Wednesday, July 26, 2017

Epidemiological investigations of the introduction of PRRSv in Chile, 2013- 2015

 2017 Jul 25;12(7):e0181569. doi: 10.1371/journal.pone.0181569. eCollection 2017.

Epidemiological investigations of the introduction of porcine reproductive and respiratory syndrome virus in Chile, 2013-2015.

Abstract

Porcine reproductive and respiratory syndrome (PRRS) is endemic in most pork producing countries. In Chile, eradication of PRRS virus (PRRSV) was successfully achieved in 2009 as a result of the combined efforts of producers and the animal health authorities. In October 2013, after several years without detecting PRRSV under surveillance activities, suspected cases were confirmed on a commercial swine farm. Here, we describe the PRRS epidemic in Chile between October 2013 and April 2015, and we studied the origins and spread of PRRSV throughout the country using official surveillance data and Bayesian phylogenetic analysis. Our results indicate that the outbreaks were caused by a PRRSV closely related to viruses present in swine farms in North America, and different from the strain that circulated in the country before 2009. Using divergence time estimation analysis, we found that the 2013-2015 PRRSV may have been circulating in Chile for at least one month before the first detection. A single strain of PRRSV spread into a limited number of commercial and backyard swine farms. New infections in commercial systems have not been reported since October 2014, and eradication is underway by clearing the disease from the few commercial and backyard farms that remain positive. This is one of the few documented experiences of PRRSV introduction into a disease-free country.
PMID:
 
28742879
 
DOI:
 
10.1371/journal.pone.0181569

Thursday, July 20, 2017

Effect of immunologic solutions on sows and gilts on time-to-stability, and on production losses in breeding herds infected with 1-7-4 PRRS virus

 2017 Sep 1;144:112-116. doi: 10.1016/j.prevetmed.2017.05.024. Epub 2017 Jun 6.

Effect of immunologic solutions on sows and gilts on time to stability, and production losses in breeding herds infected with 1-7-4 PRRSv.

Author information

1
Iowa State University College of Veterinary Medicine, 2221 Lloyd Veterinary Medicine Center, 1600 16S Street, Ames, IA, 50010, USA. Electronic address: dcl.linhares@gmail.com.
2
University of Minnesota College of Veterinary Medicine, 385B Animal Science Veterinary Medicine Building, 1988 Fitch Avenue, St. Paul, MN, 55108, USA.

Abstract

Porcine reproductive and respiratory syndrome virus (PRRSv) is an economically significant swine pathogen causing production losses in the global swine industry. Clinical impact depends on many factors including the virus itself. One method to sub-type PRRSv is using restriction fragment length polymorphism (RFLP). The RFLP pattern 1-7-4 emerged within the United States swine industry in 2014 and has become prevalent since then. This was a field study that prospectively followed 1-7-4-infected breeding herds (n=107) and compared time to stability (TTS), time to baseline production (TTBP) and total loss per 1000 sows between herds using modified-live virus vaccine (MLV) on sows and gilts (MLV-MLV), MLV on sows and MLV in addition to field virus exposure on gilts (MLV-MLV/FVE) or not deliberately exposing sows or gilts to PRRSv (Natural-Natural). Analyses were done in SAS 9.4 and results were adjusted by selected co-variates (duration of herd closure, number of previous PRRSv outbreaks of last 3 years, weaning frequency/week, gilt development unit location, herd size and production system). Survival analysis was conducted on TTS and TTBP and regression analysis on total loss. Herds in the Natural-Natural group achieved TTS and TTBP before other herds. Herds in the MLV-MLV/FVE had the longest TTS and TTBP. The total loss was numerically least in MLV-MLV herds (1194 pigs/1000 sows) compared to MLV/MLV-FVE (1810/1000 sows) and Natural-Natural (2671/1000 sows). This study provided additional information to assist veterinarians deciding between methods of exposure to manage PRRSv infection from breeding herds.

KEYWORDS: 

Control; EWMA; Elimination; Live virus exposure; Modified-live virus vaccine; PRRSv; Pigs; Statistical process control; Whole herd exposure
PMID:
 
28716191
 
DOI:
 
10.1016/j.prevetmed.2017.05.024

Optisample - sample size calculator for active surveillance activities

 2017 Jul 18;12(7):e0176863. doi: 10.1371/journal.pone.0176863. eCollection 2017.

OptisampleTM: Open web-based application to optimize sampling strategies for active surveillance activities at the herd level illustrated using Porcine Respiratory Reproductive Syndrome (PRRS).

Abstract

Porcine reproductive and respiratory syndrome virus (PRRSv) infection causes a devastating economic impact to the swine industry. Active surveillance is routinely conducted in many swine herds to demonstrate freedom from PRRSv infection. The design of efficient active surveillance sampling schemes is challenging because optimum surveillance strategies may differ depending on infection status, herd structure, management, or resources for conducting sampling. Here, we present an open web-based application, named 'OptisampleTM', designed to optimize herd sampling strategies to substantiate freedom of infection considering also costs of testing. In addition to herd size, expected prevalence, test sensitivity, and desired level of confidence, the model takes into account the presumed risk of pathogen introduction between samples, the structure of the herd, and the process to select the samples over time. We illustrate the functionality and capacity of 'OptisampleTM' through its application to active surveillance of PRRSv in hypothetical swine herds under disparate epidemiological situations. Diverse sampling schemes were simulated and compared for each herd to identify effective strategies at low costs. The model results show that to demonstrate freedom from disease, it is important to consider both the epidemiological situation of the herd and the sample selected. The approach illustrated here for PRRSv may be easily extended to other animal disease surveillance systems using the web-based application available at http://stemma.ahc.umn.edu/optisample.
PMID:
 
28719658
 
DOI:
 
10.1371/journal.pone.0176863

Friday, July 14, 2017

Quantitative tools to access epidemiology of PRRS using Morrison's SHMP data

 2017 Jun 27;4:94. doi: 10.3389/fvets.2017.00094. eCollection 2017.

A Review of Quantitative Tools Used to Assess the Epidemiology of Porcine Reproductive and Respiratory Syndrome in U.S. Swine Farms Using Dr. Morrison's Swine Health Monitoring Program Data.

Abstract

Porcine reproductive and respiratory syndrome (PRRS) causes far-reaching financial losses to infected countries and regions, including the U.S. The Dr. Morrison's Swine Health Monitoring Program (MSHMP) is a voluntary initiative in which producers and veterinarians share sow farm PRRS status weekly to contribute to the understanding, in quantitative terms, of PRRS epidemiological dynamics and, ultimately, to support its control in the U.S. Here, we offer a review of a variety of analytic tools that were applied to MSHMP data to assess disease dynamics in quantitative terms to support the decision-making process for veterinarians and producers. Use of those methods has helped the U.S. swine industry to quantify the cyclical patterns of PRRS, to describe the impact that emerging pathogens has had on that pattern, to identify the nature and extent at which environmental factors (e.g., precipitation or land cover) influence PRRS risk, to identify PRRS virus emerging strains, and to assess the influence that voluntary reporting has on disease control. Results from the numerous studies reviewed here provide important insights into PRRS epidemiology that help to create the foundations for a near real-time prediction of disease risk, and, ultimately, will contribute to support the prevention and control of, arguably, one of the most devastating diseases affecting the North American swine industry. The review also demonstrates how different approaches to analyze and visualize the data may help to add value to the routine collection of surveillance data and support infectious animal disease control.

KEYWORDS: 

Swine Health Monitoring Project; data sharing; epidemiology; porcine reproductive and respiratory syndrome; spatiotemporal analysis
PMID:
 
28702459
 
PMCID:
 
PMC5484771
 
DOI:
 
10.3389/fvets.2017.00094

Monday, June 12, 2017

PRRSV and HEV in UK Pigs at the Time of Slaughter

 2017 Jun 9;9(6). pii: E110. doi: 10.3390/v9060110.

UK Pigs at the Time of Slaughter: Investigation into the Correlation of Infection with PRRSV and HEV.

Author information

1
Animal and Plant Health Agency, Woodham Lane, New Haw, Surrey KT15 3NB, UK. jean-pierre.frossard@apha.gsi.gov.uk.
2
Animal and Plant Health Agency, Woodham Lane, New Haw, Surrey KT15 3NB, UK. Sylvia.Grierson@apha.gsi.gov.uk.
3
Animal and Plant Health Agency, Woodham Lane, New Haw, Surrey KT15 3NB, UK. tcheney87@hotmail.com.
4
Animal and Plant Health Agency, Woodham Lane, New Haw, Surrey KT15 3NB, UK. Falko.Steinbach@apha.gsi.gov.uk.
5
Animal and Plant Health Agency, Woodham Lane, New Haw, Surrey KT15 3NB, UK. Bhudipa.Choudhury@apha.gsi.gov.uk.
6
Surveillance Intelligence Unit, Animal and Plant Health Agency, Rougham Hill, Bury St Edmunds, Suffolk IP33 2RX, UK. Susanna.Williamson@apha.gsi.gov.uk.

Abstract

Hepatitis E virus (HEV) and porcine reproductive and respiratory syndrome virus (PRRSV) and are both globally prevalent in the pig population. While HEV does not cause clinical disease in pigs, its zoonotic potential has raised concerns in the food safety sector. PRRS has become endemic in the United Kingdom (UK) since its introduction in 1991, and continues to cause considerable economic losses to the swine industry. A better understanding of the current prevalence and diversity of PRRSV and HEV in the UK, and their potential association, is needed to assess risks and target control measures appropriately. This study used plasma, tonsil, and cecal content samples previously collected from pigs in 14 abattoirs in England and Northern Ireland to study the prevalence of several pathogens including PRRSV and HEV. The diversity of PRRSV strains detected in these samples was analyzed by sequencing open reading frame 5 (ORF5), revealing no substantial difference in PRRSV strains from these clinically unaffected pigs relative to those from clinical cases of disease in the UK. Despite the potential immuno-modulatory effect of PRRSV infection, previously demonstrated to affect Salmonellaand HEV shedding profiles, no significant association was found between positive PRRSV status and positive HEV status.

KEYWORDS: 

HEV; PRRSV; co-infections; evolution and molecular epidemiology; porcine viruses
PMID:
 
28598352
 
DOI:
 
10.3390/v9060110
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Friday, June 9, 2017

Modeling the spatio-temporal dynamics of PRRS cases at farm level using geographical distance and pig trade network matrices

 2017 Jun 7;13(1):163. doi: 10.1186/s12917-017-1076-6.

Modeling the spatio-temporal dynamics of porcine reproductive & respiratory syndrome cases at farm level using geographical distance and pig trade network matrices.

Author information

1
Center for Animal Disease Modeling and Surveillance (CADMS), Department of Medicine & Epidemiology, School Veterinary Medicine, University of California, 2108 Tupper Hall, one Shields Avenue, Davis, California, 95616, USA.
2
Boehringer-Ingelheim Vetmedica Inc, Saint Joseph, Missouri, USA.
3
Department of Veterinary Diagnostic and Production Animal Medicine, College of Veterinary Medicine, Iowa State University, Ames, USA.
4
Center for Animal Disease Modeling and Surveillance (CADMS), Department of Medicine & Epidemiology, School Veterinary Medicine, University of California, 2108 Tupper Hall, one Shields Avenue, Davis, California, 95616, USA. beamartinezlopez@ucdavis.edu.

Abstract

BACKGROUND: 

Porcine reproductive and respiratory syndrome (PRRS) is one of the most economically devastating infectious diseases for the swine industry. A better understanding of the disease dynamics and the transmission pathways under diverse epidemiological scenarios is a key for the successful PRRS control and elimination in endemic settings. In this paper we used a two step parameter-driven (PD) Bayesian approach to model the spatio-temporal dynamics of PRRS and predict the PRRS status on farm in subsequent time periods in an endemic setting in the US. For such purpose we used information from a production system with 124 pig sites that reported 237 PRRS cases from 2012 to 2015 and from which the pig trade network and geographical location of farms (i.e., distance was used as a proxy of airborne transmission) was available. We estimated five PD models with different weights namely: (i) geographical distance weight which contains the inverse distance between each pair of farms in kilometers, (ii) pig trade weight (PT ji ) which contains the absolute number of pig movements between each pair of farms, (iii) the product between the distance weight and the standardized relative pig trade weight, (iv) the product between the standardized distance weight and the standardized relative pig trade weight, and (v) the product of the distance weight and the pig trade weight.

RESULTS: 

The model that included the pig trade weight matrix provided the best fit to model the dynamics of PRRS cases on a 6-month basis from 2012 to 2015 and was able to predict PRRS outbreaks in the subsequent time period with an area under the ROC curve (AUC) of 0.88 and the accuracy of 85% (105/124).

CONCLUSION: 

The result of this study reinforces the importance of pig trade in PRRS transmission in the US. Methods and results of this study may be easily adapted to any production system to characterize the PRRS dynamics under diverse epidemic settings to more timely support decision-making.

KEYWORDS: 

Bayesian approach; Decision making; Disease dynamics; Parameter-driven model; Risk assessment; Risk-based surveillance
PMID:
 
28592317
 
DOI:
 
10.1186/s12917-017-1076-6

Tuesday, May 30, 2017

Oral fluids versus blood sampling for PRRSv serology

 2017 May;204:25-34. doi: 10.1016/j.vetmic.2017.04.001. Epub 2017 Apr 4.

Oral fluid versus blood sampling in group-housed sows and finishing pigs: Feasibility and performance of antibody detection for porcine reproductive and respiratory syndrome virus (PRRSV).

Author information

1
Agence Nationale de Sécurité Sanitaire (ANSES), Unité Epidémiologie et Bien-Etre du Porc, B.P. 53, 22440 Ploufragan, France; Université Bretagne-Loire, France. Electronic address: christelle.fablet@anses.fr.
2
Agence Nationale de Sécurité Sanitaire (ANSES), Unité Virologie Immunologie Porcines, B.P. 53, 22440 Ploufragan, France; Union des Groupements de Producteurs de Viande de Bretagne (UGPVB), 104 rue Eugène Pottier, CS 26553, 35065 Rennes, France; Université Bretagne-Loire, France.
3
Agence Nationale de Sécurité Sanitaire (ANSES), Unité Epidémiologie et Bien-Etre du Porc, B.P. 53, 22440 Ploufragan, France; Université Bretagne-Loire, France.
4
Agence Nationale de Sécurité Sanitaire (ANSES), Unité Virologie Immunologie Porcines, B.P. 53, 22440 Ploufragan, France; Université Bretagne-Loire, France.

Abstract

The feasibility of using individual and pen-based oral fluid samples to detect PRRSV antibodies in growing-finishing pigs and group-housed sows was investigated. The diagnostic performances of a commercial oral fluid ELISA (OF-ELISA) and a serum ELISA (SER-ELISA) performed on individual or pooled samples from 5 or 10 pigs and sows was evaluated. The performance of the OF-ELISA was also assessed for pen-based oral fluids. Eight hundred and thirty-four pigs and 1598 sows from 42 PRRSV-infected and 3 PRRSV-negative herds were oral fluid sampled and bled. PRRSV antibodies were detected by an OF-ELISA performed at individual, pool (5 or 10 samples) and pen levels. Serum samples were tested by a SER-ELISA at individual and pool levels. The sensitivity and specificity of ELISAs for individual samples were assessed by Bayesian analysis. The relative diagnostic performance for the pools was calculated by taking individual samples as the gold standard. SER-ELISA and individual OF-ELISA results were used as references for estimating OF-ELISA performance for pen-based samples. Individual oral fluid collection was feasible in all kinds of pigs, whereas pen-based samples were unsuccessful in 40% of the group-housed sow pens. High levels of sensitivity comparable to those of the SER-ELISA were found for the OF-ELISA when performed on individual, 5-sample pool or pen-based samples from pigs or sows. The OF-ELISA lacked specificity for individual samples from sows. Pooling 5 individual oral fluid samples or using pen-based samples increased test specificity.

KEYWORDS: 

Diagnostic performance; ELISA; Oral fluid; PRRSV antibody; Serum
PMID:
 
28532802
 
DOI:
 
10.1016/j.vetmic.2017.04.001