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Open Access Highly Accessed Case report

Clinical observations and management of a severe equine herpesvirus type 1 outbreak with abortion and encephalomyelitis

Jasmin Walter1*, Christoph Seeh2, Kerstin Fey3, Ulrich Bleul1 and Nikolaus Osterrieder4

Author Affiliations

1 Klinik für Reproduktionsmedizin, Vetsuisse-Fakultät Universität Zürich, Winterthurerstrasse 260, Zurich, 8057, Switzerland

2 Pferdegesundheitsdienst, Tierseuchenkasse Baden-Württemberg, Schaflandstrasse 3/3, Fellbach, 70736, Germany

3 Klinik für Pferde – Innere Medizin, Justus-Liebig-Universität, Frankfurter Strasse 126, Giessen, 35392, Germany

4 Institut für Virologie, Freie Universität Berlin, Philippstrasse 13, Berlin, 10115, Germany

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Acta Veterinaria Scandinavica 2013, 55:19  doi:10.1186/1751-0147-55-19

Published: 5 March 2013

Abstract

Latent equine herpesvirus type 1 (EHV-1) infection is common in horse populations worldwide and estimated to reach a prevalence nearing 90% in some areas. The virus causes acute outbreaks of disease that are characterized by abortion and sporadic cases of myeloencephalopathy (EHM), both severe threats to equine facilities. Different strains vary in their abortigenic and neuropathogenic potential and the simultaneous occurrence of EHM and abortion is rare. In this report, we present clinical observations collected during an EHV-1 outbreak caused by a so-called “neuropathogenic” EHV-1 G2254/D752 polymerase (Pol) variant, which has become more prevalent in recent years and is less frequently associated with abortions. In this outbreak with 61 clinically affected horses, 6/7 pregnant mares aborted and 8 horses developed EHM. Three abortions occurred after development of EHM symptoms. Virus detection was performed by nested PCR targeting gB from nasal swabs (11 positive), blood serum (6 positive) and peripheral blood mononuclear cells (9 positive) of a total of 42 horses sampled. All 6 fetuses tested positive for EHV-1 by PCR and 4 by virus isolation. Paired serum neutralization test (SNT) on day 12 and 28 after the index case showed a significant (≥ 4-fold) increase in twelve horses (n = 42; 28.6%). This outbreak with abortions and EHM cases on a single equine facility provided a unique opportunity for the documentation of clinical disease progression as well as diagnostic procedures.

Keywords:
Equine herpesvirus type 1; Neuropathogenicity; Stud; Treatment; Recovery rate; Pregnancy rate