Monday, November 7, 2016

A PRRSv candidate vaccine based on the synthetic attenuated virus engineering approach

 2016 Nov 4;34(46):5546-5553. doi: 10.1016/j.vaccine.2016.09.049. Epub 2016 Oct 11.

A porcine reproductive and respiratory syndrome virus candidate vaccine based on the synthetic attenuated virus engineering approach is attenuated and effective in protecting against homologous virus challenge.

Author information

  • 1Department of Veterinary Diagnostic and Production Animal Medicine, College of Veterinary Medicine, Iowa State University, Ames, IA, USA.
  • 2The Roslin Institute and The Royal (Dick) School of Veterinary Studies, University of Edinburgh, Midlothian, UK.
  • 3Department of Biomedical Sciences and Pathobiology, College of Veterinary Medicine, Virginia Polytechnic Institute and State University, Blacksburg, VA, USA.
  • 4Department of Veterinary Diagnostic and Production Animal Medicine, College of Veterinary Medicine, Iowa State University, Ames, IA, USA; The Roslin Institute and The Royal (Dick) School of Veterinary Studies, University of Edinburgh, Midlothian, UK. Electronic address:


Current porcine reproductive and respiratory syndrome virus (PRRSV) vaccines sometimes fail to provide adequate immunity to protect pigs from PRRSV-induced disease. This may be due to antigenic differences among PRRSV strains. Rapid production of attenuated farm-specific homologous vaccines is a feasible alternative to commercial vaccines. In this study, attenuation and efficacy of a codon-pair de-optimized candidate vaccine generated by synthetic attenuated virus engineering approach (SAVE5) were tested in a conventional growing pig model. Forty pigs were vaccinated intranasally or intramuscularly with SAVE5 at day 0 (D0). The remaining 28 pigs were sham-vaccinated with saline. At D42, 30 vaccinated and 19 sham-vaccinated pigs were challenged with the homologous PRRSV strain VR2385. The experiment was terminated at D54. The SAVE5 virus was effectively attenuated as evidenced by a low magnitude of SAVE5 viremia for 1-5 consecutive weeks in 35.9% (14/39) of the vaccinated pigs, lack of detectable nasal SAVE5 shedding and failure to transmit the vaccine virus from pig to pig. By D42, all vaccinated pigs with detectable SAVE5 viremia also had detectable anti-PRRSV IgG. Anti-IgG positive vaccinated pigs were protected from subsequent VR2385 challenge as evidenced by lack of VR2385 viremia and nasal shedding, significantly reduced macroscopic and microscopic lung lesions and significantly reduced amount of PRRSV antigen in lungs compared to the non-vaccinated VR2385-challenged positive control pigs. The nasal vaccination route appeared to be more effective in inducing protective immunity in a larger number of pigs compared to the intramuscular route. Vaccinated pigs without detectable SAVE5 viremia did not seroconvert and were fully susceptible to VR2385 challenge. Under the study conditions, the SAVE approach was successful in attenuating PRRSV strain VR2385 and protected against homologous virus challenge. Virus dosage likely needs to be adjusted to induce replication and protection in a higher percentage of vaccinated pigs.


Attenuation; Efficacy; Porcine reproductive and respiratory syndrome virus (PRRSV); Synthetic attenuated virus engineering (SAVE); Vaccine

Tuesday, May 31, 2016

Network and risk factor analyses for PRRS in regional control programs [Ontario]

 2016 Jun 1;128:41-50. doi: 10.1016/j.prevetmed.2016.03.010. Epub 2016 Mar 17.

Network, cluster and risk factor analyses for porcine reproductive and respiratory syndrome using data from swine sites participating in a disease control program.

Author information

  • 1Department of Population Medicine, University of Guelph, Guelph, ON N1G 2W1, Canada. Electronic address:
  • 2Department of Population Medicine, University of Guelph, Guelph, ON N1G 2W1, Canada.
  • 3Woodstock, ON N4S 6N8, Canada.
  • 4Strategic Solutions Group, Puslinch, ON N0B 2J0, Canada.


The objectives of this study were to describe networks of Ontario swine sites and their service providers (including trucking, feed, semen, gilt and boar companies); to categorize swine sites into clusters based on site-level centrality measures, and to investigate risk factors for porcine reproductive and respiratory syndrome (PRRS) using information gathered from the above-mentioned analyses. All 816 sites included in the current study were enrolled in the PRRS area regional control and elimination projects in Ontario. Demographics, biosecurity and network data were collected using a standardized questionnaire and PRRS status was determined on the basis of available diagnostic tests and assessment by site veterinarians. Two-mode networks were transformed into one-mode dichotomized networks. Cluster and risk factor analyses were conducted separately for breeding and growing pig sites. In addition to the clusters obtained from cluster analyses, other explanatory variables of interest included: production type, type of animal flow, use of a shower facility, and number of neighboring swine sites within 3km. Unadjusted univariable analyses were followed by two types of adjusted models (adjusted for production systems): a generalizing estimation equation model (GEE) and a generalized linear mixed model (GLMM). Results showed that the gilt network was the most fragmented network, followed by the boar and truck networks. Considering all networks simultaneously, approximately 94% of all swine sites were indirectly connected. Unadjusted risk factor analyses showed significant associations between almost all predictors of interest and PRRS positivity, but these disappeared once production system was taken into consideration. Finally, the vast majority of the variation on PRRS status was explained by production system according to GLMM, which shows the highly correlated nature of the data, and raises the point that interventions at this level could potentially have high impact in PRRS status change and/or maintenance. 
Copyright © 2016 Elsevier B.V. All rights reserved.


Cluster analysis; Disease control programs; Porcine reproductive and respiratory syndrome; Porcine reproductive and respiratory syndrome control programs; Risk factor analysis; Service provider networks
[PubMed - in process]

Friday, April 29, 2016

Concurrent vaccination of pigs with type 1 and type 2 PRRSV protected against type 1 but not against type 2 PRRSV

 2015 Dec;103:193-200. doi: 10.1016/j.rvsc.2015.10.011. Epub 2015 Oct 28.

Concurrent vaccination of pigs with type 1 and type 2 porcine reproductive and respiratory syndrome virus (PRRSV) protects against type 1 PRRSV but not against type 2 PRRSV on dually challenged pigs.


The objective of the present study was to evaluate the effect of concurrent vaccination of pigs with both type 1 and type 2 porcine reproductive and respiratory syndrome virus (PRRSV) vaccine against heterologous dual challenge of both genotypes and compare with single vaccination of pigs against heterologous single challenge of both genotypes. Pigs were administered both type 1 and type 2 PRRSV vaccine concurrently into separate anatomical sites at 28 days of age and inoculated intranasally with both genotypes at 63 days of age. Neutralizing antibodies (NA) were not detected in any pigs in any group (NA titer <2 log2) throughout the experiment. In addition, concurrent vaccination of pigs with two PRRSV genotypes had significantly lower numbers of type 1 and type 2 PRRSV-specific interferon-γ secreting cells (IFN-γ-SC) compared to vaccination of pigs with type 1 or type 2 PRRSV only. Despite the decreased induction of type 1 PRRSV-specific IFN-γ-SC, concurrent vaccination is still able to reduce type 1 PRRSV viremia whereas the decreased induction of type 2 PRRSV-specific IFN-γ-SC by concurrent vaccination correlates with lack of reduction of type 2 PRRSV viremia after dual challenge. The results of this study demonstrated that concurrent vaccination of pigs with two PRRSV genotypes is able to reduce the levels of type 1 PRRSV viremia and lung lesions but not able to reduce the levels of type 2 PRRSV viremia and lung lesions.
Copyright © 2015 Elsevier Ltd. All rights reserved.


Concurrent vaccination; Interference; Porcine reproductive and respiratory syndrome virus; Porcine reproductive and respiratory syndrome virus vaccine
[PubMed - in process]

Spatial and temporal dynamics of PRRS in Denmark from 2007 to 2010

 2015 Dec 21;11:303. doi: 10.1186/s12917-015-0617-0.

Spatial analysis and temporal trends of porcine reproductive and respiratory syndrome in Denmark from 2007 to 2010 based on laboratory submission data.



Porcine reproductive and respiratory syndrome (PRRS) has been a cause for great concern to the Danish pig industry since it was first diagnosed in 1992. The causative agent of PRRS is an RNA virus which is divided into different genotypes. The clinical signs, as well as its morbidity and mortality, is highly variable between herds and regions. Two different genotypes of PRRS virus (PRRSV) are found in Denmark: type 1 and type 2. Approximately 40% of Danish swine herds are seropositive for one or both PRRSV types. The objective of this study was to describe the temporal trend and spatial distribution of PRRSV in Danish swine herds from 2007 to 2010, based on type-specific serological tests from the PRRSsurveillance and control program in Denmark using the results stored in the information management system at the National Veterinary Institute, Technical University of Denmark (DTU Vet).


The average monthly seroprevalence of PRRSV type 1 was 9% (minimum of 5%; maximum of 13%) in breeding herds, and 20% (minimum of 14%; maximum of 26%) in production herds; PRRSV type 2 had an average seroprevalence of 3% (minimum of 1%; maximum of 9%) in breeding herds and of 9% (minimum of 5%; maximum of 13%) within production herds. The seroconversion rate followed a similar and consistent pattern, being higher for type 1 than for type 2 for both PRRSV types. Regarding the spatiotemporal results, the relative risk distribution maps changed over time as a consequence of the changes in PRRSV seroprevalence, suggesting a general decline in the extent of areas with higher relative risk for both type 1 and 2. Local spatial analysis results demonstrated the existence of statistically significant clusters in areas where the relative risk was higher for both herds.


PRRSV type 1 seroprevalence was constantly higher than for PRRSV type 2 in both herd types. Significant spatial clusters were consistently found in Denmark, suggesting that PRRSV is endemic in these areas. Furthermore, relative risk distribution maps revealed different patterns over time as a consequence of the changes in seroprevalence.
[PubMed - in process] 

Efficacy of Fostera PRRS vaccine against a virulent field strain

 2016 Jan;80(1):1-11.

Efficacy of Fostera PRRS modified live virus vaccine against a Canadian heterologous virulent field strain of porcine reproductive and respiratory syndrome virus.


Vaccination is a useful option to control infection with porcine reproductive and respiratory syndrome virus (PRRSV), and several modified live-PRRSV vaccines have been developed. These vaccines have shown some efficacy in reducing the incidence and severity of clinical disease as well as the duration of viremia and virus shedding but have failed to provide sterilizing immunity. The efficacy of modified live-virus (MLV) vaccines is greater against a homologous strain compared with heterologous PRRSV strains. The objective of this study was to evaluate the efficacy of Fostera PRRS MLV vaccine in protecting against challenge with a heterologous field strain widely circulating in the swine herds of eastern Canada. Forty-six piglets were divided into 4 groups: nonvaccinated-nonchallenged; nonvaccinated-challenged; vaccinated-challenged; and vaccinated-nonchallenged. The animals were vaccinated at 23 d of age with Fostera PRRS and challenged 23 d later with a heterologous field strain of PRRSV (FMV12-1425619). Overall, the vaccine showed some beneficial effects in the challenged animals by reducing the severity of clinical signs and the viral load. A significant difference between nonvaccinated and vaccinated animals was detected for some parameters starting 11 to 13 d after challenge, which suggested that the cell-mediated immune response or other delayed responses could be more important than pre-existing PRRSV antibodies in vaccinated animals within the context of protection against heterologous strains. 
[PubMed - in process] 
 [Available on 2016-07-01]

Thursday, April 28, 2016

Progress on the PRRS regional control project in Minnesota

 2016 Feb 19;11(2):e0149498. doi: 10.1371/journal.pone.0149498. eCollection 2016.

Measuring Progress on the Control of Porcine Reproductive and Respiratory Syndrome (PRRS) at a Regional Level: The Minnesota N212 Regional Control Project (Rcp) as a Working Example.


Due to the highly transmissible nature of porcine reproductive and respiratory syndrome (PRRS), implementation of regional programs to control the disease may be critical. Because PRRS is not reported in the US, numerous voluntary regional control projects (RCPs) have been established. However, the effect of RCPs on PRRS control has not been assessed yet. This study aims to quantify the extent to which RCPs contribute to PRRScontrol by proposing a methodological framework to evaluate the progress of RCPs. Information collected between July 2012 and June 2015 from the Minnesota Voluntary Regional PRRS Elimination Project (RCP-N212) was used. Demography of premises (e.g. composition of farms with sows = SS and without sows = NSS) was assessed by a repeated analysis of variance. By using general linear mixed-effects models, active participation of farms enrolled in the RCP-N212, defined as the decision to share (or not to share) PRRS status, was evaluated and used as a predictor, along with other variables, to assess the PRRS trend over time. Additionally, spatial and temporal patterns of farmers' participation and the disease dynamics were investigated. The number of farms enrolled in RCP-N212 and its geographical coverage increased, but the proportion of SS and NSS did not vary significantly over time. A significant increasing (p<0.001) trend in farmers' decision to share PRRS status was observed, but with NSS producers less willing to report and a large variability between counties. The incidence of PRRS significantly (p<0.001) decreased, showing a negative correlation between degree of participation and occurrence of PRRS (p<0.001) and a positive correlation with farm density at the county level (p = 0.02). Despite a noted decrease in PRRS, significant spatio-temporal patterns of incidence of the disease over 3-weeks and 3-kms during the entire study period were identified. This study established a systematic approach to quantify the effect of RCPs on PRRS control. Despite an increase in number of farms enrolled in the RCP-N212, active participation is not ensured. By evaluating the effect of participation on the occurrence of PRRS, the value of sharing information among producers may be demonstrated, in turn justifying the existence of RCPs.

[PubMed - in process] 

Financial Impacts of Swine Diseases in Vietnam

 2016 Feb 29. doi: 10.1111/tbed.12482. [Epub ahead of print]

Financial Impacts of Priority Swine Diseases to Pig Farmers in Red River and Mekong River Delta, Vietnam.


A study was conducted between May 2013 and August 2014 in three provinces of Vietnam to investigate financial impacts of swine diseases in pig holdings in 2010-2013. The aim of the study was to quantify the costs of swine diseases at producer level in order to understand swine disease priority for monitoring at local level. Financial impacts of porcine reproductive and respiratory syndrome (PRRS), foot and mouth disease (FMD), and epidemic diarrhoea were assessed for 162 pig holders in two Red River Delta provinces and in one Mekong River Delta province, using data on pig production and swine disease outbreaks at farms. Losses incurred by swine diseases were estimated, including direct losses due to mortality (100% market value of pig before disease onset) and morbidity (abortion, delay of finishing stage), and indirect losses due to control costs (treatment, improving biosecurity and emergency vaccination) and revenue foregone (lower price in case of emergency selling). Financial impacts of swine diseases were expressed as percentage of gross margin of pig holding. The gross margin varied between pig farming groups (P < 0.0001) in the following order: large farm (USD 18 846), fattening farm (USD 7014) and smallholder (USD 2350). The losses per pig holding due to PRRS were the highest: 41% of gross margin for large farm, 38% for fattening farm and 63% for smallholder. Cost incurred by FMD was lower with 19%, 25% and 32% of gross margin of pig holding in large farm, fattening farm and smallholder, respectively. The cost of epidemic diarrhoea was the lowest compared to losses due to PRRS and FMD and accounted for around 10% of gross margin of pig holding in the three pig farming groups. These estimates provided critical elements on swine disease priorities to better inform surveillance and control at both national and local level.
© 2016 Blackwell Verlag GmbH.


Vietnam; financial impact; gross margin; pig holdings; swine disease
[PubMed - as supplied by publisher]