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.