High prevalence, genetic diversity and a potentially novel genotype of Sapelovirus A (Picornaviridae) in enteric and respiratory samples in Hungarian swine farms

Non-Targeted RNA Sequencing: Towards the Development of Universal Clinical Diagnosis Methods for Human and Veterinary Infectious Diseases

Metagenomics offers the potential to replace and simplify classical methods used in the clinical diagnosis of human and veterinary infectious diseases. Metagenomics boasts a high pathogen discovery rate and high specificity, advantages absent in most classical approaches. However, its widespread adoption in clinical settings is still pending, with a slow transition from research to routine use. While longer turnaround times and higher costs were once concerns, these issues are currently being addressed by automation, better chemistries, improved sequencing platforms, better databases, and automated bioinformatics analysis. However, many technical options and steps, each producing highly variable outcomes, have reduced the technology's operational value, discouraging its implementation in diagnostic labs. We present a case for utilizing non-targeted RNA sequencing (NT-RNA-seq) as an ideal metagenomics method for the detection of infectious disease-causing agents in humans and animals. Additionally, to create operational value, we propose to identify best practices for the "core" of steps that are invariably shared among many human and veterinary protocols. Reference materials, sequencing procedures, and bioinformatics standards should accelerate the validation processes necessary for the widespread adoption of this technology. Best practices could be determined through "implementation research" by a consortium of interested institutions working on common samples.

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.

Development and application of a low-priced duplex quantitative PCR assay based on SYBR Green I for the simultaneous detection of porcine deltacoronavirus and porcine sapelovirus

Porcine deltacoronavirus (PDCoV) and porcine sapelovirus (PSV) are two viruses that can cause diarrhoea in pigs and bring great economic loss to the pig industry. In this research, a duplex real-time quantitative polymerase chain reaction (qPCR) assay based on SYBR Green I was developed to simultaneously detect PDCoV and PSV. No specific melting peaks were found in other porcine diarrhoea-associated viruses, indicating that the method developed in this study had good specificity. The detection limits of PDCoV and PSV were 1.0 × 101 copies μl-1 and 1.0 × 102 copies μl-1, respectively. The duplex real-time qPCR assay tested two hundred and three (203) intestinal and faecal samples collected from diarrhoeal and asymptomatic pigs. The positive rates of PDCoV and PSV were 20.2% and 23.2%, respectively. The co-infection rate of PDCoV and PSV was 13.8%. To evaluate the accuracy of the developed method, conventional PCR and singular TaqMan real-time qPCR assays for PDCoV/PSV were also used to detect the samples. The results showed that the duplex real-time qPCR assay was consistent with the singular assays, but its sensitivity was higher than conventional PCR methods. This duplex real-time qPCR assay provides a rapid, sensitive and reliable method in a clinic to simultaneously detect PDCoV and PSV.

Virome Analysis for Identification of a Novel Porcine Sapelovirus Isolated in Western China

Diarrhea is one of the most important problems associated with the production of piglets, which have a wide range of possible pathogens. This study identified a strain of porcine sapelovirus (PSV) by using next-generation sequencing (NGS) technologies as the pathogen among fecal samples in a pig herd. Phylogenetic analysis showed that the PSV isolates shared a unique polyprotein and clustered with Chinese isolates identified before 2013. The PSV strain was then isolated and named GS01. The in vitro and in vivo biological characteristics of this virus were then described. Our pathogenicity investigation showed that GS01 could cause an inflammatory reaction and induce serious diarrhea in neonatal piglets. To our knowledge, this is the first isolation and characterization of PSV in western China. Our results demonstrate that the PSV GS01 strain is destructive to neonatal piglets and might show an expanded role for sapeloviruses.

IMPORTANCE Porcine sapelovirus (PSV) infection leads to severe polioencephalomyelitis with high morbidity and mortality, resulting in significant economic losses. In previous studies, PSV infections were always subclinical or only involved a series of mild symptoms, including spinal cord damage, inappetence, diarrhea, and breathless. However, in our study, we isolated a novel PSV by virome analysis. We also determined the biological characteristics of this virus in vitro and in vivo. Our study showed that this novel PSV could cause an inflammatory response and induce serious diarrhea in neonatal piglets. To our knowledge, this is the first isolation and characterization of PSV in western China. These findings highlight the importance of prevention for the potential threats of PSV.

Development and Large-Scale Testing of a Novel One-Step Triplex RT-qPCR Assay for Simultaneous Detection of “Neurotropic” Porcine Sapeloviruses, Teschoviruses (Picornaviridae) and Type 3 Porcine Astroviruses (Astroviridae) in Various Samples including Nasal Swabs

Porcine sapeloviruses, teschoviruses of family Picornaviridae and type 3 porcine astroviruses of family Astroviridae are (re-)emerging enteric pathogens that could be associated with severe, disseminated infections in swine, affecting multiple organs including the central nervous system (CNS). Furthermore, small-scale pioneer studies indicate the presence of these viruses in porcine nasal samples to various extents. The laboratory diagnostics are predominantly based on the detection of the viral RNA from faecal and tissue samples using different nucleic-acid-based techniques such as RT-qPCR. In this study, a novel highly sensitive one-step triplex RT-qPCR assay was introduced which can detect all known types of neurotropic sapelo-, tescho- and type 3 astroviruses in multiple types of samples of swine. The assay was evaluated using in vitro synthesized RNA standards and a total of 142 archived RNA samples including known sapelo-, tescho- and type 3 astrovirus positive and negative CNS, enteric and nasal specimens. The results of a large-scale epidemiological investigation of these viruses on n = 473 nasal swab samples from n = 28 industrial-type swine farms in Hungary indicate that all three neurotropic viruses, especially type 3 astroviruses, are widespread and endemically present on most of the investigated farms.

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.

Discovery of Novel Viruses Associated With the Invasive Cane Toad (Rhinella marina) in Its Native and Introduced Ranges

Cane toads (Rhinella marina) are notoriously successful invaders: from 101 individuals brought to Australia in 1935, poisonous toads now cover an area >1.2 million km² with adverse effects on native fauna. Despite extensive research on the role of macroparasites in cane toad invasion, viral research is lagging. We compared viral prevalence and diversity between toads in their native range (French Guiana, n=25) and two introduced ranges: Australia (n=151) and Hawai'i (n=10) with a metatranscriptomic and metagenomic approach combined with PCR screening. Australian toads almost exclusively harbor one of seven viruses detected globally. Rhimavirus-A (Picornaviridae) exhibited low genetic diversity and likely actively infected 9% of sampled Australian toads extending across ~2,000km of Northern Australia and up to the current invasion front. In native range cane toads, we identified multiple phylogenetically distinct viruses (Iridoviridae, Picornaviridae, Papillomaviridae, and Nackedna-like virus). None of the same viruses was detected in both ranges, suggesting that Australian cane toads have largely escaped the viral infection experienced by their native range counterparts. The novel native range viruses described here are potential biocontrol agents, as Australian toads likely lack prior immunological exposure to these viruses. Overall, our evidence suggests that there may be differences between viruses infecting cane toads in their native vs. introduced ranges, which lays the groundwork for further studies on how these viruses have influenced the toads' invasion history.

Characterization of porcine sapelovirus prevalent in western Jiangxi, China

BACKGROUND

Porcine sapelovirus (PSV) infection can lead severe polioencephalomyelitis with high morbidity and mortality, which result in significant economic losses. Infection with the PSV is believed to be common yet limited information is available on the prevalence and molecular characterization of PSV in China. Therefore, the objective of this study was to characterize the prevalence and genome of PSV strains identified in the western Jiangxi province of China.

RESULTS

A high specificity and sensitivity SYBR Green I-based RT-PCR method for PSV detection was developed. Two hundred and ninety four fecal samples were collected from December 2018 to March 2019 in 4 farms. An overall PSV-positivity rate of 11.22% (33/294) was detected with the real-time RT-PCR method, and a high infection rate and viral load of PSV were found in nursery pigs. In total, complete VP1 gene sequences of 11 PSV strains (PSV-YCs) were obtained. Homology comparisons of the VP1 gene of the 11 PSV-YCs with previously reported PSVs revealed nucleotide sequence identities ranging from 63% to 96.8%, and deduced amino acid sequence identities from 61.4% to 99.7%. Phylogenetic analyses based on the VP1 gene exhibited 2 main clades corresponding to PSV-1 and PSV-2, and all PSV-YCs prevalent in western Jiangxi belonged to the traditional genotype (PSV-1). In addition, the pairwise distances of VP1 gene sequences between PSV-YCs ranged from 0.009 to 0.198, which indicating that substantial genetic diversity among the PSVs in western Jiangxi.

CONCLUSIONS

To the authors' knowledge, this is the first description of PSV in the Jiangxi province pig herds in China, and it is crucial to understand the epidemiology of the viruses in China. The results also provide an important theoretical foundation for diagnosis and early warning of epidemic diseases caused by PSVs prevailing in this region.

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.

Porcine teschovirus, sapelovirus, and enterovirus in Swiss pigs: multiplex RT-PCR investigation of viral frequencies and disease association

Porcine teschovirus (PTV), sapelovirus (PSV-A), and enterovirus (EV-G) are enteric viruses that can infect pigs and wild boars worldwide. The viruses have been associated with several diseases, primarily gastrointestinal, neurologic, reproductive, and respiratory disorders, but also with subclinical infections. However, for most serotypes, proof of a causal relationship between viral infection and clinical signs is still lacking. In Switzerland, there has been limited investigation of the occurrence of the 3 viruses. We used a modified multiplex reverse-transcription PCR protocol to study the distribution of the viruses in Swiss pigs by testing 363 fecal, brain, and placental or abortion samples from 282 healthy and diseased animals. We did not detect the 3 viruses in 94 placental or abortion samples or in 31 brain samples from healthy pigs. In brain tissue of 81 diseased pigs, we detected 5 PSV-A and 4 EV-G positive samples. In contrast, all 3 viruses were detected at high frequencies in fecal samples of both healthy and diseased pigs. In healthy animals, PTV was detected in 47%, PSV-A in 51%, and EV-G in 70% of the 76 samples; in diseased animals, frequencies in the 81 samples were 54%, 64%, and 68%, respectively. The viruses were detected more frequently in fecal samples from weaned and fattening pigs compared to suckling piglets and sows. Co-detections of all 3 viruses were the most common finding. Based on clinical and pathology data, statistical analysis yielded no evidence for an association of virus detection and disease. Further research is required to determine if pathogenicity is linked to specific serotypes of these viruses.

Detection and Characterization of Porcine Sapelovirus in Italian Pig Farms

Simple Summary

Sapelovirus (PSV) is known to infect pigs asymptomatically but, sporadically, can cause reproductive failure and severe neurologic, enteric, or respiratory signs. Sapelovirus infections have been reported worldwide in pigs. However, information about PSV circulation in Italy is unavailable and rarely investigated across Europe. In this study, we reported the circulation of PSV in three Italian pig farms and added novel information about evolutionary heterogeneity of PSV strains showing a low genetic correlation with the other strains detected worldwide. The present study gives information about PSV circulation in intensive pig farms and highlights the need for further investigation.

Abstract

Porcine sapelovirus (PSV) belongs to the genus Sapelovirus of the family Picornaviridae. PSV infects pigs asymptomatically, but it can also cause severe neurologic, enteric, and respiratory symptoms or reproductive failure. Sapelovirus infections have been reported worldwide in pigs. The objective of this study was to investigate the presence and the prevalence of PSV in Italian swine farms in animals of different ages to clarify the occurrence of the infection and the genetic characteristics of circulating strains. In the present study, 92 pools of fecal samples, collected from pigs across three farms, were analyzed by Reverse Transcriptase-polymerase Chain Reaction-PCR (RT-PCR). Fecal pools from young growers (63/64) were found positive for Sapelovirus in all farms while detection in sows (4/28) was observed in only one farm. Phylogenetic analyses of the 19 partial capsid protein nucleotide sequences (VP1) (6–7 each farm) enable the classification of the virus sequences into three distinct clades and highlighted the high heterogeneity within one farm. The whole genome sequence obtained from one strain showed the highest correlation with the Italian strain detected in 2015. The study adds novel information about the circulation and heterogeneity of PSV strains in Italy and considering the movement of pigs across Europe would also be informative for other countries.