies the phylogenetic dynamics and the evolutionary characteristics of Picornavirales.

Increased viral read counts and metagenomic full genome characterization of porcine astrovirus 4 and Posavirus 1 in sows in a swine farm with unexplained neonatal piglet diarrhea

Neonatal diarrhea in piglets may cause major losses in affected pig herds. The present study used random high-throughput RNA sequencing (metagenomic next generation sequencing, mNGS) to investigate the virome of sows from a farm with persistent neonatal piglet diarrhea in comparison to two control farms without diarrhea problems. A variety of known swine gastrointestinal viruses was detected in the control farms as well as in the problem farm (Mamastrovirus, Enterovirus, Picobirnavirus, Posavirus 1, Kobuvirus, Proprismacovirus). A substantial increase in normalized viral read counts was observed in the affected farm compared to the control farms. The increase was attributable to a single viral species in each of the sampled sows (porcine astrovirus 4 and Posavirus 1). The complete genomes of a porcine astrovirus 4 and two co-infecting Posavirus 1 were de novo assembled and characterized. The 6734 nt single-stranded RNA genome of porcine astrovirus 4 (PoAstV-4) strain Belgium/2019 contains three overlapping open reading frames (nonstructural protein 1ab, nonstructural protein 1a, capsid protein). Posavirus 1 strains Belgium/01/2019 and Belgium/02/2019 have a 9814 nt single-stranded positive-sense RNA genome encoding a single open reading frame (polyprotein precursor) containing the five expected Picornavirales-conserved protein domains. The study highlights the potential of mNGS workflows to study unexplained neonatal diarrhea in piglets and contributes to the scarce availability of both PoAstV-4 and Posavirus-1 whole genome sequences from Western Europe.

Enteroviruses in gastrointestinal diseases

Gastrointestinal diseases including diarrhoea constitute a major cause of morbidity and mortality in infants and young children especially in developing countries. Worldwide deaths among all ages due to diarrhoea during 2015 were estimated to be about 1.31 million, diarrhoeal deaths in children below 5 years of age being 499 000. Rotavirus accounted for about 200 000 deaths. Although diarrhoeal deaths decreased significantly during the last two decades, they still represent the third largest cause of infantile deaths. Several bacterial, viral, parasitic, fungal and non-infectious diarrhoea causing agents have been identified, but 30% to 40% of diarrhoeal cases remain undiagnosed. Enteroviruses transmit by the faecal-oral route and replicate first in intestinal cells before spreading to the target organ. They have been associated with diarrhoea in a few studies, but their causative role in diarrhoea in humans has not been systematically demonstrated. In view of the recent demonstration that enteroviruses cause diarrhoea in newborn mice pups, thus validating Koch's postulates, the purpose of this review is to emphasise the importance of recognising enteroviruses as major gastrointestinal pathogens associated with acute and persistent diarrhoea and non-diarrhoeal increased frequency of bowel movements in infants, young children and adults. Our studies and several other subsequent studies reported from different countries should stimulate strategies to reduce the burden of infantile gastrointestinal disease, which has hitherto remained unaddressed.

Development of a duplex SYBR GreenⅠ based real-time PCR assay for detection of porcine epidemic diarrhea virus and porcine bocavirus3/4/5

The duplex real-time PCR assay based on SYBR Green І was developed for detection of porcine epidemic diarrhea virus (PEDV) and porcine bocavirus (PBoV) 3/4/5 genotypes simultaneously. Two pairs of specific primers were designed targeting the N gene sequence of PEDV and VP1 gene sequence of PBoV3/4/5. PEDV and PBoV3/4/5 could be distinguished by their different melting temperatures (Tm) in one sample. The Tm value of PEDV was 83.5 °C, and the Tm value of PBoV3/4/5 was 78.5 °C, while other swine pathogens showed no specific melting peaks. The detection limits of this assay were 10 copies/μL for both PEDV and PBoV3/4/5. A total of sixty-three intestinal tissue samples were collected from piglets suffering from diarrhea, and the viral nucleic acids detected and identified by the real-time PCR assay and conventional PCR assay. The duplex real-time PCR detection results showed that the prevalence of PEDV and PBoV3/4/5 was 85.7% and 46%, respectively, and the co-infection rate of the two viruses was 28.6%. These results indicated that this duplex real-time PCR assay was a sensitive, specific and reproducible method for differentiating PEDV and PBoV3/4/5 or their co-infection.

Porcine sapoviruses: Pathogenesis, epidemiology, genetic diversity, and diagnosis

The first porcine Sapovirus (SaV) Cowden strain was discovered in 1980. To date, eight genogroups (GIII, V-IX) and three genogroups (GIII, GV, and GVI) of porcine SaVs have been detected from domestic pigs worldwide and wild boars in Japan, respectively based on the capsid sequences. Although GIII Cowden strain replicated in the villous epithelial cells and caused intestinal lesions in the proximal small intestines (mainly in duodenal and less in jejunum), leading to mild to severe diarrhea, in the orally inoculated neonatal gnotobiotic pigs, the significance of porcine SaVs in different ages of pigs with diarrhea in the field is still undetermined. This is due to two reasons: 1) similar prevalence of porcine SaVs was detected in diarrheic and non-diarrheic pigs; and 2) co-infection of porcine SaVs with other enteric pathogens is common in pigs. Diagnosis of porcine SaV infection is mainly based on the detection of viral nucleic acids using reverse transcription (RT)-PCR and sequencing. Much is unknown about these genetically diverse viruses to understand their role in pig health and to evaluate whether vaccines are needed to prevent SaV infection.

Torque teno viruses in health and disease

Torque teno viruses (TTVs) are small, ubiquitous, viruses with a highly diverse, single-stranded, negative sense DNA genome and wide host range. They are detected at high rates in both healthy and diseased individuals and are considered a significant part of the mammalian virome. Similar to human TTVs, swine TTVs (TTSuVs) are epidemiologically linked to several coinfections including porcine circovirus types 2 and 3 and the porcine reproductive and respiratory disease syndrome virus. Experimental infection of gnotobiotic pigs with TTSuVs resulted in lesions in multiple organs and exacerbation of coinfections, making TTSuVs the only members of the Anelloviridae family with experimental evidence for pathogenicity. However, due to the lack of reliable cell culture and animal models, mechanistic studies on viral immunity and pathogenesis are limited. The objective of this review is to summarize the current status of knowledge regarding the biology, detection, pathogenesis and public health significance of TTSuVs, while identifying gaps in knowledge which limit the field.