As the severity of PRRS virus infection vary widely, from the lack of clinical signs to devastating outbreaks, a PRRS diagnosis based solely on a clinical suspicion can be extremely complicated or lead us to error.
Diagnosis of PRRS should take into account clinical signs, clinical history and production records, but laboratory confirmation is compulsory.
Changes in production records
When herd production record data is analysed, some changes in specific reproductive parameters may suggest reproductive failure due to PRRS virus infection.
This may include: increase in late term abortions (± ≥80 days), early farrowings or number of mummified fetuses, as well as increase in number of weak-born and decrease in live-born pigs. Cyclic returns to estrus and early abortions are much less common.
Likewise, an increase in preweaning mortality and respiratory problems due to bacterial complications occur, (see section “3. Concurrent infections”) or if herd performance is suboptimal, PRRS should be included in the differential diagnosis.
It is important to keep in mind that the presence of concurrent infections in the respiratory form of PRRS is very common.
This phenomenon blurs the clinical picture and complicates the diagnosis based on the clinical signs.
The clinical history can be useful to predict or anticipate the consequences of PRRS virus infection on a given farm. Also, it can be essential to interpret the clinical signs and the changes in the production record observed during an infection.
In this sense, three main scenarios can exist (see section “3. What happens in a confirmed PRRS virus farm?”).
Briefly, PRRS virus infection in a PRRS virus-free farm can be devastating; clear clinical signs can be expected in this situation, since none of the animals have immunity against the virus.
If there is an introduction of a new strain in a PRRS virus-positive farm, the final outcome of the infection will be unpredictable, but usually a less severe outbreak would be expected.
Last of all, during the re-circulation of a farm-specific strain, a far less severe outbreak would be expected; nonetheless, once again, the final outcome is unpredictable since it depends on several factors.
Diagnosis of PRRS must be tackled differently depending on the previous status of the farm.
Distinguishing PRRS from other diseases that present similar lesions, reproductive failure or respiratory signs.
The following table shows some of the diseases that could be included in a differential diagnosis of PRRS. The diseases that should be included in the final differential diagnosis for a given case will depend largely on the clinical picture, the age of the animals, and the region.
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- Bautista EM, Meulenberg JJ, Choi CS, Molitor TW. Structural polypeptides of the American (VR-2332) strain of porcine reproductive and respiratory syndrome virus. Arch Virol. 1996:1357-65.
- Benfield DA, Nelson E, Collins JE, Harris L, Hennings JC, Shaw DP, Goyal SM, McCullough S, Morrison RB, Joo HS, Gorcyca D, Chladek D. Characterization of swine infertility and respiratory syndrome (SIRS) virus (isolate ATCC VR-2332). J Vet Diagn Invest. 1992. 4, 127-133.
- Benfield D, Nelson J, Rossow K, Nelson C, Steffen M, Rowland R. Diagnosis of persistent or prolonged porcine reproductive and respiratory syndrome virus infections Vet Res. 2000, 31:71.
- Brockmeier SL, Halbur PG, Thacker EL. Porcine respiratory disease complex. In KA Brogden, JM Guthmiller, eds, Polymicrobial Diseases. Washington, DC: ASM Press. 2002, 231-58.
- Calzada-Nova G, Schnitzlein W, Husmann R, Zuckermann FA. Characterization of the cytokine and maturation responses of pure populations of porcine plasmacytoid dendritic cells to porcine viruses and toll-like receptor agonists. Vet Immunol Immunopathol. 2010, 135:20-33.
- Chen WY, Schniztlein WM, Calzada-Nova G, Zuckermann FA. Genotype 2 strains of porcine reproductive and respiratory syndrome virus dysregulate alveolar macrophage cytokine production via the unfolded protein response. J Virol.2017, pii: JVI.01251-17.
- Christopher-Hennings J, Nelson EA, Hines RJ, Nelson JK, Swenson SL, Zimmerman JJ, Chase CL, Yaeger MJ, Benfield DA. Persistence of porcine reproductive and respiratory syndrome virus in serum and semen of adult boars. J Vet Diagn Invest. 1995, 7:456-64.
- Cortey M, Díaz I, Martín-Valls GE, Mateu E. Next-generation sequencing as a tool for the study of Porcine reproductive and respiratory syndrome virus (PRRSV) macro- and micro- molecular epidemiology. Vet Microbiol. 2017. doi: 10.1016/j.vetmic.2017.02.002.
- Darwich L, Díaz I, Mateu E. Certainties, doubts and hypotheses in porcine reproductive and respiratory syndrome virus immunobiology. Virus Res. 2010, 154:123-32.
- Díaz I, Darwich L, Pappaterra G, Pujols J, Mateu E. Different European-type vaccines against porcine reproductive and respiratory syndrome virus have different immunological properties and confer different protection to pigs. Virology. 2006, 351:249-59.
- Díaz I, Gimeno M, Darwich L, Navarro N, Kuzemtseva L, López S, Galindo I, Segalés J, Martín M, Pujols J, Mateu E. Characterization of homologous and heterologous adaptive immune responses in porcine reproductive and respiratory syndrome virus infection. Vet Res. 2012, 19:43:30.
- García-Nicolás O, Quereda JJ, Gómez-Laguna J, Salguero FJ, Carrasco L, Ramis G, Pallarés FJ. Cytokines transcript levels in lung and lymphoid organs during genotype 1 Porcine Reproductive and Respiratory Syndrome Virus (PRRSV) infection. Vet Immunol Immunopathol. 2014, 160:26-40.
- Gimeno M, Darwich L, Diaz I, de la Torre E, Pujols J, Martín M, Inumaru S, Cano E, Domingo M, Montoya M, Mateu E. Cytokine profiles and phenotype regulation of antigen presenting cells by genotype-I porcine reproductive and respiratory syndrome virus isolates. Vet Res. 2011, 42:9.
- Gómez-Laguna J, Salguero FJ, Pallarés FJ, Carrasco L. Immunopathogenesis of porcine reproductive and respiratory syndrome in the respiratory tract of pigs. Vet J. 2013, 195:148-55.
- Haynes JS, Halbur PG, Sirinarumitr T, Paul PS, Meng XJ, Huffman EL. Temporal and morphologic characterization of the distribution of porcine reproductive and respiratory syndrome virus (PRRSV) by in situ hybridization in pigs infected with isolates of PRRSV that differ in virulence. Vet Pathol. 1997, 34:39-43.
- Hill H. Overview and history of Mystery Swine Disease (swine infertility/respiratory syndrome). Proceedings of the Mystery Swine Disease Committee Meeting, Livestock Conversation Institute, Denver, CO. 1990, 29–31.
- Holtkamp DJ, Polson DD, Torremorrell M. Terminology for classifying swine herds by porcine reproductive and respiratory status. J Swine Health and Prod. 2011, 19:44-56.
- Horter DC, Pogranichniy RM, Chang CC, Evans RB, Yoon KJ, Zimmerman JJ. Characterization of the carrier state in porcine reproductive and respiratory syndrome virus infection. Vet Microbiol. 2002, 86:213-28.
- Loula T. Mystery pig disease. Agri-practice. 1991, 12:23–34.
- Lunney JK, Benfield DA, Rowland RR. Porcine reproductive and respiratory syndrome virus: an update on an emerging and re-emerging viral disease of swine. Virus Res. 2010, 154:1-6.
- Mateu E, Tello M, Coll A, Casal J, Martín M. Comparison of three ELISAs for the diagnosis of porcine reproductive and respiratory syndrome. Vet Rec. 2006, 159:717-8.
- Mateu E, Diaz I. The challenge of PRRS immunology. Vet J. 2008, 177:345-51.
- Meier WA, Galeota J, Osorio FA, Husmann RJ, Schnitzlein WM, Zuckermann FA. Gradual development of the interferon-gamma response of swine to porcine reproductive and respiratory syndrome virus infection or vaccination. Virology. 2003, 309:18-31.
- Nelson EA, Christopher-Hennings J, Benfield DA. Serum immune responses to the proteins of porcine reproductive and respiratory syndrome (PRRS) virus. J Vet Diagn Invest. 1994, 6:410-5.
- Appendices IV and V of the REPORT OF THE OIE AD HOC GROUP ON PORCINE REPRODUCTIVE RESPIRATORY SYNDROME Paris, 9 – 11 June 2008 http://www.oie.int/fileadmin/Home/eng/Our_scientific_expertise/docs/pdf/PRRS_guide_web_bulletin.pdf.
- Rodríguez-Gómez IM, Gómez-Laguna J, Carrasco L. Impact of PRRSV on activation and viability of antigen presenting cells. World J Virol. 2013, 2:146-51.
- Rovira A, Cano JP, Muñoz-Zanzi C. Feasibility of pooled-sample testing for the detection of porcine reproductive and respiratory syndrome virus antibodies on serum samples by ELISA. Vet Microbiol. 2008, 130:60-8.
- Rovira A, Clement T, Christopher-Hennings J, Thompson B, Engle M, Reicks D, Muñoz-Zanzi C. Evaluation of the sensitivity of reverse-transcription polymerase chain reaction to detect porcine reproductive and respiratory syndrome virus on individual and pooled samples from boars. J Vet Diagn Invest. 2007, 19:502-9.
- Rovira A, Reicks D, Muñoz-Zanzi C. Evaluation of surveillance protocols for detecting porcine reproductive and respiratory syndrome virus infection in boar studs by simulation modeling. J Vet Diagn Invest. 2007, 19:492-501.
- Salguero FJ, Frossard JP, Rebel JM, Stadejek T, Morgan SB, Graham SP, Steinbach F. Host-pathogen interactions during porcine reproductive and respiratory syndrome virus 1 infection of piglets. Virus Res. 2015, 202:135-43.
- Segalés J, Domingo M, Balasch M, Solano GI, Pijoan C. Ultrastructural study of porcine alveolar macrophages infected in vitro with porcine reproductive and respiratory syndrome (PRRS) virus, with and without Haemophilus parasuis. J Comp Pathol. 1998, 118:231-43.
- Sur JH, Cooper VL, Galeota JA, Hesse RA, Doster AR, Osorio FA. In vivo detection of porcine reproductive and respiratory syndrome virus RNA by in situ hybridization at different times postinfection. J Clin Microbiol. 1996, 34:2280-6.
- Terpstra C, Wensvoorst G, Pol JMA. Experimental reproduction of porcine epidemic abortion and respiratory syndrome (mystery swine disease) by infection with Lelystad virus: Koch’s postulates fulfilled. Vet Q. 1991, 13:131–36.
- Tian K, Yu X, Zhao T, Feng Y, Cao Z, Wang C, Hu Y, Chen X, Hu D, Tian X, Liu D, Zhang S, Deng X, Ding Y, Yang L, Zhang Y, Xiao H, Qiao M, Wang B, Hou L, Wang X, Yang X, Kang L, Sun M, Jin P, Wang S, Kitamura Y, Yan J, Gao GF. Emergence of fatal PRRSV variants: unparalleled outbreaks of atypical PRRS in China and molecular dissection of the unique hallmark. PLoS One. 200, 2:e526.
- Tong GZ, Zhou YJ, Hao XF, Tian ZJ, An TQ, Qiu HJ. Highly pathogenic porcine reproductive and respiratory syndrome, China. Emerg Infect Dis. 2007, 13:1434-6.
Van Alstine WG, Popielarczyk M, Albregts SR. Effect of formalin fixation on the immunohistochemical detection of PRRS virus antigen in experimentally and naturally infected pigs. J Vet Diagn Invest. 2002, 14:504-7.
- Vézina SA, Loemba H, Fournier M, Dea S, Archambault D. Antibody production and blastogenic response in pigs experimentally infected with porcine reproductive and respiratory syndrome virus. Can J Vet Res. 1996, 60:94-9.
- Wensvoort G, Terpstra C, Pol JMA, Lask EA, Bloemraad M, de Kluyver EP, Kragten C, van Butten L, den Besten A, Wagenaar F, Broekhuijsen JM, Moonen PJM, Zetstra T, de Boer EA, Tibben AhJ, de Jong MF, van’r Veld P, Groenland GJR, van Gennep JA, Voets MTh, Verheijden JHM, Braamkamp J. Mystery swine disease in the Netherlands: the isolation of Lelystad virus. Vet Q. 1991, 13:121–30.
- Wills RW, Doster AR, Galeota JA, Sur JH, Osorio FA. Duration of infection and proportion of pigs persistently infected with porcine reproductive and respiratory syndrome virus. J Clin Microbiol. 2003, 41:58-62.
- Zimmerman JJ, Benfield DA, Dee SA, Murtaugh MP, Stadejek T, Stevenson GW, Torremorell M. Porcine reproductive and respiratory syndrome virus (porcine arterivirus). In: 10th ed. Diseases of swine, Ed. Wiley-Blackwell. 2012, 31:463-86.