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Transboundary and emerging diseases2011; 59(3); 256-263; doi: 10.1111/j.1865-1682.2011.01263.x

Outbreak of equine herpesvirus myeloencephalopathy in France: a clinical and molecular investigation.

Abstract: Equid herpesvirus 1 (EHV-1)-associated myeloencephalopathy (EHM) is a disease affecting the central nervous system of horses. Despite the constantly increasing interest about this syndrome, epidemiological data are limited especially when related to the description of large outbreaks. The aim of this article is to describe clinical, virological and molecular data obtained throughout a severe outbreak of EHM, with emphasis on laboratory diagnostic methods. The epidemic disease concerned a riding school in France where 7/66 horses aged 12-22 years developed signs of neurological disease in July 2009. Diagnosis of EHM was supported by EHV-1 detection using both real-time PCR and virus culture, and SNP-PCR test for viral strain characterization. EHM morbidity was 10.6% (7/66), mortality was 7.5% (5/66) and case fatality rate was 71.4% (5/7). Clinical presentation of the disease was characterized by the fact that fever was systematically present within 2 days before the severe neurological signs were noted. EHV-1 was detected by PCR in each available blood and nasal swab samples. Neuropathogenic strain only (G(2254) ) was isolated during the current outbreak; C(t) values, used as an indicative level of the viral load, ranged 26.0-37.0 among the six sampled horses. The amount of virus in biological samples was not systematically related to the intensity of the clinical signs being observed. In conclusion, this article described a severe outbreak of EHM while limited in time and restricted to one premise. Molecular data strongly suggested taking into account any low viral load as being a potential risk factor for neurological manifestations.
© 2011 Blackwell Verlag GmbH.
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Publication Date: 2011-10-04 PubMed ID: 21975071DOI: 10.1111/j.1865-1682.2011.01263.xGoogle Scholar: Lookup
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Summary

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This article presents a detailed investigation of a severe outbreak of Equid herpesvirus 1 (EHV-1)-associated myeloencephalopathy (EHM), a neurological disease affecting horses, in a riding school in France in 2009. By sharing clinical, virological, and molecular data, the researchers underscore the importance of taking into account even low viral loads as potential risk factors for neurological manifestations of this disease.

Background to the Study

  • The disease being studied here is Equid herpesvirus 1 (EHV-1)-associated myeloencephalopathy (EHM), a condition that affects the central nervous system of horses. The interest in this disease has been growing, but there’s a lack of detailed epidemiological data, especially related to large outbreaks.
  • The study delves into a severe outbreak that happened in a riding school in France in July 2009, affecting 7 of the 66 horses aged between 12 and 22 years.

Epidemiology and Clinical Presentation

  • The researchers noted that EHM morbidity was 10.6% (7 out of 66 horses), mortality was 7.5% (5 out of 66 horses), and the case fatality rate was quite high at 71.4% (5 out of 7 cases).
  • The telltale sign of the disease was that the horses systematically developed a fever within two days before the severe neurological symptoms set in.

Diagnostic Methods and Findings

  • To support the diagnosis of EHM, the researchers employed various techniques, including real-time PCR and virus culture for EHV-1 detection, and SNP-PCR for viral strain characterization.
  • In all available samples of blood and nasal swabs collected from the horses, EHV-1 was detected by PCR. Only the neuropathogenic strain of the virus (G(2254)) was isolated during the outbreak.
  • The researchers used Cycle threshold (Ct) values as indicators of the viral load. The Ct values among the six sampled horses ranged between 26.0 and 37.0. Interestingly, they also noted that the amount of virus in the samples wasn’t always directly proportional to the severity of the observed clinical signs.

Conclusions of the Study

  • With this study, the researchers have provided a detailed description of a severe, though temporally limited and geographically restricted, outbreak of EHM.
  • The most important takeaway is the strong suggestion that even low viral loads of EHV-1 should be considered as potential risk factors for the neurological manifestations of this disease. This may have significant implications for future surveillance and management strategies for the control of EHM.

Cite This Article

APA
Pronost S, Legrand L, Pitel PH, Wegge B, Lissens J, Freymuth F, Richard E, Fortier G. (2011). Outbreak of equine herpesvirus myeloencephalopathy in France: a clinical and molecular investigation. Transbound Emerg Dis, 59(3), 256-263. https://doi.org/10.1111/j.1865-1682.2011.01263.x

Publication

Transboundary and emerging diseases
ISSN: 1865-1682
NlmUniqueID: 101319538
Country: Germany
Language: English
Volume: 59
Issue: 3
Pages: 256-263

Researcher Affiliations

Pronost, S
  • Frank Duncombe Laboratory, IFR 146 ICORE, University of Caen Basse-Normandie, Caen Cedex, France. stephane.pronost@calvados.fr
Legrand, L
    Pitel, P-H
      Wegge, B
        Lissens, J
          Freymuth, F
            Richard, E
              Fortier, G

                MeSH Terms

                • Animals
                • Disease Outbreaks / veterinary
                • Encephalomyelitis / epidemiology
                • Encephalomyelitis / prevention & control
                • Encephalomyelitis / veterinary
                • Encephalomyelitis / virology
                • Female
                • France / epidemiology
                • Herpesviridae Infections / epidemiology
                • Herpesviridae Infections / prevention & control
                • Herpesviridae Infections / veterinary
                • Herpesviridae Infections / virology
                • Herpesvirus 1, Equid
                • Horse Diseases / epidemiology
                • Horse Diseases / prevention & control
                • Horses
                • Male
                • Viral Vaccines / immunology

                Citations

                This article has been cited 18 times.
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