Dual priming oligonucleotide (DPO)-based real-time RT-PCR assay for accurate differentiation of four major viruses causing porcine viral diarrhea

An isothermal nucleic acid amplification-based enzymatic recombinase amplification method for dual detection of porcine epidemic diarrhea virus and porcine rotavirus A

Viral diarrhea is the predominant digestive tract sickness in piglings, resulting in substantial profit losses in the porcine industry. Porcine rotavirus A (PoRVA) and porcine epidemic diarrhea virus (PEDV) are the main causes of grave gastroenteritis and massive dysentery, especially in piglets. PoRVA and PEDV have high transmissibility, exhibit similar clinical symptoms, and frequently co-occur. Therefore, to avoid financial losses, a quick, highly efficient, objective diagnostic test for the prevention and detection of these diseases is required. Enzymatic recombinase amplification (ERA) is a novel technology based on isothermal nucleic acid amplification. It demonstrates high sensitivity and excellent specificity, with a short processing time and easy operability, compared with other in vitro nucleic acid amplification technologies. In this study, a dual ERA method to detect and distinguish between PEDV and PoRVA nucleic acids was established. The method shows high sensitivity, as the detection limits were 101 copies/μL for both viruses. To test the usefulness of this method in clinical settings, we tested 64 swine clinical samples. Our results were 100% matched with those acquired using a commercially available kit. Therefore, we have successfully developed a dual diagnostic ERA nucleic acids method for detecting and distinguishing between PEDV and PoRVA.

Development of a triplex quantitative reverse transcription-polymerase chain reaction for the detection of porcine epidemic diarrhea virus, porcine transmissible gastroenteritis virus, and porcine rotavirus A

Porcine viral diarrhea is caused by many pathogens and can result in watery diarrhea, dehydration and death. Various detection methods, such as polymerase chain reaction (PCR) and real-time quantitative PCR (qPCR), have been widely used for molecular diagnosis. We developed a triplex real-time quantitative reverse transcription PCR (qRT-PCR) for the simultaneous detection of three RNA viruses potentially associated with porcine viral diarrhea: porcine epidemic diarrhea virus (PEDV), porcine transmissible gastroenteritis virus (TGEV), and porcine rotavirus A (PoRVA). The triplex qRT-PCR had R2 values of 0.999 for the standard curves of PEDV, TGEV and PoRVA. Importantly, the limits of detection for PEDV, TGEV and PoRVA were 10 copies/μL. The specificity test showed that the triplex qRT-PCR detected these three pathogens specifically, without cross-reaction with other pathogens. In addition, the approach had good repeatability and reproducibility, with intra-and inter-assay coefficients of variation <1%. Finally, this approach was evaluated for its practicality in the field using 256 anal swab samples. The positive rates of PEDV, TGEV and PoRVA were 2.73% (7/256), 3.91% (10/256) and 19.14% (49/256), respectively. The co-infection rate of two or more pathogens was 2.73% (7/256). The new triplex qRT-PCR was compared with the triplex RT-PCR recommended by the Chinese national standard (GB/T 36871-2018) and showed 100% agreement for PEDV and TGEV and 95.70% for PoRVA. Therefore, the triplex qRT-PCR provided an accurate and sensitive method for identifying three potential RNA viruses for porcine viral diarrhea that could be applied to diagnosis, surveillance and epidemiological investigation.

Epidemiological monitoring and genetic variation analysis of pathogens associated with porcine viral diarrhea in southern China from 2021 to 2023

Large-scale outbreaks of virus-associated severe diarrhea have occurred in pig populations since 2010. To investigate the prevalence and genetic evolution of the diarrhea-associated viruses responsible for the outbreaks, we tested 1,791 diarrhea samples collected from 213 pig farms in five provinces in southern China between 2021 and 2023. The test results showed that porcine epidemic diarrhea virus (PEDV) was the most frequently detected virus. The prevalence rates ranged from 47.40 to 52.22% in samples and 76.06% (162/213) in pig farms. Porcine rotavirus (PoRV) was the second common virus, with prevalence rates ranging from 25.81 to 50.81% in samples and 72.77%(155/213) in pig farms. Porcine delta coronavirus (PDCoV) was the third common virus, with prevalence rates ranging from 16.33 to 17.48% in samples and 38.50% (82/213) in pig farms. The detection rates of both transmissible gastroenteritis virus (TGEV) and porcine acute diarrheal syndrome coronavirus (SADS-CoV) were very low, less than 1.01% in samples and less than 3.76% in pig farms. In this study, we found SADS-CoV only in piglet diarrhea samples from Jiangxi, Guangdong, and Guangxi provinces in China, with a prevalence rate of 5.16% (11/213) in pig farms. Co-infection with these diarrhea-associated viruses is a common occurrence. The most common co-infections were PEDV and PoRV, with a prevalence rate of 6.64% (119/1,791), followed by PDCoV and PoRV, with a prevalence rate of 4.19% (75/1,791). Phylogenetic analyses showed that PEDV and PEDV variants prevalent in southern China during the past three years clustered into genotype GIIb and recombinant PEDV subtypes. Among the currently endemic PEDV, the most common mutations occurred in the collagenase equivalent (COE) and epitope regions of the spike gene. PoRV strains were mainly dominated by the G9 subtype, followed by the G5, G3 and G4 subtypes. Our results suggest that variant PEDV, PDCoV and PoRV are the main pathogens of swine diarrhea, and singular- or co-infection with pathogenic enteric CoV is common in pig herds in southern China. Therefore, prevention and control of porcine viral diarrhea should be given high attention.

Porcine epidemic diarrhea virus strain CH/HLJ/18 isolated in China: characterization and phylogenetic analysis

BACKGROUND

Porcine epidemic diarrhea (PED) is an infectious disease of the digestive tract caused by the porcine epidemic diarrhea virus (PEDV), characterized by vomiting, severe diarrhea, and high mortality rates in piglets. In recent years, the distribution of this disease in China has remarkably increased, and its pathogenicity has also increased. PEDV has been identified as the main cause of viral diarrhea in piglets. This study aimed to understand the genetic evolution and diversity of PEDV to provide a theoretical basis for the development of new vaccines and the prevention and treatment of PED.

METHODS

A PEDV strain was isolated from the small intestine of a diarrheal piglet using Vero cells. The virus was identified using reverse transcription-polymerase chain reaction (RT-PCR), indirect immunofluorescence assay (IFA), and transmission electron microscopy. The whole genome sequence was sequenced, phylogenetic analysis was conducted using MEGA (version 7.0), and recombination analysis was performed using RDP4 and SimPlot. The S protein amino acid sequence was aligned using Cluster X (version 2.0), and the S protein was modeled using SWISS-MODEL to compare differences in structure and antigenicity. Finally, the piglets were inoculated with PEDV to evaluate its pathogenicity in newborn piglets.

RESULT

PEDV strain CH/HLJ/18 was isolated. CH/HLJ/18 shared 89.4-99.2% homology with 52 reference strains of PEDV belonging to the GII-a subgroup. It was a recombinant strain of PEDV BJ-2011-1 and PEDV CH_hubei_2016 with a breakpoint located in ORF1b. Unique amino acid deletions and mutations were observed in the CH/HLJ/18 S protein. The piglets then developed severe watery diarrhea and died within 7 d of inoculation with CH/HLJ/18, suggesting that CH/HLJ/18 was highly pathogenic to newborn piglets.

CONCLUSION

A highly pathogenic recombinant PEDV GII-a strain, CH/HLJ/18, was identified in China, with unique deletion and mutation of amino acids in the S protein that may lead to changes in protein structure and antigenicity. These results will be crucial for understanding the prevalence and variation of PEDV and for preventing and controlling PED.

A duplex nested RT-PCR method for monitoring porcine epidemic diarrhea virus and porcine delta-coronavirus

BACKGROUND

Porcine epidemic diarrhea virus (PEDV) and porcine delta-coronavirus (PDCoV) are economically important pathogens that cause diarrhea in sows and acute death of newborn piglets. Moreover, the emerging PDCoV was reported to infect children. The current situation is that vaccine prevention has not met expectations, and emergency containment strategies following outbreaks cannot prevent the damages and losses already incurred. Therefore, a more sensitive detection method, that is both convenient and enables accurate and effective sequencing, that will provide early warning of PEDV and PDCoV is necessary. This will enable active, effective, and comprehensive prevention and control, which will possibly reduce disease occurrences.

RESULTS

Duplex nested RT-PCR (dnRT-PCR) is an ideal method to achieve early warning and monitoring of PEDV and PDCoV diseases, and to additionally investigate any molecular epidemiological characteristics. In this study, two pairs of primers were designed for each virus based upon the highly conserved N protein sequences of both PEDV and PDCoV strains retrieved from the NCBI Genbank. After optimization of the reaction conditions, the dnRT-PCR assay amplified a 749-bp fragment specific to PEDV and a 344-bp fragment specific to PDCoV. Meanwhile, the specificity and sensitivity of the primers and clinical samples were tested to verify and establish this dnRT-PCR method. The limit of detection (LoD)for both PEDV and PDCoV was 10 copies/µL. The results showed that among 251 samples, 1 sample contained PEDV infection, 19 samples contained a PDCoV infection, and 8 samples were infected with both viruses, following the use of dnRT-PCR. Subsequently, the positive samples were sent for sequencing, and the sequencing results confirmed that they were all positive for the viruses detected using dnRT-PCR, and conventional RT-PCR detection was conducted again after the onset of disease. As these results were consistent with previous results, a detection method for PEDV and PDCoV using dnRT-PCR was successfully established. In conclusion, the dnRT-PCR method established in this study was able to detect both PEDV and PDCoV, concomitantly.

CONCLUSIONS

The duplex nested RT-PCR method represents a convenient, reliable, specific, sensitive and anti-interference technique for detecting PEDV and PDCoV, and can additionally be used to simultaneously determine the molecular epidemiological background.

Epidemiology of porcine deltacoronavirus among Chinese pig populations in China: systematic review and meta-analysis

Porcine deltacoronavirus (PDCoV) is a newly emerging and important porcine enteropathogenic coronavirus that seriously threatens the swine industry in China and worldwide. We conducted a systematic review and meta-analysis to access the prevalence of PDCoV infection in pig population from mainland China. Electronic databases were reviewed for PDCoV infection in pig population, and meta-analysis was performed to calculate the overall estimated prevalence using random-effect models. Thirty-nine studies were included (including data from 31,015 pigs). The overall estimated prevalence of PDCoV infection in pigs in China was 12.2% [95% confidence interval (CI), 10.2-14.2%], and that in Central China was 24.5% (95%CI, 16.1-32.9%), which was higher than those in other regions. During 2014-2021, the estimated prevalence of PDCoV infection was the highest in 2015 at 20.5% (95%CI, 10.1-31.0%) and the lowest in 2021 at 4.8% (95%CI, 2.3-7.3%). The prevalence of PDCoV infection in sows was 23.6% (95%CI, 15.8-31.4%), which was higher than those in suckling piglets, nursery piglets, and finishing pigs. The prevalence of PDCoV infection was significantly associated with sampling region, sampling year, pig stage, and clinical signs (diarrhea). This study systematically evaluated the epidemiology of PDCoV infection in Chinese pig population. The findings provide us with a comprehensive understanding of PDCoV infection and are beneficial for establishing new controlling strategies worldwide.

Metagenome of Gut Microbiota Provides a Novel Insight into the Pathogenicity of Balantioides coli in Weaned Piglets

Balantioides coli plays an important role in the diarrhea of weaned piglets, but its pathogenic potential and interaction with gut microbes remain unclear. To investigate the impact of B. coli colonization on the gut bacterial structure and function of weaned piglets, a metagenomic analysis based on shotgun sequencing was performed on fresh fecal samples collected from ten B. coli-colonized piglets and eight B. coli-free ones in this study. The results showed that decreasing diversity and shifted composition and function of the bacterial community were detected in the weaned piglets infected by B. coli. In contrast to the B. coli-negative group, the relative abundances of some members of the Firmicutes phylum including Clostridium, Ruminococcus species, and Intestinimonas butyriciproducens, which produce short-chain fatty acids, were significantly reduced in the B. coli-positive group. Notably, some species of the Prevotella genus (such as Prevotella sp. CAG:604 and Prevotella stercorea) were significantly increased in abundance in the B. coli-positive piglets. A functional analysis of the gut microbiota demonstrated that the differential gene sets for the metabolism of carbohydrates and amino acids were abundant in both groups, and the more enriched pathways in B. coli-infected piglets were associated with the sugar-specific phosphotransferase system (PTS) and the two-component regulatory system, as well as lipopolysaccharide (LPS) biosynthesis. Furthermore, several species of Prevotella were significantly positively correlated to the synthesis of lipid A, leading to the exporting of endotoxins and, thereby, inducing inflammation in the intestines of weaned piglets. Taken together, these findings revealed that colonization by B. coli was distinctly associated with the dysbiosis of gut bacterial structure and function in weaned piglets. Lower relative abundances of Clostridiaceae and Ruminococcaceae and higher abundances of Prevotella species were biomarkers of B. coli infection in weaned piglets.

Development of a Multiplex Quantitative PCR for Detecting Porcine Epidemic Diarrhea Virus, Transmissible Gastroenteritis Virus, and Porcine Deltacoronavirus Simultaneously in China

Porcine epidemic diarrhea virus (PEDV), transmissible gastroenteritis virus (TGEV), and porcine deltacoronavirus (PDCoV) belong to the category of swine enteric coronavirus that cause acute diarrhea in piglets, which has resulted in massive losses to the pig husbandry. Therefore, a sensitive and rapid detection method which can differentially detect these viruses that lead to mixed infections in clinical cases, is urgently needed. According to the conserved regions of the PEDV M gene, TGEV S gene, and PDCoV N gene, and the reference gene of porcine (β-Actin), we designed new specific primers and probes for the multiplex qPCR assay capable of simultaneously detecting three RNA viruses. This method, with a great specificity, did not cross-react with the common porcine virus. Moreover, the limit of detection of the method we developed could reach 10 copies/μL ,and the intra- and inter-group coefficients of variation of it below 3%. Applying this assay to detect 462 clinical samples which were collected in 2022-2023, indicated that the discrete positive rates of PEDV, TGEV, and PDCoV were 19.70%, 0.87%, and 10.17%, respectively. The mixed infection rates of PEDV/TGEV, PEDV/PDCoV, TGEV/PDCoV, and PEDV/TGEV/PDCoV were 3.25%, 23.16%, 0.22%, and 11.90%, respectively. All in all, the multiplex qPCR assay we developed as a tool for differential and rapid diagnosing can be put on the active prevention and control of PEDV, TGEV, and PDCoV, , which can create great value in the diagnosis of swine diarrhea diseases.

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.

Establishment and Application of a Triplex Real-Time RT-PCR Assay for Differentiation of PEDV, PoRV, and PDCoV

Porcine viral diarrhea is very common in clinical practice and has caused huge losses to the pig industry. Porcine epidemic diarrhea virus (PEDV), porcine rotavirus (PoRV), and porcine deltacoronavirus (PDCoV) are important pathogens of porcine viral diarrhea. Co-infection situations among these three viruses in clinics are common, which increases the difficulty of differential diagnosis. Currently, polymerase chain reaction (PCR) is commonly used to detect pathogens. TaqMan real-time PCR is more sensitive than conventional PCR and has better specificity and accuracy. In this study, a triplex real-time RT-PCR assay based on TaqMan probes was developed for differential detection of PEDV, PoRV, and PDCoV. The triplex real-time RT-PCR assay developed in this study could not detect unrelated pathogens and showed satisfactory specificity, sensitivity, repeatability, and reproducibility with a limit of detection (LOD) of 6.0 × 10¹ copies/μL. Sixteen clinical samples were used to compare the results of the commercial RT-PCR kit and the triplex RT-PCR for PEDV, PoRV, and PDCoV detection, and the results were completely consistent. A total of 112 piglet diarrhea samples collected from Jiangsu province were next used to study the local prevalence of PEDV, PoRV, and PDCoV. The positive rates of PEDV, PoRV, and PDCoV detected by the triplex real-time RT-PCR were 51.79% (58/112), 59.82% (67/112), and 2.68% (3/112), respectively. The co-infections of PEDV and PoRV were frequent (26/112, 23.21%), followed by the co-infections of PDCoV and PoRV (2/112, 1.79%). This study established a useful tool for simultaneous differentiation of PEDV, PoRV, and PDCoV in practice and provided valuable information on the prevalence of these diarrhea viral pathogens in Jiangsu province.

A Quadruplex qRT-PCR for Differential Detection of Four Porcine Enteric Coronaviruses

Porcine epidemic diarrhea virus (PEDV), transmissible gastroenteritis virus (TGEV), porcine deltacoronavirus (PDCoV), and swine acute diarrhea syndrome coronavirus (SADS-CoV) are four identified porcine enteric coronaviruses. Pigs infected with these viruses show similar manifestations of diarrhea, vomiting, and dehydration. Here, a quadruplex real-time quantitative PCR (qRT-PCR) assay was established for the differential detection of PEDV, TGEV, PDCoV, and SADS-CoV from swine fecal samples. The assay showed extreme specificity, high sensitivity, and excellent reproducibility, with the limit of detection (LOD) of 121 copies/μL (final reaction concentration of 12.1 copies/μL) for each virus. The 3236 clinical fecal samples from Guangxi province in China collected between October 2020 and October 2022 were evaluated by the quadruplex qRT-PCR, and the positive rates of PEDV, TGEV, PDCoV, and SADS-CoV were 18.26% (591/3236), 0.46% (15/3236), 13.16% (426/3236), and 0.15% (5/3236), respectively. The samples were also evaluated by the multiplex qRT-PCR reported previously by other scientists, and the compliance rate between the two methods was more than 99%. This illustrated that the developed quadruplex qRT-PCR assay can provide an accurate method for the differential detection of four porcine enteric coronaviruses.

Transmissible Gastroenteritis Virus Nucleocapsid Protein Interacts with Na + /H + Exchanger 3 To Reduce Na + /H + Exchanger Activity and Promote Piglet Diarrhea

A variety of coronaviruses have been found to cause severe diarrhea in hosts, including TGEV; however, the pathogenic mechanism is not clear. Therefore, prompt determination of the mechanism and identification of efficient therapeutic agents are required, both for public health reasons and for economic development.

Current State of Molecular and Serological Methods for Detection of Porcine Epidemic Diarrhea Virus

Porcine epidemic diarrhea virus (PEDV), a member of the Coronaviridae family, is the etiological agent of an acute and devastating enteric disease that causes moderate-to-high mortality in suckling piglets. The accurate and early detection of PEDV infection is essential for the prevention and control of the spread of the disease. Many molecular assays have been developed for the detection of PEDV, including reverse-transcription polymerase chain reaction (RT-PCR), real-time RT-PCR (qRT-PCR) and loop-mediated isothermal amplification assays. Additionally, several serological methods have been developed and are widely used for the detection of antibodies against PEDV. Some of them, such as the immunochromatography assay, can generate results very quickly and in field conditions. Molecular assays detect viral RNA in clinical samples rapidly, and with high sensitivity and specificity. Serological assays can determine prior immune exposure to PEDV, can be used to monitor the efficacy of vaccination strategies and may help to predict the duration of immunity in piglets. However, they are less sensitive than nucleic acid-based detection methods. Sanger and next-generation sequencing (NGS) allow the analysis of PEDV cDNA or RNA sequences, and thus, provide highly specific results. Furthermore, NGS based on nonspecific DNA cleavage in clustered regularly interspaced short palindromic repeats (CRISPR)–Cas systems promise major advances in the diagnosis of PEDV infection. The objective of this paper was to summarize the current serological and molecular PEDV assays, highlight their diagnostic performance and emphasize the advantages and drawbacks of the application of individual tests.

Study of the effect of intestinal immunity in neonatal piglets coinfected with porcine deltacoronavirus and porcine epidemic diarrhea virus

Porcine deltacoronavirus (PDCoV) and porcine epidemic diarrhea virus (PEDV) have often been detected simultaneously in piglets with coronavirus diarrhea. However, the intestinal immune response to the interaction between circulating PDCoV and PEDV is unknown. Therefore, this study was conducted to investigate the intestinal immunity of neonatal piglets that were exposed first to PDCoV and then to PEDV. The amounts and distribution of CD3⁺ T lymphocytes, B lymphocytes, and goblet cells (GCs) in the small intestine were analyzed by immunohistochemistry and periodic acid–Schiff staining, respectively. The expression levels of pattern recognition receptors and downstream mediator cytokines were analyzed by qPCR and ELISA. The results showed that the numbers of GCs, CD3⁺ T lymphocytes, and B lymphocytes in the duodenum and jejunum of the PDCoV + PEDV coinoculated piglets were increased compared with those of piglets inoculated with PEDV alone. The piglets in the PDCoV + PEDV group had significantly upregulated IFN-α and IFN-λ₁ compared with the PEDV single-inoculated piglets. These results suggest that PDCoV + PEDV-coinfected piglets can activate intestinal antiviral immunity more strongly than piglets infected with PEDV alone, which provides new insight into the pathogenesis mechanism of swine enteric coronavirus coinfection that may be used for vaccination in the future.

Visualization of copper nanoclusters for SARS-CoV-2 Delta variant detection based on rational primers design

Here, based on the design of rational primers and copper nanoclusters (CuNCs), we present a method for the accurate detection of the SARS-CoV-2 Delta variant, which is capable of distinguishing the Delta variant with its single nucleotide polymorphism from the 'wild type' coronavirus (NC_045512.2), and realizing visualization signal out. Specifically, we show that dual priming oligonucleotide (DPO) primers and AT primers can be used to distinguish between wild types and mutations of this virus by polymerase chain reaction (PCR) analysis and that visualization can be achieved via the red fluorescence of CuNCs in ultraviolet radiation. Among the results, it was found that the R-1-down (DPO)-6I and F-1-30 AT, with the single nucleotide deletion site designed at the 3' end of the downstream primer, showed the best specificity towards the Delta variant. Moreover, the use of AT primers increased the AT contents of the PCR products, thus meeting the template requirements generated by the CuNCs. It was also found that the AT primers could assist with improving detection specificity. Finally, we demonstrate that the visualization of the CuNCs-based detection assay exhibited a linear relationship in 0.5 pg μL^-1-50 ng μL^-1, with a limit of quantitation (LOQ) of 0.5 pg μL^-1.

A multiplex nanoparticle-assisted polymerase chain reaction assay for detecting three canine epidemic viruses using a dual priming oligonucleotide system

A rapid and accurate diagnosis of mixed viral infections is important for providing timely therapeutic interventions. The aim of this study was to develop a highly sensitive and specific method for the simultaneous detection of canine distemper virus (CDV), canine parvovirus (CPV) and canine coronavirus (CCV) in mixed infections by combining the high specificity of a dual priming oligonucleotide (DPO) primer system with the high sensitivity of a nanoparticle-assisted PCR (nanoPCR) assay. Under the optimised assay conditions, the multiplex DPO-nanoPCR assay developed using DPO primers was 100-fold more sensitive than the multiplex PCR assay using conventional primers. The detection limits of the multiplex DPO-nanoPCR assay for the recombinant plasmids containing the cloned CDV, CPV and CCV target sequences were 5.4 × 10², 6.5 × 10² and 1.6 × 10² copies in a 25 μL assay, respectively. No cross-reaction with other canine viruses was observed. This is the first reported use of a multiplex nanoPCR assay with the DPO primer system for the simultaneous detection of CDV, CPV and CCV in mixed infections. The high sensitivity and specificity of the assay indicated its potential for use in clinical diagnosis and field surveillance of animal epidemics.

Porcine deltacoronavirus and its prevalence in China: a review of epidemiology, evolution, and vaccine development

Porcine deltacoronavirus (PDCoV) is one of the most important enteropathogenic pathogens, and it causes enormous economic losses to the global commercial pork industry. PDCoV was initially reported in Hong Kong (China) in 2012 and subsequently emerged in swine herds with diarrhea in Ohio (USA) in 2014. Since then, it has spread to Canada, South Korea, mainland China, and several Southeast Asian countries. Information about the epidemiology, evolution, prevention, and control of PDCoV and its prevalence in China has not been comprehensively reported, especially in the last five years. This review is an update of current information on the general characteristics, epidemiology, geographical distribution, and evolutionary relationships, and the status of PDCoV vaccine development, focusing on the prevalence of PDCoV in China and vaccine research in particular. Together, this information will provide us with a greater understanding of PDCoV infection and will be helpful for establishing new strategies for controlling this virus worldwide.

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.

Alterations in the diversity and composition of gut microbiota in weaned piglets infected with Balantioides coli

Balantioides coli is a ciliated parasite that can cause diarrhea when inhabiting the colon and cecum of pigs and humans. However, information regarding the changes in structure and composition of the gut microbiome in piglets infected with B. coli remains scarce. In this study, 16S rDNA amplicon sequencing was conducted on fecal samples from both B. coli-positive piglets with diarrhea and B. coli-negative piglets without diarrhea. The results showed that Firmicutes and Bacteroidetes were the major phyla in the two groups, and the relative abundance of the phylum Firmicutes, including Ruminococcaceae and Clostridiaceae, was significantly lower in the B. coli-positive samples than in the B. coli-negative ones (p < 0.05). Compared with B. coli-negative samples, Alloprevotella and Faecalibacterium showed distinctly higher relative abundances (p < 0.05) in the B. coli-positive samples, and the abundances of some potential pathogenic bacteria, including Escherichia-Shigella and Campylobacter, were positively correlated with B. coli infection and diarrhea of weaned piglets. In addition, there were statistically significant differences in fecal microbiota diversity and abundances of predicted functional genes between B. coli-colonized and B. coli-negative samples (p <  0.05). Taken together, these findings suggest that there were significant differences in the bacterial community composition, diversity, and functions between the B. coli-positive and B. coli-negative piglets, and the colonization by B. coli may be associated with the dysbiosis of gut microbiota structure in weaned piglets.