PRRSv in wild boar populations in Korea

Abstract

No information is currently available on porcine reproductive and respiratory syndrome virus (PRRSV) infection in wild boars (Sus scrofa) in Korea. In this study, the status of PRRS in wild boars was investigated. Blood samples were collected from 267 wild boars from eight provinces in Korea. Four of the samples tested (1.5%) were positive for PRRSV antibodies and eight (3.0%) were positive for antigens. Of the virus-positive samples, three and five samples were typed as containing European (EU, type 1) or North American (NA, type 2) viruses, respectively. Two amplicons (one from type 1 and one from type 2) were used to analyze the PRRSV open reading frame 7 (ORF7) sequence. The nucleotide sequences of type 1 PRRSV ORF7 had identities between 96.1% and 98.4% with PRRSVs from domestic pigs in Korea. The sequences of type 2 PRRSV ORF7 had identities of 100% with the PRRSV strain VR-2332, which was prototypic North American strain. These results show that PRRSVs are present in wild boars in Korea, and effective PRRSV surveillance of the wild boar population might therefore be useful for disease control.

PMID:

 

23271179

 

[PubMed - in process]

Choi E, Lee C, Hyun B, Kim J, Lim S, Song J, Shin Y. A survey of porcine reproductive and respiratory syndrome among wild boar populations in Korea. Journal of veterinary science 2012;13(4):377-383.

Immunopathogenesis of PRRSv in the respiratory tract

Abstract

Porcine reproductive and respiratory syndrome (PRRS) virus (PRRSV) impairs local pulmonary immune responses by damaging the mucociliary transport system, impairing the function of porcine alveolar macrophages andinducing apoptosis of immune cells. An imbalance between pro- and anti-inflammatory cytokines, including tumour necrosis factor-α and interleukin-10, in PRRS may impair the immune response of the lung. Pulmonary macrophage subpopulations have a range of susceptibilities to different PRRSV strains and different capacities to express cytokines. Infection with PRRSV decreases the bactericidal activity of macrophages, which increases susceptibility to secondary bacterial infections. PRRSV infection is associated with an increase in concentrations of haptoglobin, which may interact with the virus receptor (CD163) and induce the synthesis of anti-inflammatory mediators. The balance between pro- and anti-inflammatory cytokines modulates the expression of CD163, which may affect the pathogenicity and replication of the virus in different tissues. With the emergence of highly pathogenic PRRSV, there is a need for more information on the immunopathogenesis of different strains of PRRS, particularly to develop more effective vaccines.

Copyright © 2012 Elsevier Ltd. All rights reserved.

Gomez Laguna J, Salguero F J, PallarÃs F J, Carrasco L. Immunopathogenesis of porcine reproductive and respiratory syndrome in the respiratory tract of pigs. The veterinary journal 2012 [in press].

Comparison of PCR assays for PRRSv detection using different sample types (semen, oral fluids, serum, blood swabs)

Abstract

The aims of this study were to compare three commercial porcine reproductive and respiratory syndrome virus (PRRSV) real-time RT-PCR assays for detection of genetically diverse PRRSV isolates in serum, semen, blood swabs, and oral fluids collected from experimentally-infected boars, and to evaluate the effects of sample pooling. Six groups of 3 boars negative for PRRSV were each inoculated with one of six PRRSV isolates (sharing 55-99% nucleotide sequence identity in ORF5). Samples were collected on days post-inoculation (dpi) -2, 1, 3, 5, 7, 14 and 21 and tested by one of three commercially available real-time RT-PCR assays (AB, TC, AD). At dpi 1, all assays detected at least one positive sample in each group. The highest detection rates were on dpi 3 and dpi 5. Between dpi 1 and 7, serum samples had the highest detection rate (90%) with 100% agreement between tests, followed by blood swabs (Kappa = 0.97) and semen (Kappa = 0.80). Oral fluids had the lowest detection rates (AB: 55%; TC: 41%; AD: 46%) and the highest disagreement between kits (Kappa = 0.63). Pools of five samples did not reduce the detection rates if there was one positive sample with a high amount of viral RNA in the pool. Serum and blood swab samples had shorter turn-around times for RNA extraction. The AB assay had a 1.6 times shorter PCR reaction time. In summary, serum and blood swabs had the best performance with highest detection rates and agreement between assays and shortest turn-around time.

PMID:

 

23224085

 

[PubMed - as supplied by publisher]

Gerber PF, O'Neill K, Owolodun O, Wang C, Harmon K, Zhang J, Halbur PG, Zhou L, Meng XJ, Opriessnig T. Comparison of commercial real-time RT-PCR assays for reliable, early and rapid detection of heterologous strains of porcine reproductive and respiratory syndrome virus (PRRSV) in experimentally infected or negative boars using different sample types (semen, oral fluids, serum, blood swabs). 2012. Journal of clinical microbiology [accepted].

Reproductive parameters following a PRRS outbreak where a whole-herd PRRS MLV vaccination strategy was instituted post-outbreak

Abstract

This study assessed the effect of whole-herd porcine reproductive and respiratory syndrome (PRRS) modified-live virus (MLV) vaccination on herd-level reproductive performance, PRRS virus (PRRSV) viremia, and antibody in a subset of females in a 1,200-sow commercial herd in Thailand. Following a PRRSV outbreak, the entire herd was vaccinated with PRRS MLV twice at 3-week intervals and at 3-month intervals, thereafter. Reproductive performance data over a 3-year period were available for analysis. Serum samples were collected before and after vaccination and tested by PRRSV ELISA and reverse transcription-polymerase chain reaction. Vaccination was statistically associated with a lower abortion rate (1.4 vs. 1.6 %), farrowing rate (83.8 vs. 90.0 %), total born (10.6 vs. 11.4 piglets/litter), liveborn (10.0 vs. 10.3 piglets/litter), stillbirths (4.6 vs. 7.0 %), mummies (0.7 vs. 1.6 %), and a higher return rate (11.3 vs. 5.9 %) when compared with the period before the PRRSV outbreak. Pregnant females vaccinated during early gestation farrowed fewer liveborn and more mummies than the comparison group, whereas females vaccinated during late gestation had a lower farrowing rate. In this herd, PRRS whole-herd vaccination had neutral, positive, and negative effects on reproductive performance. Thus, the decision to implement whole-herd vaccination should be balanced between the benefits derived from reproductive performance improvements, e.g., fewer abortions, stillborn piglets, and mummified fetuses, and the effect of vaccination on pregnant females.

Olanratmanee E, Nuntawan Na Ayudhya S, Thanawongnuwech R, Kunavongkrit A, Tummaruk P. Reproductive parameters following a PRRS outbreak where a whole-herd PRRS MLV vaccination strategy was instituted post-outbreak. Tropical animal health and production 2012 [in press].

ORF 5 vs whole genome sequencing for PRRSv

For epidemiological investigations, ORF-5 sequence has been the standard to differentiate PRRSv isolates. In the field people have used different cut offs to differentiate viruses (related vs non-related), the most common being to consider that isolates with 97 to 99% ORF 5 nucleotide similarity (within a year) to be related (Christopher-Hennings et al., JSHAP 2002; Murtaugh, Leman 2012).

However, studies comparing ORF5 sequences have failed to identify RNA segments correlated with virulence. Therefore, some PRRSv-researchers are now studying the whole genome (ORFs 1 to 7) to try to find "the million dollar answer", that is, what makes one isolate relatively avirulent and other isolates "highly pathogenic".

Some examples of PRRSv whole-genome studies that came out this week:

-----

J Virol. 2012 Dec;86(24):13883-4. doi: 10.1128/JVI.02731-12.

Complete genome sequence of a moderately pathogenic porcine reproductive and respiratory syndrome virus variant strain.

Du Y, Lu Y, Qi J, Wu J, Wang G, Wang J.

Source

Shandong Key Laboratory of Animal Disease Control and Breeding, Institute of Animal Science and Veterinary Medicine, Shandong Academy of Agricultural Sciences, Jinan, China.

Abstract

Porcine reproductive and respiratory syndrome (PRRS) has become one of the most economically important diseases to the global pork industry. The etiological agent is the PRRS virus (PRRSV). In the spring of 2006, a highly pathogenic porcine reproductive and respiratory syndrome virus (HP-PRRSV) appeared in China and caused heavy economic losses. Here we report the complete genomic sequence of a novel PRRSV variant with 174 amino acid deletions in the nonstructural protein 2 (nsp2) gene.

PMID:

 

23166276

 

[PubMed - in process]

-----

J Virol. 2012 Dec;86(24):13882. doi: 10.1128/JVI.02729-12.

Complete Genome Sequence of Porcine Reproductive and Respiratory Syndrome Virus Strain ZCYZ Isolated from Hybrid Wild Boars.

Wu J, Liu S, Du Y, Gao Y, Wang G, Wang J.

Source

Shandong Key Lab of Animal Disease Control and Breeding, Shandong Academy of Agricultural Sciences, Jinan, People's Republic of China.

Abstract

A serologic investigation of porcine reproductive and respiratory syndrome virus (PRRSV) in hybrid wild boar herds was conducted during 2008-2009. PRRSV isolates with novel genetic markers were recovered. Experimental infection of pigs indicated that hybrid wild boars are involved in the epidemiology of PRRSV.

PMID:

 

23166275

 

[PubMed - in process]

-----

J Virol. 2012 Dec;86(24):13863-4. doi: 10.1128/JVI.02642-12.

Complete Genome Sequence of a Highly Pathogenic Porcine Reproductive and Respiratory Syndrome Virus NM1 Strain from Northern China.

Li Z, Leng X, Qi Q, Wang F, Wen Y, Tan B, He Y, Xia M, Lu W, Chen L, Cheng S, Wu H.

Source

Division of Zoonoses, Institute of Special Economic Animal and Plant Sciences, Chinese Academy of Agricultural Sciences, Jilin, China.

Abstract

NM1 is a highly pathogenic North American-type porcine reproductive and respiratory syndrome virus (PRRSV). The complete genome sequence shows that NM1 shares high sequence identity (99.2 to 99.4%) to other HP-PRRSV isolates, containing two discontinuous deletions, a 1-amino-acid deletion at position 481 and a 29-amino-acid deletion at positions 533 to 651, in nonstructural protein 2.

PMID:

 

23166263

 

[PubMed - in process]

Investigation of strategies for the introduction and transportation of replacement gilts

ABSTRACT:

BACKGROUND: Porcine reproductive and respiratory syndrome (PRRS) is of major concern to the swine industry; infection with the virus can lead to production losses, morbidity, and mortality within swine operations. Biosecurity practices related to the management of replacement animals are important for the prevention and control of the PRRS virus, as well as other diseases. The objectives of this study were: (i) to describe individual biosecurity practices related to the introduction and transportation of replacement gilts on southern Ontario sow farms, and (ii) to understand patterns in the implementation of these practices. The second objective was accomplished using multiple correspondence analysis (MCA), which allows visualization of the relationships between individual practices and provides information about which practices frequently occur together, and which practices rarely occur together. These patterns constitute strategies for the implementation of biosecurity practices related to the introduction and transportation of replacement gilts. Data were collected using version 2 of the Production Animal Disease Risk Assessment Program's survey for the breeding herd. Two subsets of variables were retained for analysis; one subset pertained to how replacements were managed upon arrival to the farm, and the other pertained to the transportation of genetic animals.

RESULTS:

For both subsets of variables, the results of the MCA procedure were similar; in both solutions the 1st dimension separated herds that were closed with respect to replacement animals from herds that were open, and the 2nd dimension described how open herds managed replacements. The most interesting finding of this study was that, in some cases where a risky practice was being implemented, it was closely associated with other biosecurity practices that may mitigate that risk.

CONCLUSIONS:

The findings from this approach suggest that one cannot always examine biosecurity on a variable-by-variable basis. Even if a practice that is generally considered high-risk is being implemented, it may be balanced by other practices that mitigate that risk. Thus, the overall biosecurity strategy on a farm must be considered instead of only examining the implementation of individual practices.

PMID:

 

23140357

 

[PubMed - as supplied by publisher]

Bottoms K, Poljak Z, Dewey C, Deardon R, Holtkamp D, Friendship R. Investigation of strategies for the introduction and transportation of replacement gilts on southern Ontario sow farms. BMC veterinary research 2012;8(1):217-217.

PRRSv diversity in Romania

Abstract

Porcine reproductive and respiratory syndrome (PRRS) is a disease produced by the (PRRS) virus, characterized by endemic evolution in the majority of countries, which remains in actuality being a permanent threat to health and economic free farms, as well as for those infected. The aim of this study was to evaluate the genetic diversity of Romanian PRRSV isolates from the four most important pig farms in Romania by comparing the nucleotide sequences obtained for ORF5 and ORF7 with a wide range of sequences from GenBank belonging to the main types of PRRSV; the type 1. Eighteen different sequences were obtained for ORF5 gene and 10 for ORF7 gene. One Romanian isolate (Rom3) was found in three of the four different investigated farms. The phylogenetic analysis revealed that the Romanian PRRSV nucleotide sequences clustered in three groups within the subtype 1 of the virus. The analysis of amino acid sequences evidenced for GP5 and N-nucleocapsid proteins confirmed that the Romanian virus belonged to type 1.

PMID:

 

23109899

 

[PubMed - in process]

Zaulet M, Gurau M R, Petrovan V, Buburuzan L. Genetic diversity characterization of porcine reproductive and respiratory syndrome virus isolates in Romania, based on phylogenetic analysis. International journal of molecular sciences 2012;13(9):12046-12061.

Identifying questions in the PADRAP that are important for retrospectively classifying swine herds according to whether they reported clinical PRRS outbreaks in the previous 3 years

Abstract: The American Association of Swine Veterinarian's (AASV) Production Animal Disease Risk Assessment Program (PADRAP) is a web-based program that offers a set of risk assessment surveys being used by veterinarians who are members of the AASV. Members use PADRAP to help producers systematically assess risk factors that may be associated with clinical outcomes. As assessments are performed the completed surveys are added to the dataset maintained at the Iowa State University College of Veterinary Medicine. One of the surveys included in PADRAP is the porcine reproductive and respiratory syndrome (PRRS) Risk Assessment for the Breeding Herd. The aim of the study was to categorize questions in version 2 of the PRRS Risk Assessment for the Breeding Herd survey as important or unimportant for classifying herds according to whether they reported clinical PRRS outbreaks in the previous 3 years. The results elucidate the relative importance of risk factors and areas of risk factors for clinical outcomes and removing unimportant questions may reduce the time required to complete the survey without affecting the quality of information obtained. Surveys from 896 sow herd sites in the United States and Canada completed between March 2005 and March 2009 were included in the analysis. The survey contained a large number of questions with a complex correlation structure among the questions. Responses for several questions were dependent upon responses to others. To address these issues, an approach was developed using a series of statistical methods including random forest, principle component analysis, logistic regression and receiver operating characteristic (ROC) analysis to classify the herds using the questions in the survey as explanatory variables. Questions were ranked by importance and systematically excluded from least important to most important. The questions excluded, without significantly affecting the performance of the model for classifying herds were identified as unimportant. Thirty-eight of the 127 questions analyzed were identified as unimportant for classifying herds according to whether they reported clinical PRRS outbreaks in the previous 3 years. Sections of the survey where a large number of questions were identified as unimportant included (1) entry of semen into the breeding herd and (2) transportation of live animals. Sections with a high percentage of questions identified as unimportant included (1) characteristics of the site, (2) disposal of dead animals and waste management and (3) employee and visitors. (C) 2012 Elsevier B.V. All rights reserved.

Web of Knowledge's Accession Number: WOS:000307155000005

Holtkamp D J, Lin H, Wang C, O A M. Identifying questions in the American Association of Swine Veterinarian's PRRS risk assessment survey that are important for retrospectively classifying swine herds according to whether they reported clinical PRRS outbreaks in the previous 3 years. Preventive veterinary medicine 2012;106(1):42-52.

Genomic sequence and virulence comparison of four PRRSv strains

Abstract

Porcine reproductive and respiratory syndrome virus (PRRSV) is a ubiquitous and costly virus that exhibits substantial sequence and virulence disparity among diverse isolates. In this study, we compared the whole genomic sequence and virulence of 4 Type 2 PRRSV isolates. Among the 4 isolates, SDSU73, MN184, and NADC30 were all clearly more virulent than NADC31, and among the 3 more virulent isolates, there were subtle differences based on viral replication, lung lesions, lymphadenopathy, febrile response, decreased weight gains, and cytokine responses in the lung. Lesions consistent with bacterial bronchopneumonia were present to varying degrees in pigs infected with PRRSV, and bacteria typically associated with the porcine respiratory disease complex were isolated from the lung of these pigs. Genomic sequence evaluation indicates that SDSU73 is most similar to the nucleotide sequence of JA142, the parental strain of Ingelvac(®) PRRS ATP, while the nucleotide sequences of NADC30 and NADC31 are more similar to strain MN184. Both the NADC30 and NADC31 isolates of PRRSV, isolated in 2008, maintain the nonstructural protein 2 (nsp2) deletion seen in MN184 that was isolated in 2001, but NADC31 has two additional 15 and 36 nucleotide deletions, and these strains are 8-14% different on a nucleotide basis from the MN184 strain. These results indicate that newer U.S. Type 2 strains still exhibit variability in sequence and pathogenicity and although PRRSV strains appear to be reducing the size of the nsp2 over time, this does not necessarily mean that the strain is more virulent.

Published by Elsevier B.V.

PMID:

 

23073232

 

[PubMed - in process]

Brockmeier S L, Loving C L, Vorwald A C, Kehrli M E, Baker R B, Nicholson T L, Lager K M, Miller L C, Faaberg K S. Genomic sequence and virulence comparison of four Type 2 porcine reproductive and respiratory syndrome virus strains. Virus research 2012;169(1):212-221.

Infectiousness of pigs infected by PRRSv is time-dependent

Abstract (provisional)

The time-dependent transmission rate of Porcine Reproductive and Respiratory Syndrome Virus (PRRSV) and the correlation between infectiousness, virological parameters and antibody responses of the infected pigs were studied in experimental conditions. Seven successive transmission trials involving a total of 77 specific pathogen-free piglets were carried out from 7 to 63 days post-inoculation (dpi). A semi-quantitative real time RT-PCR was developed to assess the evolution of the viral genome load in blood and nasal swabs from inoculated and contact pigs, with time. Virus genome in blood was detectable in inoculated pigs from 7 to 77 dpi, whereas viral genome shedding was detectable from nasal swabs from 2 to 48 dpi. The infectiousness of inoculated pigs, assessed from the frequency of occurrence of infected pigs in susceptible groups in each contact trial, increased from 7 to 14 dpi and then decreased slowly until 42 dpi (3, 7, 2, 1 and 0 pigs infected at 7, 14, 21, 28 and 42 dpi, respectively). These data were used to model the time-dependent infectiousness by a lognormal-like function with a latency period of 1 day and led to an estimated basic reproduction ratio, R0 of 2.6 [1.8, 3.3]. The evolution of infectiousness was mainly correlated with the time-course of viral genome load in the blood whereas the decrease of infectiousness was strongly related to the increase in total antibodies.

Charpin C, Mahe S, Keranflec A. Infectiousness of pigs infected by the Porcine Reproductive and Respiratory Syndrome virus (PRRSV) is time-dependent. Veterinary research 2012;43(1):69-69.  doi:10.1186/1297-9716-43-69. Published: 12 October 2012.

Comparative analysis of immune responses following experimental infection of pigs with European PRRS virus strains of differing virulence

Abstract

Porcine reproductive and respiratory syndrome virus (PRRSV) is difficult to control due to a high mutation rate and the emergence of virulent strains. The objective of this study was to analyze the immunological and pathological responses after infection with the European subtype 3 strain Lena in comparison to subtype 1 strains Belgium A and Lelystad-Ter Huurne (LV). Sixteen pigs were inoculated per strain, and sixteen pigs with PBS. At days 7 and 21 post-inoculation (p.i.), four pigs per group were immunized with an Aujeszky disease vaccine (ADV) to study the immune competence after PRRSV infection. Infection with the Lena strain resulted in fever and clinical signs. This was not observed in the Belgium A or LV-infected pigs. Infection with the Lena strain resulted in high virus titers in serum, low numbers of IFN-γ secreting cells, a change in leukocyte populations and a delayed antibody response to immunization with ADV. Levels of IL-1β, IFN-α, IL-10, IL-12, TNF-α and IFN-γ mRNA of the Lena-infected pigs were increased during the first week of infection. For pigs infected with the Belgium A or LV strain, the effects of infection on these parameters were less pronounced, although for the Belgium A-infected pigs, the level of the analyzed cytokines, except for TNF-α, and leukocyte populations were comparable to the Lena-infected pigs. These results suggest that while the outcome of infection for the three strains was comparable, with mostly clearance of viremia at day 33 p.i, differences in immune responses were observed, perhaps contributing to their virulence.

Copyright © 2012. Published by Elsevier B.V.

Weesendorp E, Morgan S, Stockhofe Zurwieden N, Popma De Graaf D J, Graham S P, Rebel J M. Comparative analysis of immune responses following experimental infection of pigs with European porcine reproductive and respiratory syndrome virus strains of differing virulence. Veterinary microbiology 2012 [accepted, in press]

Comparison of the efficacy of autogenous inactivated PRRSv vaccines with that of commercial vaccines against homologous and heterologous challenges

Abstract

ABSTRACT:

BACKGROUND: The porcine reproductive and respiratory syndrome virus (PRRSV) is a rapidly evolving pathogen of swine. At present, there is a high demand for safe and more effective vaccines that can be adapted regularly to emerging virus variants. A recent study showed that, by the use of a controlled inactivation procedure, an experimental BEI-inactivated PRRSV vaccine can be developed that offers partial protection against homologous challenge with the prototype strain LV. At present, it is however not known if this vaccine can be adapted to currently circulating virus variants. In this study, two recent PRRSV field isolates (07 V063 and 08 V194) were used for BEI-inactivated vaccine production. The main objective of this study was to assess the efficacy of these experimental BEI-inactivated vaccines against homologous and heterologous challenge and to compare it with an experimental LV-based BEI-inactivated vaccine and commercial inactivated and attenuated vaccines. In addition, the induction of challenge virus-specific (neutralizing) antibodies by the different vaccines was assessed.

RESULTS:

In a first experiment (challenge with 07 V063), vaccination with the experimental homologous (07 V063) inactivated vaccine shortened the viremic phase upon challenge with approximately 2 weeks compared to the mock-vaccinated control group. Vaccination with the commercial attenuated vaccines reduced the duration of viremia with approximately one week compared to the mock-vaccinated control group. In contrast, the experimental heterologous (LV) inactivated vaccine and the commercial inactivated vaccine did not influence viremia. Interestingly, both the homologous and the heterologous experimental inactivated vaccine induced 07 V063-specific neutralizing antibodies upon vaccination, while the commercial inactivated and attenuated vaccines failed to do so.In the second experiment (challenge with 08 V194), use of the experimental homologous (08 V194) inactivated vaccine shortened viremia upon challenge with approximately 3 weeks compared to the mock-vaccinated control group. Similar results were obtained with the commercial attenuated vaccine. The experimental heterologous (07 V063 and LV) inactivated vaccines did not significantly alter viremia. In this experiment, 08 V194-specific neutralizing antibodies were induced by the experimental homologous and heterologous inactivated vaccines and a faster appearance post challenge was observed with the commercial attenuated vaccine.

CONCLUSIONS:

The experimental homologous inactivated vaccines significantly shortened viremia upon challenge. Despite the concerns regarding the efficacy of the commercial attenuated vaccines used on the farms where the field isolates were obtained, use of commercial attenuated vaccines clearly shortened the viremic phase upon challenge. In contrast, the experimental heterologous inactivated vaccines and the commercial inactivated vaccine had no or only a limited influence on viremia. The observation that homologous BEI-inactivated vaccines can provide a more or less standardized, predictable degree of protection against a specific virus variant suggests that such vaccines may prove useful in case virus variants emerge that escape the immunity induced by the attenuated vaccines.

PMID:

 

23031319

 

[PubMed - as supplied by publisher]

Geldhof M F, Vanhee M, Van Breedam W, Van Doorsselaere J, Karniychuk U, Nauwynck H J. Comparison of the efficacy of autogenous inactivated Porcine Reproductive and Respiratory Syndrome Virus (PRRSV) vaccines with that of commercial vaccines against homologous and heterologous challenges. BMC veterinary research 2012;8(1):182-182.

Risk factors for PRRSv infection and resulting challenges for effective disease surveillance

Abstract

ABSTRACT:

BACKGROUND: This study aimed to identify risk factors for active porcine reproductive and respiratory syndrome virus (PRRSV) infection at farm level and to assess the probability of an infected farm being detected through passive disease surveillance in England. Data were obtained from a cross-sectional study on 147 farrow-to-finish farms conducted from April 2008 -- April 2009. The risk factors for active PRRSV infection were identified using multivariable logistic regression analysis. The surveillance system was evaluated using a stochastic scenario tree model.

RESULTS:

Evidence of PRRSV circulation was confirmed on 35.1% (95%CI: 26.8-43.4) of farms in the cross sectional study, with a higher proportion of infected farms in areas with high pig density (more than 15000 pigs within 10 km radius from the farm). Farms were more likely to have active PRRSV infection if they used the live virus vaccine-Porcilis PRRS (OR=7.5, 95%CI: 2.5-22.8), were located in high pig density areas (OR=2.9, 95%CI: 1.0-8.3) or had dead pigs collected (OR=5.6, 95%CI: 1.7-18.3). Farms that weaned pigs at 28 days of age or later had lower odds of being PRRSV positive compared to those weaning at 21-27 days (OR=0.2, 95%CI: 0.1-0.7). The probability of detecting an infected farm through passive surveillance for disease was low (mode=0.074, 5th and 95th percentiles: 0.067; 0.083 respectively). In particular farms which used live virus vaccine had lower probabilities for detection compared to those which did not.

CONCLUSIONS:

Risk factors identified highlight the importance of biosecurity measures for the incursion of PRRSV infection. The results further indicate that a combined approach of surveillance for infection and disease diagnosis is needed to assist effective control and/or elimination of PRRSV from the pig population.

PMID:

 

23034160

 

[PubMed - as supplied by publisher]

Velasova M, Alarcon P, Williamson S, Wieland B. Risk factors for porcine reproductive and respiratory syndrome virus infection and resulting challenges for effective disease surveillance. BMC veterinary research 2012;8(1):184-184.

Gilt replacement strategies used in Quebec in regard to PRRSv

Abstract: Objectives: To describe gilt replacement strategies in regard to porcine reproductive and respiratory syndrome virus (PRRSV) and to assess differences between high density (HD) and moderate density (MD) pig areas. Materials and methods: A cross-sectional study was conducted in breeding sites located in an HD (n = 68) and an MD area (n = 52) in Quebec between May 2005 and August 2008. A questionnaire on strategies used to introduce replacement gilts was completed and PRRSV status was assessed by enzyme-linked immunosorbent assay or reverse-transcription polymerase chain reaction. Sites housing at least one pig positive by either test were classified as PRRSV-positive. Strategies were described according to herd characteristics, PRRSV status, and area. Results: Self-replacement and purchase of mature or immature gilts were observed on 37%, 35%, and 28% of sites, respectively. In positive sites purchasing mature gilts, 18% had a PRRSV-positive supplier, and gilts were introduced either directly into the sow herd (15%) or after isolation (41%) or acclimatization (44%). Most positive sites purchasing immature gilts practiced acclimatization (93%), either by commingling gilts with commercial pigs (93%) or inoculating serum (7%). Acclimatization processes were rarely monitored through diagnostic procedures. Lower sow inventory, higher prevalence of PRRSV infection, and higher frequency of self-replacement were observed in the HD compared to the MD area. Negative and positive sites practicing voluntary exposure to PRRSV both clustered spatially within the MD area. Implication: Replacement strategies may have weaknesses that should be addressed to facilitate PRRSV management at the herd and regional levels.

Web of Knowledge accession Number: WOS:000308267600006

Lambert M, Denicourt M, Poljak Z, D S. Gilt replacement strategies used in two swine production areas in Quebec in regard to porcine reproductive and respiratory syndrome virus. Journal of swine health and production 2012;20(5):223-230.

Evidence for Recombination between Vaccine and Wild-Type PRRSV Strains

Porcine reproductive and respiratory syndrome virus (PRRSV) is the etiologic agent of porcine reproductive and respiratory syndrome (PRRS), which can evolve continuously by random mutation or intragenic recombination. Here we report the com- plete genomic sequence of a PRRSV variant with nucleotide acid deletions and insertions in the nonstructural protein 2 (nsp2) gene and a possible recombination event between a modified live virus (MLV) vaccine strain and a prototype Chinese field strain.

Wenhui Lu, Zhongyan W, Guanqun Z, Zhili Li, JingYun Ma. Complete Genome Sequence of a Novel Variant Porcine Reproductive and Respiratory Syndrome Virus (PRRSV) Strain: Evidence for Recombination between Vaccine and Wild-Type PRRSV Strains. Journal of virology 2012;86(17):9543-9543.

Antigenic and molecular diversity of British PRRSv isolates and implications for diagnosis

Abstract: Porcine reproductive and respiratory syndrome (PRRS) is an endemic disease of pigs, caused by PRRS virus, a member of the Arteriviridae family. First seen in Britain in 1991, the disease continues to be a significant economic and welfare problem for pig producers. 

To date, only PRRSV genotype 1 has been found in Britain. At the genetic level, a considerable increase has been reported in the diversity of PRRS viruses isolated in Britain between 2003 and 2007, versus the early 1990s. In this study, the diversity has been shown to extend to the antigenic level too, with potential consequences for diagnostic methods. Antigenic diversity was assessed using a panel of twelve monoclonal antibodies, only one of which reacted with all isolates tested. Nine diverse viruses were compared as potential antigens in immunoperoxidase monolayer assays, where each one produced quite different results for a common panel of sera. As a single virus is used in each diagnostic assay, results must therefore be interpreted cautiously. 

For a real-time RT-PCR assay, published oligonucleotide primer and probe sequences were evaluated against available genetic sequences of British and European viruses, and were re-designed where considerable mismatches were found. The multiplex assay incorporating these modified primers to detect genotype 1 and 2 PRRS viruses was then validated for use with diagnostic sera and tissues. 

As the increasing degree of diversity exhibited by British strains is mirrored in other countries, PRRSV will continue to provide an ongoing challenge to diagnosis at a global, as well as national level.

Crown Copyright (C) 2012 Published by Elsevier B.V. All rights reserved.

Frossard J, Fearnley C, Naidu B, Errington J, Westcott D G. Porcine reproductive and respiratory syndrome virus: Antigenic and molecular diversity of British isolates and implications for diagnosis. Veterinary microbiology 2012;158(3-4):308-315.

Effects of challenge with a virulent genotype II strain of PRRS virus on piglets vaccinated with an attenuated genotype I strain vaccine

Abstract: Porcine reproductive and respiratory syndrome virus (PRRSV) is endemic in most parts of Asia, where genotype I and II strains of diverse virulence may coexist. This study evaluated the outcome of infection with a highly virulent Asian genotype II PRRSV isolate in piglets vaccinated with a genotype 1 vaccine. Twenty-one 3-week-old piglets were divided in three groups: Pigs in group V (n = 8) were vaccinated with an attenuated genotype I commercial PRRSV vaccine, while pigs in group U (n = 8) and a control group (group C; n = 5) were unvaccinated; 6 weeks later, pigs in groups V and U were challenged intranasally with a highly virulent strain of genotype II PRRSV (1 x 10(5) 50% tissue culture infectious doses/mL), while pigs in group C received a placebo. Over a period of 21 days after challenge, vaccinated pigs had significantly lower mortality (0/8 versus 2/8), fewer days of fever, a lower frequency of catarrhal bronchopneumonia, higher weight gains (13.4 versus 6.6 kg) and lower levels of viraemia compared to unvaccinated challenged pigs. Immunisation with a genotype I attenuated PRRSV vaccine provided partial protection against challenge with a highly virulent genotype II strain. (C) 2011 Elsevier Ltd. All rights reserved.
Accession Number: WOS:000307478200018.

Roca M, Gimeno M, Bruguera S, Segales J, Diaz I. Effects of challenge with a virulent genotype II strain of porcine reproductive and respiratory syndrome virus on piglets vaccinated with an attenuated genotype I strain vaccine. The veterinary journal 2012;193(1):92-96.

Evidence for recombination between vaccine and wild-type PRRSv

Abstract

Porcine reproductive and respiratory syndrome virus (PRRSV) is the etiologic agent of porcine reproductive and respiratory syndrome (PRRS), which can evolve continuously by random mutation or intragenic recombination. Here we report the complete genomic sequence of a PRRSV variant with nucleotide acid deletions and insertions in the nonstructural protein 2 (nsp2) gene and a possible recombination event between a modified live virus (MLV) vaccine strain and a prototype Chinese field strain.

Wenhui Lu, Zhongyan W, Guanqun Z, Zhili Li, Jingyun Ma, Qingmei X, Baoli S, Yingzuo Bi. Complete Genome Sequence of a Novel Variant Porcine Reproductive and Respiratory Syndrome Virus (PRRSV) Strain: Evidence for Recombination between Vaccine and Wild-Type PRRSV Strains. Journal of virology 2012;86(17):9543-9543.

PRRSv: Interlaboratory ring trial to evaluate RT-PCR detection methods

Abstract

To compare the real-time reverse transcription quantitative polymerase chain reaction (RT-qPCR) assays used for the diagnosis of Porcine reproductive and respiratory syndrome virus (PRRSV), a Europe-wide interlaboratory ring trial was conducted. A variety of PRRSV strains including North American (NA) and European (EU) genotype isolates were analyzed by the participants. Great differences regarding qualitative diagnostics as well as analytical sensitivity were observed between the individual RT-qPCR systems, especially when investigating strains from the EU genotype. None of the assays or commercial kits used in the ring trial could identify all different PRRSV strains with an optimal analytical and diagnostic sensitivity. The genetic variability of the PRRSV strains, which is supposed to hinder the diagnostic of the RT-PCR because of mutations at the primer binding sites, was also confirmed by sequencing and subsequent phylogenetic analysis. In summary, a major problem in PRRSV diagnostics by RT-qPCR is false-negative results. To achieve maximum safety in the molecular diagnosis of PRRSV, the combined usage of different assays or kits is highly recommended.

PMID:

 

22807507

 

[PubMed - as supplied by publisher]

Wernike K, Bonilauri P, Dauber M, Errington J, Leblanc N, Revilla-Fernndez S, Hjulsager C, Isaksson M, Stadejek T, Beer M, Hoffmann B. Porcine reproductive and respiratory syndrome virus: Interlaboratory ring trial to evaluate real-time reverse transcription polymerase chain reaction detection methods. Journal of veterinary diagnostic investigation 2012 [accepted, in press];

Pathogenicity and distribution of highly pathogenic PRRSv in pigs

Abstract

The pathogenesis of highly pathogenic porcine reproductive and respiratory syndrome virus (PRRSV) strain (HuN4) is poorly understood. Therefore, highly pathogenic PRRSV strain (HuN4) and its derivative strain (HuN4-F112) (obtained by propagation in MARC145 cells for 112 passages) were inoculated into a total of 48 PRRSV-sero-negative pigs (age: 4-5 weeks) by the intranasal route. Virological, pathological and in situ hybridization analyses were performed. The results exhibited that pigs infected with HuN4 showed a loss of appetite, decrease in body weight, raised body temperature and respiratory symptoms, along with interstitial pneumonia lesions. In the HuN4 group, multifocal interstitial pneumonia with macrophage infiltration was found in the lung. The lesions in the lymph node were characterized by collapsed follicles, depletion of germinal centres and reduction in lymphocytes. Perivascular cuffing and glial nodules were observed in the brains of some pigs. By comparison, the HuN4-F112 group had milder lesions. PRRSV was detected in macrophages, alveolar epithelial cells and vascular endothelial cells in the tonsil and lymph nodes. The PRRSV amounts in the pigs infected with HuN4 were 10(5) -10(9)  copies/ml in the blood and 10(10) -10(11)  copies/g in the lung tissues, whereas the virus amounts with HuN4-F112 were 10(2.15) -10(3.13)  copies/ml in the blood and 10(3.0) -10(3.6)  copies/g in the lung. Our results demonstrate that the PRRS HuN4 virus infects alveolar epithelial cells, macrophages and vascular endothelial cells causing diffuse alveolar damage and lymph node necrosis. Its higher pathogenicity compared with HuN4-F112 virus may be explained in part by higher replication rate in the previously mentioned organs.

© 2012 Blackwell Verlag GmbH.

PMID:

 

22762447

 

[PubMed - as supplied by publisher]

Hu S P, Zhang Z, Liu Y G, Tian Z J, Wu D L, Cai X H, He X J. Pathogenicity and Distribution of Highly Pathogenic Porcine Reproductive and Respiratory Syndrome Virus in Pigs. Transboundary and emerging diseases 2012 [in press]

Evaluation of the long-term effect of air filtration on the occurrence of new PRRSv infections in large breeding herds in swine-dense regions

Abstract

Airborne transmission of porcine reproductive and respiratory syndrome virus (PRRSV) is a risk factor for the infection of susceptible populations. Therefore, a long‑term sustainability study of air filtration as a means to reduce this risk was conducted. Participating herds (n = 38) were organized into 4 independent cohorts and the effect of air filtration on the occurrence of new PRRSV infections was analyzed at 3 different levels from September 2008 to January 2012 including the likelihood of infection in contemporary filtered and non-filtered herds, the likelihood of infection before and after implementation of filtration and the time to failure in filtered and non-filtered herds. Results indicated that new PRRSV infections in filtered breeding herds were significantly lower than in contemporary non-filtered control herds (P < 0.01), the odds for a new PRRSV infection in breeding herds before filtration was 7.97 times higher than the odds after filtration was initiated (P < 0.01) and the median time to new PRRSV infections in filtered breeding herds of 30 months was significantly longer than the 11 months observed in non-filtered herds (P < 0.01). In conclusion, across all 3 levels of analysis, the long-term effect of air filtration on reducing the occurrence of new PRRSV infections in the study population was demonstrated.

PMID:

 

22754642

 

[PubMed - in process]

Dee S, Cano J P, Spronk G, Reicks D, Ruen P, Pitkin A, Polson D. Evaluation of the Long-Term Effect of Air Filtration on the Occurrence of New PRRSV Infections in Large Breeding Herds in Swine-Dense Regions. Viruses 2012;4(5):654-662.

Correlation among genetic, Euclidean, temporal, and herd ownership distances of porcine reproductive and respiratory syndrome virus strains in Quebec, Canada

ABSTRACT:
BACKGROUND:

Porcine reproductive and respiratory syndrome (PRRS) is a viral disease that has a major economic impact for the swine industry. Its control is mostly directed towards preventing its spread which requires a better understanding of the mechanisms of transmission of the virus between herds. The objectives of this study were to describe the genetic diversity and to assess the correlation among genetic, Euclidean and temporal distances and ownership to better understand pathways of transmission.
RESULTS:

A cross-sectional study was conducted on sites located in a high density area of swine production in Quebec. Geographical coordinates (longitude/latitude), date of submission and ownership was obtained for each site. ORF5 sequencing was attempted on PRRSV positive sites. Proportion of pairwise combinations of strains having [greater than or equal to]98% genetic homology were analysed according to Euclidean distances and ownership. Correlations between genetic, Euclidean and temporal distances and ownership were assessed using Mantel tests on continuous and binary matrices. Sensitivity of the correlations between genetic and Euclidean as well as temporal distances was evaluated for different Euclidean and temporal distance thresholds. An ORF5 sequence was identified for 132 of the 176 (75%) PRRSV positive sites; 122 were wild-type strains. The mean (min-max) genetic, Euclidean and temporal pairwise distances were 11.6% (0-18.7), 15.0 km (0.04-45.7) and 218 days (0-852), respectively. Significant positive correlations were observed between genetic and ownership, genetic and Euclidean and between genetic and temporal binary distances. The relationship between genetic and ownership suggests either common sources of animals or semen, employees, technical services or vehicles, whereas that between genetic and Euclidean binary distances is compatible with area spread of the virus. The latter correlation was observed only up to 5 km.
CONCLUSIONS:

This study suggests that transmission of PRRSV is likely to occur between sites belonging to the same owner or through area spread within a 5 km distance. Both should be considered in the perspective of prevention.
PMID: 22676411 [PubMed - as supplied by publisher]

Lambert M, Arsenault J, Poljak Z, D S. Correlation among genetic, Euclidean, temporal, and herd ownership distances of porcine reproductive and respiratory syndrome virus strains in Quebec, Canada. BMC veterinary research 2012;8(1):76-76.

Infectivity of PRRS virus in pig manure at different ambient temperatures

Linhares DCL, Torremorell M, Joo H S, Morrison R B. Infectivity of PRRS virus in pig manure at different ambient temperatures [Veterinary Microbiology, DOI 10.1016/j.vetmic.2012.05.009].

Abstract

PRRSv is an economically important swine pathogen which can be disseminated from infected pig herds via movement of contaminated manure. The process of manure handling and inadequate cleaning of transport vehicles are commonly implicated as sources of PRRSv transmission. Stability of PRRSv in pig manure at different temperatures is unknown. The objective of this study was to determine PRRSv-infectivity half-life in manure and in a cell culture medium at 4, 20, 60 and 80°C. To assure sample consistency across the study, all samples were prepared from common homogenized solutions (MEM and manure) and frozen at -20°C. Samples were thawed, transferred to a water bath set at a specific temperature, inoculated with 100μl of PRRSv at designated time points and then tested for virus infectivity. Regression models were created to estimate PRRSv half-life based on incubation temperature. There was an exponential decrease in PRRSv infectivity with increasing temperature. At every temperature tested, PRRSv had shorter half-life when incubated in manure compared to MEM. PRRSv half-life in MEM and manure was estimated at 112.6 and 120.5h at 4°C, 14.6 and 24.5h at 20°C, 1.6 and 1.7h at 40°C, 2.9 and 8.5min at 60°C, and 0.36-0.59min at 80°C, respectively. Results of this study can be used as basis for developing strategies to inactivate PRRSv present in manure-contaminated environments using heating treatments. For example, these data suggest that submitting transport trailers to temperature of 50°C for 8h would decrease PRRSv from 10(6) TCID(50)/ml to less than 10(1) TCID(50)/ml.

Copyright © 2012 Elsevier B.V. All rights reserved.

PMID:

 

22658630

 

[PubMed - as supplied by publisher]