title: Quantitative analysis of the probability of introducing equine encephalosis virus (EEV) into The Netherlands.
abstract: Equine encephalosis is a midge-borne viral disease of equines caused by equine encephalosis virus (EEV, Orbivirus, Reoviridae), and closely related to African horse sickness virus (AHSV). EEV and AHSV share common vectors and show similar transmission patterns. Until now EEV has caused outbreaks in Africa and Israel. This study aimed to provide insight in the probability of an EEV outbreak in The Netherlands caused by infected vectors or hosts, the contribution of potential source areas (risk regions) to this probability, and the effectiveness of preventive measures (sanitary regimes). A stochastic risk model constructed for risk assessment of AHSV introduction was adapted to EEV. Source areas were categorized in risk regions (high, low, and very low risk) based on EEV history and the presence of competent vectors. Two possible EEV introduction pathways were considered: importation of infected equines and importation of infected vectors along with their vertebrate hosts. The probability of EEV introduction (PEEV) was calculated by combining the probability of EEV release by either pathway and the probability of EEV establishment. The median current annual probability of EEV introduction by an infected equine was estimated at 0.012 (90% uncertainty interval 0.002-0.020), and by an infected vector at 4.0 10(-5) (90% uncertainty interval 5.3 10(-6)-2.0 10(-4)). Equines from high risk regions contributed most to the probability of EEV introduction with 74% on the EEV introduction by equines, whereas low and very low risk regions contributed 18% and 8%, respectively. International movements of horses participating in equestrian events contributed most to the probability of EEV introduction by equines from high risk regions (86%), but also contributed substantially for low and very low risk regions with 47% and 56%. The probability of introducing EEV into The Netherlands is much higher than the probability of introducing AHSV with equines from high risk countries contributing most. The introduction by an infected equine is the most likely pathway. Control measures before exportation of equines showed to have a strong mitigating effect on the probability of EEV introduction. The risk of EEV outbreaks should be taken into account when altering these import regulations.
authors.affiliation: Central Veterinary Institute, Part of Wageningen UR, P.O. Box 65, 8200AB Lelystad, The Netherlands; Department of Farm Animal Health, Faculty of Veterinary Medicine, Utrecht University, Yalelaan 7, 3584 CL Utrecht, The Netherlands. Electronic address: e.a.j.fischer@uu.nl.
authors.forename: Egil Andreas Joor
authors.initials: EAJ
authors.lastname: Fischer
authors.affiliation: Central Veterinary Institute, Part of Wageningen UR, P.O. Box 65, 8200AB Lelystad, The Netherlands.
authors.forename: Evelyn Pamela
authors.initials: EP
authors.lastname: Martínez López
authors.affiliation: Central Veterinary Institute, Part of Wageningen UR, P.O. Box 65, 8200AB Lelystad, The Netherlands.
authors.forename: Clazien J
authors.initials: CJ
authors.lastname: De Vos
authors.affiliation: Central Veterinary Institute, Part of Wageningen UR, P.O. Box 65, 8200AB Lelystad, The Netherlands; INRA UR346 Animal Epidemiology, Vetagrosup, F-69280 Marcy l'Etoile, France. Electronic address: celine.faverjon@vetagro-sup.fr.
authors.forename: Céline
authors.initials: C
authors.lastname: Faverjon
mesh_terms: D000818:Animals; D006734:Horse Diseases / Q000635:transmission* / Q000821:virology; D006736:Horses; D009426:Netherlands; D018163:Orbivirus; D011336:Probability; D012088:Reoviridae Infections / Q000635:transmission / Q000662:veterinary* / Q000821:virology; D012307:Risk Factors
keywords: African horse sickness; Culicoides; Equestrian horses; Equines; Establishment; Import risk assessment; Release; Transmission pattern; Vector-borne