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.