(!) Sampling guidelines for oral fluids-based surveys of group-housed animals

Vet Microbiol. 2017 Feb 17. pii: S0378-1135(16)30527-2. doi: 10.1016/j.vetmic.2017.02.004. [Epub ahead of print]

Sampling guidelines for oral fluid-based surveys of group-housed animals.

Rotolo ML1, Sun Y2, Wang C3, Giménez-Lirola L4, Baum DH4, Gauger PC4, Harmon KM4, Hoogland M5, Main R4, Zimmerman JJ4.

Author information

1

Department of Veterinary Diagnostic and Production Animal Medicine, College of Veterinary Medicine, Iowa State University, Ames, IA, USA. Electronic address: mrotolo@iastate.edu.

2

Department of Statistics, College of Liberal Arts and Sciences, Iowa State University, Ames, IA, USA.

3

Department of Veterinary Diagnostic and Production Animal Medicine, College of Veterinary Medicine, Iowa State University, Ames, IA, USA; Department of Statistics, College of Liberal Arts and Sciences, Iowa State University, Ames, IA, USA.

4

Department of Veterinary Diagnostic and Production Animal Medicine, College of Veterinary Medicine, Iowa State University, Ames, IA, USA.

5

Smithfield Foods, Algona, IA, USA.

Abstract

Formulas and software for calculating sample size for surveys based on individual animal samples are readily available. However, sample size formulas are not available for oral fluids and other aggregate samples that are increasingly used in production settings. Therefore, the objective of this study was to develop sampling guidelines for oral fluid-based porcine reproductive and respiratory syndrome virus (PRRSV) surveys in commercial swine farms. Oral fluid samples were collected in 9 weekly samplings from all pens in 3 barns on one production site beginning shortly after placement of weaned pigs. Samples (n=972) were tested by real-time reverse-transcription PCR (RT-rtPCR) and the binary results analyzed using a piecewise exponential survival model for interval-censored, time-to-event data with misclassification. Thereafter, simulation studies were used to study the barn-level probability of PRRSV detection as a function of sample size, sample allocation (simple random sampling vs fixed spatial sampling), assay diagnostic sensitivity and specificity, and pen-level prevalence. These studies provided estimates of the probability of detection by sample size and within-barn prevalence. Detection using fixed spatial sampling was as good as, or better than, simple random sampling. Sampling multiple barns on a site increased the probability of detection with the number of barns sampled. These results are relevant to PRRSV control or elimination projects at the herd, regional, or national levels, but the results are also broadly applicable to contagious pathogens of swine for which oral fluid tests of equivalent performance are available.

Copyright © 2017 The Authors. Published by Elsevier B.V. All rights reserved.

KEYWORDS: 

Modeling; Monitoring; Oral fluid; PRRSV; Probability of detection; Sample size; Sampling; Surveillance

PMID:

 

28284415

 

DOI:

 

10.1016/j.vetmic.2017.02.004

Transmission of PRRSv from and from vaccinated pigs

Vet Microbiol. 2017 Mar;201:18-25. doi: 10.1016/j.vetmic.2016.12.012. Epub 2016 Dec 23.

Transmission of Porcine reproductive and respiratory syndrome virus 1 to and from vaccinated pigs in a one-to-one model.

Pileri E1, Gibert E2, Martín-Valls GE2, Nofrarias M2, López-Soria S2, Martín M1, Díaz I2, Darwich L1, Mateu E3.

Author information

1

UAB, Centre de Recerca en Sanitat Animal (CReSA, IRTA-UAB), Campus de la Universitat Autònoma de Barcelona, 08193 Bellaterra, Spain; Departament de Sanitat i Anatomia Animals, Facultat de Veterinària, UAB, 08193 Bellaterra, Barcelona, Spain.

2

Departament de Sanitat i Anatomia Animals, Facultat de Veterinària, UAB, 08193 Bellaterra, Barcelona, Spain.

3

UAB, Centre de Recerca en Sanitat Animal (CReSA, IRTA-UAB), Campus de la Universitat Autònoma de Barcelona, 08193 Bellaterra, Spain; Departament de Sanitat i Anatomia Animals, Facultat de Veterinària, UAB, 08193 Bellaterra, Barcelona, Spain. Electronic address: enric.mateu@uab.cat.

Abstract

The present study examined transmission by contact of Porcine reproductive and respiratory syndrome virus (PRRSV) 1 in a one-to-one model to vaccinated and unvaccinated pigs and from vaccinated infected pigs to other vaccinated pigs. The experiment started by randomly assigning weaned pigs to groups V (n=24) and U (n=26). V pigs were vaccinated with a commercial live attenuated PRRSV vaccine and the U animals were kept as unvaccinated controls. Twenty-eight days later, 6U pigs were separated and allocated in individual boxes. The remaining 20U pigs were intranasally inoculated with PRRSV isolate 3267 (from now on designated as seeder (S) pigs) and 48h later were distributed in boxes where they were commingled with either V or U pigs in 1:1 groups (first contact phase), resulting in 6S:U and 14S:V pairs. As soon as a V pig was detected to be viremic because of contact with a S, the infected V (from now on designated as Vinf) was transferred (<24h after detection) to a new pen where it was comingled with a new V pig (designated as V2) in a second contact phase. For the first contact phase, pigs were maintained 21days at maximum and for the second contact phase the maximum exposure period was 14days. Two V pigs tested positive for the vaccine virus (>99.5% similarity) when they were relocated with the corresponding V2 pigs and they were removed; thus, only 12Vinf were finally considered. All V pigs (12/12) exposed to S animals became infected although the first detection of viremia occurred at 13.6±3.6days, one week later than in U (p<0.05). Also, duration of viremia was shorter for Vinf compared to U, (5.5±4.3days versus 12.5±2.7days). The Vinf group showed remarkable individual variability: eight animals had a viremic period of 5 or less days (3.0±1.4) while the remaining four had a longer viremic period of more than one week (10.8±2.9). This situation was not observed in U. In the second contact phase, transmission from Vinf to V2 pigs occurred in 7/8 cases (87.5%). The mean duration of viremia for V2 was 4.8±3.4 and two different patterns were again observed: two animals had viremias of 9-10days and the rest averaged 3.0±1.4days (range: 2-5days). Vaccinated groups Vinf and V2 had a significantly lower PRRSV shedding in oral fluids for at least the first 9days after the onset of the viremia compared to U, and shedding for V2 was even significantly lower (p<0.05) than shedding for Vinf. Our experimental design reproduced the worst-case scenario for evaluating the effect of vaccination and, under such conditions; it was still efficacious in slowering PRRSV transmission and decreasing the global viral load and particularly oral shedding.

Copyright © 2016. Published by Elsevier B.V.

KEYWORDS: 

Porcine reproductive and respiratory syndrome virus; Transmission; Vaccination

PMID:

 

28284607

 

DOI:

 

10.1016/j.vetmic.2016.12.012

Outbreak investigations of PRRSV in regional control projects in Ontario, Canada

Transbound Emerg Dis. 2017 Feb;64(1):89-100. doi: 10.1111/tbed.12343. Epub 2015 Mar 11.

Investigation of the Occurrence of Porcine Reproductive and Respiratory Virus in Swine HerdsParticipating in an Area Regional Control and Elimination Project in Ontario, Canada.

Arruda AG1, Friendship R1, Carpenter J2, Hand K3, Ojkic D4, Poljak Z1.

Author information

1

Department of Population Medicine, University of Guelph, Guelph, ON, Canada.

2

Ontario Swine Health Advisory Board, Stratford, ON, Canada.

3

Strategic Solutions Group, Puslinch, ON, Canada.

4

Animal Health Laboratory, University of Guelph, Guelph, ON, Canada.

Abstract

The main goal of this study was to investigate the occurrence of porcine reproductive and respiratory syndrome virus (PRRSV)-specific genotypes in swine sites in Ontario (Canada) using molecular, spatial and network data from a porcine reproductive and respiratorysyndrome (PRRS) regional control project. For each site, location, animal movement service provider (truck companies), PRRSV status and sequencing data of the open reading frame 5 (ORF5) were obtained. Three-kilometre buffers were created to evaluate neighbourhood characteristics for each site. Social network analysis was conducted on swine sites and trucking companies to assemble the network and define network components. Three different PRRSV genotypes were used as outcomes for statistical analysis based on the region's phylogenetic tree of the ORF5. Multivariable exact logistic regression was conducted to investigate the association between being positive for a specific genotype and two main exposures of interest: (i) having at least one neighbour within three km also positive for the same genotype outside the production system and (ii) having at least one positive site for the same genotype in the same truck network component outside the production system. Results showed that the importance of area spread and truck network on PRRSV occurrence differed according to genotype. Additionally, the Ontario PRRS database appears suitable for conducting regional disease investigations. Finally, the use of relatively new tools available for network, spatial and molecular analysis could be useful in investigation, control and prevention of endemic infectious diseases in animal populations.

© 2015 Blackwell Verlag GmbH.

KEYWORDS: 

Porcine reproductive and respiratory syndrome; disease investigation; molecular epidemiology; network analysis

PMID:

 

25766306

 

DOI:

 

10.1111/tbed.12343

MLV vaccines to reduce seminal shedding of type 1 PRRSv

Transbound Emerg Dis. 2017 Feb;64(1):194-203. doi: 10.1111/tbed.12361. Epub 2015 Apr 16.

Two Commercial Type 1 Porcine Reproductive and Respiratory Syndrome Virus (PRRSV)-ModifiedLive Vaccines Reduce Seminal Shedding of Type 1 PRRSV but not Type 2 PRRSV in InfectedBoars.

Park C1, Kim T1, Choi K1, Jeong J1, Kang I1, Park SJ1, Chae C1.

Author information

1

Department of Veterinary Pathology, College of Veterinary Medicine, Seoul National University, Seoul, Korea.

Abstract

The objective of this study was to compare the effects of two commercial type 1 porcine reproductive and respiratory syndrome virus(PRRSV)-modified live vaccines on type 1 and type 2 PRRSV shedding in the semen of experimentally infected boars. Upon challenge with PRRSV, unvaccinated boars exhibited an increase in daily rectal temperature (39.4-39.7°C). Vaccination of boars with type 1PRRSV significantly reduced the amount of type 1 PRRSV load in blood and semen after challenge with type 1 PRRSV, but barely reduced the amount of type 2 PRRSV load in blood and semen after the type 2 PRRSV challenge. There were no significant differences in the reduction of viremia and seminal shedding of type 1 and type 2 PRRSV between the two commercial vaccines. The seminalshedding of PRRSV is independent of viremia. The reduction of type 1 PRRSV seminal shedding coincided with the appearance of type1 PRRSV-specific interferon-γ secreting cells (IFN-γ-SC) in vaccinated type 1 PRRSV-challenged boars. The frequencies of type 1PRRSV-specific IFN-γ-SC induced by type 1 PRRSV vaccine are relatively high compared to type 2 PRRSV-specific IFN-γ-SC induced by the same vaccine which may explain why type 1 PRRSV vaccine is more effective in reducing seminal shedding of type 1 PRRSVwhen compared to type 2 PRRSV in vaccinated challenged boars. These results provide clinical information on how to reduce seminalshedding of type 1 PRRSV in boars using type 1 PRRSV-modified live vaccine.

© 2015 Blackwell Verlag GmbH.

KEYWORDS: 

boar; cross-protection; porcine reproductive and respiratory syndrome virus; semen; vaccine

PMID:

 

25879825

 

DOI:

 

10.1111/tbed.12361

Area control and elimination of PRRS using MLV and management practices

Acta Vet Scand. 2017 Jan 5;59(1):4. doi: 10.1186/s13028-016-0270-z.

Control and eradication of porcine reproductive and respiratory syndrome virus type 2 using a modified-live type 2 vaccine in combination with a load, close, homogenise model: an area elimination study.

Rathkjen PH1, Dall J2.

Author information

Abstract

BACKGROUND: 

Porcine reproductive and respiratory syndrome virus (PRRSV) causes significant animal and economic losses worldwide. The infection is difficult to control and PRRSV elimination at local level requires coordinated intervention among multiple farms. This case study describes a successful elimination of PRRSV from all 12 herds on the Horne Peninsula, Denmark, using a combination of load, close, homogenise (LCH) using PRRSV type 2 modified-live vaccine, optimised pig flow, and'10 Golden Rules' (10GR) for biosecurity management. To the authors' knowledge, this is the first successful European PRRSV area elimination project documented in detail. The PRRSV type 2 modified-live vaccine was used as part of the LCH method in breeding herds. Complete or partial depopulation was performed in some infected herds. A simplified biosecurity protocol (10GR) based on the McREBEL™ system of pig flow management, was employed in all herds and at all times throughout the study.

RESULTS: 

At study commencement, all herds were infected with PRRSV, and most were actively shedding virus. In just over 18 months, all 12 herds on the Horne Peninsula were confirmed to be PRRSV negative by polymerase chain reaction testing and negative for antibodies against PRRSV by enzyme-linked immunosorbent assay testing. All herds were subsequently obtained 'Specific Pathogen Free' status for PRRSV.

CONCLUSIONS: 

This study provides compelling evidence suggesting that an area elimination plan combining LCH with PRRSV type 2vaccination, optimised pig flow, and 10GR for biosecurity management can effectively eliminate PRRSV from a geographic area. Additionally this study confirms the value of a previously unpublished, simplified alternative to the McREBEL system for controlling PRRSV.

KEYWORDS: 

Area regional control; Elimination; Load close homogenise; Modified-live vaccine; PRRS

PMID:

 

28057035

 

PMCID:

 

PMC5217557

 

DOI:

 

10.1186/s13028-016-0270-z

Modeling PRRS transmission at slaughter plan lairage

Factors that influence mechanical transmission of porcine reproductive and respiratory syndrome virus at the time of unloading animals into slaughter plant lairage

By:Lowe, J (Lowe, James); McCann, R (McCann, Ryan) ; Greiner, L (Greiner, Laura)

JOURNAL OF SWINE HEALTH AND PRODUCTION

Volume: 25

 

Issue: 1

 

Pages: 19-23

Published: JAN-FEB 2017

Abstract

Objectives: To estimate the impact of environmental conditions and management practices on the likelihood of cross-contamination of a pig transport vehicle with porcine reproductive and respiratory syndrome virus (PRRSV) during market-animal unloading. 

Materials and methods: An experimental model was developed to simulate indirect contact involving footwear between an unloading dock and a pig transport vehicle. Two experiments were conducted. Experiment 1 evaluated temperature on the. model 0 trailer (4 degrees C, 15 degrees C, or 28 degrees C) for 60 minutes after contact with the contaminated dock (32 contact replicates per temperature). In Experiment 2, 'conditions on the model dock were evaluated in a 2 x 2 x 2 factorial arrangement with repeated measures. Main effects were temperature (4 degrees C or 32 degrees C), ultraviolet light (ambient or supplemental), and mechanical scraping (de-bulked or not) with four contact events per combination. Samples were collected using a Swiffern (Procter 8c Gamble, Cincinnati, Ohio). All samples were tested for PRRSV using reverse -transcription polymerase chain reaction. 

Results: Experiment 1: Temperature did not affect the amount of PRRSV RNA recovered. If PRRSV RNA was detected on the model dock, it was transferred and detected on the model trailer 80% of the time (95% CI, 70.0%-90.0%). Experiment 2: De-bulking resulted in a significant reduction in the likelihood of transfer (odds ratio = 0.14; 95% CI, 0.06-0.32). 

Implications: Contact at the harvest plant lairage unloading is a risk factor for PRRSV transmission with inadequate livestock trailer hygiene. This risk can be mitigated through mechanical removal of gross contamination of the dock.

Patterns of PRRSv and IAV detection in pig oral fluids

Res Vet Sci. 2016 Dec;109:74-80. doi: 10.1016/j.rvsc.2016.09.014. Epub 2016 Sep 21.

Detection of porcine reproductive and respiratory syndrome virus (PRRSV) and influenza A virus(IAV) in oral fluid of pigs.

Biernacka K1, Karbowiak P2, Wróbel P3, Charęza T4, Czopowicz M5, Balka G6, Goodell C7, Rauh R8, Stadejek T9.

Author information

1

Warsaw University of Life Sciences - SGGW, Faculty of Veterinary Medicine, Department of Pathology and Veterinary Diagnostics, Nowoursynowska 159c, 02-776 Warsaw, Poland.

2

Vet-Com L.L.C., Jagiellońska 71, 10-237 Olsztyn, Poland.

3

Swine Vet Consulting L.L.C., Bolewskiego 40, 63-700 Krotoszyn, Poland.

4

Poldanor SA, Dworcowa 25, 77-320 Przechlewo, Poland.

5

Warsaw University of Life Sciences - SGGW, Faculty of Veterinary Medicine, Laboratory of Veterinary Epidemiology and Economics, Nowoursynowska 159c, 02-776 Warsaw, Poland.

6

University of Veterinary Medicine, Department of Pathology, István u. 2, H-1078 Budapest, Hungary.

7

IDEXX Laboratories, Inc., Westbrook, ME, USA.

8

Tetracore Inc, 9901 Belward Campus Drive Suite 300, Rockville, MD 20850, USA.

9

Warsaw University of Life Sciences - SGGW, Faculty of Veterinary Medicine, Department of Pathology and Veterinary Diagnostics, Nowoursynowska 159c, 02-776 Warsaw, Poland. Electronic address: tomasz_stadejek@sggw.pl.

Abstract

Recently oral fluid has become a novel sample type for pathogen nucleic acid and antibody detection, as it is easy to obtain with non-invasive procedures. The objective of the study was to analyze porcine reproductive and respiratory syndrome virus (PRRSV) and influenza A virus (IAV) circulation in growing pigs from three Polish production farms, using Real Time PCR and ELISA testing of oralfluid and serum. Oral fluids were collected every 2weeks, in the same 3-4 pens of pigs aged between 5 and 17weeks. Additionally, blood samples were collected every 4weeks from 4 pigs corresponding to the same pens as oral fluid and tested for the presence of PRRSVnucleic acid (pooled by 4) and antibodies. In farm A no PRRSV circulation was detected and only maternal antibodies were present. In farm B and farm C antibodies to PRRSV in serum and oral fluid were detected in most samples. In farm B PRRSV Type 1 was detected in 80.9% of oral fluid samples and in 58.3% of serum pools, and in farm C in 92.8% of oral fluid samples and 75% serum pools. Striking differences were observed between different pens in PRRSV detection patterns. In farms B and C ORF5 sequence analysis showed the presence of wild type strains which were about 84-85% identical to the modified live vaccine used. In all three farms two waves of IAVshedding with oral fluid were detected, in weaners and fatteners.

Copyright © 2016 Elsevier Ltd. All rights reserved.

KEYWORDS: 

ELISA; IAV; Oral fluid; PRRSV; Real time PCR

PMID:

 

27892877

 

DOI:

 

10.1016/j.rvsc.2016.09.014

Modeling effectiveness of PRRS control strategies in breeding herds

PLoS One. 2016 Nov 22;11(11):e0166596. doi: 10.1371/journal.pone.0166596. eCollection 2016.

Evaluation of Control Strategies for Porcine Reproductive and Respiratory Syndrome (PRRS) in Swine Breeding Herds Using a Discrete Event Agent-Based Model.

Arruda AG1, Friendship R1, Carpenter J2, Greer A1, Poljak Z1.

Author information

Abstract

The objective of this study was to develop a discrete event agent-based stochastic model to explore the likelihood of the occurrence of porcine reproductive and respiratory syndrome (PRRS) outbreaks in swine herds with different PRRS control measures in place. The control measures evaluated included vaccination with a modified-live attenuated vaccine and live-virus inoculation of gilts, and both were compared to a baseline scenario where no control measures were in place. A typical North American 1,000-sow farrow-to-wean swineherd was used as a model, with production and disease parameters estimated from the literature and expert opinion. The modelconstructed herein was not only able to capture individual animal heterogeneity in immunity to and shedding of the PRRS virus, but also the dynamic animal flow and contact structure typical in such herds under field conditions. The model outcomes included maximum number of females infected per simulation, and time at which that happened and the incidence of infected weaned piglets during the first year of challenge-virus introduction. Results showed that the baseline scenario produced a larger percentage of simulations resulting in outbreaks compared to the control scenarios, and interestingly some of the outbreaks occurred over long periods after virus introduction. The live-virus inoculation scenario showed promising results, with fewer simulations resulting in outbreaks than the other scenarios, but the negative impacts of maintaining a PRRS-positive population should be considered. Finally, under the assumptions of the current model, neither of the control strategies prevented the infection from spreading to the piglet population, which highlights the importance of maintaining internal biosecurity practices at the farrowing room level.

PMID:

 

27875546

 

PMCID:

 

PMC5119772

 

DOI:

 

10.1371/journal.pone.0166596

Comparison of PRRSv RNA and antibody detection in pen-based oral fluids and individual serum samples in growing pigs

PLoS One. 2016 Nov 7;11(11):e0166300. doi: 10.1371/journal.pone.0166300. eCollection 2016.

Comparison of PRRSV Nucleic Acid and Antibody Detection in Pen-Based Oral Fluid and Individual Serum Samples in Three Different Age Categories of Post-Weaning Pigs from Endemically Infected Farms.

De Regge N1, Cay B1.

Author information

1

Enzootic and (Re)emerging Diseases, Operational Direction Viral Diseases, CODA-CERVA, Groeselenberg 99, 1180 Ukkel, Belgium.

Abstract

BACKGROUND: 

Porcine reproductive and respiratory syndrome virus (PRRSV) is the causative agent of an economically important disease in swine. Since it has been shown that PRRSV and PRRSV specific antibodies can be detected in oral fluid, many differentaspects have been studied to show that oral fluid could be a worthy alternative diagnostic sample to serum for monitoring and surveillance of this disease. Thorough field evaluations are however missing to convincingly show its usefulness under representative field conditions.

METHODOLOGY: 

Pen-based oral fluid samples and serum samples from all individual pigs in the corresponding pens were collected from post-weaning pigs of three different age categories in eight endemically PRRSV infected farms and one PRRSV free farm in Belgium. All samples were tested by quantitative reverse transcription polymerase chain reaction (qRT-PCR) and ELISA to detect PRRSV RNA and PRRSV specific antibodies, respectively.

RESULTS: 

While the relative specificity of PRRSV detection by qRT-PCR in pen-based oral fluid compared to serum collected from individual pigs was high in all age categories (>90%), the relative sensitivity decreased with the age of the pigs (89, 93 and 10% in 8-12w, 16-20w and 24-28w old pigs, respectively). The latter correlated with a lower percentage of PRRSV positive pigs in serum/pen in the different age categories (55, 29 and 6%, respectively). Irrespective of the age category, pen-based oral fluid samples were always found PCR positive when at least 30% of the individual pigs were positive in serum. PRRSV specific antibody detection in oral fluid by ELISA showed a 100% relative sensitivity to detection in serum since oral fluid samples were always positive as soon as one pig in the pen was positive in serum. On the other hand, two false positive oral fluid samples in 11 pens without serum positive pigs were found, resulting in a relative specificity of 82%. Indications are however present that the oral fluid result indicated the correct infection status but the absence of a golden standard test makes it difficult to define definitive test characteristics.

CONCLUSIONS: 

Overall it can be concluded that oral fluid seems to be a useful matrix for diagnosis of PRRSV under field conditions and that differences in kinetics of PRRSV and PRRSV specific antibody detection in oral fluid and serum of individual pigs can also be reflected in pen-based oral fluid results.

PMID:

 

27820859