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)