Genetic diversity in the capsid protein gene of porcine circovirus type 3 in Vietnam from 2018 to 2019.

Porcine circovirus type 3 (PCV3) was first detected in 2016 and has been reported in many pig-producing countries around the world, including Vietnam. PCV3 has been found in complex cases with multiple clinical syndromes in swine. In this study, we investigated the genetic diversity of PCV3 strains circulating in Vietnam. A total of 249 samples were collected from swine farms located in eight provinces of Vietnam, and 11.65% (29/249) of these samples were found to contain PCV3. The ORF2 genes from the 29 PCV3-positive samples were amplified, purified, and sequenced. Phylogenetic analysis showed that 23 of these strains belonged to the PCV3b subtype, while the remaining six strains belonged to subtype c and subtype a (a-1 and a-2). Analysis of the ORF2 genes indicated that the 29 PCV3 strains had high sequence identity (96.90-100% at the genomic level and 96.19-100% at the amino acid level). Fifteen amino acid substitutions were found in predicted B-cell epitopes in the capsid proteins of the Vietnamese PCV3 strains.

Porcine circovirus genotypes and their copathogens in pigs with respiratory disease in southern provinces of Vietnam.

This study was conducted to investigate the genetic diversity of porcine circovirus type 2 (PCV2) and its coinfecting pathogens in pigs with respiratory disease in Vietnam. Samples from 127 clinical cases were obtained from different southern provinces of Vietnam from January 2018 to January 2020 for PCR and sequence analysis. The infection rate of PCV2 was 78.8%, and the major pathogens found in coinfections with PCV2 were porcine reproductive and respiratory syndrome virus, Mycoplasma hyopneumoniae, and Haemophilus parasuis. Forty-three PCV2-positive clinical samples were selected for amplification and sequencing of the ORF2 region. Phylogenetic analysis of PCV2 ORF2 showed that five of the sequences belonged to PCV2b (11.6%) and 38 belonged to PCV2d (88.4%), indicating that PCV2d strains were predominant in southern provinces of Vietnam. Alignment of the predicted amino acid sequences of the PCV2 capsid protein revealed polymorphic sites in the antibody recognition regions. This study demonstrates the prevalence of the PCV2d genotype in southern Vietnam and presents a comprehensive overview of the coinfecting pathogens associated with PCV2 in young pigs with respiratory disease.

The efficacy and performance impact of Fostera PRRS in a Vietnamese commercial pig farm naturally challenged by a highly pathogenic PRRS virus.

Highly pathogenic porcine reproductive and respiratory syndrome virus (HP-PRRSV) is characterized by high fever, respiratory distress, and high mortality in pigs of all ages and has severely affected the Vietnam pork industry in recent years. The study was conducted to compare the efficacy, safety, and overall performance of a modified live PRRSV-2 vaccine (Fostera PRRS) to an existing PRRSV modified live vaccine on a farm with a recent history of HP-PRRSV-associated respiratory diseases. A total of 351 pigs were randomly allocated to three treatment groups: (i) vaccinated with Fostera PRRS at 1 day of age (n = 118), (ii) vaccinated with Fostera PRRS (n = 118) at 21 days of age, and (iii) vaccinated with Amervac PRRS (n = 115) at 21 days of age. The Fostera PRRS vaccinated pigs had milder clinical symptoms, lower levels of HP-PRRSV viremia, fewer pathological changes in the lung, and higher body weight gain at the end of the study compared with the Amervac PRRS group. Vaccination of pigs with Fostera PRRS at 1 day of age also significantly reduced viral loads in their blood (P < 0.05) and induced higher anti-PRRSV antibody titers (P < 0.01) compared with pigs vaccinated with Amervac PRRS at 21 days of age. Fostera PRRS vaccination at 1 day of age can be useful in protecting young piglets from early HP-PRRSV infection because the immunized pigs were marketed 20 days earlier than their peers immunized at 21-day old as they reached the target market weight earlier in this study.

Simulated Clinical Skills for Veterinary Students Supplement Limited Animal and Clinical Resources in Developing Countries.

As part of an OIE Veterinary Education Twinning Project linking The University of Queensland, Australia and Nong Lam University, Vietnam, the limited access to animal and clinical resources was identified as an impediment to high quality veterinary education at Nong Lam University. However, student focused, simulated learning spaces, which have been widely adopted in veterinary training, are a cost-effective opportunity to provide initial clinical skills to students in countries where resourcing is constrained. In clinical skills training facilities, students use models and simulators to practice their clinical skills to develop the confidence, competence and muscle memory to enter the clinical phase of their training. While high-fidelity veterinary simulators and models are expensive, effective models for foundational clinical skills development can be built in-house for students to practice their skills authentically. This article outlines the cost effective establishment of a veterinary clinical skills training facility at Nong Lam University.

Nucleotide sequence analysis of Vietnamese highly pathogenic porcine reproductive and respiratory syndrome virus from 2013 to 2014 based on the NSP2 and ORF5 coding regions.

A total of 34 highly pathogenic porcine reproductive and respiratory syndrome virus (HP-PRRSV) strains isolated from Vietnam during 2013-2014 were sequenced and analyzed. A partial sequence of ORF1a corresponding to the nonstructural protein 2 (Nsp2) coding region and the full sequence of open reading frame 5 (ORF5) gene was used for the analysis. The HP-PRRSV strains were isolated from pig herds that had never been vaccinated for PRRSV. Nucleotide sequence identities in the portions of ORF1a corresponding to the nonstructural protein 2 (Nsp2) coding region and ORF5 ranged from 96.4 to 100 % and 83.2 to 100 %, respectively. All of the 34 Vietnamese HP-PRRSV strains showed two discontinuous 30-amino-acid deletions in the Nsp2 coding region as a genetic marker of prototypic Chinese HP-PRRSV. The amino acid arginine (R) was present at positions 13 and 151 in ORF5 in 29 out of 34 Vietnamese HP-PRRSV isolates, as well as in the prototypic Chinese HP-PRRSV. Sequence analysis of the ORF5 genes of all Vietnamese HP-PRRSVs revealed six subgroups: Viet 1 to 4, JAX1-like, and VR-2332-like. Nucleotide and amino acid sequence analysis of 34 Vietnamese HP-PRRSV isolates from 2013-2014 indicated that Vietnamese HP-PRRSV has undergone rapid evolutionary changes in recent years when compared with Vietnamese HP-PRRSV isolated before 2012.

Co-circulation and genetic characteristics of porcine circoviruses in postweaning multisystemic wasting syndrome cases in commercial swine farms.

This study aimed to investigate the co-infection and genetic characteristics of Porcine circoviruses in PMWS-affected pigs in five commercial farrow-to-finish swine farms in Vietnam. By the end of 2022, the percentage of PMWS-affected pigs in these farms has increased significantly compared to previous years. The lymph node samples from ten PMWS typical cases were randomly collected to test for the presence of PRRSV, PCV2, PCV3 and PCV4. While PRRSV and PCV4 were not found in these cases, 10 and 3 out of 10 samples were positive for PCV2 and PCV3, respectively. Three farms in the study showed the co-infection of PCV2 and PCV3 in affected pigs. Besides, all PCV-positive samples were sequenced to evaluate genetic characterization of PCVs in PMWS-affected cases. Phylogenetic analysis showed that all PCV3 strains in the study were clustered into PCV3b genotype. 8 out of 10 PCV2 strains belonged to PCV2d genotype while the remaining two strains belonged to PCV2b genotypes. Two farms had co-circulation of PCV2b and PCV2d genotypes in two different age groups of pigs, which is reported for the first time in Vietnam. Several amino acid substitutions were identified in important antigenic regions in the capsid protein of the PCV2 field strains compared to vaccine strains. Taken together, the results showed the high co-prevalence of PCV3 and PCV2, and the wide genetic diversity of PCV2 field and vaccine strains may be the cause of the increased PMWS situation in these pig farms. Supplementary Information: The online version contains supplementary material available at 10.1007/s13337-023-00849-4.

Development of optimized protocol for culturing African swine fever virus field isolates in MA104 cells.

The goal of this study was to identify a candidate commercial cell line for the replication of African swine fever virus (ASFV) by comparing several available cell lines with various medium factors. In the sensitivity test of cells, MA104 and MARC-145 had strong potential for ASFV replication. Next, MA104 cells were used to compare the adaptation of ASFV obtained from tissue homogenates and blood samples in various infectious media. At the 10th passage, the ASFV obtained from the blood sample had a significantly higher viral load than that obtained from the tissue sample (P = 0.000), exhibiting a mean cycle threshold (Ct) value = 20.39 ± 1.99 compared with 25.36 ± 2.11. For blood samples, ASFV grew on infectious medium B more robustly than on infectious medium A (P = 0.006), corresponding to a Ct value = 19.58 ± 2.10 versus 21.20 ± 1.47. African swine fever virus originating from blood specimens continued to multiply gradually and peaked in the 15th passage, exhibiting a Ct value = 14.36 ± 0.22 in infectious medium B and a Ct value = 15.42 ± 0.14 in infectious medium A. When ASFV was cultured from tissue homogenates, however, there was no difference (P = 0.062) in ASFV growth between infectious media A and B. A model was developed to enhance ASFV replication through adaptation to MA104 cells. The lack of mutation at the genetic segments encoding p72, p54, p30, and the central hypervariable region (CVR) in serial culture passages is important in increasing the probability of maintaining immunogenicity when developing a vaccine candidate.

L'objectif de cette étude était d'identifier une lignée cellulaire commerciale candidate pour la réplication du virus de la peste porcine africaine (ASFV) en comparant plusieurs lignées cellulaires disponibles et différents milieux. Lors du test de sensibilité des cellules, MA104 et MARC-145 présentaient un fort potentiel pour la réplication d'AFSV. Par la suite, les cellules MA104 ont été utilisées pour comparer l'adaptation d'ASFV obtenu d'homogénats de tissus et d'échantillons de sang dans différents milieux. Au dixième passage, l'ASFV obtenu de l'échantillon de sang avait une charge virale significativement plus élevée que celle obtenue de l'échantillon de tissu (P = 0,000), avec une valeur seuil moyenne de cycles (Ct) de 20,39 ± 1,99 comparativement à 25,36 ± 2,11. Pour les échantillons sanguins, l'ASFV a poussé sur le milieu B de manière plus robuste que sur le milieu A (P = 0,006), ce qui correspond à une valeur Ct de 19,58 ± 2,10 versus 21,20 ± 1,47. L'ASFV provenant des échantillons sanguins continua de se multiplier graduellement et atteignit un pic au 15e passage, avec une valeur Ct de 14,36 ± 0,22 dans le milieu B et une valeur Ct de 15,42 ± 0,14 dans le milieu A. Toutefois, lorsque l'ASFV fut cultivé à partir des homogénats de tissus, il n'y avait pas de différence (P = 0,062) dans la croissance d'ASFV entre les milieux A et B. Un modèle a été développé pour augmenter la réplication d'ASFV par adaptation aux cellules MA104. L'absence de mutation au segment génétique codant pour p72, p54, p30, et la région hypervariable centrale (CVR) dans des passages en série en culture est importante en augmentant la probabilité de maintenir une immunogénicité lors du développement d'un vaccin candidat.(Traduit par Docteur Serge Messier).

The Isolation and Replication of African Swine Fever Virus in Primary Renal-Derived Swine Macrophages.

African swine fever virus (ASFV) causes hemorrhagic disease in domestic pigs by replicating mainly in monocyte/macrophage lineages. Various primary cells including pulmonary alveolar macrophages have been used for the propagation of ASFV on this account. However, ethical constraints and consistency problems exist as it is necessary to harvest same phenotype of primary cells in order to continue a study. We suggested renal-derived swine macrophages as a novel primary cell candidate to address these issues. These primary cells proved to be permissive to both cell adapted ASFV and a wild-type ASFV. Compared to the commercial cell line MA-104, the renal-derived macrophages were more suitable to isolate the field virus. The consistent molecular characteristics of the renal-derived macrophages were demonstrated by immunocytochemistry with antibodies against macrophage cell surface markers including CD163, CD172a, and Iba-1. Viral protein p30 and p72 expression in ASFV infected macrophages was confirmed by immunocytochemistry by use of specific monoclonal antibodies. We observed increase of cell-free viral DNA and infectious virus titer in infected cell supernatant in successive days-post-infection. These results demonstrated that primary renal-derived swine macrophages are useful for ASFV isolation and propagation in terms of cell phenotypes, susceptibility to the virus, and virus production.

Comparison of two genetically distant type 2 porcine reproductive and respiratory syndrome virus (PRRSV) modified live vaccines against Vietnamese highly pathogenic PRRSV.

Highly pathogenic porcine reproductive and respiratory syndrome virus (HP-PRRSV) known as pig high fever disease was first reported in China and has spread rapidly in neighboring southeastern Asian countries. The objective of this study was to evaluate the efficacy of a new type 2 PRRSV modified live vaccine (vaccine A) against a challenge with a HP-PRRSV and to compare the efficacy of two genetically distant type 2 PRRSV modified vaccines (vaccine A for lineage 8 and vaccine B for lineage 5) against HP-PRRSV (lineage 8) challenge. Pigs were divided into 4 groups (n=12/group); vaccinated challenged (2 groups), unvaccinated challenged, and unvaccinated unchallenged groups. Regardless of vaccines, vaccinated challenged pigs showed significantly lower (P<0.05) mean rectal temperatures and respiratory scores, levels of HP-PRRSV viremia, and lung lesions and HP-PRRSV antigens within lung lesions compared to unvaccinated challenged pigs. Vaccinated challenged pigs had significantly higher (P<0.05) numbers of interferon-γ secreting cells (IFN-γ-SC) compared to unvaccinated challenged pigs. Significant differences were also found when comparing two type 2 PRRSV vaccines after HP-PRRSV challenge. The use of type 2 PRRSV vaccine A was able to significantly reduce fever when compared to type 2 PRRSV vaccine B in vaccinated challenged pigs. Vaccination of pigs with vaccine A reduced viral loads in their blood and induced higher numbers of HP-PRRSV-specific IFN-γ-SC than vaccination of pigs with vaccine B. This study demonstrates partial protection of two genetically distant type 2 PRRSV vaccines against HP-PRRSV challenge in growing pigs.