title: Evaluating perspectives for PRRS virus elimination from pig dense areas with a risk factor based herd index.
abstract: Porcine reproductive and respiratory syndrome virus (PRRSV) is wide-spread in pig populations globally. In many regions of Europe with intensive pig production and high herd densities, the virus is endemic and can cause disease and production losses. This fuels discussion about the feasibility and sustainability of virus elimination from larger geographic regions. The implementation of a program aiming at virus elimination for areas with high pig density is unprecedented and its potential success is unknown. The objective of this work was to approach pig population data with a simple method that could support assessing the feasibility of a sustainable regional PRRSV elimination. Based on known risk factors such as pig herd structure and neighborhood conditions, an index characterizing individual herds' potential for endemic virus circulation and reinfection was designed. This index was subsequently used to compare data of all pig herds in two regions with different pig- and herd-densities in Lower Saxony (North-West Germany) where PRRSV is endemic. Distribution of the indexed herds was displayed using GIS. Clusters of high herd index densities forming potential risk hot spots were identified which could represent key target areas for surveillance and biosecurity measures under a control program aimed at virus elimination. In an additional step, for the study region with the higher pig density (2463 pigs/km(2) farmland), the potential distribution of PRRSV-free and non-free herds during the implementation of a national control program aiming at national virus elimination was modeled. Complex herd and trade network structures suggest that PRRSV elimination in regions with intensive pig farming like that of middle Europe would have to involve legal regulation and be accompanied by important trade and animal movement restrictions. The proposed methodology of risk index mapping could be adapted to areas varying in size, herd structure and density. Interpreted in the regional context, this could help to classify the density of risk and to accordingly target resources and measures for elimination.
authors.affiliation: Veterinary Public Health Institute, Vetsuisse Faculty, University of Bern, Switzerland. Electronic address: as.fahrion@gmail.com.
authors.forename: A S
authors.initials: AS
authors.lastname: Fahrion
authors.affiliation: Field Station for Epidemiology, University of Veterinary Medicine Hannover, Foundation, Büscheler Strasse 9, 49456 Bakum, Germany. Electronic address: elisabeth.grosse.beilage@tiho-hannover.de.
authors.forename: E grosse
authors.initials: Eg
authors.lastname: Beilage
authors.affiliation: Clinic for Swine, Department of Clinical Veterinary Medicine, Vetsuisse Faculty, University of Bern, Bremgartenstrasse 109A, 3012 Bern, Switzerland. Electronic address: heiko.nathues@vetsuisse.unibe.ch.
authors.forename: H
authors.initials: H
authors.lastname: Nathues
authors.affiliation: Veterinary Public Health Institute, Vetsuisse Faculty, University of Bern, Switzerland. Electronic address: salomeduerr@gmx.ch.
authors.forename: S
authors.initials: S
authors.lastname: Dürr
authors.affiliation: Institute for Veterinary Epidemiology and Biostatistics, Department of Veterinary Medicine at the Freie Universität, Berlin, Germany. Electronic address: marcus.doherr@fu-berlin.de.
authors.forename: M G
authors.initials: MG
authors.lastname: Doherr
mesh_terms: D000822:Animal Husbandry; D000818:Animals; D005858:Germany; D019318:Porcine Reproductive and Respiratory Syndrome / Q000453:epidemiology / Q000517:prevention & control*; D019316:Porcine respiratory and reproductive syndrome virus / Q000302:isolation & purification*; D012307:Risk Factors; D013552:Swine
keywords: Endemic production diseases; Geographic information system (GIS); Porcine reproductive and respiratory syndrome virus (PRRSV); Risk factor; Virus circulation