Betaarterivirus suid 1

PRRS earlier known as "mystery swine disease" and "blue ear disease" during 1987–1988 in the United States and Canada{{Cite journal |last=Goyal |first=S. M. |date=1993 |title=Porcine reproductive and respiratory syndrome |journal=Journal of Veterinary Diagnostic Investigation |volume=5 |issue=4 |pages=656–664 |doi=10.1177/104063879300500435 |issn=1040-6387 |pmid=8286480|s2cid=27005012 |doi-access=free }} caused first undiagnosed outbreaks, characterized by reproductive losses combined with respiratory signs. In 1990-1991, a similar disease was reported in several European countries such as Germany, The Netherlands, Belgium, Denmark, France, the United Kingdom, and Spain.{{Cite journal |last1=Plana |first1=Joan |last2=Vayreda |first2=Montserrat |last3=Vilarrasa |first3=Jaume |last4=Bastons |first4=Merce |last5=Rosell |first5=Rosa |last6=Martinez |first6=M. |last7=San Gabriel |first7=Alberto |last8=Pujols |first8=Joan |last9=Badiola |first9=Jose Luis |last10=Ramos |first10=Jose A. |last11=Domingo |first11=Mariano |date=1992 |title=Porcine epidemic abortion and respiratory syndrome (mystery swine disease). Isolation in Spain of the causative agent and experimental reproduction of the disease |url=https://linkinghub.elsevier.com/retrieve/pii/037811359290048X |journal=Veterinary Microbiology |language=en |volume=33 |issue=1–4 |pages=203–211 |doi=10.1016/0378-1135(92)90048-X|pmid=1481358 |url-access=subscription }} The emergence of PRRS in Japan, Taiwan and mainland China was reported in 1987, 1991 and 1996, respectively.{{Cite journal |last1=Shimizu |first1=Mitsugu |last2=Yamada |first2=Shunji |last3=Murakami |first3=Yosuke |last4=Morozumi |first4=Tetsuo |last5=Kobayashi |first5=Hideki |last6=Mitani |first6=Kenji |last7=Ito |first7=Nobuyosi |last8=Kubo |first8=Masanori |last9=Kimura |first9=Kumiko |last10=Kobayashi |first10=Masaru |last11=Yamamoto |first11=Koushi |last12=Miura |first12=Yasuo |last13=Yamamoto |first13=Teruji |last14=Watanabe |first14=Kazuo |date=1994 |title=Isolation of Porcine Reproductive and Respiratory Syndrome (PRRS) Virus from Heko-Heko Disease of Pigs. |url=http://www.jstage.jst.go.jp/article/jvms1991/56/2/56_2_389/_article |journal=Journal of Veterinary Medical Science |language=en |volume=56 |issue=2 |pages=389–391 |doi=10.1292/jvms.56.389 |pmid=8075233 |issn=0916-7250|doi-access=free |url-access=subscription }}{{Citation |last1=Chueh |first1=L. L. |date=1998 |url=http://dx.doi.org/10.1007/978-1-4615-5331-1_103 |pages=795–799 |place=Boston, MA |publisher=Springer US |isbn=978-1-4613-7432-9 |access-date=2022-11-20 |last2=Lee |first2=K. H. |last3=Wang |first3=F. I. |last4=Pang |first4=V. F. |last5=Weng |first5=C. N.|title=Coronaviruses and Arteriviruses |chapter=Sequence Analysis of the Nucleocapsid Protein Gene of the Porcine Reproductive and Respiratory Syndrome Virus Taiwan MD-001 Strain |series=Advances in Experimental Medicine and Biology |volume=440 |doi=10.1007/978-1-4615-5331-1_103 |pmid=9782360 |url-access=subscription }}{{Cite journal |last1=Deng |first1=Ming-Chung |last2=Chang |first2=Chia-Yi |last3=Huang |first3=Tien-Shine |last4=Tsai |first4=Hsiang-Jung |last5=Chang |first5=Chieh |last6=Wang |first6=Fun-In |last7=Huang |first7=Yu-Liang |date=2015-08-06 |title=Molecular epidemiology of porcine reproductive and respiratory syndrome viruses isolated from 1991 to 2013 in Taiwan |journal=Archives of Virology |volume=160 |issue=11 |pages=2709–2718 |doi=10.1007/s00705-015-2554-4 |pmid=26246243 |s2cid=254056814 |issn=0304-8608|doi-access=free }}{{Cite journal |last1=Guo |first1=BQ |last2=Chen |first2=ZS |last3=Liu |first3=WX |last4=Cui |first4=YZ |date=1996 |title=Isolation and identification of porcine reproductive and respiratory syndrome (PRRS) virus from aborted fetuses suspected of PRRS. |journal=Chin. J. Anim. Poult. Infect. Dis. |language=Chinese |volume=2 |issue=2 |pages=117–124}}

According to the WOAH, the disease is now present throughout the world, especially in countries with major pig production. Australia, New Zealand, Norway, Sweden and Switzerland are PRRS free.{{Cite journal |last1=Nathues |first1=C. |last2=Zimmerli |first2=U. |last3=Hauser |first3=R. |last4=Nathues |first4=H. |last5=grosse Beilage |first5=E. |last6=Schüpbach-Regula |first6=G. |date=2014 |title=Risk Assessment of the Introduction of Porcine Reproductive and Respiratory Syndrome Virus via Boar Semen into Switzerland as an Example of a PRRSV-Free Country |url=https://onlinelibrary.wiley.com/doi/10.1111/tbed.12059 |journal=Transboundary and Emerging Diseases |language=en |volume=61 |issue=6 |pages=546–554 |doi=10.1111/tbed.12059|pmid=23356485 }}

A better picture of PRRSV's genetic diversity suggested that the virus was present in the field before the "original" outbreaks.{{Cite journal |last=Plagemann |first=Peter G.W. |date=2003 |title=Porcine Reproductive and Respiratory Syndrome Virus: Origin Hypothesis |url=http://wwwnc.cdc.gov/eid/article/9/8/03-0232_article.htm |journal=Emerging Infectious Diseases |volume=9 |issue=8 |pages=903–908 |doi=10.3201/eid0908.030232 |issn=1080-6040 |pmc=3020618 |pmid=12967485}}{{Cite journal |last1=Shi |first1=Mang |last2=Lam |first2=Tommy Tsan-Yuk |last3=Hon |first3=Chung-Chau |last4=Hui |first4=Raymond Kin-Hei |last5=Faaberg |first5=Kay S. |last6=Wennblom |first6=Trevor |last7=Murtaugh |first7=Michael P. |last8=Stadejek |first8=Tomasz |last9=Leung |first9=Frederick Chi-Ching |date=2010 |title=Molecular epidemiology of PRRSV: A phylogenetic perspective |url=https://linkinghub.elsevier.com/retrieve/pii/S0168170210002911 |journal=Virus Research |language=en |volume=154 |issue=1–2 |pages=7–17 |doi=10.1016/j.virusres.2010.08.014|pmid=20837072 |url-access=subscription }} The lack of recorded data concerning the prevalence prior to the epidemic was due to unawareness of PRRS.

A hypothesis has been proposed that PRRSV derived of closely related murine lactate dehydrogenase-elevating virus. Phylogeographic analysis of PRRSV epidemiology suggested that the virus diversified into unique subpopulations in Russia and Belarus, approximately 110–140 years ago.{{Cite journal |last=Forsberg |first=Roald |date=2005-11-01 |title=Divergence Time of Porcine Reproductive and Respiratory Syndrome Virus Subtypes |url=http://academic.oup.com/mbe/article/22/11/2131/1256710/Divergence-Time-of-Porcine-Reproductive-and |journal=Molecular Biology and Evolution |language=en |volume=22 |issue=11 |pages=2131–2134 |doi=10.1093/molbev/msi208 |pmid=16000650 |issn=1537-1719|url-access=subscription }}{{Cite journal |last1=Nguyen |first1=V. G. |last2=Kim |first2=H. K. |last3=Moon |first3=H. J. |last4=Park |first4=S. J. |last5=Chung |first5=H. C. |last6=Choi |first6=M. K. |last7=Park |first7=B. K. |date=2014 |title=A Bayesian Phylogeographical Analysis of Type 1 Porcine Reproductive and Respiratory Syndrome Virus (PRRSV) |url=https://onlinelibrary.wiley.com/doi/10.1111/tbed.12058 |journal=Transboundary and Emerging Diseases |language=en |volume=61 |issue=6 |pages=537–545 |doi=10.1111/tbed.12058|pmid=23336975 |url-access=subscription }} However, still there is an uncertainty as to how, when and where the PRRSV emerged.{{Cite journal |last1=Murtaugh |first1=Michael P. |last2=Stadejek |first2=Tomasz |last3=Abrahante |first3=Juan E. |last4=Lam |first4=Tommy T.Y. |last5=Leung |first5=Frederick C.-C. |date=2010 |title=The ever-expanding diversity of porcine reproductive and respiratory syndrome virus |url=https://linkinghub.elsevier.com/retrieve/pii/S0168170210002923 |journal=Virus Research |language=en |volume=154 |issue=1–2 |pages=18–30 |doi=10.1016/j.virusres.2010.08.015|pmid=20801173 |url-access=subscription }}{{Cite journal |last1=Stadejek |first1=Tomasz |last2=Stankevicius |first2=Arunas |last3=Murtaugh |first3=Michael P. |last4=Oleksiewicz |first4=Martin B. |date=2013 |title=Molecular evolution of PRRSV in Europe: Current state of play |url=https://linkinghub.elsevier.com/retrieve/pii/S0378113513001570 |journal=Veterinary Microbiology |language=en |volume=165 |issue=1–2 |pages=21–28 |doi=10.1016/j.vetmic.2013.02.029|pmid=23528651 |url-access=subscription }}

Several important factors allowed PRRSV to expand further. The transformation of the pig industry worldwide in the 20th century plays a key role. The emergence of high-density confinement management practices and adoption of artificial insemination facilitated wide expansion and diversification of PRRSV. There is abundant evidence that PRRSV is present in wild boars.{{Cite journal |last1=Stankevicius |first1=Arunas |last2=Buitkuviene |first2=Jurate |last3=Sutkiene |first3=Virginija |last4=Spancerniene |first4=Ugne |last5=Pampariene |first5=Ina |last6=Pautienius |first6=Arnoldas |last7=Oberauskas |first7=Vaidas |last8=Zilinskas |first8=Henrikas |last9=Zymantiene |first9=Judita |date=2015 |title=Detection and molecular characterization of porcine reproductive and respiratory syndrome virus in Lithuanian wild boar populations |journal=Acta Veterinaria Scandinavica |language=en |volume=58 |issue=1 |pages=51 |doi=10.1186/s13028-016-0232-5 |issn=1751-0147 |pmc=5016999 |pmid=27608974 |doi-access=free }} Wild animals may act as a natural reservoir for PRRSV and could be considered as an additional source of viral infections in domestic pigs.

PRRSV is highly dynamic in nature. Increasing genetic diversity allows emergence of severe outbreaks characterized by an elevated abortion rate as well as mortality in growing pigs and sows. This happened in 1996, 2000 and 2007 in the US and in 2006 in China.{{Cite journal |last=Murtaugh |first=M |date=2009 |title=Update on PRRSV immunology and viral genetics: from hopeless to hopeful. |journal=Proceedings of the 40th Annual Meeting of the American Association of Swine Veterinary, Dallas. |pages=459–462}} Highly pathogenic and virulent "atypical" PRRSV isolates are regularly reported in different European countries: Belarus,{{Cite journal |last1=Karniychuk |first1=Uladzimir U |last2=Geldhof |first2=Marc |last3=Vanhee |first3=Merijn |last4=Van Doorsselaere |first4=Jan |last5=Saveleva |first5=Tamara A |last6=Nauwynck |first6=Hans J |date=2010 |title=Pathogenesis and antigenic characterization of a new East European subtype 3 porcine reproductive and respiratory syndrome virus isolate |journal=BMC Veterinary Research |language=en |volume=6 |issue=1 |pages=30 |doi=10.1186/1746-6148-6-30 |issn=1746-6148 |pmc=2898778 |pmid=20525333 |doi-access=free }} Belgium,{{Cite journal |last1=Frydas |first1=Ilias S |last2=Trus |first2=Ivan |last3=Kvisgaard |first3=Lise K |last4=Bonckaert |first4=Caroline |last5=Reddy |first5=Vishwanatha RAP |last6=Li |first6=Yewei |last7=Larsen |first7=Lars E |last8=Nauwynck |first8=Hans J |date=2015 |title=Different clinical, virological, serological and tissue tropism outcomes of two new and one old Belgian type 1 subtype 1 porcine reproductive and respiratory virus (PRRSV) isolates |journal=Veterinary Research |language=en |volume=46 |issue=1 |pages=37 |doi=10.1186/s13567-015-0166-3 |issn=1297-9716 |pmc=4367851 |pmid=25885416 |doi-access=free }} Hungary,{{Cite journal |last1=Bálint |first1=Ádám |last2=Balka |first2=Gyula |last3=Horváth |first3=Péter |last4=Kecskeméti |first4=Sándor |last5=Dán |first5=Ádám |last6=Farsang |first6=Attila |last7=Szeredi |first7=Levente |last8=Bányai |first8=Krisztián |last9=Bartha |first9=Dániel |last10=Olasz |first10=Ferenc |last11=Belák |first11=Sándor |last12=Zádori |first12=Zoltán |date=2015 |title=Full-length genome sequence analysis of a Hungarian porcine reproductive and respiratory syndrome virus isolated from a pig with severe respiratory disease |url=http://link.springer.com/10.1007/s00705-014-2265-2 |journal=Archives of Virology |language=en |volume=160 |issue=2 |pages=417–422 |doi=10.1007/s00705-014-2265-2 |pmid=25361819 |s2cid=254063523 |issn=0304-8608|url-access=subscription }} Austria{{Cite journal |last1=Sinn |first1=Leonie J |last2=Klingler |first2=Eva |last3=Lamp |first3=Benjamin |last4=Brunthaler |first4=Rene |last5=Weissenböck |first5=Herbert |last6=Rümenapf |first6=Till |last7=Ladinig |first7=Andrea |date=2016 |title=Emergence of a virulent porcine reproductive and respiratory syndrome virus (PRRSV) 1 strain in Lower Austria |journal=Porcine Health Management |language=en |volume=2 |issue=1 |pages=28 |doi=10.1186/s40813-016-0044-z |issn=2055-5660 |pmc=5382404 |pmid=28405454 |doi-access=free }} and others. Immunization programs of swine herds worldwide with attenuated vaccines made of both PRRSV genotypes provided initially optimistic results in the 1990s.{{Cite journal |last1=Nauwynck |first1=H. J. |last2=Van Gorp |first2=H. |last3=Vanhee |first3=M. |last4=Karniychuk |first4=U. |last5=Geldhof |first5=M. |last6=Cao |first6=A. |last7=Verbeeck |first7=M. |last8=Van Breedam |first8=W. |date=2012-01-09 |title=Micro-Dissecting the Pathogenesis and Immune Response of PRRSV Infection Paves the Way for More Efficient PRRSV Vaccines |journal=Transboundary and Emerging Diseases |volume=59 |pages=50–54 |doi=10.1111/j.1865-1682.2011.01292.x |pmid=22225918 |issn=1865-1674|doi-access=free }}

At present PRRS, is one of the most significant infectious disease affecting the swine industry.{{Cite journal |last1=Zuckermann |first1=Federico A. |last2=Garcia |first2=Esther Alvarez |last3=Luque |first3=Ivan Diaz |last4=Christopher-Hennings |first4=Jane |last5=Doster |first5=Alan |last6=Brito |first6=Monica |last7=Osorio |first7=Fernando |date=2007-07-20 |title=Assessment of the efficacy of commercial porcine reproductive and respiratory syndrome virus (PRRSV) vaccines based on measurement of serologic response, frequency of gamma-IFN-producing cells and virological parameters of protection upon challenge |url=https://linkinghub.elsevier.com/retrieve/pii/S037811350700079X |journal=Veterinary Microbiology |language=en |volume=123 |issue=1–3 |pages=69–85 |doi=10.1016/j.vetmic.2007.02.009|pmid=17376612 |url-access=subscription }} It was also named as "pig AIDS" for emerging through accidental transspecies transmission and significant economic losses in worldwide pig production.{{Cite journal |last1=Thanawongnuwech |first1=Roongroje |last2=Suradhat |first2=Sanipa |date=2010 |title=Taming PRRSV: Revisiting the control strategies and vaccine design |url=https://linkinghub.elsevier.com/retrieve/pii/S0168170210003254 |journal=Virus Research |language=en |volume=154 |issue=1–2 |pages=133–140 |doi=10.1016/j.virusres.2010.09.003|pmid=20851723 |url-access=subscription }}{{Cite journal |last1=Zhou |first1=Ao |last2=Zhang |first2=Shujun |date=2012 |title=Regulation of cell signaling and porcine reproductive and respiratory syndrome virus |url=https://linkinghub.elsevier.com/retrieve/pii/S0898656812000095 |journal=Cellular Signalling |language=en |volume=24 |issue=5 |pages=973–980 |doi=10.1016/j.cellsig.2012.01.004|pmid=22274732 |url-access=subscription }}

File:A phylogenetic tree of viruses belonging to the family Arteriviridae.png

PRRSV is a member of the family Arteriviridae, and order Nidovirales.{{Cite book|chapter-url=http://www.horizonpress.com/avir|author=Balasuriya and Snijder|year=2008|chapter=Arteriviruses|title=Animal Viruses: Molecular Biology|publisher=Caister Academic Press| isbn =978-1-904455-22-6}} Other members of the family Arteriviridae include: equine arteritis virus (EAV), simian hemorrhagic fever virus (SHFV), wobbly possum disease virus, and lactate dehydrogenase elevating virus (LDV).{{cite journal |last1=Kappes |first1=MA |last2=Faaberg |first2=KS |date=May 2015 |title=PRRSV structure, replication and recombination: Origin of phenotype and genotype diversity |journal=Virology |volume=479–480 |pages=475–86 |doi=10.1016/j.virol.2015.02.012 |pmc=7111637 |pmid=25759097 |doi-access=free}}

PRRSV is a small, single-stranded, positive-sense, enveloped RNA virus.{{cite journal |last1=Pileri |first1=E |last2=Mateu |first2=E |date=28 October 2016 |title=Review on the transmission porcine reproductive and respiratory syndrome virus between pigs and farms and impact on vaccination |journal=Veterinary Research |volume=47 |issue=1 |pages=108 |doi=10.1186/s13567-016-0391-4 |pmc=5086057 |pmid=27793195 |doi-access=free }} The 15 kb genome consists of one linear, single stranded RNA molecule consisting of a 5′ untranslated region (UTR), ten open reading frames (ORFs 1a-1b-2a-2b-3-4-5-5a-6-7) and a 3′ UTR followed by a polyadenylation tail.{{Cite journal |last1=Lunney |first1=Joan K. |last2=Fang |first2=Ying |last3=Ladinig |first3=Andrea |last4=Chen |first4=Nanhua |last5=Li |first5=Yanhua |last6=Rowland |first6=Bob |last7=Renukaradhya |first7=Gourapura J. |date=2016-02-15 |title=Porcine Reproductive and Respiratory Syndrome Virus (PRRSV): Pathogenesis and Interaction with the Immune System |url=https://www.annualreviews.org/doi/10.1146/annurev-animal-022114-111025 |journal=Annual Review of Animal Biosciences |language=en |volume=4 |issue=1 |pages=129–154 |doi=10.1146/annurev-animal-022114-111025 |pmid=26646630 |issn=2165-8102|url-access=subscription }}

File:PRRSV genome organization.png

Two large ORFs (1a and 1b) comprise 75% of the viral genome. They are translated and processed into 14 non-structural proteins including four proteases and the RNA-dependent RNA polymerase.{{Cite journal |last=Dokland |first=Terje |date=2010 |title=The structural biology of PRRSV |journal=Virus Research |language=en |volume=154 |issue=1–2 |pages=86–97 |doi=10.1016/j.virusres.2010.07.029 |pmc=7114433 |pmid=20692304}}

A PRRSV particle is composed of eight viral structural proteins encoded by ORFs 2-7. They consist of envelope proteins (GP2a, E, GP3, GP4, GP5, ORF5a and M) and the nucleocapsid (N) protein. The most conserved proteins within the whole family of Arteriviridae and PRRSV, in particular, are nsp9 (RNA-dependent RNA polymerase) and nucleocapsid (N) protein. Similarity analysis demonstrates the presence of hyper-variable regions in nsp2 and GP4.

An assembled PRRSV virion appears as a spherical particle with a mean diameter of 56 nm. The particles display a very smooth outline of the lipid bilayer of the envelope with few protruding features represented by the two major envelope protein complexes: M-GP5 and GP2-GP3-GP4. These complexes interact with the well-characterized receptors CD169 (sialoadhesin) and CD163, respectively.

File:A phylogenetic tree of PRRSV.png

PRRSV is subdivided in two major types, the European (also known as Type 1) and the North American (also known as type 2). Prototype sequences for each PRRSV type have been defined. For the European PRRSV, this is the Lelystad virus (LV), while for the North American PRRSV, this is the VR-2332. The European and North American PRRSV strains cause similar clinical symptoms, but represent two distinct viral genotypes whose genomes diverge by approximately 40%, thus creating a veil of mystery about the origin of this virus. It was suggested that the emergence of these distant types of PRRSV was a result of two independent evolutionary events.{{Cite journal |last1=Stadejek |first1=Tomasz |last2=Oleksiewicz |first2=Martin B. |last3=Scherbakov |first3=Alexei V. |last4=Timina |first4=Anna M. |last5=Krabbe |first5=Jonas S. |last6=Chabros |first6=Katarzyna |last7=Potapchuk |first7=Denis |date=2008 |title=Definition of subtypes in the European genotype of porcine reproductive and respiratory syndrome virus: nucleocapsid characteristics and geographical distribution in Europe |url=http://link.springer.com/10.1007/s00705-008-0146-2 |journal=Archives of Virology |language=en |volume=153 |issue=8 |pages=1479–1488 |doi=10.1007/s00705-008-0146-2 |pmid=18592131 |s2cid=31075692 |issn=0304-8608|url-access=subscription }} To accommodate the clear divergence of the Type 1 and Type 2 PRRSV, they were split into two separate viruses.{{Cite journal |last1=Kuhn |first1=Jens H. |last2=Lauck |first2=Michael |last3=Bailey |first3=Adam L. |last4=Shchetinin |first4=Alexey M. |last5=Vishnevskaya |first5=Tatyana V. |last6=Bào |first6=Yīmíng |last7=Ng |first7=Terry Fei Fan |last8=LeBreton |first8=Matthew |last9=Schneider |first9=Bradley S. |last10=Gillis |first10=Amethyst |last11=Tamoufe |first11=Ubald |last12=Diffo |first12=Joseph Le Doux |last13=Takuo |first13=Jean Michel |last14=Kondov |first14=Nikola O. |last15=Coffey |first15=Lark L. |date=2016 |title=Reorganization and expansion of the nidoviral family Arteriviridae |journal=Archives of Virology |language=en |volume=161 |issue=3 |pages=755–768 |doi=10.1007/s00705-015-2672-z |issn=0304-8608 |pmc=5573231 |pmid=26608064}}

The genetic variation among the viruses isolated from different places{{cite journal |vauthors=Shi M, Lam TT, Hon CC, Murtaugh MP, Davies PR, Hui RK, Li J, Wong LT, Yip CW, Jiang JW, Leung FC | title = Phylogeny-based evolutionary, demographical, and geographical dissection of North American type 2 porcine reproductive and respiratory syndrome viruses | journal = Journal of Virology | volume = 84 | issue = 17 | pages = 8700–8711 |date=Sep 2010 | pmid = 20554771 | pmc = 2919017 | doi = 10.1128/JVI.02551-09}}{{cite journal |vauthors= Paploski IA, Corzo C, Rovira A, Murtaugh MP, Sanhueza JM, Vilalta C, Schroeder DC, VanderWaal K | title = Temporal Dynamics of Co-circulating Lineages of Porcine Reproductive and Respiratory Syndrome Virus | journal = Frontiers in Microbiology | volume = 1 | issue = 10 | pages = 2486 |date=Nov 2019 | pmid = 31736919 | pmc = 6839445 | doi = 10.3389/fmicb.2019.02486| doi-access = free }} increases the difficulty of developing vaccines against it. Similarly, maintaining diagnostic PCR detection assays is difficult due to the high mutation rate of this virus.

In Europe, a geographical demarcation exists between areas of low (Western and Central Europe) and high (Eastern Europe) PRRSV1 diversity. Current genetic classification based on the size of open reading frame (ORF) 7 revealed the existence of three different subtypes within PRRSV1 strains: subtype 1, with Lelystad virus as prototype, is present in Europe and Russia, subtype 2 in Russia and Lithuania and subtype 3 in Belarus.{{Cite journal |last1=Stadejek |first1=T. |last2=Oleksiewicz |first2=M. B. |last3=Potapchuk |first3=D. |last4=Podgórska |first4=K. |date=2006-07-01 |title=Porcine reproductive and respiratory syndrome virus strains of exceptional diversity in eastern Europe support the definition of new genetic subtypes |journal=Journal of General Virology |language=en |volume=87 |issue=7 |pages=1835–1841 |doi=10.1099/vir.0.81782-0 |pmid=16760385 |issn=0022-1317|doi-access=free }} Besides known subtypes, a recent study showed non-subtypeable PRRSV1 isolates.

The pattern of PRRSV transmission is mainly via contact and airborne. PRRSV transmission is highly dependent on the route of exposure, virus isolate and the virus dose.{{Cite journal |last1=Cutler |first1=Timothy D. |last2=Wang |first2=Chong |last3=Hoff |first3=Steven J. |last4=Kittawornrat |first4=Apisit |last5=Zimmerman |first5=Jeffrey J. |date=2011 |title=Median infectious dose (ID50) of porcine reproductive and respiratory syndrome virus isolate MN-184 via aerosol exposure |url=https://linkinghub.elsevier.com/retrieve/pii/S0378113511001416 |journal=Veterinary Microbiology |language=en |volume=151 |issue=3–4 |pages=229–237 |doi=10.1016/j.vetmic.2011.03.003|pmid=21474258 |url-access=subscription }}

It was shown that pigs could be infected with PRRS virus by several routes of exposure: intranasal, intramuscular, peroral, intrauterine, and vaginal.{{Cite journal |last1=Hermann |first1=J.R. |last2=Muñoz-Zanzi |first2=C.A. |last3=Roof |first3=M.B. |last4=Burkhart |first4=K. |last5=Zimmerman |first5=J.J. |date=2005 |title=Probability of porcine reproductive and respiratory syndrome (PRRS) virus infection as a function of exposure route and dose |url=https://linkinghub.elsevier.com/retrieve/pii/S0378113505002324 |journal=Veterinary Microbiology |language=en |volume=110 |issue=1–2 |pages=7–16 |doi=10.1016/j.vetmic.2005.06.012|pmid=16098692 |url-access=subscription }} Pigs are most susceptible to infection via intramuscular inoculation (10^2.2 tissue culture infectious dose with a 50% endpoint (TCID₅₀)), followed by the intranasal route (10^4.0 TCID₅₀) and peroral route (10^5.3 TCID₅₀).

Temperature was found to have a great effect on the half-life (T_1/2) of infectious PRRSV. Virus is quickly inactivated by heating, drying or by pH extremes. Experiments showed that aerosolized PRRSV was least stable (T_1/2 = 3.6 min) at 41.0 °C and 73.0% relative humidity and most stable (T_1/2 = 192.7 min) at 5.0 °C and 17.1% relative humidity.{{Cite journal |last1=Hermann |first1=Joseph |last2=Hoff |first2=Steve |last3=Muñoz-Zanzi |first3=Claudia |last4=Yoon |first4=Kyoung-Jin |last5=Roof |first5=Michael |last6=Burkhardt |first6=Anna |last7=Zimmerman |first7=Jeffrey |date=2007 |title=Effect of temperature and relative humidity on the stability of infectious porcine reproductive and respiratory syndrome virus in aerosols |journal=Veterinary Research |volume=38 |issue=1 |pages=81–93 |doi=10.1051/vetres:2006044 |pmid=17156739 |issn=0928-4249|doi-access=free }}

The basic reproduction number (R₀) for Type 1 PRRSV could range from approximately 2 to 5 in naïve pigs.{{Cite journal |last1=Pileri |first1=Emanuela |last2=Mateu |first2=Enric |date=2016 |title=Review on the transmission porcine reproductive and respiratory syndrome virus between pigs and farms and impact on vaccination |journal=Veterinary Research |language=en |volume=47 |issue=1 |pages=108 |doi=10.1186/s13567-016-0391-4 |issn=1297-9716 |pmc=5086057 |pmid=27793195 |doi-access=free }} Compared to Type 1 PRRSV isolates, Type 2 PRRSV strains are considered to be of higher virulence.

File:Pig with Porcine reproductive and respiratory syndrome (PRRS).jpg Domesticated pigs and other Suidae are the only known natural hosts of PRRSV. Typical clinical symptoms of PRRS include respiratory disease in piglets and reproductive failure in sows.

Cells of the monocyte/macrophage lineage (macrophages in lungs, lymph nodes, spleen, placenta and other organs, and dendritic cells) are the primary targets for viral replication in vivo.{{Cite journal |last1=Lunney |first1=Joan K. |last2=Benfield |first2=David A. |last3=Rowland |first3=Raymond R.R. |date=2010 |title=Porcine reproductive and respiratory syndrome virus: An update on an emerging and re-emerging viral disease of swine |journal=Virus Research |language=en |volume=154 |issue=1–2 |pages=1–6 |doi=10.1016/j.virusres.2010.10.009 |pmc=7172856 |pmid=20951175}} Replication cycle begins with the interaction between the GP5-M complex of PRRSV and the cellular receptors heparan sulfate and CD169 (sialoadhesin). Upon binding and internalization, GP2-GP3-GP4 interacts with CD163 mediating the disassembly and release of the nucleocapsid.

PRRSV infection starts with an acute infection during which tonsils and lungs serve as preferential sites of infection leading to respiratory problems in young pigs. The first stage of infection results in a cell-free viremia starting from 6–12 h post infection and lasting for several weeks despite the induction of circulating antibodies. Subsequently, depending on the immune status of the pigs, the acute infection may be continued with a persistent stage with viral replication localized in lymphoid organs, including tonsils, spleen and lymph nodes. At the final stage of infection, PRRSV replication gradually declines until the virus becomes eliminated in the host. However, the virus may persist in pigs for a longer period of time. The mechanism of persistence may be based on the high mutation rate of the PRRSV RNA genome allowing an escape from the host immune surveillance.{{Cite journal |last1=Costers |first1=Sarah |last2=Vanhee |first2=Merijn |last3=Van Breedam |first3=Wander |last4=Van Doorsselaere |first4=Jan |last5=Geldhof |first5=Marc |last6=Nauwynck |first6=Hans J. |date=2010 |title=GP4-specific neutralizing antibodies might be a driving force in PRRSV evolution |url=https://linkinghub.elsevier.com/retrieve/pii/S0168170210003230 |journal=Virus Research |language=en |volume=154 |issue=1–2 |pages=104–113 |doi=10.1016/j.virusres.2010.08.026|pmid=20837070 |url-access=subscription }}{{Cite journal |last1=Lauring |first1=Adam S. |last2=Andino |first2=Raul |date=2010-07-22 |editor-last=Manchester |editor-first=Marianne |title=Quasispecies Theory and the Behavior of RNA Viruses |journal=PLOS Pathogens |language=en |volume=6 |issue=7 |pages=e1001005 |doi=10.1371/journal.ppat.1001005 |issn=1553-7374 |pmc=2908548 |pmid=20661479 |doi-access=free }}{{Cite journal |last1=Lauring |first1=Adam S. |last2=Frydman |first2=Judith |last3=Andino |first3=Raul |date=2013 |title=The role of mutational robustness in RNA virus evolution |journal=Nature Reviews Microbiology |language=en |volume=11 |issue=5 |pages=327–336 |doi=10.1038/nrmicro3003 |issn=1740-1526 |pmc=3981611 |pmid=23524517}}

After an extensive viremia, the virus reaches macrophages in different internal organs (e.g. lymphoid tissues and maternal endometrium) resulting in disorders, such as reproductive failure in sows. At a late stage of gestation, PRRSV can cross the placental barrier and infect fetuses. Depending on the viral strain and immune status of the host, PRRSV may cause both subclinical and severe reproductive and/or respiratory disease. PRRSV can suppress the host immune defense system, which allows the establishment of secondary infections.

The clinical outcome of a PRRSV infection can be aggravated by co-infections with other pathogens. It is characterized by problems with growth performance and clinical signs such as fever, cough, anorexia and dyspnea. Along with PRRSV, porcine circovirus type 2 (PCV2), Pasteurella multocida and porcine mycoplasmas are the most frequently detected pathogens in porcine respiratory disease complex affected pigs. PRRSV infection may also decrease the efficacy of vaccines used in pigs.{{Cite journal |last1=Kitikoon |first1=Pravina |last2=Vincent |first2=Amy L. |last3=Jones |first3=Katherine R. |last4=Nilubol |first4=Dachrit |last5=Yu |first5=Shan |last6=Janke |first6=Bruce H. |last7=Thacker |first7=Brad J. |last8=Thacker |first8=Eileen L. |date=2009 |title=Vaccine efficacy and immune response to swine influenza virus challenge in pigs infected with porcine reproductive and respiratory syndrome virus at the time of SIV vaccination |url=https://linkinghub.elsevier.com/retrieve/pii/S0378113509002879 |journal=Veterinary Microbiology |language=en |volume=139 |issue=3–4 |pages=235–244 |doi=10.1016/j.vetmic.2009.06.003|pmid=19595522 |url-access=subscription }}{{Cite journal |last1=Suradhat |first1=S. |last2=Kesdangsakonwut |first2=S. |last3=Sada |first3=W. |last4=Buranapraditkun |first4=S. |last5=Wongsawang |first5=S. |last6=Thanawongnuwech |first6=R. |date=2006-03-24 |title=Negative impact of porcine reproductive and respiratory syndrome virus infection on the efficacy of classical swine fever vaccine |url=https://linkinghub.elsevier.com/retrieve/pii/S0264410X05012430 |journal=Vaccine |language=en |volume=24 |issue=14 |pages=2634–2642 |doi=10.1016/j.vaccine.2005.12.010|pmid=16406169 |url-access=subscription }} Due to these problems, PRRS is considered worldwide as a serious threat for the pig industry.{{Cite journal |last1=Neumann |first1=Eric J. |last2=Kliebenstein |first2=James B. |last3=Johnson |first3=Colin D. |last4=Mabry |first4=John W. |last5=Bush |first5=Eric J. |last6=Seitzinger |first6=Ann H. |last7=Green |first7=Alice L. |last8=Zimmerman |first8=Jeffrey J. |date=2005-08-01 |title=Assessment of the economic impact of porcine reproductive and respiratory syndrome on swine production in the United States |url=https://avmajournals.avma.org/view/journals/javma/227/3/javma.2005.227.385.xml |journal=Journal of the American Veterinary Medical Association |volume=227 |issue=3 |pages=385–392 |doi=10.2460/javma.2005.227.385 |pmid=16121604 |issn=0003-1488|url-access=subscription }}

The designation of the term "high pathogenicity" tends to be relative. In general, the highly pathogenic PRRS shows higher reproductive failure rate in pregnant sows, high morbidity and high mortality in pigs of all ages.{{Cite journal |last1=Huang |first1=Chen |last2=Du |first2=Yinping |last3=Yu |first3=Zhibin |last4=Zhang |first4=Qiong |last5=Liu |first5=Yihao |last6=Tang |first6=Jun |last7=Shi |first7=Jishu |last8=Feng |first8=Wen-hai |date=2016 |title=Highly Pathogenic Porcine Reproductive and Respiratory Syndrome Virus Nsp4 Cleaves VISA to Impair Antiviral Responses Mediated by RIG-I-like Receptors |journal=Scientific Reports |volume=6 |issue=1 |page=28497 |doi=10.1038/srep28497 |pmid=27329948 |pmc=4916416 |bibcode=2016NatSR...628497H |s2cid=4966712 |issn=2045-2322|doi-access=free }} Infected pigs display a range of respiratory (dyspnea, sneezing, coughing) and systemic clinical signs (a long-lasting high fever of over +41 °C, depression, anorexia, discoloration of the skin and the ears), conjunctivitis.{{Cite journal |last1=Guo |first1=Baoqing |last2=Lager |first2=Kelly M. |last3=Henningson |first3=Jamie N. |last4=Miller |first4=Laura C. |last5=Schlink |first5=Sarah N. |last6=Kappes |first6=Matthew A. |last7=Kehrli |first7=Marcus E. |last8=Brockmeier |first8=Susan L. |last9=Nicholson |first9=Tracy L. |last10=Yang |first10=Han-Chun |last11=Faaberg |first11=Kay S. |date=2013 |title=Experimental infection of United States swine with a Chinese highly pathogenic strain of porcine reproductive and respiratory syndrome virus |url=http://dx.doi.org/10.1016/j.virol.2012.09.013 |journal=Virology |volume=435 |issue=2 |pages=372–384 |doi=10.1016/j.virol.2012.09.013 |pmid=23079105 |pmc=7111980 |issn=0042-6822}}{{Cite journal |last=An |first=Tong-Qing |date=2011 |title=Highly Pathogenic Porcine Reproductive and Respiratory Syndrome Virus, Asia |url=http://dx.doi.org/10.3201/eid1709.110411 |journal=Emerging Infectious Diseases |volume=17 |issue=9 |pages=1782–1784 |doi=10.3201/eid1709.110411 |pmid=21888830 |pmc=3322091 |issn=1080-6040}} Neurological signs could be seen in some cases.{{Cite journal |last1=Chen |first1=Xin-xin |last2=Quan |first2=Rong |last3=Guo |first3=Xue-kun |last4=Gao |first4=Li |last5=Shi |first5=Jishu |last6=Feng |first6=Wen-hai |date=2014 |title=Up-regulation of pro-inflammatory factors by HP-PRRSV infection in microglia: Implications for HP-PRRSV neuropathogenesis |url=http://dx.doi.org/10.1016/j.vetmic.2014.01.031 |journal=Veterinary Microbiology |volume=170 |issue=1–2 |pages=48–57 |doi=10.1016/j.vetmic.2014.01.031 |pmid=24581811 |issn=0378-1135|url-access=subscription }} The common lesions at necropsy may include inflammation of lungs and lymph nodes, fibrinous pleuropneumonia and pericarditis, peritonitis.

Laboratory-based diagnostic tests have evolved significantly since initial discovery of the PRRS virus in the late 1980s. Initially viral culture was used to confirm PRRSV in serum or tissue samples. This process involves growing the virus in-vitro on cell lines over a period of 3–14 days or longer. If cytopathic effect is observed during culture, the culture is confirmed as the PRRS virus by direct fluorescent antibody or other confirmation method prior to reporting the sample as positive for presence of PRRSV.

In the late 1990s, nested PCR was used to the detect the virus as it showed improved sensitivity over non-nested PCR.{{cite journal |last=Christopher-Hennings |first=Jane |display-authors=etal |date=July 1995 |title=Detection of Porcine Reproductive and Respiratory Syndrome Virus in Boar Semen by PCR |journal=Journal of Clinical Microbiology |volume=33 |issue=7 |pages=1730–1734 |doi=10.1128/JCM.33.7.1730-1734.1995 |pmc=228258 |pmid=7665637}} Now, quantitative PCR assays offered as-good or better sensitivity than nested PCR, fast turnaround time in the lab, and lower rates of cross-contamination via closed-tube amplification.

A variety of management strategies have been proposed to control and eliminate PRRSV:{{Cite journal |last1=Corzo |first1=Cesar A. |last2=Mondaca |first2=Enrique |last3=Wayne |first3=Spencer |last4=Torremorell |first4=Montserrat |last5=Dee |first5=Scott |last6=Davies |first6=Peter |last7=Morrison |first7=Robert B. |date=2010 |title=Control and elimination of porcine reproductive and respiratory syndrome virus |url=https://linkinghub.elsevier.com/retrieve/pii/S0168170210002935 |journal=Virus Research |language=en |volume=154 |issue=1–2 |pages=185–192 |doi=10.1016/j.virusres.2010.08.016|pmid=20837071 |url-access=subscription }}{{Cite journal |last1=Batista |first1=L |last2=Pijoan |first2=C |last3=Torremorell |first3=M |date=2002 |title=Experimental injection of gilts with porcine reproductive and respiratory syndrome virus (PRRSV) during acclimatization. |journal=Journal of Swine Health and Production |volume=10 |issue=4 |pages=147–150|doi=10.54846/jshap/335 }}{{Cite journal |last1=Štukelj |first1=Marina |last2=Plut |first2=Jan |last3=Toplak |first3=Ivan |date=2015 |title=Serum inoculation as a possibility for elimination of porcine reproductive and respiratory syndrome (PRRS) from a farrow-to-finish pig farm |url=https://akjournals.com/view/journals/004/63/3/article-p389.xml |journal=Acta Veterinaria Hungarica |volume=63 |issue=3 |pages=389–399 |doi=10.1556/004.2015.037 |pmid=26551429 |issn=0236-6290}}

• gilt acclimatization,
• isowean (isolated weaning),
• herd stabilization,
• total and partial depopulation/repopulation,
• test and removal,
• herd closure and rollover,
• mass vaccination with unidirectional pig flow and herd closure,
• McRebel (Management Changes to Reduce Exposure to Bacteria to Eliminate Losses),
• semen quality monitoring,
• regional elimination program.

Active immunization is currently the only widely available way of PRRS control in swine herds worldwide. For specific immunization of animals against PRRS, several types of vaccines and live virus inoculation are used.{{Cite journal |last1=Linhares |first1=D.C.L. |last2=Cano |first2=J.P. |last3=Torremorell |first3=M. |last4=Morrison |first4=R.B. |date=2014 |title=Comparison of time to PRRSv-stability and production losses between two exposure programs to control PRRSv in sow herds |url=https://linkinghub.elsevier.com/retrieve/pii/S0167587714001962 |journal=Preventive Veterinary Medicine |language=en |volume=116 |issue=1–2 |pages=111–119 |doi=10.1016/j.prevetmed.2014.05.010|pmid=24931129 |url-access=subscription }}

The first PRRSV2 live vaccine, Ingelvac PRRS MLV (Boehringer Ingelheim Vetmedica, Inc.), is available for prevention and control of PRRS since 1994.{{Cite journal |last1=Opriessnig |first1=T. |last2=Halbur |first2=P. G. |last3=Yoon |first3=K.-J. |last4=Pogranichniy |first4=R. M. |last5=Harmon |first5=K. M. |last6=Evans |first6=R. |last7=Key |first7=K. F. |last8=Pallares |first8=F. J. |last9=Thomas |first9=P. |last10=Meng |first10=X. J. |date=2002 |title=Comparison of Molecular and Biological Characteristics of a Modified Live Porcine Reproductive and Respiratory Syndrome Virus (PRRSV) Vaccine (Ingelvac PRRS MLV), the Parent Strain of the Vaccine (ATCC VR2332), ATCC VR2385, and Two Recent Field Isolates of PRRSV |url=http://dx.doi.org/10.1128/jvi.76.23.11837-11844.2002 |journal=Journal of Virology |volume=76 |issue=23 |pages=11837–11844 |doi=10.1128/jvi.76.23.11837-11844.2002 |pmid=12414926 |pmc=136866 |issn=0022-538X}} It was obtained by continuous passages in MARC-145 cells. To date, a number of commercial PRRS vaccines have been successfully employed in the global market.{{Cite journal |last1=Murtaugh |first1=Michael P. |last2=Genzow |first2=Marika |date=2011 |title=Immunological solutions for treatment and prevention of porcine reproductive and respiratory syndrome (PRRS) |url=https://linkinghub.elsevier.com/retrieve/pii/S0264410X11014198 |journal=Vaccine |language=en |volume=29 |issue=46 |pages=8192–8204 |doi=10.1016/j.vaccine.2011.09.013|pmid=21925560 |url-access=subscription }}{{Cite journal |last=Charerntantanakul |first=Wasin |date=2012 |title=Porcine reproductive and respiratory syndrome virus vaccines: Immunogenicity, efficacy and safety aspects |journal=World Journal of Virology |language=en |volume=1 |issue=1 |pages=23–30 |doi=10.5501/wjv.v1.i1.23 |issn=2220-3249 |pmc=3782261 |pmid=24175208 |doi-access=free }}{{Cite journal |last1=Hu |first1=J. |last2=Zhang |first2=C. |date=2014 |title=Porcine Reproductive and Respiratory Syndrome Virus Vaccines: Current Status and Strategies to a Universal Vaccine |journal=Transboundary and Emerging Diseases |language=en |volume=61 |issue=2 |pages=109–120 |doi=10.1111/tbed.12016|pmid=23343057 |doi-access=free }} The great genetic diversity of PRRSV and the absence of clear immunological parameters correlating with the protection are substantial barriers to new PRRS vaccine development.

Pigs resistant to PRRS have been engineered using gene editing technologies by the biotechnology company Genus.{{cite web | last=Devlin | first=Hannah | title=Scientists genetically engineer pigs immune to costly disease | website=The Guardian | date=20 June 2018 | url=http://www.theguardian.com/science/2018/jun/20/scientists-genetically-engineer-pigs-immune-to-costly-disease | access-date=11 December 2021}}

• Porcine reproductive and respiratory syndrome virus 2
• Porcine epidemic diarrhoea
• Animal viruses
• Virology

{{Reflist}}

• [http://www.prrs.com www.prrs.com], The complete guide to PRRS understanding and control.
• [https://web.archive.org/web/20150604233336/http://www.oie.int/fileadmin/Home/eng/Media_Center/docs/pdf/Disease_cards/PPRS-EN.pdf OIE Q&A about the Porcine reproductive and respiratory syndrome]
• [https://www.nytimes.com/2007/08/16/business/worldbusiness/16pigs.html New York Times article on the 2007 epidemic]
• {{Cite news

| title=Europe's piglets die in mystery plague

| publisher=New Scientist

| date=May 4, 1991

| url=https://www.newscientist.com/article/mg13017671.900-europes-piglets-die-in-mystery-plague-.html

| access-date=2007-06-28 }}

• [http://www.horizonpress.com/gateway/animal-viruses.html Animal viruses]
• [https://web.archive.org/web/20111004154046/http://www.prrsresearch.com/ PRRS Research Award for PRRS Eradication ]
• [https://web.archive.org/web/20110601232319/http://www.padrap.org/ PADRAP Production Animal Disease Risk Assessment Program PRRS Risk Survey]
• [https://www.pigprogress.net/Health/Health-Tool/diseases/Porcine-Reproductive-and-Respiratory-Syndrome-PRRS-/ PRRS information], from the Pig Progress Health Tool

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Category:Arteriviridae

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