Friday, December 18, 2015

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.
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]


Wednesday, December 16, 2015

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

 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.

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 farmsbiosecurity 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]

Tuesday, December 8, 2015

Gene-edited pigs are protected from PRRSv

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

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

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.

Thursday, November 12, 2015

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


 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.

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]

Tuesday, November 10, 2015

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

 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.

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]

Tuesday, October 27, 2015

High path PRRSv infection, commercial pig production in South Korea

 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.

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] 

Wednesday, October 21, 2015

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

 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.

Abstract

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]