This is not quite an "applied" research, but it is good to know that such technologies are being evaluated and therefore available for "commercial" use soon:

A multiplex method for the simultaneous serological detection of porcine reproductive and respiratory syndrome virus and porcine circovirus type 2.

Lin K, Wang C, Murtaugh MP, Ramamoorthy S.

Source

Department of Veterinary Diagnostic and Production Animal Medicine, Veterinary Diagnostic Laboratory, Iowa State University, Ames, IA 50011.

Abstract

Porcine circovirus type 2 (PCV2) and porcine reproductive and respiratory syndrome virus (PRRSV) are major contributors to the porcine respiratory disease complex (PRDC). Routine serological diagnosis and surveillance play an important role in the prevention of PRDC as it is a leading cause of economic losses to the swine industry. We herein describe an advanced microsphere-based immunoassay that permits the simultaneous detection of antibodies to PCV2 and PRRSV; thereby reducing the time and effort involved in testing. Recombinant PRRSV N protein antigen and the PCV2 capsid antigen were coupled to fluorophore dyed beads with distinct spectral addresses. Weekly sera samples from 72 pigs that were experimentally exposed to either PCV2, PRRSV or both PCV2 and PRRSV were used to validate the microbead assay (MBA) in comparison with the gold-standard ELISAs. The kinetics of the PCV2 and PRRSV-specific antibody responses as measured by the microbead assay was comparable to those of the standard assays; Spearman's Rank correlation was 0.72 (p<0.001) for PRRSV and 0.80 (p<0.001) for PCV2. Diagnostic sensitivity and specificity were determined using field sera whose positive or negative status was determined by the standard tests. The diagnostic sensitivity and specificity were both 98% for PCV2 and were 91% and 93% for PRRSV (Kappa coefficient: 0.85 and 0.67 for PCV2 and PRRSV respectively). Multiplexing did not interfere with assay performance or diagnostic sensitivity. Therefore, the described study demonstrates proof of concept for the development of more versatile and economical microbead array based multiplex serological test panels for veterinary use.

Reference:
Lin K, Wang C, Murtaugh M P, Ramamoorthy S. A multiplex method for the simultaneous serological detection of porcine reproductive and respiratory syndrome virus and porcine circovirus type 2. Journal of clinical microbiology 2011 [accepted]

Clustering of and Risk Factors for the Porcine High Fever Disease in a Region of Vietnam

This paper is about risk factors associated with PHFD. It has been suggested that PRRSv might be associated with PHFD, so I included this paper in our blog. In fact, results of this study are in line with what has been reported for PRRSv in terms of risk factors associated with infection and clinical severity of the disease.
Enjoy:

ABSTRACT
Porcine high fever disease (PHFD) emerged in 2006 in China and spread to Vietnam. Little work has been carried out to investigate PHFD risk factors and space–time dynamics. To fill this gap, we investigated probable cases of PHFD at household level as the outcome. A study area, approximately 100 sq. km, was selected from a province of southern Vietnam that had reported the out- break of PHFD in 2008. A survey was conducted in the study area to collect information about swine health problems during 2008. The questionnaire included three sections: general information, clinical signs of disease in pigs and production factors believed to be risk factors. Cases were defined at the household level and included interpretation of clinical signs in series. Logistic regression with a random intercept at the hamlet level was used to assess risk factors for PHFD at the household level. Spatial clustering was investigated using the D-function and a Cuzick–Edward’s test. Spatial clusters were evalu- ated using a spatial relative risk surface and the spatial scan statistic using a Bernoulli model. Space–time clustering was explored using a space–time K-function and Knox’s test. Space–time clusters were evaluated using a space– time permutation model in SaTScan. Of 955 households with questionnaire data, 33.4% were classified as cases. The statistical significance of space and space–time clustering differed between methods employed. The risk factors associated with occurrence of cases were higher numbers of sows and finishing pigs (log 2 transformed), receiving pigs from an external source and the inter- action between using ‘water green crop’ (WGC) as pig feed and owning ducks with or without direct contact with pigs. The interaction between the presence of ducks and feeding WGC to pigs suggested the involvement of pathogens that might be present in water (environment) and could further replicate in or on ducks.

REFERENCE:
Le H, Poljak Z, Deardon R, Dewey C E. Clustering of and Risk Factors for the Porcine High Fever Disease in a Region of Vietnam. Transboundary and emerging diseases 2011; doi:10.1111/j.1865-1682.2011.01239.x.

The assessment of efficacy of porcine reproductive respiratory syndrome virus inactivated vaccine based on the viral quantity and inactivation methods.

Kim H, Kim HK, Jung JH, Choi YJ, Kim J, Um CG, Hyun SB, Shin S, Lee B, Jang G, Kang BK, Moon HJ, Song DS.

Abstract

ABSTRACT:

BACKGROUND:

There have been many efforts to develop efficient vaccines for the control of porcine reproductive and respiratory syndrome virus (PRRSV). Although inactivated PRRSV vaccines are preferred for their safety, they are weak at inducing humoral immune responses and controlling field PRRSV infection, especially when heterologous viruses are involved.

RESULTS:

In all groups, the sample to positive (S/P) ratio of IDEXX ELISA and the virus neutralization (VN) titer remained negative until challenge. While viremia did not reduce in the vaccinated groups, the IDEXX-ELISA-specific immunoglobulin G increased more rapidly and to significantly greater levels 7 days after the challenge in all the vaccinated groups compared to the non-vaccinated groups (p < 0.05). VN titer was significantly different in the 106 PFU/mL PRRSV vaccine-inoculated and binary ethylenimine (BEI)-inactivated groups 22 days after challenge (p < 0.05). Consequently, the inactivated vaccines tested in this study provided weak memory responses with sequential challenge without any obvious active immune responses in the vaccinated pigs.

CONCLUSIONS:

The inactivated vaccine failed to show the humoral immunity, but it showed different immune response after the challenge compared to mock group. Although the 106 PFU/mL-vaccinated and BEI-inactivated groups showed significantly greater VN titers 22 days after challenge, all the groups were already negative for viremia.

Virol J. 2011 Jun 27;8(1):323. [Epub ahead of print]

Porcine reproductive and respiratory syndrome virus (PRRSV) influences infection dynamics of porcine circovirus type 2 (PCV2) subtypes PCV2a and PCV2b by prolonging PCV2 viremia and shedding.

Abstract

The objective of this study was to determine the effect of porcine reproductive and respiratory syndrome virus (PRRSV) infection on porcine circovirus type 2 (PCV2) subtypes a (PCV2a) or b (PCV2b) viremia and shedding characteristics in oral, nasal and fecal samples in experimentally infected pigs. Twenty-three, 2- to 6-week-old pigs were randomly divided into five groups: negative control (n=3), PCV2a-I (n=5), PCV2a-PRRSV-CoI (n=5), PCV2b-I (n=5), and PCV2b-PRRSV-CoI (n=5). Blood, oral, nasal and fecal swabs were collected in regular intervals from day post inoculation (dpi) 0 until dpi 70 and tested by quantitative real-time PCR for the presence and amount of PCV2 DNA and by ELISA for the presence of PCV2-specific antibodies. The results indicate that there were significantly (P<0.05) higher loads of PCV2a and PCV2b DNA in serum, oral swabs, nasal swabs and fecal swabs and a higher prevalence of detectable PCV2 antigen in tissues of pigs concurrently infected with PCV2 and PRRSV compared to pigs singularly infected with PCV2 further confirming that PRRSV enhances replication of PCV2. Moreover, PRRSV infection significantly prolonged the presence of PCV2 DNA in serum and increased the amount of PCV2 DNA in oral and nasal secretions and fecal excretions in the later stages of infection between dpi 28 and 70. Shedding patterns were similar between groups infected with PCV2a and PCV2b, indicating that there was no subtype-specific interaction with the PRRSV isolate used in this study. The results from this study highlight the interaction between PRRSV and PCV2 and the importance of controlling PRRSV infection in order to reduce PCV2 virus loads in pig populations.

Sinha A, Shen H G, Schalk S, Beach N M, Huang Y W, Meng X J, Halbur P G, Opriessnig T. Porcine reproductive and respiratory syndrome virus (PRRSV) influences infection dynamics of porcine circovirus type 2 (PCV2) subtypes PCV2a and PCV2b by prolonging PCV2 viremia and shedding. Veterinary microbiology 2011 [accepted].

nothing new in this past weeks.

Stay tuned. Our system is checking for new "field PRRS" publications in a daily basis. We will keep you posted.
Thank you.

Daniel Linhares

Airborne transmission reviewed and discussed!

Desrosiers R. Transmission of swine pathogens: different means, different needs. Anim Health Res Rev 2011 Jan:1-13.

Abstract

There seems to be two main types of pathogens that cause diseases in swine: those that are mainly introduced through direct pig contacts, and those that are often, and in some situations mainly introduced by indirect transmission means. In this review, the mange mite (Sarcoptes scabiei), toxigenic Pasteurella multocida and Brachyspira hyodysenteriae will be used as examples of the first type, and foot and mouth disease virus, Mycoplasma hyopneumoniae and porcine reproductive and respiratory syndrome (PRRS) virus as examples of the second. It is now clear from various epidemiological studies as well as experimental and field data that aerosol transmission of some swine pathogens plays an important role in their epidemiology. As previous biosecurity programs did not take this factor into consideration, it can at least partially explain why many of these programs suffered frequent failures and why air filtration is now becoming increasingly popular in North America. Identifying and quantifying transmission means should be a priority for every important infectious disease for which it has not been done.

Keywords: Swine, pathogen, transmission, direct, indirect

Median infectious dose (ID50) of PRRS isolate MN-184 via aerosol exposure

 Cutler T D, Wang C, Hoff S J, Kittawornrat A, Zimmerman J. 2011. Median infectious dose (ID(50)) of porcine reproductive and respiratory syndrome virus isolate MN-184 via aerosol exposure. Veterinary microbiology

Abstract

The median infectious dose (ID(50)) of porcine reproductive and respiratory syndrome (PRRS) virus isolate MN-184 was determined for aerosol exposure. In 7 replicates, 3-week-old pigs (n=58) respired 10l of airborne PRRS virus from a dynamic aerosol toroid (DAT) maintained at -4°C. Thereafter, pigs were housed in isolation and monitored for evidence of infection. Infection occurred at virus concentrations too low to quantify by microinfectivity assays. Therefore, exposure dose was determined using two indirect methods ("calculated" and "theoretical"). "Calculated" virus dose was derived from the concentration of rhodamine B monitored over the exposure sequence. "Theoretical" virus dose was based on the continuous stirred-tank reactor model. The ID(50) estimate was modeled on the proportion of pigs that became infected using the probit and logit link functions for both "calculated" and "theoretical" exposure doses. Based on "calculated" doses, the probit and logit ID(50) estimates were 1×10(-0.13)TCID(50) and 1×10(-0.14)TCID(50), respectively. Based on "theoretical" doses, the probit and logit ID(50) were 1×10(0.26)TCID(50) and 1×10(0.24)TCID(50), respectively. For each point estimate, the 95% confidence interval included the other three point estimates. The results indicated that MN-184 was far more infectious than PRRS virus isolate VR-2332, the only other PRRS virus isolate for which ID(50) has been estimated for airborne exposure. Since aerosol ID(50) estimates are available for only these two isolates, it is uncertain whether one or both of these isolates represent the normal range of PRRS virus infectivity by this route.

Copyright © 2011 Elsevier B.V. All rights reserved.

PMID: 21474258 [PubMed - as supplied by publisher]

Keywords:

PRRS virus, Aerobiology, Transmission, Infectious dose ID50, Dose–response