Economic Analysis of Immunization Strategies for PRRS Control

This is an open access paper. Full version is available at:
http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0144265

PLoS One. 2015 Dec 16;10(12):e0144265. doi: 10.1371/journal.pone.0144265.

Economic Analysis of Vaccination Strategies for PRRS Control.

Linhares DC1, Johnson C2, Morrison RB3.

Author information

• 1Veterinary Diagnostic and Production Animal Medicine Department, College of Veterinary Medicine, Iowa State University, Ames, IA.
• 2Swine Health Department, The Maschhoffs LLC, Carlyle, IL.
• 3Department of Veterinary Population Medicine, College of Veterinary Medicine, University of Minnesota, St Paul, MN.

Abstract

Porcine reproductive and respiratory syndrome virus (PRRSv) is a swine-specific pathogen that causes significant increases in production costs. When a breeding herd becomes infected, in an attempt to hasten control and elimination of PRRSv, some veterinarians have adopted a strategy called load-close-expose which consists of interrupting replacement pig introductions into the herd for several weeks (herd closure) and exposing the whole herd to a replicating PRRSv to boost herd immunity. Either modified-live virus (MLV) vaccine or live field-virus inoculation (FVI) is used. This study consisted of partial budget analyses to compare MLV to FVI as the exposure method of load-close-expose program to control and eliminate PRRSv from infected breeding herds, and secondly to estimate benefit / cost of vaccinating sow herds preventatively. Under the assumptions used in this study, MLV held economic advantage over FVI. However, sensitivity analysis revealed that decreasing margin over variable costs below $ 47.32, or increasing PRRSv-attributed cost above $18.89 or achieving time-to-stability before 25 weeks resulted in advantage of FVI over MLV. Preventive vaccination of sow herds was beneficial when the frequency of PRRSv infection was at least every 1 year and 9 months. The economics of preventative vaccination was minimally affected by cost attributed to field-type PRRSv infection on growing pigs or by the breeding herd productivity level. The models developed and described in this paper provide valuable tools to assist veterinarians in their efforts to control PRRSv.

PMID: 26673898 [PubMed - as supplied by publisher]

Expert opinion on the importance of biosecurity measures for cattle and swine

PLoS One. 2015 Dec 10;10(12):e0144533. doi: 10.1371/journal.pone.0144533.

Expert Opinion on the Perceived Effectiveness and Importance of On-Farm Biosecurity Measures for Cattle and Swine Farms in Switzerland.

Kuster K1, Cousin ME2, Jemmi T3, Schüpbach-Regula G1, Magouras I1.

Author information

Abstract

Biosecurity is crucial for safeguarding livestock from infectious diseases. Despite the plethora of biosecurity recommendations, published scientific evidence on the effectiveness of individual biosecurity measures is limited. The objective of this study was to assess the perception of Swiss experts about the effectiveness and importance of individual on-farm biosecurity measures for cattle and swine farms (31 and 30 measures, respectively). Using a modified Delphi method, 16 Swiss livestock disease specialists (8 for each species) were interviewed. The experts were asked to rank biosecurity measures that were written on cards, by allocating a score from 0 (lowest) to 5 (highest). Experts ranked biosecurity measures based on their importance related to Swiss legislation, feasibility, as well as the effort required for implementation and the benefit of each biosecurity measure. The experts also ranked biosecurity measures based on their effectiveness in preventing an infectious agent from entering and spreading on a farm, solely based on transmission characteristics of specific pathogens. The pathogens considered by cattle experts were those causing Bluetongue (BT), Bovine Viral Diarrhea (BVD), Foot and Mouth Disease (FMD) and Infectious Bovine Rhinotracheitis (IBR). Swine experts expressed their opinion on the pathogens causing African Swine Fever (ASF), Enzootic Pneumonia (EP), Porcine Reproductive and Respiratory Syndrome (PRRS), as well as FMD. For cattle farms, biosecurity measures that improve disease awareness of farmers were ranked as both most important and most effective. For swine farms, the most important and effective measures identified were those related to animal movements. Among all single measures evaluated, education of farmers was perceived by the experts to be the most important and effective for protecting both Swiss cattle and swine farms from disease. The findings of this study provide an important basis for recommendation to farmers and policy makers.

PMID:

 

26656893

 

[PubMed - as supplied by publisher]

Gene-edited pigs are protected from PRRSv

Nat Biotechnol. 2015 Dec 7. doi: 10.1038/nbt.3434. [Epub ahead of print]

Gene-edited pigs are protected from porcine reproductive and respiratory syndrome virus.

Whitworth KM1, Rowland RR2, Ewen CL2, Trible BR2, Kerrigan MA2, Cino-Ozuna AG2, Samuel MS1, Lightner JE3, McLaren DG3, Mileham AJ3, Wells KD1, Prather RS1.

Author information

• 1Division of Animal Science, University of Missouri, Columbia, Missouri, USA.
• 2Department of Diagnostic Medicine and Pathobiology, Kansas State University, Manhattan, Kansas, USA.
• 3Genus plc, DeForest, Wisconsin, USA.

PMID:

 

26641533

 

[PubMed - as supplied by publisher]

Since this paper was a short communication, there was no abstract. Here are my comments about it:

A recent study conducted by Missouri/Kansas/Genus PIC reported genes associated with resistance to PRRSv infection. Three piglets born from a sow and a boar lacking CD 163 (PRRSv receptor in macrophages) gene appeared to be resistant to infection with the PRRSv isolate NVSL 97-7895 (known to be infectious and virulent). Positive control pigs (pigs with "regular" CD 163 genes) did seroconvert, developed viremia, PRRSv clinical signs and had lungs PRRSv-positive on IHC test. "Resistant" pigs remained PRRSv negative (serology, PCRs, clinical signs and lung IHC) 35 days after experimental inoculation (nasal and intramuscular routes).

It is yet to be determined how feasible and consistent it would be to produce entire litters with the right combination of genes (to confer PRRSv resistance). Further studies also need to clarify the “cost” of this “mutation” on feed efficiency/productivity/immune response to other pathogens, so on… Moreover, it is also not known if those pigs would be resistant to other PRRSv strains. Anyways, this is an exciting news and provides great step towards the "fight" against PRRSv.

Keywords: PRRSv resistance, gene editing, CRISPR, CRISPR-Cas9, pigs, swine.

Evaluation of PCV1 as vaccine vector to express antigenic epitopes of PRRSv

Virus Res. 2015 Nov 7. pii: S0168-1702(15)30112-X. doi: 10.1016/j.virusres.2015.11.005. [Epub ahead of print]

Evaluation of the use of non-pathogenic porcine circovirus type 1 as a vaccine delivery virus vector to express antigenic epitopes of porcine reproductive and respiratory syndrome virus.

Piñeyro PE1, Kenney SP2, Giménez-Lirola LG3, Opriessnig T4, Tian D2, Heffron CL2, Meng XJ5.

Author information

• 1Department of Biomedical Sciences & Pathobiology, Virginia-Maryland College of Veterinary Medicine, Virginia Polytechnic Institute and State University, Blacksburg, VA 24060, USA; Department of Veterinary Diagnostic and Production Animal Medicine, Iowa State University College of Veterinary Medicine, Ames, Iowa 5001, USA.
• 2Department of Biomedical Sciences & Pathobiology, Virginia-Maryland College of Veterinary Medicine, Virginia Polytechnic Institute and State University, Blacksburg, VA 24060, USA.
• 3Department of Veterinary Diagnostic and Production Animal Medicine, Iowa State University College of Veterinary Medicine, Ames, Iowa 5001, USA.
• 4Department of Veterinary Diagnostic and Production Animal Medicine, Iowa State University College of Veterinary Medicine, Ames, Iowa 5001, USA; The Roslin Institute and The Royal (Dick) School of Veterinary Studies, University of Edinburgh, Edinburgh, United Kingdom.
• 5Department of Biomedical Sciences & Pathobiology, Virginia-Maryland College of Veterinary Medicine, Virginia Polytechnic Institute and State University, Blacksburg, VA 24060, USA. Electronic address: xjmeng@vt.edu.

Abstract

We previously demonstrated that the C-terminus of the capsid gene of porcine circovirus type 2 (PCV2) is an immune reactive epitope displayed on the surface of virions. Insertion of foreign epitope tags in the C-terminus produced infectious virions that elicited humoral immune responses against both PCV2 capsid and the inserted epitope tags, whereas mutation in the N terminus impaired viral replication. Since the non-pathogenic porcine circovirus type 1 (PCV1) shares similar genomic organization and significant sequence identity with pathogenic PCV2, in this study we evaluated whether PCV1 can serve as a vaccine delivery virus vector. Four different antigenic determinants of porcine reproductive and respiratory syndrome virus (PRRSV) were inserted in the C-terminus of the PCV1 capsid gene, the infectivity and immunogenicity of the resulting viruses are determined. We showed that an insertion of 12 (PRRSV-GP2 epitope II, PRRSV-GP3 epitope I, and PRRSV-GP5 epitope I), and 14 (PRRSV-GP5 epitope IV) amino acid residues did not affect PCV1 replication. We successfully rescued and characterized four chimeric PCV1 viruses expressing PRRSV linear antigenic determinants (GP2 epitope II: aa 40-51, ASPSHVGWWSFA; GP3 epitope I: aa 61-72, QAAAEAYEPGRS; GP5 epitope I: aa 35-46, SSSNLQLIYNLT; and GP5 epitope IV: aa 187-200, TPVTRVSAEQWGRP). We demonstrated that all chimeric viruses were stable and infectious in vitro and three chimeric viruses were infectious in vivo. An immunogenicity study in pigs revealed that PCV1-VR2385EPI chimeric viruses elicited neutralizing antibodies against PRRSV-VR2385. The results have important implications for further evaluating PCV1 as a potential vaccine delivery vector.

Copyright © 2015. Published by Elsevier B.V.

KEYWORDS: 

Antigenic epitopes; Porcine circovirus type 1 (PCV1); Porcine circovirus type 2 (PCV2); Porcine reproductive and respiratory syndrome virus (PRRSV); Vaccine delivery vector

PMID:

 

26555162

 

[PubMed - as supplied by publisher]

Serum inoculation for elimination of PRRS from a farrow-to-finish farm

Acta Vet Hung. 2015 Sep;63(3):389-399.

Serum inoculation as a possibility for elimination of porcine reproductive and respiratory syndrome (PRRS) from a farrow-to-finish pig farm.

Štukelj M1, Plut J1, Toplak I2.

Author information

• 1Institute for the Health Care of Pigs, University of Ljubljana , Gerbičeva 60, 1000 Ljubljana , Slovenia.
• 2Institute for Microbiology and Parasitology, Veterinary Faculty, University of Ljubljana , Gerbičeva 60, 1000 Ljubljana , Slovenia.

Abstract

The large heterogeneity among porcine reproductive and respiratory syndrome virus (PRRSV) isolates is probably the main obstacle to its effective control using current commercial vaccines. Intentionally exposing all breeding pigs to PRRSV circulating on the farm could eliminate porcine reproductive and respiratory syndrome (PRRS) from the herd. The objective of this study was to eliminate PRRS from a farrow-to-finish pig farm by serum inoculation. The owner was acquainted with the strict biosecurity measures. Breeding pigs were immunised with serum, which was obtained from PRRSV-positive weaners from the same farm. The percent of antibody high positive breeding pigs decreased six months after serum inoculation, while 34 months after serum inoculation no more antibody high positive pigs were detected and 56.8% of breeding pigs and all other categories were free of antibodies. In the breeding herd no virus was detected during all testing while PRRSV circulated in 2-month-old weaners until 12 months after serum inoculation. Later all tested samples from weaners, growers and fatteners were negative. Herd closure and the adoption of strict biosecurity measures are essential. Serum inoculation of the breeding herd proved to be a successful measure for eliminating PRRS from this farrow-to-finish farm.

KEYWORDS: 

PRRS; Porcine; elimination; immunisation; serum inoculation

PMID:

 

26551429

 

[PubMed - as supplied by publisher]

High path PRRSv infection, commercial pig production in South Korea

BMC Vet Res. 2015 Oct 24;11(1):272.

Unusual severe cases of type 1 porcine reproductive and respiratory syndrome virus (PRRSV) infection in conventionally reared pigs in South Korea.

Lyoo KS1, Yeom M2, Choi JY3, Park JH4, Yoon SW5, Song D6.

Author information

Abstract

BACKGROUND: 

Porcine reproductive and respiratory syndrome virus (PRRSV) causes a loss of approximately US$ 70 million every year to the South Korean pork industry. There are two distinct genotypes: European (type 1) and North American (type 2). In South Korea, type 1 and type 2 PRRSV are widely distributed and have evolved continuously since the infection was first described. Here, we present two field cases of type 1 PRRSV infection with unusually severe pathogenicity.

CASE PRESENTATION: 

The first case farm was a two-site production system comprising farrow-to-grower and grower-to-finish units and was historically free from PRRSV infections. The PRRSV vaccine had not been used in both units. In October 2014, pigs in the grower-to-finish unit experienced severe respiratory distress with the mortality rate reaching to 22 %. Despite antibiotic treatment, clinical signs were still noticed in most pigs. The second case farm was also a two-site production system, but had two separate farrow-to-grower units (unit A and unit B). Historically, type 1 PRRSV was continuously present in unit A, but unit B was free from PRRSV. Thus, all grower pigs of unit B were vaccinated before being moved to the grower-to-finish unit. In November 2014, severe respiratory distress was seen in pigs of the grower-to-finish unit. Significant respiratory distress was observed in only the grower herd moved from unit B, and the mortality of those pigs was ~50 %. However, no disease was shown in the grower pigs from unit A.

CONCLUSIONS: 

To our knowledge, the present study is the first observation of the cases of infection by highly pathogenic type 1 PRRSV in South Korea. The Korean type 1 PRRSV strains have undergone unique evolutionary dynamics for the last decade in this country. Although there are known to be three clusters of Korean type 1 PRRSV, their pathogenicity could not be categorized owing to their high level of genetic diversity. Therefore, further studies are needed to demonstrate the novel classification of Korean type 1 PRRSV strains according to their virulence factors.

PMID:

 

26497589

 

[PubMed - as supplied by publisher] 

Comparison between the 2013-2014 and 2009-2012 annual USA PRRSv epidemics

Can Vet J. 2015 Oct;56(10):1087-9.

Comparison between the 2013-2014 and 2009-2012 annual porcine reproductive and respiratory syndrome virus epidemics in a cohort of sow herds in the United States.

Tousignant SJ1, Perez A1, Morrison R1.

Abstract

in English, French

The purpose of this study was to describe the 2013/2014 porcine reproductive and respiratory syndrome virus (PRRSV) epidemic in the United States and compare it with the previous 4 y of data from 2009 to 2012. A total of 371 herds participated in the study, representing nearly 1.2 million sows in 15 States. There were significantly fewer PRRSV cases during this study period and the onset of the annual epidemic was delayed approximately 3 wk. Cluster analysis revealed a pattern similar to previous years. The roles of spurious observations, increased awareness of PRRSV epidemics, and porcine epidemic diarrhea virus detection in the United States swine herd are considered. 

PMID:

 

26483586

 

[PubMed - in process] 

Network model to simulate regional transmission of PRRSv

Vet Microbiol. 2015 Sep 21. pii: S0378-1135(15)30028-6. doi: 10.1016/j.vetmic.2015.09.010. [Epub ahead of print]

Development of a network based model to simulate the between-farm transmission of the porcine reproductive and respiratory syndrome virus.

Thakur KK1, Sanchez J2, Hurnik D2, Poljak Z3, Opps S4, Revie CW2.

Abstract

Contact structure within a population can significantly affect the outcomes of infectious disease spread models. The objective of this study was to develop a network based simulation model for the between-farm spread of porcine reproductive and respiratory syndrome virus to assess the impact of contact structure on between-farm transmission of PRRS virus. For these farm level models, a hypothetical population of 500 swine farms following a multistage production system was used. The contact rates between farms were based on a study analyzing movement of pigs in Canada, while disease spread parameters were extracted from published literature. Eighteen distinct scenarios were designed and simulated by varying the mode of transmission (direct versus direct and indirect contact), type of index herd (farrowing, nursery and finishing), and the presumed network structures among swine farms (random, scale-free and small-world). PRRS virus was seeded in a randomly selected farm and 500 iterations of each scenario were simulated for 52 weeks. The median epidemic size by the end of the simulated period and percentage die-out for each scenario, were the key outcomes captured. Scenarios with scale-free network models resulted in the largest epidemic sizes, while scenarios with random and small-world network models resulted in smaller and similar epidemic sizes. Similarly, stochastic die-out percentage was least for scenarios with scale-free networks followed by random and small-world networks. Findings of the study indicated that incorporating network structures among the swine farms had a considerable impact on the spread of PRRS virus, highlighting the importance of understanding and incorporating realistic contact structures when developing infectious disease spread models for similar populations.

Copyright © 2015 Elsevier B.V. All rights reserved.

KEYWORDS: 

AnyLogic; Between-farm; Infectious diseases; Network model; PRRS virus; Porcine reproductive and respiratory syndrome virus; Swine

PMID:

 

26464321

 

[PubMed - as supplied by publisher]

Descriptive analysis and spatial epidemiology of PRRS for sites in Ontario ARC&E

Can J Vet Res. 2015 Oct;79(4):268-78.

Descriptive analysis and spatial epidemiology of porcine reproductive and respiratory syndrome (PRRS) for swine sites participating in area regional control and elimination programs from 3 regions of Ontario.

Arruda AG¹, Poljak Z¹, Friendship R¹, Carpenter J¹, Hand K¹.

Author information

Abstract

in English, French

The objectives of this study were to describe demographics, basic biosecurity practices, ownership structure, and prevalence of porcine reproductive and respiratory syndrome (PRRS) in swine sites located in 3 regions in Ontario, and investigate the presence of spatial clustering and clusters of PRRS positive sites in the 3 regions. A total of 370 swine sites were enrolled in Area Regional Control and Elimination projects in Niagara, Watford, and Perth from 2010 to 2013. Demographics, biosecurity, and site ownership data were collected using a standardized questionnaire and site locations were obtained from an industry organization. Status was assigned on the basis of available diagnostic tests and/or assessment by site veterinarians. Spatial dependence was investigated using the D-function, the spatial scan statistic test and the spatial relative risk method. Results showed that the use of strict all-in all-out (AIAO) pig flow and shower before entry are uncommon biosecurity practices in swine sites, but a larger proportion of sites reported having a Danish entry. The prevalence of PRRS in the 3 regions ranged from 17% to 48% and localized high and low risk clusters were detected. Sites enrolled in the PRRS control projects were characterized by membership in multiple and overlapping ownership structures and networks, which complicates the way the results of monitoring and disease management measures are communicated to the target population.

PMID: 26424906 [PubMed - in process]

Efficacy of M.hp and/or PRRSv vaccination in dually infected pigs

Vet Microbiol. 2015 Sep 21. pii: S0378-1135(15)30033-X. doi: 10.1016/j.vetmic.2015.09.015. [Epub ahead of print]

Efficacy of combined vaccination against Mycoplasma hyopneumoniae and porcine reproductive and respiratory syndrome virus in dually infected pigs

Bourry O¹, Fablet C², Simon G³, Marois-Créhan C⁴.

Abstract

Porcine respiratory disease complex (PRDC) is one of the main causes of economic losses for swine producers. This complex is due to a combination of different pathogens and their interactions. Two major pathogens involved in PRDC are Mycoplasma hyopneumoniae (Mhp) and porcine reproductive and respiratory syndrome virus (PRRSV). The objectives of this study were (i) to develop an experimental model of dual Mhp/PRRSV infection in SPF pigs with European strains of Mhp and PRRSV and (ii) to assess and compare the effects of single Mhp, single PRRSV or combined Mhp/PRRSV vaccination against this dual infection. Pigs dually infected with Mhp and PRRSV showed a combination of symptoms characteristic of each pathogen but no significant exacerbation of pathogenicity. Thus, the co-infected pigs displayed coughing and pneumonia typical of Mhp infection in addition to PRRSV-related hyperthermia and decrease in average daily gain (ADG). Hyperthermia was reduced in PRRSV vaccinated animals (single or combined vaccination), whereas ADG was restored in Mhp/PRRSV vaccinated pigs only. Regarding respiratory symptoms and lung lesions, no vaccine decreased coughing. However, all vaccines reduced the pneumonia score but more so in animals receiving the Mhp vaccine, whether single or combined. This vaccine also decreased the Mhp load in the respiratory tract. In conclusion, combined vaccination against both Mhp and PRRSV efficiently pooled the efficacy of each single PRRSV and Mhp vaccination and could be an interesting tool to control PRDC in European swine production.
Copyright © 2015 Elsevier B.V. All rights reserved.

KEYWORDS:

Dual infection; European strain; Mycoplasma hyopneumoniae; PRDC; PRRS; Vaccine

PMID: 26422712 [PubMed - as supplied by publisher]

A serosurvey for pathogens in European wild boars

Vet Rec Open. 2015 Aug 28;2(2):e000077. doi: 10.1136/vetreco-2014-000077. eCollection 2015.

A serosurvey for selected pathogens in Greek European wild boar.

Touloudi A¹, Valiakos G¹, Athanasiou LV², Birtsas P³, Giannakopoulos A², Papaspyropoulos K⁴, Kalaitzis C⁴, Sokos C⁵, Tsokana CN², Spyrou V⁶, Petrovska L⁷, Billinis C¹.

Abstract

OBJECTIVES:

Serum samples, collected from 94 European wild boar (Sus scrofa) during the hunting seasons 2006 -2010 from different regions of Greece, were examined in order to estimate the role of these wildlife species as reservoir of pathogens important for livestock and/or public health.

MATERIALS AND METHODS:

The assays used for this purpose were commercial indirect ELISA for the detection of antibodies against porcine circovirus type 2 (PCV-2), porcine reproductive and respiratory syndrome (virus) (PRRSV), Aujeszky's disease virus (ADV), influenza A (IA) virus, Actinobacillus pleuropneumoniae, Mycoplasma hyopneumoniae, Salmonella species, Trichinella species and indirect immunofluorescence antibody test for the detection of antibodies against Toxoplasma gondii and Neospora caninum.

RESULTS:

Antibodies against PCV-2, PRRSV, ADV, IA virus,A. pleuropneumoniae, M. hyopneumoniae, Salmonella species, Trichinella species, T. gondii and N. caninum were detected in 19.1 per cent, 12.8 per cent, 35.1 per cent, 1.1 per cent, 57.4 per cent, 0 per cent, 4.3 per cent, 6.4 per cent, 5.2 per cent and 1.1 per cent of the samples, respectively. Cluster analysis revealed a hot spot of seropositivity near Bulgarian border; seropositivity to ADV was more common among female animals.

CONCLUSIONS:

These results indicate exposure of wild boar to most of the above-mentioned pathogens, raising concern about the possibility that these species may pose a significant health risk for livestock and/or humans.

KEYWORDS:

GIS; Greece; Infectious diseases; Serology; Wild boar; swine

PMID:26392908 [PubMed]

Genetic diversity of PRRSv collected from air in high pig density regions

Viruses. 2014 Nov 14;6(11):4424-36. doi: 10.3390/v6114424.

Genetic diversity of PRRS virus collected from air samples in four different regions of concentrated swine production during a high incidence season

Brito B, Dee S, Wayne S, Alvarez J, Perez A.

Abstract

Porcine Reproductive and Respiratory Syndrome (PRRS) is one of the most relevant swine diseases in the US, costing the industry millions of dollars per year. Unfortunately, disease control is difficult because of the virus dynamics, as PRRS virus (PRRSV) can be transmitted by air between farms, especially, in regions with high density of swine operations. While long distance airborne transport of PRRSV has been reported, there is little information regarding the dynamics of PRRSV airborne challenge in concentrated regions. The objective of this study was to describe the frequency of detection, dose and diversity of PRRSV in air samples collected across four concentrated production regions during the PRRS-high risk season in the Midwestern US (October-December) in 2012. Between 29% and 42% of the air samples were positive in all four sampling sites. Sequencing of the recovered virus showed a wide diversity of field and vaccine variants. Higher frequency, dose, and diversity of PRRSV were observed in air at locations with higher pig density. These findings suggest that regional spread of PRRSV due to aerosol transmission of PRRSV represents a significant risk to susceptible herds in concentrated regions of domestic pig production where PRRSV is endemic.

PMID:25405592 [PubMed]

Temporal and spatial dynamics of PRRSv infection in the United States

Am J Vet Res. 2015 Jan;76(1):70-6. doi: 10.2460/ajvr.76.1.70.

Temporal and spatial dynamics of porcine reproductive and respiratory syndrome virus infection in the United States

Tousignant SJ, Perez AM, Lowe JF, Yeske PE, Morrison RB.

Abstract

OBJECTIVE:

To measure incidence and estimate temporal and spatial dynamics of porcine reproductive and respiratory syndrome virus (PRRSV) infection in US sow herds.

ANIMALS:

371 sow herds in the United States from 14 production companies.

PROCEDURES:

The exponentially weighted moving average was used to monitor incident PRRSV infections for onset of an epidemic. The spatial scan statistic was used to identify areas at significantly high risk of PRRS epidemics. A χ(2) test was used to estimate whether there were significant differences in the quarterly and annual PRRS incidence among time periods, and a bivariable logistic regression model was used to estimate whether PRRSV infection during a given year increased the odds of that herd being infected in the following year.

RESULTS:

During the 4-year period of this study, 29% (91/319; 2009 to 2010), 33% (106/325; 2010 to 2011), 38% (135/355; 2011 to 2012), and 32% (117/371; 2012 to 2013) of the herds reported new infections. Weekly incidence was low during spring and summer and high during fall and winter. The exponentially weighted moving average signaled the onset of a PRRSV epidemic during the middle 2 weeks of October each year. Disease incidence was spatially clustered. Infection in the previous year increased the odds of infection in 2010 to 2011 and 2011 to 2012.

CONCLUSIONS AND CLINICAL RELEVANCE:

Results indicated a striking repeatability in annual PRRSV temporal and spatial patterns across 4 years of data among herds from 14 production companies, which suggested that efforts to control PRRSV at a regional level should continue to be supported.

PMID:25535663 [PubMed - indexed for MEDLINE]

Production outcomes following exposure of gestation gilts to attenuated PRRSv vaccine

Vaccine. 2014 Aug 6;32(36):4639-43. doi: 10.1016/j.vaccine.2014.06.073. Epub 2014 Jun 24.

Reproductive, productivity, and mortality outcomes in late-gestation gilts and their litters following simulation of inadvertent exposure to a modified-live vaccine strain of porcine reproductive and respiratory syndrome (PRRS) virus.

Schelkopf A¹, Nerem J¹, Cowles B², Amodie D², Swalla R², Dee S¹.

¹Pipestone Veterinary Clinic, 1300 S. Highway 75, Pipestone, MN 56164, USA. ²Outcomes Research, Zoetis Inc, 100 Campus Drive, Florham Park, NJ 07932, USA.

Abstract

The study evaluated the safety of a modified live-virus (MLV) porcine reproductive and respiratory syndrome (PRRS) vaccine in susceptible, pregnant gilts. To simulate inadvertent exposure secondary to postvaccination shedding of PRRS-MLV, seronegative gilts (n=51) were exposed by IM vaccination at 90 days of gestation. Vaccinated and nonvaccinated, seronegative control gilts (n=25) were maintained in separate facilities. The PRRS-MLV vaccine was given in a 2mL dose on day 0. On day 7 all vaccinated gilts were PRRSV-PCR-positive for PRRSV and had responded serologically as determined by an ELISA. All control gilts remained PRRSV-PCR- and ELISA-negative throughout the study. Abortions did not occur in gilts from either group. The difference between vaccinated and control gilts in average number of piglets per litter (12.43 and 12.16, respectively), number of live births per litter (11.21 and 11.54), and mean piglet birth weight (3.22 and 3.26 lbs) were not significantly different. Piglets in the control group had significantly greater average daily gain versus piglets from vaccinated gilts (0.52 vs. 0.46 lbs, P<0.0001). Preweaning mortality was significantly greater (P=0.0023) in piglets from the vaccinated gilts (19.7% vs. 10.9%). A single gilt accounted for 18.2% of stillbirths in the vaccinated group. Air samples were borderline PRRSV-PCR-positive for PRRSV on days 29 and 32, after more than 98% of gilts had farrowed. Results demonstrated that vaccination of pregnant gilts at the time of peak fetal susceptibility was non-abortigenic and that the PRRS-MLV agent did not significantly affect reproductive outcomes. Lower ADG in piglets from vaccinated gilts may be due to PRRS-MLV viremia following transplacental or post-farrowing exposure. Air sampling results indicated that environmental contamination with PRRS-MLV shed from vaccinated gilts was minimal.
Copyright © 2014 Elsevier Ltd. All rights reserved.

KEYWORDS:

Fostera; Porcine; Reproductive; Respiratory; Syndrome; Vaccine; Virus

Chimeric PRRSv confers cross-protection in pigs

Virology. 2015 Sep 2;485:402-413. doi: 10.1016/j.virol.2015.08.021. [Epub ahead of print]

Chimeric porcine reproductive and respiratory syndrome virus containing shuffled multiple envelope genes confers cross-protection in pigs.

Tian D¹, Ni YY¹, Zhou L¹, Opriessnig T², Cao D¹, Piñeyro P³, Yugo DM¹, Overend C¹, Cao Q¹, Lynn Heffron C¹, Halbur PG⁴, Pearce DS⁵, Calvert JG⁵, Meng XJ⁶.

Author information

Abstract

The extensive genetic diversity of porcine reproductive and respiratory syndrome virus (PRRSV) strains is a major obstacle for vaccine development. We previously demonstrated that chimeric PRRSVs in which a single envelope gene (ORF3, ORF4, ORF5 or ORF6) was shuffled via DNA shuffling had an improved heterologous cross-neutralizing ability. In this study, we incorporate all of the individually-shuffled envelope genes together in different combinations into an infectious clone backbone of PRRSV MLV Fostera^® PRRS. Five viable progeny chimeric viruses were rescued, and their growth characteristics were characterized in vitro. In a pilot pig study, two chimeric viruses (FV-SPDS-VR2,FV-SPDS-VR5) were found to induce cross-neutralizing antibodies against heterologous strains. A subsequent vaccination/challenge study in 72 pigs revealed that chimeric virus FV-SPDS-VR2 and parental virus conferred partial cross-protection when challenged with heterologous strains NADC20 or MN184B. The results have important implications for future development of an effective PRRSV vaccine that confers heterologous protection.
Copyright © 2015 Elsevier Inc. All rights reserved.

KEYWORDS:

Cross-protection; DNA shuffling; Envelope genes; Heterologous strains; Porcine reproductive and respiratory syndrome virus (PRRSV); Vaccines

PMID: 26342466 [PubMed - as supplied by publisher]

Persistence and Retention of PRRSv in Stable Flies

J Med Entomol. 2015 Jul 12. pii: tjv096. [Epub ahead of print]

Persistence and Retention of Porcine Reproductive and Respiratory Syndrome Virus in Stable Flies (Diptera: Muscidae).

Rochon K1, Baker RB2, Almond GW3, Gimeno IM3, Pérez de León AA4, Watson DW5.

Author information

Abstract

We investigated the acquisition of porcine reproductive and respiratory syndrome (PRRS) virus by the stable fly (Diptera: Muscidae; Stomoxys calcitrans (L.)) through a bloodmeal, and virus persistence in the digestive organs of the fly using virus isolation and quantitative reverse-transcription PCR (qRT-PCR). Stable flies were fed blood containing live virus, modified live vaccine virus, chemically inactivated virus, or no virus. Stable flies acquired PRRSV from the bloodmeal and the amount of virus in the flies declined with time, indicating virus did not replicate in fly digestive tissues. Virus RNA was recovered from the flies fed live virus up to 24 h postfeeding using virus isolation techniques and 96 h using qRT-PCR. We further examined the fate of PRRSV in the hemolymph of the flies following intrathoracic injection to bypass the midgut barrier. PRRSV was detected in intrathoracically inoculated adult stable flies for 10 d using qRT-PCR. In contrast to what we observed in the digestive tract, detectable virus quantities in the intrathoracically inoculated stable flies followed an exponential decay curve. The amount of virus decreased fourfold in the first 3 d and remained stable thereafter, up to 10 d.

© The Authors 2015. Published by Oxford University Press on behalf of Entomological Society of America. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

KEYWORDS: 

Stomoxys calcitrans; intrathoracic inoculation; midgut barrier; virus persistence

PMID:

 

26336236

 

[PubMed - as supplied by publisher]

Concentration, Size Distribution, and Infectivity of Airborne Particles Carrying Swine Viruses

Alonso C, Raynor PC, Davies PR, Torremorell M. Concentration, Size Distribution, and Infectivity of Airborne Particles Carrying Swine Viruses. PLoS One. 2015 Aug 19;10(8):e0135675. doi: 10.1371/journal.pone.0135675.

Abstract

When pathogens become airborne, they travel associated with particles of different size and composition. Particle size determines the distance across which pathogens can be transported, as well as the site of deposition and the survivability of the pathogen. Despite the importance of this information, the size distribution of particles bearing viruses emitted by infectious animals remains unknown. In this study we characterized theconcentration and size distribution of inhalable particles that transport influenza A virus (IAV), porcine reproductive and respiratory syndrome virus (PRRSV), and porcine epidemic diarrhea virus (PEDV) generated by acutely infected pigs and assessed virus viability for each particle size range. Aerosols from experimentally infected pigs were sampled for 24 days using an Andersen cascade impactor able to separate particles by size(ranging from 0.4 to 10 micrometer (μm) in diameter). Air samples collected for the first 9, 20 and the last 3 days of the study were analyzed for IAV, PRRSV and PEDV, respectively, using quantitative reverse transcription polymerase chain reaction (RT-PCR) and quantified as geometric mean copies/m3 within each size range. IAV was detected in all particle size ranges in quantities ranging from 5.5x102 (in particles ranging from 1.1 to 2.1μm) to 4.3x105 RNA copies/m3 in the largest particles (9.0-10.0μm). PRRSV was detected in all size ranges except particles between 0.7 and 2.1μm in quantities ranging from 6x102 (0.4-0.7μm) to 5.1x104 RNA copies/m3 (9.0-10.0μm). PEDV, an enteric virus, was detected in all particle sizes and in higher quantities than IAV and PRRSV (p < 0.0001) ranging from 1.3x106 (0.4-0.7μm) to 3.5x108 RNA copies/m3 (9.0-10.0μm). Infectious status was demonstrated for the 3 viruses, and in the case of IAV and PRRSV, viruses were isolated from particles larger than 2.1μm. In summary, our results indicated that airborne PEDV, IAV and PRRSV can be found in a wide range of particle sizes. However, virus viability is particle size dependent.

PMID:

 

26287616

 

[PubMed - as supplied by publisher]

Association Influenza A virus and PRRSv in sow farms with post-weaning mortality.

Alvarez J, Sarradell J, Kerkaert B, Bandyopadhyay D, Torremorell M, Morrison R, Perez A. Association of the presence of influenza A virus and porcine reproductive and respiratory syndrome virus in sow farms with post-weaning mortality. Prev Vet Med. 2015 Jul 17. pii: S0167-5877(15)00235-4. doi: 10.1016/j.prevetmed.2015.07.003.

Abstract

Influenza A virus (IAV) and porcine reproductive and respiratory syndrome virus (PRRSV) are among the most important pathogens affecting pigs worldwide. Their effect on post-weaning mortality can be substantial and may be potentiated by other concomitant factors. Here, the objective was to evaluate the association between IAV and PRRSV infection at weaning with post-weaning mortality observed in wean-to-finish farms in order to better quantify the full impact of their presence in breeding herds. IAV and PRRSV presence was assessed by real time reverse transcription (RRT)-PCR on oral fluid samples from suckling piglets in nine sow farms. Production data from 177 batches of growing pigs weaned one week before/after IAV and PRRSV testing were analyzed to measure the association between IAV and/or PRRSV test results and mortality recorded for a given batch through the use of Bayesian mixed effects negative binomial multivariable regression model. The model accounted for potential confounders such as flow, date at weaning, days on feed and batch size. A statistically important association between IAV (incidence ratio (IR)=1.18, 95% posterior probability interval 1.15-1.21) and PRRSV (IR=1.41, 95% PPI 1.30-1.52) with post-weaning mortality was detected, with season and number of days on feed also associated. Our results suggest that infection with IAV or PRRSV in the pre-weaning period is associated with an increase in post-weaning mortality. This association should be taken into consideration when measuring the impact of IAV and PRRSV in breeding herds.

Copyright © 2015 Elsevier B.V. All rights reserved.

KEYWORDS:

Bayesian modeling; Influenza A virus; Porcine reproductive and respiratory syndrome virus; Post-weaning mortality; Swine

PMID:

 

26210012

 

[PubMed - as supplied by publisher]