Porcine circovirus type 3 (PCV3) is a newly identified circovirus from swine in the USA, China and Poland. This novel circovirus has been associated with porcine dermatitis and nephropathy syndrome (PDNS), reproductive failure and multisystemic inflammation; moreover, PCV3 poses a potential threat to the swine industry. In this retrospective study, a phylogenetic analysis was conducted to address the epidemiology and evolutionary dynamics of this novel circovirus. The total positive sample rate of PCV3 was 26.7% (76/285) and has increased gradually over the past 3 years. Of these PCV3-positive samples, 22.3% (17/76) were coinfected with PCV2. PCV3 can be detected in multiple sample types with different positive rates, and the positive rate is highest among stillborn. We also divide PCV3 into three clades (PCV3a, PCV3b and PCV3c) based on two amino acid mutations (A24V and R27K) on the cap protein in this study. In addition, the origin of PCV3 was approximately 1966 and may have originated from a bat-associated circovirus. Our results suggested that PCV3 is widely distributed in southern China and has been circulating in swine herds for nearly half a century. PCV3 has evolved into different clades caused by mutations in cap proteins; thus, further research on PCV3 epidemiology should be conducted.

Insights into the epidemic characteristics and evolutionary history of the novel porcine circovirus type 3 in southern China

Porcine circovirus 2 (PCV2) is the etiological agent that causes porcine circovirus diseases and porcine circovirus-associated diseases (PCVD/PCVAD), which are present in every major swine-producing country in the world. PCV2 infections may downregulate the host immune system and enhance the infection and replication of other pathogens. However, the exact mechanisms of PCVD/PCVAD are currently unknown. To date, many studies have reported that several cofactors, such as other swine viruses or bacteria, vaccination failure, and stress or crowding, in combination with PCV2, lead to PCVD/PCVAD. Among these cofactors, co-infection of PCV2 with other viruses, such as porcine reproductive and respiratory syndrome virus, porcine parvovirus, swine influenza virus and classical swine fever virus have been widely studied for decades. In this review, we focus on the current state of knowledge regarding swine co-infection with different PCV2 genotypes or strains, as well as with PCV2 and other swine viruses.

https://www.mdpi.com/1999-4915/11/2/185/pdf

Co-Infection of Swine with Porcine Circovirus Type 2 and Other Swine Viruses.

Porcine circovirus 4 (PCV4), a new circovirus with a distinct relationship to other circoviruses, was identified in 2019 in several pigs with severe clinical disease in Hunan Province, China. To investigate the epidemic profile and genetic diversity of the virus, 63 clinical samples were collected from 24 different pig farms in 14 cities in Henan and Shanxi Provinces, China, between February 2018 and December 2019, and the partial Cap gene of PCV4 was amplified by PCR. Among the 63 samples, 16 (25.40%) were positive for PCV4, and 50% (12/24) of the pig farms were positive for PCV4. PCV4 was detected in samples from pigs with different clinical presentations. One PCV4 strain (Henan-LY1-2019) was sequenced in this study, and shared 98.4% genomic nucleotide identity with PCV4 strain HNU-AHG1-2019 (accession no. MK986820) detected on a pig farm in Hunan Province in 2019. A phylogenetic analysis based on the genomes of Henan-LY1-2019 and 31 reference strains showed that the Henan-LY1-2019 strain together with PCV4 strain HNU-AHG1-2019 was grouped in a relatively independent sub-branch, and separated from other viruses in the genus Circovirus. The results of this study extend our understanding of the molecular epidemiology of PCV4.

Molecular detection and phylogenetic analysis of Porcine circovirus 4 in Henan and Shanxi Provinces of China.

Globally, Porcine circovirus type 2 (PCV2) is a recognized viral pathogen of great economic value in pig farming. It is the major cause of ravaging postweaning multisystemic wasting syndrome (PMWS) and many other disease syndromes generally regarded as Porcine circovirus associated diseases (PCVAD) in Europe. PCV2 infections, specifically PMWS, had impacted huge economic loss on swine production at different regions of the world. It has been studied and reported at different parts of the globe including: North and South America, Europe, Asia, Oceania, Middle East, and the Caribbean. However, till date, this virus and its associated diseases have been grossly understudied in sub-Sahara African region and the entire continent at large. Two out of forty-nine, representing just about 4% of countries that make up sub-Sahara Africa presently, have limited records on reported cases and occurrence of the viral pathogen despite the ubiquitous nature of the virus. This review presents an overview of the discovery of Porcine circovirus and its associated diseases in global pig herds and emphasizes the latest trends in PCV2 vaccines and antiviral drugs development and the information gaps that exist on the occurrence of this important viral pathogen in swine herds of sub-Saharan Africa countries. This will serve as wake-up call for immediate and relevant actions by stakeholders in the region.

/pdf/global-status-of-porcine-circovirus-type-2-and-its-2l72g8dest.pdf

Global Status of Porcine circovirus Type 2 and Its Associated Diseases in Sub-Saharan Africa.

Porcine circovirus type 2 (PCV2) is the cause of postweaning multisystemic wasting syndrome (PMWS), which encompasses several distinct symptoms in pigs PCV2 infection and clinical incidence of PMWS have increased in recent years, possibly due to shifts in viral populations and mutations In this study, we identified PVC2 strains currently afflicting pig populations in mainland China, because this is a prerequisite for developing a specific vaccine to control the spread of PMWS We collected 235 tissue samples from 16 provinces between 2014 and 2016 Of these, 152 samples were positive for PCV2 We compared the sequences we obtained for the PVC2 capsid gene, ORF2, to those of the Chinese PCV2 sequences deposited in GenBank between 2002 and 2016 (n = 648) Phylogenetic analyses demonstrated that the PCV2d genotype was the most prevalent strain in the sample population included in GenBank and among the positive samples from this study We also found one PCV2c strain among the GenBank sequences Furthermore, PCV2a-2F was the predominant genotype in the PCV2a cluster Amino acid sequence comparisons demonstrated 708–100% identity within PCV ORF2 and several consistent mutations in ORF2 More interestingly, six isolates were classified as recombinant strains Cumulatively, this study represents the first comprehensive description of PCV2 strains distribution, including recent samples, in Chinese porcine populations We demonstrate the existence of high genetic variability among PVC2 strains and the ability of this virus to rapidly evolve

Genetic analysis of porcine circovirus type 2 in China.

A total of 450 samples from domestic pigs in China were tested for porcine parvoviruses (PPVs) and co-infections with porcine circovirus type 2 (PCV2), and their complete capsid genes were sequenced. The prevalence of PPV1, PPV2, PPV3, PPV4, and PCV2 was 5.56 %, 39.56 %, 45.11 %, 21.56 %, and 47.33 %, respectively, and co-infection with PCV2 occurred in 4 % (PPV1), 22.44 % (PPV2), 24 % (PPV3), and 12 % (PPV4) of the samples. Phylogenetic analysis revealed two main lineages for each virus, and residues that differentiated these viruses were identified. The co-infections of emerging PPVs and PCV2 were prevalent, indicating their cooperative roles in porcine circovirus-associated diseases.

Prevalence of emerging porcine parvoviruses and their co-infections with porcine circovirus type 2 in China.

The processivity factors (PFs) of herpesviruses confer processivity to the DNA polymerase. Understanding whether the herpesvirus PFs function as monomers or multimers is important for clarifying the mechanism by which they provide the DNA polymerase with processivity. Herpes simplex virus type 1 UL42 is a monomer, whereas human cytomegalovirus UL44, Epstein-Barr virus BMRF1, and Kaposi's sarcoma-associated herpesvirus PF-8 exist as dimers. However, the oligomeric status of the pseudorabies virus (PRV) DNA polymerase PF UL42 has not been determined. Using fluorescence confocal microscopy and chemical crosslinking, we confirmed that UL42 is a monomer when expressed in vitro. Crosslinking of nuclear extracts from PRV-infected or uninfected PK-15 cells verified that UL42 exists as a monomer in vivo. Our demonstration that UL42 exists as a monomer in vitro and in vivo contributes to the further investigation of the mechanism used by UL42 to achieve processivity.

Wen-Juan Du

Papers

Prevalence of emerging porcine parvoviruses and their co-infections with porcine circovirus type 2 in China.

The pseudorabies virus DNA polymerase processivity factor UL42 exists as a monomer in vitro and in vivo