Venteo A, Rebollo B, Sarraseca J, Rodriguez M J, Sanz A. A novel double recognition enzyme-linked immunosorbent assay based on the nucleocapsid protein for early detection of European porcine reproductive and respiratory syndrome virus infection. Journal of virological methods 2012 [in press].
Abstract
Precise and rapid detection of porcine reproductive respiratory syndrome virus (PRRSV) infection in swine farms is critical. Improvement of control procedures, such as testing incoming gilt and surveillance of seronegative herds requires more rapid and sensitive methods. However, standard serological techniques detect mainly IgG antibodies. A double recognition enzyme-linked immunosorbent assay (DR-ELISA) was developed for detection of antibodies specific to European PRRSV. This new assay can recognize both IgM and IgG antibodies to PRSSV which might be useful for detecting in routine surveillance assays pigs that are in the very early stages of infection and missed by conventional assays detecting only IgG antibodies. DR-ELISA is based on the double recognition of antigen by antibody. In this study, the recombinant nucleocapsid protein (N) of PRRSV was used both as the coating and the enzyme-conjugated antigen. To evaluate the sensitivity of the assay at early stages of the infection, sera from 69 pigs infected with PRRSV were collected during successive days post infection (pi) and tested. While standard methods showed low sensitivity rates before day 14 pi, DR-ELISA detected 88.4% seropositive samples at day 7 showing greater sensitivity at early stages of the infection. Further studies were carried out to assess the efficiency of the new assay, and the results showed DR-ELISA to be a sensitive and accurate method for early diagnosis of EU-PRRSV infection.
Wednesday, February 22, 2012
Wednesday, February 15, 2012
Evaluation of FTA cards for collection and transport of samples for detection of PRRSv by RT-PCR
Abstract. Blood, tissue and oral fluid samples collected from experimentally infected animals and field cases were used to evaluate the safety, diagnostic sensitivity and specificity of Flinders Technology Associates (FTA) cards for Porcine reproductive and respiratory syndrome virus (PRRSV) reverse transcription polymerase chain reaction (RT-PCR) diagnostics. The analytical sensitivity of PRRSV RT-PCR from serum and oral fluids in FTA cards was reduced, although the virus could still be detected at concentrations of 101 and 103 TCID/ml, respectively. The sensitivity and specificity of PRRSV RT-PCR detection from serum, blood, and tissue samples in cards collected from experimentally infected animals were 100%. Sensitivity for oral fluids was 45% (95% CI: 19.97–73.01) compared to fresh. For field samples, sensitivity was 89% (95% CI: 77.35–95.63) and 100% (95% CI: 80.00–100) for serum and lung samples, respectively. The sensitivity was the same for samples stored in cards at room temperature or at 4oC, and tested overnight or after 14 days. Cards inoculated with PRRSV-positive samples did not yield replicating virus after cell culture. In conclusion, FTA cards proved to be a safe, simple, and sensitive alternative method to transport serum, blood, and tissue samples for PRRSV RT-PCR diagnostics; however, a significant decrease in RT-PCR sensitivity should be expected from oral fluid samples.
Key words: Diagnostics; FTA cards; polymerase chain reaction; porcine reproductive and respiratory syndrome; swine.
Linhares DCL, Rovira A, Torremorell M. Evaluation of Flinders Technology Associates cards for collection and transport of samples for detection of Porcine reproductive and respiratory syndrome virus by reverse transcription polymerase chain reaction. J Vet Diagn Invest, March 2012: 24:(2), DOI: 10.1177/1040638711429492.
Key words: Diagnostics; FTA cards; polymerase chain reaction; porcine reproductive and respiratory syndrome; swine.
Linhares DCL, Rovira A, Torremorell M. Evaluation of Flinders Technology Associates cards for collection and transport of samples for detection of Porcine reproductive and respiratory syndrome virus by reverse transcription polymerase chain reaction. J Vet Diagn Invest, March 2012: 24:(2), DOI: 10.1177/1040638711429492.
Tuesday, February 7, 2012
Immunological solutions for treatment and prevention of porcine reproductive and respiratory syndrome (PRRS)
Murtaugh M P, Genzow M. Immunological solutions for treatment and prevention of porcine reproductive and respiratory syndrome (PRRS). Vaccine 2011;29(46):8192-8204.
Vaccination is the principal means used to control and treat porcine reproductive and respiratory syn- drome virus (PRRSV) infection. An array of PRRS vaccine products is available in various regions of the world. However, despite extensive efforts, little progress has been made to improve efficacy since the first introduction of a live, attenuated vaccine in 1994 in the USA. Key limitations include: (a) uncer- tainty about the viral targets of protective immunity that prevents a research focus on individual viral structures and proteins, and frustrates efforts to design novel vaccines; (b) inability to establish clear immunological correlates of protection that requires laborious in vivo challenge models for evaluation of protection against challenge; and (c) the great genetic diversity of PRRSV which requires that challenge experiments be interpreted cautiously since it is not possible to predict how immunological protection against one isolate will translate to broadly cross-protective immunity. Economically significant levels of cross-protection that are provided to a variety of field isolates still cannot assure that effective protection will be conferred to isolates that might emerge in the future. In addition to these substantial barriers to new PRRSV vaccine development, there are enormous gaps in our understanding of porcine immuno- logical mechanisms and processes that provide immunity to PRRSV infection and memory responses for long-term protection. Despite these impediments, we should be confident that progress will be made. Sequencing of the swine genome is providing a rich source of primary knowledge of gene structure and transcriptional regulation that is certain to reveal important insights about the mechanisms of anti-PRRSV immunity, and continued efforts to unravel the details of the interaction of PRRSV with pigs will lead to new insights that overcome the current limitations in the field.
© 2011 Elsevier Ltd. All rights reserved.
An evaluation of interventions for reducing the risk of PRRSV introduction to filtered farms via retrograde air movement through idle fan
Alonso C, Otake S, Davies P, Dee S. An evaluation of interventions for reducing the risk of PRRSV introduction to filtered farms via retrograde air movement through idle fans. Veterinary microbiology 2012 [in press]
Abstract
Porcine reproductive and respiratory syndrome virus (PRRSV) is an economically significant pathogen of pigs that can be transported via the airborne route out to 9.1 km. To reduce this risk, large swine facilities have started to implement systems to filter contaminated incoming air. A proposed means of air filtration failure is the retrograde movement of air (back-drafting) from the external environment into the animal air space through non-filtered points such as idle wall fans; however, this risk has not been validated. Therefore, the purpose of this study was threefold: (1) to prove that PRRSV introduction via retrograde air movement through idle fans is a true risk; (2) to determine the minimum retrograde air velocity necessary to introduce PRRSV to an animal airspace from an external source; and (3) to evaluate the efficacy of different interventions designed to reduce this risk. A retrograde air movement model was used to test a range of velocities and interventions, including a standard plastic shutter, a plastic shutter plus a canvas cover, a nylon air chute, an aluminum shutter plus an air chute and a double shutter system. Results indicated that retrograde air movement is a real risk for PRRSV introduction to a filtered air space; however, it required a velocity of 0.76 m/s. In addition, while all the interventions designed to reduce this risk were superior when compared to a standard plastic shutter, significant differences were detected between treatments.
ß 2012 Elsevier B.V. All rights reserved.
Abstract
Porcine reproductive and respiratory syndrome virus (PRRSV) is an economically significant pathogen of pigs that can be transported via the airborne route out to 9.1 km. To reduce this risk, large swine facilities have started to implement systems to filter contaminated incoming air. A proposed means of air filtration failure is the retrograde movement of air (back-drafting) from the external environment into the animal air space through non-filtered points such as idle wall fans; however, this risk has not been validated. Therefore, the purpose of this study was threefold: (1) to prove that PRRSV introduction via retrograde air movement through idle fans is a true risk; (2) to determine the minimum retrograde air velocity necessary to introduce PRRSV to an animal airspace from an external source; and (3) to evaluate the efficacy of different interventions designed to reduce this risk. A retrograde air movement model was used to test a range of velocities and interventions, including a standard plastic shutter, a plastic shutter plus a canvas cover, a nylon air chute, an aluminum shutter plus an air chute and a double shutter system. Results indicated that retrograde air movement is a real risk for PRRSV introduction to a filtered air space; however, it required a velocity of 0.76 m/s. In addition, while all the interventions designed to reduce this risk were superior when compared to a standard plastic shutter, significant differences were detected between treatments.
ß 2012 Elsevier B.V. All rights reserved.
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