update

No update lately because we had no news on field-applied PRRSv studies recently...
I'll keep monitoring and I'll post another comment as soon as we have news.

Lunney, Joan K., David A. Benfield and Raymond R R Rowland. "Porcine Reproductive and Respiratory Syndrome Virus: An update on an emerging and re-emerging viral disease of swine." Virus research (2010)

Virus Res. 2010 Oct 13. [Epub ahead of print]

Porcine Reproductive and Respiratory Syndrome Virus: An update on an emerging and re-emerging viral disease of swine.

Lunney JK, Benfield DA, Rowland RR.

Animal Parasitic Diseases Laboratory, BARC, ARS, USDA, Beltsville, MD 20705 USA.

Abstract

Recognized in the late 1980's in North America and Europe the syndrome that caused reproductive and respiratory problems in swine was initially called "Mystery Swine Disease" and is now termed "Porcine Reproductive and Respiratory Syndrome (PRRS)". In the early 1990's an arterivirus, referred to as PRRS virus (PRRSV), was determined to be the etiologic agent of this disease. Since then research has progressed substantially. Most recently "Porcine high fever disease" was reported in China starting in 2006 with PRRSV being a critical virus associated with high morbidity and mortality (20%) associated with this syndrome which in 2010 is still causing severe pathology in pigs in China, with spread to Vietnam and Cambodia. This volume contains a series of reviews that highlight the virus, its pathogenesis, epidemiology, immunology, vaccinology and host genetic control. This paper provides a brief historical review of PRRS and the associated PRRSV. It presents areas of research gaps that inhibit current progress towards PRRS elimination through production of effective vaccines and current plans for PRRS elimination or eradication programs. It is hoped that this discussion will stimulate further collaboration between researchers and swine veterinarians throughout the world to provide answers that enhance our understanding of PRRS and PRRSV in an effort to eliminate this economically important disease.

Copyright © 2010. Published by Elsevier B.V.

PMID: 20951175 [PubMed - as supplied by publisher]

Can J Vet Res. 2010 Jul;74(3):170-7.

Clinical signs and their association with herd demographics and porcine reproductive and respiratory syndrome (PRRS) control strategies in PRRS PCR-positive swine herds in Ontario.

Young B, Dewey C, Poljak Z, Rosendal T, Carman S.

Department of Population Medicine, University of Guelph, Guelph, Ontario. youngbet@missouri.edu

Abstract

The purposes of this study were to describe the clinical signs observed in PRRS positive herds during a porcine reproductive and respiratory syndrome (PRRS) outbreak in Ontario and to determine associations between these clinical signs and herd demographics and PRRS control strategies. All PRRS polymerase chain reaction-(PCR)-positive submissions to a diagnostic laboratory between September 1, 2004 and August 31, 2007 were identified (n = 1864). After meeting eligibility requirements and agreeing to voluntary study participation, producers from 455 of these submissions were surveyed for information on clinical signs observed in their herds, herd demographics, and PRRS control strategies used in their herds at the time that the PCR-positive samples were taken. Larger herd size was associated with an increased risk of reporting abortion, weakborn piglets, off-feed sows, and sow mortality in sow herds, and with an increased risk of reporting mortality in finishing herds. When disease control strategies were examined, use of a commercial PRRS vaccine in sows and gilts was associated with a decreased risk of reporting weakborn pigs and high pre-weaning mortality, while the use of serum inoculation in breeding animals was associated with an increased risk of reporting off-feed sows and sow mortality. Providing biofeedback of stillborn/mummified piglets, placenta or feces to gilts was associated with an increased risk of reporting respiratory disease and mortality in finishing pigs while all-in/all-out flow in farrowing rooms was associated with an increased risk of reporting sow mortality and weakborn piglets.

PMID: 20885840 [PubMed - in process]PMCID: PMC2896797Free PMC Article

Can J Vet Res. 2010 Jul;74(3):223-7.

Serodiagnosis of porcine reproductive and respiratory syndrome virus infection with the use of glycoprotein 5 antigens.

Pyo H, Seo J, Suh G, Kim K, Lee J, Kim T.

Department of Veterinary Medicine, College of Veterinary Medicine, Chonnam National University, Gwangju 500-757, Republic of Korea.

Abstract

Glycoprotein 5 (GP5) of porcine reproductive and respiratory syndrome virus (PRRSV) has been studied extensively as a target for vaccine development. This study evaluated the serodiagnostic application of PRRSV GP5 by enzyme-linked immunosorbent assay (ELISA). Two immunodominant peptides (VR #1 and VR #2) and two neutralizing ectodomain-containing peptides (Ecto #1 and Ecto #2), as well as recombinant GP5 (rGP5) as a control, were prepared. Serum from unvaccinated pigs was screened for the antibodies that bind to these peptide and protein antigens. The results were compared with those from a commercially available diagnostic ELISA kit (HerdChek), which uses the nucleocapsid (N) protein as an antigen. Only VR #1+#2 showed a result statistically similar to that of N protein. Ecto #1 and Ecto #2 had a lower sensitivity than VR #1+#2 and rGP5. The peptides and rGP5 showed significant associations with the N protein (P < 0.05 or 0.01), which suggests that GP5 may also be a candidate serodiagnostic antigen. Since antibodies against GP5 persist much longer than those against the N protein, GP5 itself and some of its fragments are thought to be good targets for serodiagnosis. In addition, the presence of antibodies against the PRRSV structural antigens showed significant antigen-dependent differences.

PMID: 20885848 [PubMed - in process]PMCID: PMC2896805Free PMC Article

Clin Vaccine Immunol. 2010 Oct 6. [Epub ahead of print]

Porcine reproductive and respiratory syndrome virus (PRRSV) infection at the time of porcine circovirus type 2 (PCV2) vaccination has no impact on vaccine efficacy.

Sinha A, Shen HG, Schalk S, Beach NM, Huang YW, Halbur PG, Meng XJ, Opriessnig T.

Department of Veterinary Diagnostic and Production Animal Medicine, College of Veterinary Medicine, Iowa State University, Ames, Iowa, USA; Department of Biomedical Sciences and Pathobiology, Center for Molecular Medicine and Infectious Diseases, College of Veterinary Medicine, Virginia Polytechnic Institute and State University, Blacksburg, Virginia, USA.

Abstract

Several porcine circovirus type 2 (PCV2) vaccines are now commercially available and have been shown to be effective at decreasing the occurrence of porcine circovirus associated disease (PCVAD). Many herds are coinfected with PCV2 and porcine reproductive and respiratory syndrome virus (PRRSV). Some producers and veterinarians are concerned that if pigs are vaccinated for PCV2 at or near the time they typically are infected with PRRSV, the efficacy of the PCV2 vaccine will be compromised. The impact of PRRSV on PCV2 vaccination is unclear and has not been investigated under controlled conditions. The objective of the present study was to determine whether the presence of PRRSV viremia has an effect on the efficacy of commercial PCV2 vaccinations. Three-week-old PCV2-negative conventional pigs with passively-derived anti-PCV2-antibodies were either vaccinated with one of three commercial PCV2 vaccines or left non-vaccinated. A portion of the pigs were infected with PRRSV one week prior to PCV2 vaccination. To determine vaccine efficacy, a PCV2 challenge was conducted at 8 weeks of age. PCV2 vaccination regardless of PRRSV infection status at the time of vaccination was similarly effective in inducing an anti-PCV2-IgG response in the presence of maternally-derived immunity and in protecting the pigs from PCV2 challenge as determined by reduction in PCV2 viremia and reduction of prevalence and amount of PCV2 antigen in lymphoid tissues compared to non-vaccinated pigs. The results indicate that acute PRRSV infection at the time of PCV2 vaccination has no adverse effect on PCV2 vaccine efficacy.

PMID: 20926694 [PubMed - as supplied by publisher]

Sinha, A., et al. "Porcine reproductive and respiratory syndrome virus (PRRSV) infection at the time of porcine 

circovirus type 2 (PCV2) vaccination has no impact on vaccine efficacy." Clinical and vaccine immunology (2010

Shi, Mang, et al. "Molecular Epidemiology of PRRSV: A Phylogenetic Perspective." Virus research (2010)

Virus Res. 2010 Sep 10. [Epub ahead of print]

Molecular Epidemiology of PRRSV: A Phylogenetic Perspective.

Shi M, Lam TT, Hon CC, Hui RK, Faaberg KS, Wennblom T, Murtaugh MP, Stadejek T, Leung FC.

School of Biological Sciences, The University of Hong Kong, Hong Kong, China.

Abstract

Since its first discovery two decades ago, porcine reproductive and respiratory syndrome virus (PRRSV) has been the subject of intensive research due to its huge impact on the worldwide swine industry. Thanks to the phylogenetic analyses, much has been learned concerning the genetic diversity and evolution history of the virus. In this review, we focused on the evolutionary and epidemiological aspects of PRRSV from a phylogenetic perspective. We first described the diversity and transmission dynamics of Type 1 and 2 PRRSV, respectively. Then, we focused on the more ancient evolutionary history of PRRSV: the time of onset of all existing PRRSV and an original hypothesis were discussed. Finally, we summarized the results from previous recombination studies to assess the potential impact of recombination on the virus epidemiology.

PMID: 20837072 [PubMed - as supplied by publisher]

Corzo, Cesar A., et al. "Control and elimination of porcine reproductive and respiratory syndrome virus." Virus research (2010)

Virus Res. 2010 Sep 10. [Epub ahead of print]

Control and elimination of porcine reproductive and respiratory syndrome virus.

Corzo CA, Mondaca E, Wayne S, Torremorell M, Dee S, Davies P, Morrison RB.

Department of Veterinary Population Medicine, College of Veterinary Medicine, University of Minnesota, Saint Paul, Minnesota.

Abstract

Porcine reproductive and respiratory syndrome virus (PRRSv) can have a significant, economic impact on swine herds due to reproductive failure, preweaning mortality and reduced, performance in growing pigs. Control at the farm level is pursued through different management, procedures (e.g. pig flow, gilt acclimation, vaccination). PRRSv is commonly eliminated from sow, herds by a procedure called herd closure whereby the herd is closed to new introductions for a period, of time during which resident virus dies out. However, despite thorough application of biosecurity, procedures, many herds become re-infected from virus that is present in the area. Consequently, some, producers and veterinarians are considering a voluntary regional program to involve all herds present, within an area. Such a program was initiated in Stevens County in west central Minnesota in 2004., PRRSv has been eliminated from most sites within the region and the area involved has expanded to, include adjacent counties. The program has been relatively successful and reflects local leadership, a, cooperative spirit, and a will to eliminate virus from the region.

PMID: 20837071 [PubMed - as supplied by publisher]

LinkOut - more resources

The interaction between PRRSV and the late gestation pig fetus.

Rowland, Raymond R R. "The interaction between PRRSV and the late gestation pig fetus." Virus research (2010)

Abstract

Porcine reproductive and respiratory syndrome virus (PRRSV) crosses the placenta during late gestation and productively infects the fetus. Virus replication and cytokine responses were measured in tissues of fetuses recovered at 109 to 112 days of gestation, just prior to parturition. At the time of recovery, gross anatomical abnormalities were evident in both infected and non- infected fetuses from the infected dams. Virus isolation and immunohistochemistry identified the thymus as the primary site of virus replication. Steady state RT-PCR amplification of inflammatory, Th1 and Th2 cytokines, showed elevated IFN-γ and TNF-α mRNAs in tissues from infected fetuses, which corresponded to elevated cytokine proteins in serum but not amniotic fluid. Further evidence for induction of immunity was found in the hyperplastic response of lymph nodes, which included the development of germinal centers occupied CDw75+ B cells. Collectively, these data support the notion that the immunocompetent fetus is capable of initiating an antiviral response, which is compartmentalized within the infected fetus. Furthermore, fetal pathology may not be a direct result of virus replication in the fetus.

Key words. Porcine reproductive and respiratory syndrome virus (PRRSV), congenital infection, tumor necrosis factor-α (TNF-α ), interferon-γ (IFN-γ)

A prospective study evaluating duration of swine breeding herd PRRS virus-free status and its relationship with measured risk

Holtkamp, Derald J., et al. "A prospective study evaluating duration of swine breeding herd PRRS virus-free status and its relationship with measured risk." Preventive Veterinary Medicine 96.3-4 (2010):186-193.

abstract

A variety of methods for eliminating the PRRS virus from pig production sites have been successfully applied. However, success in maintaining a PRRS virus-free status for extended periods of time following elimination has been inconsistent and unpredictable. The objec- tive of this study was to evaluate whether risks measured using version 1 of the American Association of Swine Veterinarians (AASV) PRRS Risk Assessment for the Breeding Herd, season of year and method by which swine breeding herd sites were established PRRS virus-free were associated with how long they retained their virus-free status.

Thirty-three swine farrow-to-wean breeding herd sites that were established as PRRS virus-free by either populating a new site with virus-free breeding animals or by com- pletely depopulating the site and repopulating with PRRS virus-free breeding animals were enrolled in this study. Survival analysis, using the Cox proportional hazards model and Kaplan-Meier survival curves, was performed where the outcome was the duration of time PRRS virus-free breeding herd sites remained virus-free (“survived”). Covariates evaluated included the internal and external risk scores measured by the PRRS Risk Assessment for the Breeding Herd as well as the season and the method by which the site was established free of the PRRS virus.

All but 5 (15%) of the 33 sites became positive to the PRRS virus during the course of the study and approximately 40% became positive within 1 year from when they were established free of the PRRS virus. A higher external risk score was associated with a greater risk of becoming positive to the PRRS virus and shorter survival times. The internal risk score was not significantly associated with survival. Establishing breeding herd sites free of the PRRS virus in winter months (November through February) was associated with a greater risk of becoming positive to the PRRS virus and shorter survival times compared to those established in non-winter months. The association between the risk of becoming positive to the PRRS virus and the external risk score was confounded by the method the site was established PRRS virus-free.

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Thank you Dr Corzo for sending this article to Field PRRS

The Ever-Expanding Diversity of Porcine Reproductive and Respiratory Syndrome Virus

Murtaugh, Michael P., et al. "The Ever-Expanding Diversity of Porcine Reproductive and Respiratory Syndrome Virus." Virus research (2010)

Abstract

Porcine reproductive and respiratory syndrome (PRRS) virus appeared 20 years ago as the causeof a new disease in swine. Today PRRS is the most significant swine disease worldwide in spiteof intensive immunological interventions. The virus showed remarkable genetic variation withtwo geographically distinct genotypes at the time of its discovery, indicating the possibility ofprolonged evolutionary divergence prior to its appearance as a swine pathogen. Since then, both type 1 and type 2 have spread geographically, radiated genetically, and acquired new phenotypic characteristics, especially increased virulence. Here, we explore various hypotheses that mightaccount for rapid expansion and diversification of PRRSV, including mechanisms specific to PRRSV and other arteriviruses, cellular modification processes, and immunological selection. Phylogenetic analysis of PRRSV has provided a broadly applicable means to relate diverseisolates, but it does not explain biological variation in virulence or immunological cross-protection. We present other methods of classification and review their limitations. Major questions about PRRSV remain unanswered despite intensive investigation, suggesting that theinteraction of PRRSV with pigs involves novel biological processes that may be relevant to other RNA virus and host interactions

Porcine reproductive and respiratory syndrome virus (PRRSV) in serum and oral fluid samples from individual boars: Will oral fluid replace serum for PRRSV surveillance?

Title: Porcine reproductive and respiratory syndrome virus (PRRSV) in serum and oral fluid samples from individual boars: Will oral fluid replace serum for PRRSV surveillance?

Citation: Kittawornrat, A., Prickett, J., Chittick, W., Wang, C., Engle, M., Johnson, J., Patnayak, D., Schwartz, T., Whitney, D., Olsen, C., Schwartz, K., Zimmerman, J., Porcine reproductive and respiratory syndrome virus (PRRSV) in serum and oral fluid samples from individual boars: Will oral fluid replace serum for PRRSV surveillance?, Virus Research (2010), doi:10.1016/j.virusres.2010.07.025

Abstract: The purpose of this study was to determine whether oral fluid samples could be used to monitorindividually-housed adult boars for porcine reproductive and respiratory syndrome virus(PRRSV) infection. In 3 trials, 24 boars were intramuscularly (IM) inoculated with a modified-live PRRSV (MLV) vaccine (Trial 1), a Type 1 PRRSV isolate (Trial 2), or a Type 2 isolate(Trial 3). Oral fluid samples were collected daily and serum samples were collected twiceweekly. Following the completion of the study, samples were randomized and blind-tested forPRRSV by real-time quantitative reverse-transcription polymerase chain reaction (qRT-PCR).PRRSV was detected in oral fluids at DPI 1 and all oral fluid specimens were PRRSV qRT-PCRpositive at DPI 4. Although PRRSV was detected in both serum and oral fluid specimensthrough DPI 21, a comparison of matched samples from individual boars showed that oral fluidwas equal to serum for the detection of PRRSV at DPI 7 and more likely to be positive thanserum on DPI 14 and 21. Overall, oral fluid was superior to serum for the detection of PRRSVusing PCR over the 21 day observation period in this study. The results of this experimentsuggest that individually-penned oral fluid sampling could be an efficient, cost-effectiveapproach to PRRSV surveillance in boar studs and other swine populations.


Keywords: PRRSV, surveillance, monitor, diagnosis, detection, oral fluid, serum

The structural biology of PRRSV

Dokland, Terje. "The structural biology of PRRSV." Virus research (2010) accepted manuscript

This article is not applied research, but it has good description about the virus itself, with good images and figures!

Porcine reproductive and respiratory syndrome virus (PRRSV) is an enveloped, positive-sense single- stranded RNA virus belonging to the Arteriviridae family. Arteriviruses and coronaviruses are grouped together in the order Nidovirales, based on similarities in genome organization and expression strategy. Over the past decade, crystal structures of several viral proteins, electron microscopic studies of the virion, as well as biochemical and in vivo studies on protein–protein interactions have led to a greatly increased understanding of PRRSV structural biology. At this point, crystal structures are available for the viral proteases NSP1alpha, NSP1beta and NSP4 and the nucleocapsid protein, N. The NSP1alpha and NSP1beta structures have revealed additional non-protease domains that may be involved in modulation of host functions. The N protein forms a dimer with a novel fold so far only seen in PRRSV and other nidoviruses. Cryo-electron tomographic studies have shown the three-dimensional organization of the PRRSV virion and suggest that the viral nucleocapsid has an asymmetric, linear arrangement, rather than the isometric core previously described. Together, these studies have revealed a closer structural relationship between arteri- and coronaviruses than previously anticipated.

Secondary infection with Streptococcus suis serotype 7 increases the virulence of highly pathogenic porcine reproductive and respiratory syndrome virus in pigs.

Xu, Min., et al. "Secondary infection with Streptococcus suis serotype 7 increases the virulence of highly pathogenic porcine reproductive and respiratory syndrome virus in pigs." Virology journal 7.1 (2010):184-184.

Abstract

Background

Porcine reproductive and respiratory syndrome virus (PRRSV) and Streptococcus suis are common pathogens in pigs. In samples collected during the porcine high fever syndrome (PHFS) outbreak in many parts of China, PRRSV and S. suis serotype 7 (SS7) have always been isolated together. To determine whether PRRSV-SS7 coinfection was the cause of the PHFS outbreak, we evaluated the pathogenicity of PRRSV and/or SS7 in a pig model of single and mixed infection.

Results

Respiratory disease, diarrhea, and anorexia were observed in all infected pigs. Signs of central nervous system (CNS) disease were observed in the highly pathogenic PRRSV (HP-PRRSV)-infected pigs (4/12) and the coinfected pigs (8/10); however, the symptoms of the coinfected pigs were clearly more severe than those of the HP- PRRSV-infected pigs. The mortality rate was significantly higher in the coinfected pigs (8/10) than in the HP-PRRSV- (2/12) and SS7-infected pigs (0/10). The deceased pigs of the coinfected group had symptoms typical of PHFS, such as high fever, anorexia, and red coloration of the ears and the body. The isolation rates of HP- PRRSV and SS7 were higher and the lesion severity was greater in the coinfected pigs than in monoinfected pigs.

Conclusion

HP-PRRSV infection increased susceptibility to SS7 infection, and coinfection of HP- PRRSV with SS7 significantly increased the pathogenicity of SS7 to pigs.

Genetic control of host resistance to porcine reproductive and respiratory syndrome virus (PRRSV) infection

Lunney, Joan K., and Hongbo Chen. "Genetic control of host resistance to porcine reproductive and respiratory syndrome virus (PRRSV) infection." Virus research (2010) - accepted manuscript

ABSTRACT This manuscript focuses on the advances made using genomic approaches to identify biomarkers that define genes and pathways that are correlated with swine resistance to infection with porcine reproductive and respiratory syndrome virus (PRRSV), the most economically important swine viral pathogen worldwide. International efforts are underway to assess resistance and susceptibility to infectious pathogens using tools such as gene arrays, single nucleotide polymorphisms (SNPs) chips, genome-wide association studies (GWAS), proteomics,and advanced bioinformatics. These studies should identify new candidate genes and biological pathways associated with host PRRS resistance and alternate viral disease processes and mechanisms; they may unveil biomarkers that account for genetic control of PRRS or, alternately, that reveal new targets for therapeutics or vaccines. Previous genomic approaches have expanded our understanding of quantitative trait loci (QTL) controlling traits of economic importance in pig production, e.g., feed efficiency, meat production, leanness; only recently have these included health traits and disease resistance. Genomic studies should have substantial impact for the pig industry since it is now possible to include the use of biomarkers for basic health traits along side broader set of markers utilized for selection of pigs for improved performance and reproductive traits, as well as pork quality. Additionally these studies may reveal alternate PRRSV control mechanisms that can be exploited for novel drugs, bio-therapeutics and vaccine designs.

Keywords: genetic resistance to PRRS; genetic susceptibility to PRRS; biomarkers; genomic approaches; single nucleotide polymorphisms (SNPs), genome-wide association studies (GWAS)