Porcine Dermatitis And Nephropathy Syndrome Research Articles

Molecular detection and genetic characteristics of porcine circovirus 3 and porcine circovirus 4 in central China.

Porcine circoviruses (PCVs) are a significant cause of concern for swine health, with four genotypes currently recognized. Two of these, PCV3 and PCV4, have been detected in pigs across all age groups, in both healthy and diseased animals. These viruses have been associated with various clinical manifestations, including porcine dermatitis and nephropathy syndrome (PDNS) and respiratory and enteric signs. In this study, we detected PCV3 and PCV4 in central China between January 2022 and February 2023. We tested fecal swabs and tissue samples from growing-finishing and suckling pigs with or without respiratory and systemic manifestations and found the prevalence of PCV3 to be 15.15% (15/99) and that of PCV3/PCV4 coinfection to be 4.04% (4/99). This relatively low prevalence might be attributed to the fact that most of the clinical samples were collected from pigs exhibiting respiratory signs, with only a few samples having been obtained from pigs with diarrhea. In some cases, PCV2 was also detected, and the coinfection rates of PCV2/3, PCV2/4, and PCV2/3/4 were 6.06% (6/99), 5.05% (5/99), and 3.03% (3/99), respectively. The complete genomic sequences of four PCV3 and two PCV4 isolates were determined. All four of the PCV3 isolates were of subtype PCV3b, and the two PCV4 isolates were of subtype PCV4b. Two mutations (A24V and R27K) were found in antibody recognition domains of PCV3, suggesting that they might be associated with immune escape. This study provides valuable insights into the molecular epidemiology and evolution of PCV3 and PCV4 that will be useful in future investigations of genotyping, immunogenicity, and immune evasion strategies.

Investigation of porcine circovirus type 2 and porcine circovirus type 3 infections based on dual TaqMan fluorescent quantitative PCR method and genetic evolutionary analysis of these two viruses.

Porcine circovirus type 2 (PCV2) is the pathogen of Porcine Circovirus Associated Diseases. Porcine circovirus type 3 (PCV3) is a novel porcine circovirus associated with porcine dermatitis and nephropathy syndrome (PDNS) and reproductive failure. PCV2 is clearly pathogenic, while the pathogenicity of PCV3 remains controversial, so it is crucial to monitor the prevalence of PCV2 and PCV3 in healthy and diseased pigs to investigate the effects of PCV3 and PCV2 on the health status of pigs. Here, we developed a PCV2 and PCV3 dual TaqMan quantitative PCR (qPCR) method to test samples from healthy and diseased pigs, to clarify the differences in the positive rates and viral copy numbers of PCV2 and PCV3, and to analyze the genetic evolution and molecular characterization of the viral genomes obtained with sequence alignment and phylogenetic analysis, homology and structural analysis of Cap proteins, and selection pressure analysis. We successfully established a dual TaqMan qPCR method for PCV2 and PCV3 with good repeatability, specificity and sensitivity. In total, 1,385 samples from 15 Chinese provinces were tested with the established qPCR. The total positive rates were 37.47% for PCV3 and 57.95% for PCV2, and the coinfection rate for was 25.49%. The positive rates of PCV3 and PCV2 in 372 healthy pigs were 15.05 and 69.89%, respectively, and the coinfection rate was 12.90%. The positive rates of PCV3 and PCV2 in 246 diseased pigs were 55.69 and 83.33%, respectively, and the coinfection rate was 47.97%. Eighteen PCV3 genomes and 64 PCV2 genomes were identified, including nine each of the PCV3a-1 and PCV3b genotypes, eight of PCV2a, 16 of PCV2b, and 40 of PCV2d. The amino acid identity within the PCV3 Cap proteins was 94.00-100.0%, whereas the PCV2 Cap proteins showed an identity of 81.30-100.0%. PCV3 Cap was most variable at amino acid sites 24, 27, 77, 104 and 150, whereas PCV2 Cap had 10-13 unique sites of variation between genotypes. These results clarify the prevalence and variations of PCV2 and PCV3 in healthy and diseased pigs, which will provide a basis for the prevention and control of the two viral infections.

Emergence of novel circoviruses in humans and pigs and their possible importance for xenotransplantation and blood transfusions.

As sequencing is becoming more broadly available, virus discovery continues. Small DNA viruses contribute to up to 60% of the overall virus load in pigs. Porcine circoviruses (PCVs) are small DNA viruses with a single-stranded circular genome. They are common in pig breeds and have not been properly addressed for their potential risk in xenotransplantation. Whereas PCV1 is non-pathogenic in pigs, PCV2 has been associated with various disease manifestations. Recently two new circoviruses have been described, PCV3 and PCV4. While PCV4 is currently present mainly in Asia, PCV3 is widely distributed, and has been identified in commercial pigs, wild boars, and pigs generated for xenotransplantation. In one case PCV3 was transmitted by pigs to baboons via heart transplantation. PCV3 pathogenicity in pigs was controversial initially, however, the virus was found to be associated with porcine dermatitis and nephropathy syndrome (PDNS), reproductive failure, and multisystemic inflammation. Inoculation studies with PCV3 infectious clones confirmed that PCV3 is pathogenic. Most importantly, recently discovered human circoviruses (CV) are closely related to PCV3. Literature was evaluated and summarized. A dendrogram of existing circoviruses in pigs, humans, and other animal species was created and assessed at the species level. We found that human circoviruses can be divided into three species, human CV1, CV2, and CV3. Human CV2 and CV3 are closest to PCV3. Circoviruses are ubiquitous. This communication should create awareness of PCV3 and the newly discovered human circoviruses, which may be a problem for blood transfusions and xenotransplantation in immune suppressed individuals.

Exploring the surface epitope and nuclear localization analysis of porcine circovirus type 3 capsid protein

Porcine circovirus 3 (PCV3) is a newly emerging virus associated with porcine dermatitis and nephropathy syndrome (PDNS) and reproductive disorders, impacting global pig populations. Porcine circoviruses contain two major open reading frames (ORFs), and the ORF2 encodes the viral capsid protein (Cap). Cap is the most antigenic structural protein and an ideal candidate for the development of vaccines and diagnostic reagents. This study generated a monoclonal antibody (MAb) specific to PCV3 Cap, MAb CCC160, for diagnosis and pathogenesis studies of this novel virus. The MAb specifically recognized PCV3-infected swine lymph node tissue in an immunohistochemical analysis confirming its clinical diagnostic potential. In addition, a novel linear B-cell epitope recognized by MAb CCC160 was identified at the amino acid region 120–134 of Cap. Nuclear localization analysis of PCV3 Cap revealed a potential nuclear localization signal (NLS) in the middle region (aa 131–143) in addition to the dominant N-terminal NLS that is already known. A cell viability assay further demonstrated that the cytotoxicity of PCV3 Cap is correlated with its nuclear localization, indicating a crucial role of Cap in the pathogenic mechanism of PCV3. A full-length construct of PCV3 Cap was successfully expressed using a baculovirus expression system and purified recombinant proteins self-assembled into virus-like particles (VLPs). The protein constitution of the VLPs was confirmed by MAb CCC160 recognition, indicating the correct conformation and specificity of VLP and exhibiting the linear epitope aa 120–134 on the VLP surface. These results provide insights for developing diagnostic tools and potential VLP vaccines for PCV3, revealing its pathogenesis and antigenic properties.

Detection of Porcine Circovirus Type 3 in Serum, Semen, Oral Fluid, and Preputial Fluid Samples of Boars.

Porcine circovirus type 3 (PCV3) is commonly associated with clinical symptoms such as porcine dermatitis and nephropathy syndrome (PDNS)-like lesions, respiratory signs, and reproductive disorders. This study aimed to investigate the epidemiology of PCV3 in a boar stud. The objectives were to detect PCV3 in semen, as well as matched serum, oral fluid, and preputial fluid samples from adult boars using quantitative polymerase chain reaction (qPCR), analyze PCV3-IgG antibody data, and genetically characterize a positive sample. A total of 112 samples from 28 boars were collected from a large-scale pig farm in Guangxi, China. The qPCR results showed that the PCV3 DNA was not detected in semen, with a positive rate of 0% (0/28), while it was detected in serum (3.57%-1/28), oral fluid (64.28%-18/28), and preputial fluid (46.4%-13/28). The seropositivity rate of PCV3-IgG in serum was 82.14% (23/28) according to the indirect enzyme-linked immunosorbent serologic assay (ELISA) results. Phylogenetic analysis revealed that one of the PCV3 isolates belonged to the PCV3c clades. This is the first report of PCV3 detection in preputial fluid from boars. The results suggest that PCV3 is transmitted among boars on pig farms and exhibits epidemic characteristics.

Pathogenicity and immune modulation of porcine circovirus 3

Porcine circoviruses (PCVs) are members of the genus Circovirus of the family Circoviridae, and four species of PCVs have been discovered and named PCV1–PCV4, respectively. With the first report of PCV3 in America in 2016, the pathogenic variant was found to be associated with various clinical features, called porcine circovirus associated disease (PCVAD), including multisystemic inflammation, porcine dermatitis and nephropathy syndrome (PDNS), reproductive disorders, respiratory or digestive disorders. Increasing experimental data have shown that PCV3 is widespread around the world, but the failure of virus isolation and propagation has put obstacles in the way of PCV3 research. Moreover, a large number of reports demonstrate that PCV3 usually co-infects with other pathogens in pigs. Thus, whether PCV3 alone causes clinical manifestations needs to be fully discussed. In addition, the host cell immune response was activated during PCV3 infection, and PCV3-encoded proteins may regulate immune responses to facilitate its replication. An in-depth understanding of PCV3 pathogenesis and immune regulation strategies is critical for PCVAD prevention. In this review, the advances in pathogenicity and innate immune modulation of PCV3 were summarized, which could deepen the understanding of this virus and PCV3-related diseases.

First molecular detection of porcine circovirus type 4 (PCV4) in Malaysia.

Porcine circovirus type 4 (PCV4) is the newest member in the porcine circovirus family, first reported in 2020. To date, the presence of PCV4 has only been reported in China, South Korea and most recently in Thailand. Detection of PCV4 have been reported in various production stages of pigs from piglets, finishers to sows; associated with a myriad of clinical manifestations including porcine dermatitis and nephropathy syndrome (PDNS), postweaning multisystemic wasting syndrome (PMWS), respiratory, enteric and neurological diseases. While successful virus isolation and culture has yet to be reported, pathogenicity of PCV4 has been demonstrated through infectious clone studies. The objective of this study is to investigate the presence of PCV4 in Malaysian porcine population to update the epidemiology of porcine circoviruses in Malaysia. A total of 49 samples from commercial intensive pig farms, abattoir and wild boar population were subjected to conventional polymerase chain reaction assay to detect PCV4 capsid (cap) genome. Resulting cap nucleotide sequences were analyzed for maximum likelihood phylogeny relationship. Results revealed that PCV4 is present in Peninsular Malaysia at a molecular prevalence of 4.08% (2 / 49 samples). Both PCV4 positive samples originated from clinically healthy finishers. Malaysian PCV4 strains were classified as genotype PCV4b, and were found to be phylogenetically distinct from the China, South Korea and Thailand strains. With this latest update of the novel PCV4 in Malaysia, it is clear that more attention needs to be given to the investigation of novel porcine circoviruses (PCV) and management of PCV diseases.

Heme Oxygenase-1 and Its Metabolites Carbon Monoxide and Biliverdin, but Not Iron, Exert Antiviral Activity against Porcine Circovirus Type 3.

Porcine circovirus type 3 (PCV3) is a newly discovered pathogen that causes porcine dermatitis and nephropathy syndrome (PDNS)-like clinical signs, multisystemic inflammation, and reproductive failure. Heme oxygenase-1 (HO-1), a stress-inducible enzyme, exerts protective functions by converting heme into carbon monoxide (CO), biliverdin (BV), and iron. However, the effects of HO-1 and its metabolites on PCV3 replication remain unknown. In this study, experiments involving specific inhibitors, lentivirus transduction, and small interfering RNA (siRNA) transfection revealed that active PCV3 infection reduced HO-1 expression and that the expression of HO-1 negatively regulated virus replication in cultured cells, depending on its enzymatic activity. Subsequently, the effects of the HO-1 metabolites (CO, BV, and iron) on PCV3 infection were investigated. The CO inducers (cobalt protoporphyrin IX [CoPP] or tricarbonyl dichloro ruthenium [II] dimer [CORM-2]) mediate PCV3 inhibition by generating CO, and this inhibition is reversed by hemoglobin (Hb; a CO scavenger). The inhibition of PCV3 replication by BV depended on BV-mediated reactive oxygen species (ROS) reduction, as N-acetyl-l-cysteine affected PCV3 replication while reducing ROS production. The reduction product of BV, bilirubin (BR), specifically promoted nitric oxide (NO) generation and further activated the cyclic GMP/protein kinase G (cGMP/PKG) pathway to attenuate PCV3 infection. Both the iron provided by FeCl3 and the iron chelated by deferoxamine (DFO) with CoPP treatment failed to affect PCV3 replication. Our data demonstrate that the HO-1-CO-cGMP/PKG, HO-1-BV-ROS, and HO-1-BV-BR-NO-cGMP/PKG pathways contribute crucially to the inhibition of PCV3 replication. These results provide important insights regarding preventing and controlling PCV3 infection. IMPORTANCE The regulation of host protein expression by virus infection is the key to facilitating self-replication. As an important emerging pathogen of swine, clarification of the interaction between PCV3 infection and the host enables us to understand the viral life cycle and pathogenesis better. Heme oxygenase-1 (HO-1) and its metabolites carbon monoxide (CO), biliverdin (BV), and iron have been demonstrated to involve a wealth of viral replications. Here, we, for the first time, demonstrated that HO-1 expression decreases in PCV3-infected cells and negatively regulates PCV3 replication and that the HO-1 metabolic products CO and BV inhibit PCV3 replication by the CO- or BV/BR/NO-dependent cGMP/PKG pathway or BV-mediated ROS reduction, but the iron (the third metabolic product) does not. Specifically, PCV3 infection maintains normal proliferation by downregulating HO-1 expression. These findings clarify the mechanism by which HO-1 modulates PCV3 replication in cells and provide important targets for preventing and controlling PCV3 infection.

Histopathological Changes and Inflammatory Response in Specific Pathogen-Free (SPF) with Porcine Circovirus Type 3 Infection.

Since the first report of PCV3 virus infection in 2016, it has been linked to multisystemic inflammation, reproductive failure, cardiac pathology, and clinical indications resembling porcine dermatitis and nephropathy syndrome (PDNS). However, the pathogenesis and clinical significance of PCV3 is still unclear. In this study, a PCV3 infection model was created using SPF pigs, and histopathology and fluorescence quantitative PCR were utilized to examine PCV3's pathogenicity. Reductions in body weight gain and fever were observed during this study. However, other clinical signs such as Dermatitis and Nephropathy Syndrome were not observed through the study. Viremia was detected in the PCV3-inoculated group from 17 days post-inoculation (p.i.) until the end of the study. Nasal shedding was detected from 21 to 35 dpi and fecal shedding was detected during 25-33 days and 39 days, respectively. Gross lesions and histological evaluation were detected in various tissues and organs, including the lung, heart, kidney, lymph nodes, spleen, liver, small intestine, and testis. The heart, lung, liver, kidney, lymph nodes, and spleen showed pathological changes. The pathological features include swelling, inflammation, cell degeneration, necrosis, and hemorrhage. The lesions are consistent with multisystemic inflammation. Tissue viral load results showed only heart, lung, liver, kidney, lymph nodes, and spleen was positive by qRT-PCR. Moreover, the pro-inflammation cytokines in serum increased a lot in the PCV3-inoculated group compared to the control group, demonstrating that the induced inflammation response may be the cause of tissue damage in PCV3-infection. This study demonstrated that PCV3 can produce mild pathological damage to multiple organs, especially multisystemic inflammatory cell infiltration and prolonged viremia, viral shedding in nasal secretions. This is the first in vivo characterization of PCV3 infection in the SPF piglets model using isolated PCV3 strain, and this is also the first time to show the gross and pathological lesion with all tissue and organs in the PCV3-inoculated group. Our findings might serve as a starting point for more investigation into PCV3's pathogenic mechanism.

Porcine dermatitis and nephropathy syndrome on natural infection of Porcine Circovirus Type-2 in pigs in Kerala, southern India

Porcine circovirus type-2 (PCV-2), is a widely studied pathogen in the swine population during the last decade. Even though, PCV-2 has many disease manifestations, the objective of the current study was to investigate the cutaneous and renal lesions in PCV-2 infected cases. Swine carcasses presented for post-mortem examination with a history of skin lesions, inappetance, dyspnoea and diarrhoea, during September 2021 to April 2022 from different parts of Kerala were utilised in this study. The samples were collected and screened with Polymerase chain reaction (PCR) after which, histological and immunohistochemical examination were performed. Three samples were found positive for PCV-2 out of 25 samples using PCR. Microscopically, skin revealed congestion, haemorrhages and infiltration of mononuclear infiltration cells and neutrophils in dermis and spongiosis in epidermis. Kidney revealed haemorrhages, congestion, tubular necrosis and degenerative alterations, interstitial mononuclear cell infiltration with occasional glomerulitis and vasculitis in the renal pelvis. Localisation of PCV-2 antigen was observed in renal tissue and lymph node with immunohistochemistry. Altogether, these findings were suggestive of porcine dermatitis and nephropathy syndrome (PDNS) in pigs. These results indicate the importance of including PCV-2 in the differential diagnosis of cutaneous lesions caused by bacterial and viral etiologies in pigs.

Retrospective assessment of porcine circovirus 3 (PCV-3) in formalin-fixed, paraffin-embedded tissues from pigs affected by different clinical-pathological conditions

BackgroundPorcine circovirus 3 (PCV-3) is a recently discovered pathogen of swine that has been associated with several conditions. However, many questions remain unanswered regarding its infection, especially in terms of pathogenesis and disease impact. The aim of the present study was to retrospectively investigate the presence of PCV-3 genome by real time quantitative PCR (qPCR) and in situ hybridization (ISH) on selected formalin-fixed paraffin-embedded tissues of pigs affected by different clinical conditions and histological lesions.Materials and methodsConditions investigated included porcine dermatitis and nephropathy syndrome (PDNS), periweaning failure-to-thrive syndrome (PFTS), congenital tremors type AII, reproductive disorders, and pigs affected by systemic periarteritis/arteritis, myocarditis, or encephalitis. Studied cases (n = 587) were investigated from a diagnostic database (n = 4162) that comprised samples collected within the period 1998–2021. From each condition/lesion, 10 to 12 cases were subsequently selected and tested by qPCR and ISH (72 cases total).ResultsA total of 587 cases fulfilled inclusion criteria of the different studied conditions and were distributed among the seven groups. For the further selected cases, PCV-3 genome was found by qPCR in 12/12 periarteritis, 5/10 reproductive disease, 5/10 PFTS, 3/10 myocarditis, 1/10 encephalitis and 1/10 congenital tremor cases. PCV-3 was not found in any of the PDNS cases assessed. In periarteritis cases, tissues more commonly affected were mesenteric arteries and kidney. Reproductive disease cases associated to PCV-3 genome consistently displayed myocarditis. The lesions and labelling distribution of PFTS cases with presence of PCV-3 genome were comparable to those of the periarteritis group. qPCR and ISH yielded similar results within each studied case and were statistically comparable.ConclusionOur results suggest that periarteritis is the hallmark lesion of PCV-3-SD, and that mesenteric lymph node and kidney appeared to be the most reliable organs to confirm the presence of PCV-3 genome in cases with periarteritis.

Prevalence and phylogenetic analysis of porcine circovirus type 2 (PCV2) and type 3 (PCV3) in the Southwest of China during 2020-2022.

Porcine circovirus type 2 (PCV2) is considered one of the viruses with substantial economic impact on swine industry in the word. Recently, porcine circovirus type 3 (PCV3) has been found to be associated with porcine dermatitis and nephropathy syndrome (PDNS)-like disease. And the two viruses were prone to co-infect clinically. To further investigate the prevalence and genetic diversity of the two viruses, 257 pig samples from 23 different pig farms in southwest China with suspected PCVAD at different growth stages were analyzed by real-time PCR between 2020 and 2022 to determine the presence of PCV2 and PCV3. Results showed high prevalence of PCV2 and PCV3: 26.46% samples were PCV2 positive and 33.46% samples were PCV3 positive. The coinfection rate was doubled from 2020 (5.75%) to 2022 (10.45%). Subsequently, the whole genome sequences of 13 PCV2 and 18 PCV3 strains were obtained in this study. Of these, 1 strain was PCV2a, 5 strains were PCV2b and 7 strains were PCV2d, indicating that PCV2d was the predominant PCV2 genotype prevalent in the Southwest of China. In addition, the phylogenetic analysis of PCV3 showed high nucleotide homology (>98%) between the sequences obtained in this study and reference sequences. And 3 mutations (A24V, R27K and E128D) were found in PCV3 antibody recognition domains, which might be related to the mechanism of viral immune escape. Thus, this study will enhance our understanding of the molecular epidemiology and evolution of PCV2 and PCV3, which are conducive to the further study of the genotyping, immunogenicity and immune evasion of PCVs.

Pathomorphology, immunohistochemical, and molecular detection of an atypical porcine dermatitis and nephropathy syndrome (PDNS) due to PCV-2d-2 in naturally affected grower pigs of India

Porcine circovirus type 2 (PCV-2) is of great economic significance to porcine industry worldwide. PCV-2 variants and genotypes, alternating world over, are the etiological agent of several clinical syndromes such as porcine dermatitis and nephropathy syndrome (PDNS), post-weaning multi-systemic wasting syndrome (PMWS) and others in pigs. This study is reporting an atypical manifestation of PDNS in twelve grower pigs, 3- to - 4.5 months age and either sex, died of the disease, with predominant lesions of nephropathy and no obvious clinical lesions in skin. Necropsy examination of pigs showed lesions of petechial -to- ecchymotic hemorrhages in the kidneys and in the right auricular musculature of the hearts. Microscopic lesions in H & E sections of the kidneys showed acute glomerulonephritis, interstitial nephritis, and vasculitis, but the skin morphology and architecture remained unaltered in contrast to the pathognomonic lesions of PDNS described in the literature. Other syndromic associations of PDNS in these cases included-perimyocarditis, interstitial pneumonia, depleted lymphoid tissues, tonsillitis, enteritis, and meningo-encephalitis. The lesional sites in duplicate paraffin tissue sections of kidneys, heart, lungs, spleen, lymph nodes, intestine, and brain demonstrated PCV-2 antigen in the cytoplasm of cells as highlighted by the intense immunolabeling on IHC staining. The PCV-2 positive organs reconfirmed by PCR, targeting ORF2 gene, which yielded 481bp size of products. The sequencing results of 481bp products on phylogenetic analysis showed 94% similarity with that of PCV-2 sequences in the database that grouped into PCV2d-2 genotype. The present report confirms, probably for the first time, the atypical PDNS cases due to PCV2d-2 genotype in naturally affected grower pigs of India.

Genetic Variation Analysis of Porcine Circovirus Type 4 in South China in 2019 to 2021.

Porcine circovirus type 4 (PCV4) is a novel virus associated with porcine dermatitis and nephropathy syndrome (PDNS)-like signs identified firstly in China in 2019. However, the details of the molecular epidemiology of PCV4 are unclear at this time. A total of forty-two related sequences were selected from the GenBank database to explore the spread of PCV4 and its rule in genetic evolution. Of the selected strains, 41 were from south China in 2019 to 2021 and the other was a foreign representative strain. Phylogenetic tree construction, nucleotide and amino acid (aa) sequence alignment, gene recombination and antigen structure prediction were performed on the collected sequences using bioinformatics softwares. The 42 PCV4 strains were divided into two subgenotypes: PCV4a (35/42) and PCV4b (7/42), according to the constructed genetic evolution tree. PCV4a is the main epidemic strain, and it can be further divided into two different gene clusters: PCV4a-1 (22/35) and PCV4a-2 (13/35). The pairwise comparison analysis showed that the complete genome sequence similarity of the 42 PCV4 strains ranged between 97.9% and 100%, and the aa sequences of the Cap proteins of 42 PCV4 strains had three major heterogenic or hypervariable regions—27–28, 96 and 212—all located near the antigenic epitope of the Cap protein. The results of this study can provide some basis for further studying the spread and epidemic growth of PCV4, and the prevention and control of PCV4 infection in China.

Reconstruction of the Evolutionary Origin, Phylodynamics, and Phylogeography of the Porcine Circovirus Type 3.

Porcine circovirus type 3 (PCV3) is a newly identified virus associated with porcine dermatitis and nephropathy syndrome (PDNS) and multisystemic inflammatory responses in pigs. Recent studies suggests that PCV3 originated from bat circoviruses; however, the origin time, mode of spread, and geographic distribution of PCV3 remain unclear. In this study, the evolutionary origin, phylodynamics, and phylogeography of PCV3 were reconstructed based on the available complete genome sequences. PCV3 showed a closer relationship with bird circovirus than with bat circovirus, but their common ancestor was bat circovirus, indicating that birds may be intermediate hosts for the spread of circoviruses in pigs. Using the BEAST and phylogenetic analyses, three different clades of PCV3 (PCV3a, PCV3b, and PCV3c) were identified, with PCV3a being the most prevalent PCV3 clade. Further studies indicated that the earliest origin of PCV3 can be traced back to 1907.53–1923.44, with a substitution rate of 3.104 × 10–4 to 6.8524 × 10–4 substitution/site/year. A phylogeographic analysis highlighted Malaysia as the earliest location of the original PCV3, which migrated to Asia, America, and Europe. Overall, this study provides novel insights into the evolutionary origin, spread mode, and geographic distribution of PCV3, which will facilitate the prevention and control of PCV3 epidemics in the future.

Revisiting Porcine Circovirus Disease Diagnostic Criteria in the Current Porcine Circovirus 2 Epidemiological Context.

Current knowledge on porcine circovirus diseases (PCVD) caused by Porcine circovirus 2 (PCV-2) includes the subclinical infection (PCV-2-SI), systemic (PCV-2-SD) and reproductive (PCV-2-RD) diseases, and porcine dermatitis and nephropathy syndrome (PDNS). Criteria to establish the diagnosis of these conditions have not changed over the years; thus, the triad composed by clinical signs, lesions and viral detection in lesions are still the hallmark for PCV-2-SD and PCV-2-RD. In contrast, PCV-2-SI diagnosis is not usually performed since this condition is perceived to be controlled by default through vaccination. PDNS is diagnosed by gross and histopathological findings, and PCV-2 detection is not recognized as a diagnostic criterion. Molecular biology methods as a proxy for PCVD diagnoses have been extensively used in the last decade, although these techniques should be mainly considered as monitoring tools rather than diagnostic ones. What has changed over the years is the epidemiological picture of PCV-2 through the massive use of vaccination, which allowed the decrease in infectious pressure paralleled with a decrease in overall herd immunity. Consequently, the need for establishing the diagnosis of PCVD has increased lately, especially in cases with a PCV-2-SD-like condition despite vaccination. Therefore, the objective of the present review is to update the current knowledge on diagnostic criteria for PCVDs and to contextualize the interest of using molecular biology methods in the overall picture of these diseases within variable epidemiological scenarios of PCV-2 infection.

Detection of porcine circovirus type 3 DNA in serum and semen samples of boars from a German boar stud

Porcine circovirus type 3 (PCV3) is regularly reported in association with various clinical presentations, including porcine dermatitis and nephropathy syndrome (PDNS)-like lesions, respiratory signs, congenital tremor, and reproductive disorders. To investigate the epidemiology of PCV3 in a boar stud, we analysed fresh boar semen and matching sera from 181 boars from a German stud supplying semen for artificial insemination (AI) to approximately 740 breeder farms for PCV3 DNA. PCV3 DNA was detected in 1.7% semen samples and 24.3% sera. Spearman rho correlation demonstrated a significant positive correlation between boar age and quantitative DNA (by PCR quantification cycles [Cq] values) in serum samples (r = 0.636; P < 0.001). Sera from boars up to 12 months of age had higher viral loads (P < 0.001) and were PCV3-positive significantly more often (P < 0.01) than older boars. Detection of PCV3 DNA was not associated with breed (P> 0.05). PCV3 DNA was detected sporadically in fresh boar semen. Based on the assumption that processing fresh semen reduces viral load in semen used for AI, it is likely that the risk of sexual transmission of PCV3 during AI in is low. However, young boars may contribute to the maintenance of PCV3 infection in boar studs.

First detection and phylogenetic analysis of porcine circovirus 3 in female donkeys with reproductive disorders

BackgroundPCV3 is a pathogen associated with porcine dermatitis and nephropathy syndrome (PDNS)-like clinical signs, reproductive failure, and cardiac and multiorgan inflammation, which was newly identified in 2016 in sows in USA. Recently, PCV3 has also been identified from several non-porcine species like (cattle, dog, wild boar, deer, mice and ticks). However, PCV3 infection in donkey is not well established. Since 2019, 300 blood samples were collected from female donkey, which was characterized by abortion and sterility, in Liaocheng city of China.ResultsIn the present study, an investigation of PCV3 in donkey blood samples was undertaken employing by real time PCR. Positive rates of PCV3 in donkeys reach to 21.0 %. In addition, one full-length PCV3 genome sequence was obtained, and it had a highest identity with porcine circovirus 3 PCV3/CN/Nanjing2017 strain and is clustered to PCV3a genotype based on ORF2 sequences.ConclusionsThis is the first report of detection of PCV3 from female donkeys presenting reproductive failure in large-scale donkey farms, China. In addition, the PCV3 strain identified in this study shared the closest relationship with those from porcine, suggesting that PCV3 may be transmitted from pigs to donkeys. Totally, PCV3 infection in donkey should be concerned although the association between it and reproductive failure are not better understood.

Comparative immunopathogenesis and biology of recently discovered porcine circoviruses.

Porcine circoviruses are important pathogens of production swine. Porcine circovirus type 1 (PCV1) is non-pathogenic, and discovered as a contaminant of a porcine kidney cell line, PK-15. The discovery of pathogenic variant, PCV2, occurred in the late 90s in association with post-weaning multi-systemic wasting disease syndrome (PMWS), which is characterized by wasting, respiratory signs and lymphadenopathy in weanling pigs. A new PCV type, designated as PCV3, was discovered in 2016, in pigs manifesting porcine dermatitis and nephropathy syndrome (PDNS), respiratory distress and reproductive failure. Pathological manifestations of PCV3 Infections include systemic inflammation, vasculitis and myocarditis. A fourth PCV type, PCV4, was identified in 2020 in pigs with PDNS, respiratory and enteric signs. All the pathogenic PCV types are detected in both healthy and morbid pigs. They cause chronic, systemic infections with various clinical manifestations. Dysregulation of the immune system homeostasis is a pivotal trigger for pathogenesis in porcine circoviral infections. While the study of PCV3 immunobiology is still in its infancy lessons learned from PCV2 and other circular replication-associated protein (Rep)-encoding single stranded (ss) (CRESS) DNA viruses can inform the field of exploration for PCV3. Viral interactions with the innate immune system, interference with dendritic cell function coupled with the direct loss of lymphocytes compromises both innate and adaptive immunity in PCV2 infections. Dysregulated immune responses leading to the establishment of a pro-inflammatory state, immune complex associated hypersensitivity, and the necrosis of lymphocytes and immune cells are key features of PCV3 immunopathogenesis. A critical overview of the comparative immunopathology of PCV2 and PCV3/4, and directions for future research in the field are presented in this review.

What do we know about porcine circovirus 3 (PCV3) diagnosis so far?: A review.

Porcine circovirus 3 (PCV3) was first discovered in 2016, almost concomitantly by two groups of researchers in the United States. The novel case was reported in a group of sows with chronic reproductive problems with clinical presentation alike porcine dermatitis and nephropathy syndrome (PDNS), where metagenomic sequencing revealed a genetically divergent porcine circovirus designated PCV3. The discovery of PCV3 in a PDNS case, which used to be considered as part of PCVAD attributed to PCV2 (porcine circovirus 2), has garnered attention and effort in further research of the novel virus. Just when an infectious molecular DNA clone of PCV3 has been developed and successfully used in an in vivo pathogenicity study, yet another novel PCV strain surfaced, designated PCV4 (porcine circovirus 4). So far, PCV3 has been reported in domestic swine population globally at low to moderate prevalence, from almost all sample types including organ tissues, faecal, semen and colostrum samples. PCV3 has been associated with a myriad of clinical presentations, from PDNS to porcine respiratory disease complex (PRDC). This review paper summarizes the studies on PCV3 to date, with focus on diagnosis.