Development of a SYBR green-based real-time RT-PCR assay for rapid detection of the emerging swine acute diarrhea syndrome coronavirus

Emerging Trends of Gold Nanostructures for Point-of-Care Biosensor-Based Detection of COVID-19

In 2019, a worldwide pandemic caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) emerged. SARS-CoV-2 is the deadly microorganism responsible for coronavirus disease 2019 (COVID-19), which has caused millions of deaths and irreversible health problems worldwide. To restrict the spread of SARS-CoV-2, accurate detection of COVID-19 is essential for the identification and control of infected cases. Although recent detection technologies such as the real-time polymerase chain reaction delivers an accurate diagnosis of SARS-CoV-2, they require a long processing duration, expensive equipment, and highly skilled personnel. Therefore, a rapid diagnosis with accurate results is indispensable to offer effective disease suppression. Nanotechnology is the backbone of current science and technology developments including nanoparticles (NPs) that can biomimic the corona and develop deep interaction with its proteins because of their identical structures on the nanoscale. Various NPs have been extensively applied in numerous medical applications, including implants, biosensors, drug delivery, and bioimaging. Among them, point-of-care biosensors mediated with gold nanoparticles (GNPSs) have received great attention due to their accurate sensing characteristics, which are widely used in the detection of amino acids, enzymes, DNA, and RNA in samples. GNPS have reconstructed the biomedical application of biosensors because of its outstanding physicochemical characteristics. This review provides an overview of emerging trends in GNP-mediated point-of-care biosensor strategies for diagnosing various mutated forms of human coronaviruses that incorporate different transducers and biomarkers. The review also specifically highlights trends in gold nanobiosensors for coronavirus detection, ranging from the initial COVID-19 outbreak to its subsequent evolution into a pandemic.

A multiplex real-time RT-qPCR assay for simultaneous detection of porcine epidemic diarrhea virus, porcine deltacoronavirus, and swine acute diarrhea syndrome coronavirus

Porcine epidemic diarrhea virus (PEDV), porcine deltacoronavirus (PDCoV), and swine acute diarrhea syndrome coronavirus (SADS-CoV) cause intestinal diseases with similar manifestations in suckling piglets. In this study, we developed a multiplex real-time PCR for differential diagnosis of PEDV, PDCoV, and SADS-CoV. The assay demonstrated high specificity with a detection limit of 5 copies/µl for each virus. The assay specifically detected PEDV, PDCoV, and SADS-CoV and excluded all other swine pathogens circulating in pigs. Furthermore, the assay exhibited satisfactory performance in analyzing clinical samples. The data indicate that the newly developed multiplex real-time PCR method can be applied for differential diagnosis of porcine enteric coronaviruses.

Research Advances on Swine Acute Diarrhea Syndrome Coronavirus

Swine acute diarrhea syndrome coronavirus (SADS-CoV) is a virulent pathogen that causes acute diarrhea in piglets. The virus was first discovered in Guangdong Province, China, in 2017 and has since emerged in Jiangxi, Fujian, and Guangxi Provinces. The outbreak exhibited a localized and sporadic pattern, with no discernable temporal continuity. The virus can infect human progenitor cells and demonstrates considerable potential for cross-species transmission, representing a potential risk for zoonotic transmission. Therefore, continuous surveillance of and comprehensive research on SADS-CoV are imperative. This review provides an overview of the temporal and evolutionary features of SADS-CoV outbreaks, focusing on the structural characteristics of the virus, which serve as the basis for discussing its potential for interspecies transmission. Additionally, the review summarizes virus-host interactions, including the effects on host cells, as well as apoptotic and autophagic behaviors, and discusses prevention and treatment modalities for this viral infection.

The Significance and Importance of dPCR, qPCR, and SYBR Green PCR Kit in the Detection of Numerous Diseases

Digital PCR (dPCR) is the latest technique that has become commercially accessible for various types of research. This method uses Taq polymerase in a standard polymerase chain reaction (PCR) to amplify a target DNA fragment from a complex sample, like quantitative PCR (qPCR) and droplet digital PCR (dd- PCR). ddPCR may facilitate microRNA (miRNA) measurement, particularly in liquid biopsy, because it has been proven to be more effective and sensitive, and in this method, ddPCR can provide an unprecedented chance for deoxyribonucleic acid (DNA) methylation research because of its capability to increase sensitivity and precision over conventional PCR-based methods. qPCR has also been found to be a valuable standard technique to measure both copy DNA (cDNA) and genomic DNA (gDNA) levels, although the finding data can be significantly variable and non-reproducible without relevant validation and verification of both primers and samples. The SYBR green quantitative real-time PCR (qPCR) method has been reported as an appropriate technique for quantitative detection and species discrimination, and has been applied profitably in different experiments to determine, quantify, and discriminate species. Although both TaqMan qRT-PCR and SYBR green qRT-PCR are sensitive and rapid, the SYBR green qRT-PCR assay is easy and the TaqMan qRT-PCR assay is specific but expensive due to the probe required. This review aimed to introduce dPCR, qPCR, SYBR green PCR kit, and digital PCR, compare them, and also introduce their advantages in the detection of different diseases.

Molecular Characterization of Porcine Epidemic Diarrhea Virus from Field Samples in South Korea

Porcine epidemic diarrhea virus (PEDV) is a highly contagious enteric pathogen of swine. PEDV has been a major problem in the pig industry since its first identification in 1992. The aim of this study was to investigate the diversity, molecular characteristics, and phylogenetic relationships of PEDVs in field samples from Korea. Six PEDVs were identified from the field samples, and the full spike (S) glycoprotein gene sequences were analyzed. A phylogenetic analysis of the S gene sequences from the six isolates revealed that they were clustered into the G2b subgroup with genetic distance. The genetic identity of the nucleotide sequences and deduced amino acid sequences of the S genes of those isolates was 97.9-100% and 97.4-100%, respectively. A BLAST search for new PEDVs revealed an identity greater than 99.5% compared to the highest similarity of two different Korean strains. The CO-26K equivalent (COE) epitope had a 521H→Y/Q amino acid substitution compared to the subgroup G2b reference strain (KNU-1305). The CNU-22S11 had 28 amino acid substitutions compared to the KNU-1305 strain, which included two newly identified amino acid substitutions: 562S→F and 763P→L in the COE and SS6 epitopes, respectively. Furthermore, the addition and loss of N-linked glycosylation were observed in the CNU-22S11. The results suggest that various strains of PEDV are prevalent and undergoing evolution at swine farms in South Korea and can affect receptor specificity, virus pathogenicity, and host immune system evasion. Overall, this study provides an increased understanding of the prevalence and control of PEDV in South Korea.

A Customized Novel Blocking ELISA for Detection of Bat-Origin Swine Acute Diarrhea Syndrome Coronavirus Infection

Swine acute diarrhea syndrome coronavirus (SADS-CoV) is a newly discovered emerging alphacoronavirus. SADS-CoV shares over 90% genome sequence identity with bat alphacoronavirus HKU2. SADS-CoV was associated with severe diarrhea and high mortality rates in piglets. Accurate serological diagnosis of SADS-CoV infection is key in managing the emerging SADS-CoV. However, thus far there have been no effective antibody-based diagnostic tests for diagnose of SADS-CoV exposure. Here, monoclonal antibody (MAb) 6E8 against SADS-CoV N protein accurately recognized SADS-CoV infection. Then, MAb 6E8 was utilized as a blocking antibody to develop blocking ELISA (bELISA). We customized the rN coating antigen with concentration 0.25 μg/mL. According to receiver operator characteristic curve analysis, the cutoff value of the bELISA was determined as 38.19% when the max Youden index was 0.955, and specificity was 100%, and sensitivity was 95.5%. Specificity testing showed that there was no cross-reactivity with other serum positive swine enteric coronaviruses, such as porcine epidemic diarrhea virus (PEDV), transmissible gastroenteritis virus (TGEV), porcine deltacoronavirus (PDCoV), porcine rotavirus (PoRV), and porcine sapelovirus (PSV). In conclusion, we customized a novel and high-quality blocking ELISA for detection of SADS-CoV infection, and the current bELISA will be linked to a clinical and epidemiological assessment of SADS-CoV infection. IMPORTANCE SADS-CoV was reported to be of high potential for dissemination among various of host species. Accurate serological diagnosis of SADS-CoV infection is key in managing the emerging SADS-CoV. However, thus far there have been no effective antibody-based diagnostic tests for diagnose of SADS-CoV exposure. We customed a novel and high-quality bELISA assay for detection of SADS-CoV N protein antibodies, and the current bELISA will be linked to a clinical and epidemiological assessment of SADS-CoV infection.

Development of a novel double-antibody sandwich quantitative ELISA for detecting SADS-CoV infection

Swine acute diarrhea syndrome coronavirus (SADS-CoV) is an emerging swine enteric alphacoronavirus that can cause acute diarrhea, vomiting, dehydration, and death of newborn piglets. In this study, we developed a double-antibody sandwich quantitative enzyme-linked immunosorbent assay (DAS-qELISA) for detection of SADS-CoV by using an anti-SADS-CoV N protein rabbit polyclonal antibody (PAb) and a specific monoclonal antibody (MAb) 6E8 against the SADS-CoV N protein. The PAb was used as the capture antibodies and HRP-labeled 6E8 as the detector antibody. The detection limit of the developed DAS-qELISA assay was 1 ng/mL of purified antigen and 10^1.08TCID₅₀/mL of SADS-CoV, respectively. Specificity assays showed that the developed DAS-qELISA has no cross-reactivity with other swine enteric coronaviruses, such as porcine epidemic diarrhea virus (PEDV), transmissible gastroenteritis virus (TGEV), and porcine deltacoronavirus (PDCoV). Three-day-old piglets were challenged with SADS-CoV and collected anal swab samples which were screened for the presence of SADS-CoV by using DAS-qELISA and reverse transcriptase PCR (RT-PCR). The coincidence rate of the DAS-qELISA and RT-PCR was 93.93%, and the kappa value was 0.85, indicating that DAS-qELISA is a reliable method for applying antigen detection of clinical samples. KEY POINTS: • The first double-antibody sandwich quantitative enzyme-linked immunosorbent assay for detection SADS-CoV infection. • The custom ELISA is useful for controlling the SADS-CoV spread.

Development of a sensitive real-time quantitative RT-PCR assay for the detection of pear chlorotic leaf spot-associated virus

Pear chlorotic leaf spot associated virus (PCLSaV) belongs to the genus Emaravirus and possesses a genome composed of five negative-sense single-stranded RNA (-ssRNA) segments. This study developed a SYBR green-based reverse transcription quantitative PCR (RT-qPCR) assay for the detection of PCLSaV infecting pear trees. A set of two primers q5-F2/q5-R2 designed based on the viral RNA5 sequences showed high specificity and feasibility for PCLSaV detection. The standard curve was established. RT-qPCR assays showed that PCLSaV content was greatly higher in diseased branch and symptomatic leaf samples than that in un-diseased branch and asymptomatic leaf samples. The RT-qPCR was reliability in the detection of the virus in field and in-vitro cultured pear samples. This technique would be useful for the supervision of the viral disease and the certification of pear planting materials.

Establishment of a recombinase polymerase amplification (RPA) fluorescence assay for the detection of swine acute diarrhea syndrome coronavirus (SADS-CoV)

BACKGROUND

Swine acute diarrhea syndrome coronavirus (SADS-CoV) causes acute vomiting and diarrhea in piglets, leading to significant financial losses for the pig industry. Recombinase polymerase amplification (RPA) is a rapid nucleic acid amplification technology used under constant temperature conditions. The study established a real-time reverse transcription (RT)-RPA assay for early diagnosis of SADS-CoV.  RESULTS: The detection limit of the real-time RT-RPA was 74 copies/µL of SADS-CoV genomic standard recombinant plasmid in 95% of cases. The assay was performed in less than 30 min and no cross-reactions were observed with eight other common viruses that affect swine, including classical swine fever virus (CSFV), porcine reproductive and respiratory syndrome virus (PRRSV), pseudo rabies virus (PRV), swine influenza virus (SIV), seneca valley virus (SVA), transmissible gastroenteritis virus (TGEV), porcine epidemic diarrhea virus (PEDV) and porcine deltacoronavirus (PDCoV). The coefficient of variation (C.V.) values of the two standards dilutions and three positive clinical sample ranged from 2.95% to 4.71%. A total of 72 clinical fecal samples from swine with diarrheal symptoms were analyzed with the developed RT-RPA and quantitative RT-PCR. There was 98.61% agreement between the RT-RPA and the quantitative real-time PCR results.

CONCLUSIONS

These results indicated that the developed RT-RPA assay had good specificity, sensitivity, stability and repeatability. The study successfully established a broadly reactive RT-RPA assay for SADS-CoV detection.

A Novel, Reverse Transcription, Droplet Digital PCR Assay for the Combined, Sensitive Detection of Severe Acute Respiratory Syndrome Coronavirus 2 with Swine Acute Diarrhea Syndrome Coronavirus

Background

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has rapidly spread over the world since its emergence. Although the dominant route of SARS-CoV-2 infection is respiratory, a number of studies revealed infection risk from contaminated surfaces and products, including porcine-derived food and other products. The SARS-CoV-2 outbreak has been severely threatening public health, and disrupting porcine products trade and the pig industry. Swine acute diarrhea syndrome coronavirus (SADS-CoV), which was responsible for large-scale, fatal disease in piglets, emerged in 2017 and has caused enormous economic losses in the pig industry. Currently, reverse transcription real-time PCR (RT-rPCR) is the gold standard method for SARS-CoV-2 diagnosis and is most commonly used for SADS-CoV detection. However, inaccurate detection of the SARS-CoV-2 infection obtained by RT-rPCR is increasingly reported, especially in specimens with low viral load.

Objective

This study aimed to develop an accurate reverse transcription droplet digital PCR (RT-ddPCR) assay for the detection of SARS-CoV-2 and SADS-CoV simultaneously.

Methods

Two pairs of primers and one double-quenched probe targeting the RNA-dependent RNA polymerase (RDRP) region of the open reading frame 1ab (ORF1ab) gene of SARS-CoV-2 and the corresponding ORF1ab region of SADS-CoV were designed to develop the RT-ddPCR assay. The sensitivity, specificity, repeatability, and reproducibility were tested using complementary RNAs (cRNAs) and clinical specimens.

Results

The detection limits of RT-ddPCR were 1.48 ± 0.18 and 1.38 ± 0.17 copies in a 20 μL reaction for SARS-CoV-2 and SADS-CoV cRNAs, respectively (n = 8), showing approximately 4- and 10-fold greater sensitivity than the RT-rPCR assay. This assay also exhibited good specificity, repeatability, and reproducibility.

Conclusion

The established RT-ddPCR assay was shown to be a highly effective, accurate, and reliable method for the sensitive detection of SARS-CoV-2 and SADS-CoV.

Highlights

This RT-ddPCR assay could be used to detect both SARS-CoV-2 and SADS-CoV in a sample with one double-quenched probe, and is also the first reported RT-ddPCR assay for SADS-CoV detection.

Novel approaches for rapid detection of COVID-19 during the pandemic: A review

The rapid spread of the SARS-CoV-2 virus that caused the COVID-19 disease, has highlighted our urgent need for sensitive, fast and accurate diagnostic technologies. In fact, one of the main challenges for flatting COVID-19 spread charts is the ability to accurately and rapidly identify asymptomatic cases that result in spreading the virus to close contacts. SARS-CoV-2 virus mutation is also relatively rapid, which makes the detection of COVID-19 diseases still crucial even after the vaccination. Conventional techniques, which are commercially available have focused on clinical manifestation, along with molecular and serological detection tools that can identify the SARS-CoV-2 virus however, owing to various disadvantages including low specificity and sensitivity, a quick, low cost and easy approach is needed for diagnosis of COVID-19. Scientists are now showing extensive interest in an effective portable and simple detection method to diagnose COVID-19. There are several novel methods and approaches that are considered viable advanced systems that can meet the demands. This study reviews the new approaches and sensing technologies that work on COVID-19 diagnosis for easy and successful detection of SARS-CoV-2 virus.

Analytical Technologies for Liquid Biopsy of Subcellular Materials

Liquid biopsy markers, which can be secured from a simple blood draw or other biological samples, are used to manage a variety of diseases and even monitor for bacterial or viral infections. Although there are several different types of liquid biopsy markers, the subcellular ones, including cell-free DNA, microRNA, extracellular vesicles, and viral particles, are evolving in terms of their utility. A challenge with liquid biopsy markers is that they must be enriched from the biological sample prior to analysis because they are a vast minority in a mixed population, and potential interferences may be present in the sample matrix that can inhibit profiling the molecular cargo from the subcellular marker. In this article, we discuss existing and developing analytical enrichment platforms used to isolate subcellular liquid biopsy markers, and discuss their figures of merit such as recovery, throughput, and purity.

Development of an indirect ELISA for detecting swine acute diarrhoea syndrome coronavirus IgG antibodies based on a recombinant spike protein

Swine acute diarrhoea syndrome coronavirus (SADS-CoV) is a newly identified swine enteropathogenic coronavirus that causes watery diarrhoea in neonatal piglets, leading to significant economic losses to the swine industry. Currently, there are no suitable serological methods to assess the infection of SADS-CoV and effectiveness of vaccines, making an urgent need to exploit effective enzyme-linked immunosorbent assay (ELISA) to compensate for this deficiency. Here, a recombinant plasmid that expresses the spike (S) protein of SADS-CoV fused to the Fc domain of human IgG was constructed to generate recombinant baculovirus and expressed in HEK 293F cells. The S-Fc protein was purified with protein G Resin, which retained reactivity with anti-human Fc and anti-SADS-CoV antibodies. The S-Fc protein was then used to develop an indirect ELISA (S-iELISA) and the reaction conditions of S-iELISA were optimized. As a result, the cut-off value was determined as 0.3711 by analyzing OD_450nm values of 40 SADS-CoV-negative sera confirmed by immunofluorescence assay (IFA) and western blot. The coefficient of variation (CV) of 6 SADS-CoV-positive sera within and between runs of S-iELISA were both less than 10%. The cross-reactivity assays demonstrated that S-iELISA was non-cross-reactive with other swine viruses' sera. Furthermore, the overall coincidence rate between IFA and S-iELISA was 97.3% based on testing 111 clinical serum samples. Virus neutralization test with seven different OD_450nm values of the sera showed that the OD_450nm values tested by S-iELISA are positively correlated with the virus neutralization assay. Finally, a total of 300 pig field serum samples were tested by S-iELISA and commercial kits of other swine enteroviruses showed that the IgG-positive for SADS-CoV, TGEV, PDCoV and PEDV was 81.7, 54, 65.3 and 6%, respectively. The results suggest that this S-iELISA is specific, sensitive, repeatable and can be applied for the detection of the SADS-CoV infection in the swine industry.

Simultaneous detection and differentiation of porcine circovirus 3 and 4 using a SYBR Green І-based duplex quantitative PCR assay

Porcine circovirus 4 (PCV4) was a novel circovirus identified from diseased pigs in 2019 in Hunan Province, China, and PCV3 and PCV4 co-infection has been reported. In order to detect and differentiate PCV3 and PCV4 simultaneously, the SYBR Green І-based duplex quantitative PCR (qPCR) assay was established in the present study. The two viruses could be easily distinguished by different Tm values: 86.5°C for PCV3 and 79°C for PCV4, while other porcine pathogens did not shown specific melting peaks. The detection limits of this duplex qPCR assay were 51.7 copies/μL for PCV3 and 67.7 copies/μL for PCV4, and both of the intra-assay and inter-assay of the CV analysis of this assay were less than 2.0 %. Sixty-four clinical samples from 22 different swine farms were screened by the duplex qPCR assay. The results showed that the positive detection rate of PCV3 was 37.5 % (24/64) and PCV4 was 34.38 % (22/64), and PCV3 and PCV4 co-infection rate was 17.19 % (11/64). The detection rate of the duplex qPCR assay was higher than that of the conventional PCR assay. The duplex qPCR was of high sensitivity and specificity, being able to provide technical support for clinical detection, differential diagnosis and control of PCV3 and PCV4.

The Inclusive Review on SARS-CoV-2 Biology, Epidemiology, Diagnosis, and Potential Management Options

A novel coronavirus member was reported in Wuhan City, Hubei Province, China, at the end of the year 2019. Initially, the infection spread locally, affecting the Wuhan people, and then expanded rapidly throughout the world. On 11 March 2020, the World Health Organization (WHO) proclaimed it a global pandemic. The virus is a new strain most closely related to a bat coronavirus (RaTG13) which was not previously discovered in humans and is now formally known as the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Coronavirus disease 2019 (COVID-19) is the disease syndrome that the SARS-CoV-2 virus triggers. It is suggested that SARS-CoV-2 can be transmitted through aerosols, direct/indirect contact, and also during medical procedures and specimen handling. The infection is characterized by isolated flu-like symptoms, but there may be specific signs of fever, fatigue, cough, and shortness of breath, as well as the loss of smell and breathing difficulty. Within this report, we tried to review the most current scientific literature published by January 2021 on various aspects of the outbreak, including virus structure, pathogenesis, clinical presentation, epidemiology, diagnostic approaches, potential therapeutics and vaccines, and prospects. We hope this article makes a beneficial impact on public education to better deal with the SARS-CoV-2 crisis and push a step forward in the near term towards its prevention and control.

Establishment of an SYBR Green-based real-time PCR assay for porcine circovirus type 4 detection

Porcine circovirus 4 (PCV4) is a novel circovirus first discovered in China in April 2019. Here, we established an SYBR Green I-based real-time PCR for quantitative detection of PCV4. A pair of specific primers was designed based on the conserved region of Cap of PCV4. The standard curve of the established real-time PCR. assay showed a good linear relationship. The sensitivity of the established real-time PCR was 100 times greater than that of conventional PCR, and the detection limit of the assay was 3 × 10¹ copies. There was no cross-reactivity with other swine DNA viruses, showing good specificity. The intra-group variation coefficient was 0.37-0.78 %, and the inter-group variation coefficient was 0.57-0.94%, indicating that the assay has good repeatability. Moreover, the analysis of clinical samples showed that the positive detection rate of PCV4 was 10.71% (18/168), while that of conventional PCR was 8.93% (15/168). Interestingly, co-infection with PCV2 or PCV3, or both PCV2 and PCV3, was also detected. In conclusion, the established SYBR Green I-based real-time PCR may be a cost-effective and rapid method for PCV4 clinical diagnosis.

Swine enteric alphacoronavirus (swine acute diarrhea syndrome coronavirus): An update three years after its discovery

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A summary of the research progress in SeACoV (SADS-CoV) from 2017 to 2020.

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Bat-derived SeACoV was most recently recognized prior to SARS-CoV-2 associated with COVID-19.

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Focusing on the etiology, epidemiology, evolutionary perspective, potential for interspecies transmission, pathogenesis and diagnosis.

Discovered in 2017, swine enteric alphacoronavirus (SeACoV), also known as swine acute diarrhea syndrome coronavirus (SADS-CoV) or porcine enteric alphacoronavirus (PEAV), is the fifth porcine CoV identified in diarrheal piglets. The presumed name “SADS-CoV” may not be appropriate since current studies have not provided strong evidence for high pathogenicity of the virus. SeACoV was the most recently recognized CoV of potential bat origin prior to the novel human severe acute respiratory syndrome CoV 2 (SARS-CoV-2), associated with the pandemic CoV disease 2019 (COVID-19). Although SeACoV is recognized as a regional epizootic virus currently, it possesses the most extensive cell species tropism in vitro among known CoVs. This review summarizes the emergence of SeACoV and updates the research progress made from 2017 to early 2020, mainly focusing on the etiology, epidemiology, evolutionary perspective, potential for interspecies transmission, pathogenesis and diagnosis.

Porcine deltacoronavirus causes diarrhea in various ages of field-infected pigs in China

Porcine deltacoronavirus (PDCoV) is a novel coronavirus that causes acute diarrhea in suckling piglets. In Henan province of China, three swine farms broke out diarrhea in different ages of pigs during June of 2017, March of 2018 and January of 2019, respectively. PCR method, Taqman real-time RT-PCR method, sequencing, histopathology and immunohistochemistry (IHC) were conducted with the collected samples, and the results showed that PDCoV was detected among the suckling piglets, commercial fattening pigs and sows with diarrhea. PDCoV-infected suckling piglets were characterized with thin and transparent intestinal walls from colon to caecum, spot hemorrhage at mesentery and intestinal bleeding. PDCoV RNA was detected in multiple organs and tissues by Taqman real-time RT-PCR, which had high copies in ileum, inguinal lymph node, rectum and spleen. PDCoV antigen was detected in the basal layer of jejunum and ileum by IHC. In this research, we found that PDCoV could infect various ages of farmed pigs with watery diarrhea and anorexia in different seasons in a year.