The first report of porcine parvovirus 8 (PPV8) on the American continent is associated with pigs in Colombia with porcine respiratory disease.

Seven novel porcine parvoviruses (PPV2 to PPV8) have been discovered in the last two decades. The last one reported was PPV8 in China in 2022, which was proposed to be a member of the genus Protoparvovirus. Here, we report the first detection of PPV8 outside China - in two provinces from Colombia. Six out of 146 (4.1%) pigs showing porcine respiratory disease (PRD) tested positive for PPV8. Sequencing and phylogenetic analysis of two Colombian PPV8 isolates (GenBank database accession numbers PP335559 and PP335560) showed them to be members of the genus Protoparvovirus. Furthermore, PPV8 was detected in coinfections with porcine circovirus type 2 (PCV2) and porcine reproductive and respiratory syndrome virus (PRRSV), which are associated with PRD.

The emergence, isolation, and phylogenetic analysis of a closely related human strain of parainfluenza virus 5 from a case of porcine reproductive and respiratory syndrome in China.

Reports of Parainfluenza virus 5 (PIV5) epidemics have been on a global upward trend, with an expanding host range across various animals. In 2020, we isolated a PIV5 strain from a PRRSV-positive serum sample. This strain was named GX2020. Genetic analysis revealed that GX2020 belongs to group A, represented by the AGS strain isolated from a human in the USA. Comparisons of amino acid identity in the coding regions showed that GX2020 had the highest amino acid identity (99.6%) with the AGS strain. The emergence of PIV5 strains genetically similar to human strains in pigs highlights its zoonotic potential and underscores the need for enhanced PIV5 surveillance in the future.

Recombination of Porcine Reproductive and Respiratory Syndrome Virus: Features, Possible Mechanisms, and Future Directions.

Recombination is a pervasive phenomenon in RNA viruses and an important strategy for accelerating the evolution of RNA virus populations. Recombination in the porcine reproductive and respiratory syndrome virus (PRRSV) was first reported in 1999, and many case reports have been published in recent years. In this review, all the existing reports on PRRSV recombination events were collected, and the genotypes, parental strains, and locations of the recombination breakpoints have been summarized and analyzed. The results showed that the recombination pattern constantly changes; whether inter- or intra-lineage recombination, the recombination hotspots vary in different recombination patterns. The virulence of recombinant PRRSVs was higher than that of the parental strains, and the emergence of virulence reversion was caused by recombination after using MLV vaccines. This could be attributed to the enhanced adaptability of recombinant PRRSV for entry and replication, facilitating their rapid propagation. The aim of this paper was to identify common features of recombinant PRRSV strains, reduce the recombination risk, and provide a foundation for future research into the mechanism of PRRSV recombination.

Genetic Characterization and Pathogenicity of a Recombinant Porcine Reproductive and Respiratory Syndrome Virus Strain in China.

Since it was first reported in 2013, the NADC30-like PRRSV has been epidemic in China. Hubei Province is known as China's key hog-exporting region. To understand the prevalence and genetic variation of PRRSV, herein, we detected and analyzed 317 lung tissue samples from pigs with respiratory disease in Hubei Province, and demonstrated that the NADC30-like strain was the second-most predominant strain during 2017-2018, following the highly pathogenic PRRSV (HP-PRRSV). Additionally, we isolated a new NADC30-like PRRSV strain, named CHN-HB-2018, which could be stably passaged in Marc-145 cells. Genetic characterization analysis showed that compared with the NADC30 strain, the CHN-HB-2018 strain had several amino acid variations in glycoprotein (GP) 3, GP5, and nonstructural protein 2 (NSP2). Moreover, the CHN-HB-2018 strain showed a unique 5-amino acid (aa) deletion in NSP2, which has not previously been reported. Gene recombination analysis identified the CHN-HB-2018 strain as a potentially recombinant PRRSV of the NADC30-like strain and HP-PRRSV. Animal experiments indicated that the CHN-HB-2018 strain has a mild pathogenicity, with no mortality and only mild fever observed in piglets. This study contributes to defining the evolutionary characteristics of PRRSV and its molecular epidemiology in Hubei Province, and provides a potential candidate strain for PRRSV vaccine development.

Prevalence, Time of Infection, and Diversity of Porcine Reproductive and Respiratory Syndrome Virus in China.

Porcine reproductive and respiratory syndrome virus (PRRVS) is a major swine viral pathogen that affects the pig industry worldwide. Control of early PRRSV infection is essential, and different types of PRRSV-positive samples can reflect the time point of PRRSV infection. This study aims to investigate the epidemiological characteristics of PRRSV in China from Q4 2021 to Q4 2022, which will be beneficial for porcine reproductive and respiratory syndrome virus (PRRSV)control in the swine production industry in the future. A total of 7518 samples (of processing fluid, weaning serum, and oral fluid) were collected from 100 intensive pig farms in 21 provinces, which covered all five pig production regions in China, on a quarterly basis starting from the fourth quarter of 2021 and ending on the fourth quarter of 2022. Independent of sample type, 32.1% (2416/7518) of the total samples were PCR-positive for PRRSV, including 73.6% (1780/2416) samples that were positive for wild PRRSV, and the remaining were positive for PRRSV vaccine strains. On the basis of the time of infection, 58.9% suckling piglets (processing fluid) and 30.8% weaning piglets (weaning serum) showed PRRSV infection at an early stage (approximately 90% of the farms). The sequencing analysis results indicate a wide range of diverse PRRSV wild strains in China, with lineage 1 as the dominant strain. Our study clearly demonstrates the prevalence, infection stage, and diversity of PRRSV in China. This study provides useful data for the epidemiological understanding of PRRSV, which can contribute to the strategic and systematic prevention and control of PRRSV in China.

Fidelity Characterization of Highly Pathogenic Porcine Reproductive and Respiratory Syndrome Virus and NADC30-like Strain.

The porcine reproductive and respiratory syndrome virus (PRRSV) has significantly impacted the global pork industry for over three decades. Its high mutation rates and frequent recombination greatly intensifies its epidemic and threat. To explore the fidelity characterization of Chinese highly pathogenic PRRSV JXwn06 and the NADC30-like strain CHsx1401, self-recombination and mutation in PAMs, MARC-145 cells, and pigs were assessed. In vitro, CHsx1401 displayed a higher frequency of recombination junctions and a greater diversity of junction types than JXwn06. In vivo, CHsx1401 exhibited fewer junction types yet maintained a higher junction frequency. Notably, JXwn06 showed more accumulation of mutations. To pinpoint the genomic regions influencing their fidelity, chimeric viruses were constructed, with the exchanged nsp9-10 regions between JXwn06 and CHsx1401. The SJn9n10 strain, which incorporates JXwn06's nsp9-10 into the CHsx1401 genome, demonstrated reduced sensitivity to nucleotide analogs compared to CHsx1401. Conversely, compared with JXwn06, the JSn9n10 strain showed increased sensitivity to these inhibitors. The swapped nsp9-10 also influences the junction frequency and accumulated mutations as their donor strains. The results indicate a propensity for different types of genetic variations between these two strains and further highlight the nsp9-10 region as a critical determinant of their fidelity.

Evolution Characterization and Pathogenicity of an NADC34-like PRRSV Isolated from Inner Mongolia, China.

Porcine reproductive and respiratory syndrome virus (PRRSV) is a pathogen that causes severe abortions in sows and high piglet mortality, resulting in huge economic losses to the pig industry worldwide. The emerging and novel PRRSV isolates are clinically and biologically important, as there are likely recombination and pathogenic differences among PRRSV genomes. Furthermore, the NADC34-like strain has become a major epidemic strain in some parts of China, but the characterization and pathogenicity of the latest strain in Inner Mongolia have not been reported in detail. In this study, an NADC34-like strain (CHNMGKL1-2304) from Tongliao City, Inner Mongolia was successfully isolated and characterized, and confirmed the pathogenicity in pigs. The phylogenetic tree showed that this strain belonged to sublineage 1.5 and had high homology with the strain JS2021NADC34. There is no recombination between CHNMGKL1-2304 and any other domestic strains. Animal experiments show that the CHNMGKL1-2304 strain is moderately virulent to piglets, which show persistent fever, weight loss and high morbidity but no mortality. The presence of PRRSV nucleic acids was detected in both blood, tissues, nasal and fecal swabs. In addition, obvious pathological changes and positive signals were observed in lung, lymph node, liver and spleen tissues when subjected to hematoxylin-eosin (HE) staining and immunohistochemistry (IHC). This report can provide a basis for epidemiological investigations and subsequent studies of PRRSV.

WGS- versus ORF5-Based Typing of PRRSV: A Belgian Case Study.

Porcine reproductive and respiratory syndrome virus (PRRSV) is the causative agent of one of the most widespread and economically devastating diseases in the swine industry. Typing circulating PRRSV strains by means of sequencing is crucial for developing adequate control strategies. Most genetic studies only target the highly variable open reading frame (ORF) 5, for which an extensive database is available. In this study, we performed whole-genome sequencing (WGS) on a collection of 124 PRRSV-1 positive serum samples that were collected over a 5-year period (2015-2019) in Belgium. Our results show that (nearly) complete PRRSV genomes can be obtained directly from serum samples with a high success rate. Analysis of the coding regions confirmed the exceptionally high genetic diversity, even among Belgian PRRSV-1 strains. To gain more insight into the added value of WGS, we performed phylogenetic cluster analyses on separate ORF datasets as well as on a single, concatenated dataset (CDS) containing all ORFs. A comparison between the CDS and ORF clustering schemes revealed numerous discrepancies. To explain these differences, we performed a large-scale recombination analysis, which allowed us to identify a large number of potential recombination events that were scattered across the genome. As PRRSV does not contain typical recombination hot-spots, typing PRRSV strains based on a single ORF is not recommended. Although the typing accuracy can be improved by including multiple regions, our results show that the full genetic diversity among PRRSV strains can only be captured by analysing (nearly) complete genomes. Finally, we also identified several vaccine-derived recombinant strains, which once more raises the question of the safety of these vaccines.

Evolutionary Dynamics of Type 2 Porcine Reproductive and Respiratory Syndrome Virus by Whole-Genome Analysis.

Porcine reproductive and respiratory syndrome virus (PRRSV), an important pathogen in the swine industry, is a genetically highly diverse RNA virus. However, the phylogenetic and genomic recombination properties of this virus are not yet fully understood. In this study, we performed an integrated analysis of all available whole-genome sequences of type 2 PRRSV (n = 901) to reveal its evolutionary dynamics. The results showed that there were three distinct phylogenetic lineages of PRRSV in their distribution patterns. We identified that sublineage 2.7 (L2.7), associated with a NADC30 cluster, had the highest substitution rate and higher viral genetic diversity, and inter-lineage recombination is observed more frequently in L2.7 PRRSV compared to other sublineages. Most inter-lineage recombination events detected are observed between L2.7 PRRSVs (as major parents) and L3.4 (a JXA1-R-related cluster)/L3.7 (a WUH3-related cluster) PRRSVs (as minor parents). Moreover, the recombination hotspots are located in the structural protein gene ORF2 and ORF4, or in the non-structural protein gene nsp7. In addition, a GM2-related cluster, L3.2, shows inconsistent recombination modes compared to those of L2.7, suggesting that it may have undergone extensive and unique recombination in their evolutionary history. We also identified several amino acids under positive selection in GP2, GP4 and GP5, the major glycoproteins of PRRSV, showing the driving force behind adaptive evolution. Taken together, our results provide new insights into the evolutionary dynamics of PPRSV that contribute to our understanding of the critical factors involved in its evolution and guide future efforts to develop effective preventive measures against PRRSV.

Porcine Reproductive and Respiratory Syndrome (PRRS) Epidemiology in an Integrated Pig Company of Northern Italy: A Multilevel Threat Requiring Multilevel Interventions.

Porcine reproductive and respiratory syndrome (PRRS) is probably the most relevant viral disease affecting pig farming. Despite the remarkable efforts paid in terms of vaccination administration and biosecurity, eradication and long-term control have often been frustrated. Unfortunately, few studies are currently available that objectively link, using a formal statistical approach, viral molecular epidemiology to the risk factors determining the observed scenario. The purpose of the present study is to contribute to filling this knowledge gap taking advantage of the advancements in the field of phylodynamics. Approximately one-thousand ORF7 sequences were obtained from strains collected between 2004 and 2021 from the largest Italian pig company, which implements strict compartmentalization among independent three-sites (i.e., sow herds, nurseries and finishing units) pig flows. The history and dynamics of the viral population and its evolution over time were reconstructed and linked to managerial choices. The viral fluxes within and among independent pig flows were evaluated, and the contribution of other integrated pig companies and rurally risen pigs in mediating such spreading was investigated. Moreover, viral circulation in Northern Italy was reconstructed using a continuous phylogeographic approach, and the impact of several environmental features on PRRSV strain persistence and spreading velocity was assessed. The results demonstrate that PRRSV epidemiology is shaped by a multitude of factors, including pig herd management (e.g., immunization strategy), implementation of strict-independent pig flows, and environmental features (e.g., climate, altitude, pig density, road density, etc.) among the others. Small farms and rurally raised animals also emerged as a potential threat for larger, integrated companies. These pieces of evidence suggest that none of the implemented measures can be considered effective alone, and a multidimensional approach, ranging from individual herd management to collaboration and information sharing among different companies, is mandatory for effective infection control.

Temporal lineage dynamics of the ORF5 gene of porcine reproductive and respiratory syndrome virus in Korea in 2014-2019.

Porcine reproductive and respiratory syndrome virus (PRRSV) is the most important pathogen in the Korean swine industry. Despite efforts including improved biosecurity and vaccination protocols, the virus continues to circulate and evolve. Based on phylogenetic analysis of open reading frame 5 (ORF5), Korean PRRSVs are known to form not only globally circulating lineages but also country-specific lineages (Lin Kor A, B, and C). To understand the recent epidemiological status of PRRSV in Korea, a total of 1349 ORF5 sequences of Korean PRRSV isolates from 2014 to 2019 were analyzed. Phylogenetic analysis was conducted using the maximum-likelihood method, and temporal changes in the relative prevalence of lineages were investigated. The analysis showed that PRRSV1 and PRRSV2 were both highly prevalent throughout the years examined. Among the PRRSV1 isolates, subgroup A (90.1%) and vaccine-like subgroup C (9.0%) composed most of the population. For PRRSV2 isolates, vaccine-like lineage 5 (36.3%) was dominant, followed by Lin Kor B (25.9%), Kor C (16.6%), lineage 1 (11.6%), and Kor A (9.1%). The PRRSV2 lineage 1 population increased from 2014 (1.8%) to 2019 (29.6%) in Korea due to the continual spread of sublineage 1.8 (NADC30-like) and introduction of sublineage 1.6 into the country. Additional genetic analysis, including analysis of non synonymous and synonymous mutations, revealed evidence of diversification and positive selection in immunologically important regions of the genome, suggesting that current vaccination is failing and promoting immune-mediated selection. Overall, these findings provide insights into the epidemiological and evolutionary dynamics of cocirculating viral lineages, and constant surveillance of PRRSV occurrence is needed.

Efficacy of a live attenuated highly pathogenic PRRSV vaccine against a NADC30-like strain challenge: implications for ADE of PRRSV.

BACKGROUND: Porcine reproductive and respiratory syndrome virus (PRRSV) infection can cause severe reproductive failure in sows and respiratory distress in pigs of all ages, leading to major economic losses. To date, there are still no effective strategies to prevent and control PRRSV. Antibody-dependent enhancement (ADE), a phenomenon in which preexisting non-neutralizing antibodies or sub-neutralizing antibodies facilitate virus entry and replication, may be a significant obstacle in the development of effective vaccines for many viruses, including PRRSV. However, the contribution of ADE to PRRSV infection remains controversial, especially in vivo. Whether attenuated PRRSV vaccines prevent or worsen subsequent disease in pigs infected by novel PRRSV strains requires more research. In the present study, in vivo experiments were conducted to evaluate ADE under different immune statuses, which were produced by waiting different lengths of time after vaccination with a commercially available attenuated highly pathogenic PRRSV (HP-PRRSV) vaccine (JXA1-R) before challenging the pigs with a novel heterologous NADC30-like strain. RESULTS: Piglets that were vaccinated before being challenged with PRRSV exhibited lower mortality rates, lower body temperatures, higher bodyweight gain, and lower viremia. These results demonstrate that vaccination with JXA1-R alleviated the clinical signs of PRRSV infection in all vaccinated groups. CONCLUSIONS: The obtained data indicate that the attenuated vaccine test here provided partial protection against the NADC30-like strain HNhx. No signs of enhanced PRRSV infection were observed under the applied experimental conditions. Our results provide some insight into the molecular mechanisms underlying vaccine-induced protection or enhancement in PRRSV.

Evolutionary Patterns of Codon Usage in Major Lineages of Porcine Reproductive and Respiratory Syndrome Virus in China.

Porcine reproductive and respiratory syndrome virus (PRRSV) is economically important and characterized by its extensive variation. The codon usage patterns and their influence on viral evolution and host adaptation among different PRRSV strains remain largely unknown. Here, the codon usage of ORF5 genes from lineages 1, 3, 5, and 8, and MLV strains of type 2 PRRSV in China was analyzed. A compositional property analysis of ORF5 genes revealed that nucleotide C is most frequently used at the third position of codons, accompanied by rich GC3s. The effective number of codon (ENC) and codon pair bias (CPB) values indicate that all ORF5 genes have low codon bias and the differences in CPB scores among four lineages are almost not significant. When compared with host codon usage patterns, lineage 1 strains show higher CAI and SiD values, with a high similarity to pig, which might relate to its predominant epidemic propensity in the field. The CAI, RCDI, and SiD values of ORF5 genes from different passages of MLV JXA1R indicate no relation between attenuation and CPB or codon adaptation decrease during serial passage on non-host cells. These findings provide a novel way of understanding the PRRSV's evolution, related to viral survival, host adaptation, and virulence.

Analysis of ORF5 sequences of Porcine Reproductive and Respiratory Syndrome virus (PRRSV) circulating within swine farms in Costa Rica.

BACKGROUND: Worldwide, Porcine Reproductive and Respiratory Syndrome (PRRS) is among the diseases that cause the highest economic impact in modern pig production. PRRS was first detected in Costa Rica in 1996 and has since then severely affected the local swine industry. Studies of the molecular characterization of circulating strains, correlation with clinical records, and associations with pathogens associated with Porcine Respiratory Disease Complex (PRDC) have not been done in Costa Rica. RESULTS: Sequencing and phylogenetic analysis of ORF5 proved that PRRSV-2 was the only species detected in all locations analyzed. These sequences were grouped into three clusters. When comparing samples from San Jose, Alejuela, and Puntarenas to historical isolates of the previously described lineages (1 to 9), it has been shown that these were closely related to each other and belonged to Lineage 5, along with the samples from Heredia. Intriguingly, samples from Cartago clustered in a separate clade, phylogenetically related to Lineage 1. Epitope analysis conducted on the GP5 sequence of field isolates from Costa Rica revealed seven peptides with at least 80% amino acid sequence identity with previously described and experimentally validated immunogenic regions. Previously described epitopes A, B, and C, were detected in the Santa Barbara-Heredia isolate. CONCLUSIONS: Our data suggest that the virus has three distinct origins or introductions to the country. Future studies will elucidate how recently introduced vaccines will shape the evolutionary change of circulating field strains.

Gene expression in tonsils in swine following infection with porcine reproductive and respiratory syndrome virus.

BACKGROUND: Porcine reproductive and respiratory syndrome (PRRS) is a threat to pig production worldwide. Our objective was to understand mechanisms of persistence of PRRS virus (PRRSV) in tonsil. Transcriptome data from tonsil samples collected at 42 days post infection (dpi) were generated by RNA-seq and NanoString on 51 pigs that were selected to contrast the two PRRSV isolates used, NVSL and KS06, high and low tonsil viral level at 42 dpi, and the favorable and unfavorable genotypes at a genetic marker (WUR) for the putative PRRSV resistance gene GBP5. RESULTS: The number of differentially expressed genes (DEGs) differed markedly between models with and without accounting for cell-type enrichments (CE) in the samples that were predicted from the RNA-seq data. This indicates that differences in cell composition in tissues that consist of multiple cell types, such as tonsil, can have a large impact on observed differences in gene expression. Based on both the NanoString and the RNA-seq data, KS06-infected pigs showed greater activation, or less inhibition, of immune response in tonsils at 42 dpi than NVSL-infected pigs, with and without accounting for CE. This suggests that the NVSL virus may be better than the KS06 virus at evading host immune response and persists in tonsils by weakening, or preventing, host immune responses. Pigs with high viral levels showed larger CE of immune cells than low viral level pigs, potentially to trigger stronger immune responses. Presence of high tonsil virus was associated with a stronger immune response, especially innate immune response through interferon signaling, but these differences were not significant when accounting for CE. Genotype at WUR was associated with different effects on immune response in tonsils of pigs during the persistence stage, depending on viral isolate and tonsil viral level. CONCLUSIONS: Results of this study provide insights into the effects of PRRSV isolate, tonsil viral level, and WUR genotype on host immune response and into potential mechanisms of PRRSV persistence in tonsils that could be targeted to improve strategies to reduce viral rebreaks. Finally, to understand transcriptome responses in tissues that consist of multiple cell types, it is important to consider differences in cell composition.

Development of a bead-based assay for detection and differentiation of field strains and four vaccine strains of type 2 porcine reproductive and respiratory syndrome virus (PRRSV-2) in the USA.

Porcine reproductive and respiratory syndrome (PRRS) remains one of the most economically devastating diseases in swine population in the United States of America. Due to high mutation rate of the PRRS virus (PRRSV) genome, it is difficult to develop an accurate diagnostic assay with high strain coverage. Differentiation of field strains from the four vaccines that have been used in the USA, namely Ingelvac PRRS MLV, Ingelvac ATP, Fostera PRRS and Prime Pac PRRS, adds an additional challenge. It is difficult to use current real-time PCR systems to detect and differentiate the field strains from the vaccine strains. Luminex xTAG technology allows us to detect more molecular targets in a single reaction with a cost similar to a single real-time PCR reaction. By analysing all available 678 type 2 PRRSV (PRRSV-2) complete genome sequences, including the 4 vaccine strains, two pairs of detection primers were designed targeting the conserved regions of ORF4-ORF7, with strain coverage of 98.8% (670/678) based on in silico analysis. The virus strains sharing ≥98% identity of the complete genomes with the vaccine strains were considered vaccine or vaccine-like strains. One pair of primers for each vaccine strain were designed targeting the nsp2 region. In silico analysis showed the assay matched 94.7% (54/57) of Ingelvac PRRS® MLV (MLV) strain and the MLV-like strains, and 100% of the other three vaccine strains. Analytical sensitivity of the Luminex assay was one to two logs lower than that of the reverse transcription real-time PCR assay. Evaluated with 417 PRRSV-2 positive clinical samples, 95% were detected by the Luminex assay. Compared to ORF5 sequencing results, the Luminex assay detected 92.4% (73/79) of MLV strains, 78.3% (18/23) of Fostera strains and 50% (2/4) of ATP strains. None of the 472 samples were the Prime Pac strain tested by either ORF5 sequencing or the Luminex assay.

Porcine reproductive and respiratory syndrome virus dissemination across pig production systems in the United States.

Porcine reproductive and respiratory syndrome virus (PRRSV) remains widespread in the North American pig population. Despite improvements in virus characterization, it is unclear whether PRRSV infections are a product of viral circulation within production systems (local) or across production systems (external). Here, we examined the local and external dissemination dynamics of PRRSV and the processes facilitating its spread in three production systems. Overall, PRRSV genetic diversity has declined since 2018, while phylodynamic results support frequent external transmission. We found that PRRSV dissemination predominantly occurred mostly through transmission between farms of different production companies for several months, especially from November until May, a timeframe already established as PRRSV season. Although local PRRSV dissemination occurred mainly through regular pig flow (from sow to nursery and then to finisher farms), an important flux of PRRSV dissemination also occurred in the opposite direction, from finisher to sow and nursery farms, highlighting the importance of downstream farms as sources of the virus. Our results also showed that farms with pig densities of 500 to 1,000 pig/km2 and farms located at a range within 0.5 km and 0.7 km from major roads were more likely to be infected by PRRSV, whereas farms at an elevation of 41 to 61 meters and surrounded by denser vegetation were less likely to be infected, indicating their role as dissemination barriers. In conclusion, our results demonstrate that external dissemination was intense, and reinforce the importance of farm proximity on PRRSV spread. Thus, consideration of farm location, geographic characteristics and animal densities across production systems may help to forecast PRRSV collateral dissemination.

Genetic characterization of a novel recombined porcine reproductive and respiratory syndrome virus 2 among Nadc30-like, Jxa1-like and TJ-like strains.

Porcine reproductive and respiratory syndrome (PRRS) is one of the most economically devastating viral diseases in the global pig industry, including China. Recently, we successfully isolated a porcine reproductive and respiratory syndrome virus (PRRSV) from lung tissue and peripheral blood of piglets at a farm from Dujiangyan in Sichuan, China, and named it the DJY-19 strain. The full-length genome sequence of DJY-19 shared 86.8%-94.1% nucleotide similarity with NADC30-like and NADC30 PRRSV strains. We compared the open reading frame (ORF) 5 gene of DJY-19 with 34 PRRSV strains from Genbank. Phylogenetic analysis showed that DJY-19 clustered with NADC30 strains, characterized by a predicted 131-amino-acid deletion in the nonstructural protein (NSP) 2. The results of homology analysis showed that the homology between DJY-19 and NADC30 (JN654459.1) strains was the highest (95.9%), whereas homology with other domestic strains was lower (80.9%-92.6%). Furthermore, we identified four recombination breakpoints in the DJY-19 genome; they separated the DJY-19 genome into four regions. The 8106-9128 nucleotide (nt) region of DIY-19 was highly similar to the TJ strain, and the 12106-12580 nt region of DIY-19 was highly similar to the JXA1-R strain. Our findings demonstrate that DJY-19 arose from the recombination of North America NADC30 strain and TJ strain and JXA1-R in China. The application of multiple attenuated vaccine strains has led to complex recombination of PRRSV strains in China. This study provides a theoretical basis for making a more reasonable PRRS virus control and prevention strategy.

An Outbreak of a Respiratory Disorder at a Russian Swine Farm Associated with the Co-Circulation of PRRSV1 and PRRSV2.

We conducted a cross-sectional study to identify the major respiratory pathogen responsible for an outbreak of respiratory disease at a swine farm in West Siberia in 2019. We discovered that the peak of morbidity and mortality coincided with a high level of porcine reproductive and respiratory syndrome virus (PRRSV) 1 and 2-related viremia. Based on longer PRRSV2 viremia, the dominant role of PRRSV2 over PRRSV1 in the outbreak was assumed. Phylogenetic analysis revealed that the PRRSV1 strain belonged to sub-genotype 2-one of the predominant groups of genotype 1 PRRSVs in Russia. A partial open reading frame 7 sequence of the PRRSV2 isolate demonstrated a high identity with modified live vaccine-related strains from Denmark (93%) and wild-type VR2332 (92%). We identified the first instance of PRRSV1/PRRSV2 mixed infection in Russia. This finding indicates that further field investigations are needed to access PRRSV2 epidemiology in eastern Europe.

Histopathological Lesions Accompanied with First-Time Isolation of a PRRSV-2 Strain in Greece.

Genotype 2 strains of Porcine Reproductive and Respiratory Syndrome Virus (PRRSV-2) have been reported sporadically in Europe. Even if, PRRSV-2 reported to be genetically homogenous in Europe due to the introduction of an MLV vaccine strain, independent introductions of PRRSV-2 field strains have been reported. The aim of the present study was to report the complete genome sequence and evaluate the histopathological lesions of a PRRSV-2 strain, isolated for the first time in Greece. During a routine blood sampling in a commercial pig farm, the results revealed positive samples in weaners of 40-60 days for the PRRSV-2, using real-time polymerase chain reaction. The clinical picture was characterized from respiratory symptoms in weaners, as well as coughing and poor performance at finishing stage and less than 3% mortality rate from weaning stage to finishing stage. The use of ORF5 for PRRSV phylogenetic analysis of the isolated PRRSV strain, named "x1544-1 strain", was successfully determined, belonging to the genotype PRRSV-2. Comparison of the obtained sequence revealed nucleotide sequence identity >98% with PRRSV-2 strain VR2332 and other related strains from Denmark and China. The histopathological evaluation revealed diffuse interstitial pneumonia, multifocal interstitial nephritis, while in the lymphoid organs, follicular and paracortical hyperplasia, coexisting with necrosis and depletion of germ cells were detected. The results of current study undersign the importance for veterinary practitioners to have up-to-date access to phylogenetic data linked to phenotypic information to follow-up the control and prevention strategies against PRRSV.