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Journal of veterinary internal medicine2024; 38(3); 1799-1807; doi: 10.1111/jvim.17070

Long-term performance of show-jumping horses and relationship with severity of ataxia and complications associated with myeloencephalopathy caused by equine herpes virus-1.

Abstract: Equine herpesvirus myeloencephalopathy (EHM) has severe impact on the sport horse population. Objective: Study the influence of EHM on the likelihood of affected horses to return to their previous performance and investigate the association of clinical variables with prognosis. Methods: Twenty-six horses positive for equine herpesvirus type 1 (EHV-1) were admitted to a veterinary teaching hospital (VTH) during a natural EHM outbreak at an international jumping event. Methods: Data collected from the VTH, the International Equestrian Federation, and surveys completed by the riders and horse owners were retrospectively analyzed. Results: Horses affected by EHM had 68% chance of returning to exercise, and 52.9% were able to achieve their preoutbreak performance level. Horses with an ataxia grade at admission ≥4/5 had an increased fatality rate (P < .05) and 10% chance of reaching their preoutbreak performance level. None of the horses with both vascular and urinary complications returned to their previous performance level. Finally, horses vaccinated against EHV-1 and those with urinary complications had a 71.4% and 43.7% fatality rate, respectively. Conclusions: Horses affected by EHM were able to return to their previous performance levels, but certain clinical variables were negatively associated with postoutbreak performance. Ataxia grade upon admission and the development of systemic signs of vasculitis and urinary complications were potential poor prognostic indicators in sport horses. Variables linked to fatality included prior vaccination against EHV-1, ataxia grade upon admission, and the development of urinary complications.
© 2024 The Authors. Journal of Veterinary Internal Medicine published by Wiley Periodicals LLC on behalf of American College of Veterinary Internal Medicine.
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Publication Date: 2024-04-12 PubMed ID: 38609161PubMed Central: PMC11099729DOI: 10.1111/jvim.17070Google Scholar: Lookup
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  • Journal Article

Summary

This research summary has been generated with artificial intelligence and may contain errors and omissions. Refer to the original study to confirm details provided. Submit correction.

Overview

  • This study investigated the long-term impact of equine herpesvirus myeloencephalopathy (EHM) on show-jumping horses, focusing on their ability to return to previous performance levels and identifying clinical factors that predict outcomes.
  • It analyzed data from horses affected during a natural EHM outbreak, evaluating their neurological status, complications, and vaccination status to determine prognosis and performance recovery.

Background and Objective

  • Equine Herpesvirus Myeloencephalopathy (EHM): A serious neurological disease in horses caused by equine herpesvirus type 1 (EHV-1), leading to varying degrees of neurological impairment such as ataxia (loss of coordination).
  • Impact on Sport Horses: EHM can affect the performance and career longevity of sport horses, especially those competing in show jumping.
  • Objective: The researchers aimed to determine how EHM influences the likelihood of horses returning to previous exercise and performance levels, and to identify clinical variables that predict outcomes and fatality.

Methods

  • Population Studied: 26 horses confirmed infected with EHV-1 admitted to a veterinary teaching hospital during a natural EHM outbreak at an international jumping event.
  • Data Collection:
    • Medical records from the veterinary teaching hospital.
    • Performance data from the International Equestrian Federation.
    • Surveys completed by riders and horse owners to assess recovery and performance after infection.
  • Retrospective Analysis: All data sources were combined retrospectively to analyze long-term outcomes.

Key Results

  • Return to Exercise and Performance:
    • 68% of horses affected by EHM returned to exercise.
    • Approximately 53% (52.9%) were able to reach their pre-outbreak competition performance levels.
  • Ataxia Severity:
    • Horses with a high ataxia grade (≥ 4/5 at admission) had a significantly increased fatality rate.
    • Only about 10% of these severely ataxic horses recovered to pre-outbreak performance levels.
  • Complications Affecting Prognosis:
    • Horses presenting both vascular complications (signs of vasculitis) and urinary complications did not return to their prior performance levels.
    • Development of these systemic signs appeared to be poor prognostic indicators.
  • Vaccination and Fatality:
    • Interestingly, horses vaccinated against EHV-1 had a high fatality rate of 71.4%.
    • Urinary complications were also associated with a 43.7% fatality rate.

Conclusions and Clinical Implications

  • Recovery Potential: Many horses affected by EHM can survive and resume competitive athletic activity, with over half regaining their previous performance levels.
  • Prognostic Indicators:
    • Higher ataxia grade scores at admission strongly predict poor outcome and decreased likelihood of performance recovery.
    • Systemic complications like vasculitis and urinary dysfunction are associated with worse outcomes and inability to resume prior performance.
  • Vaccination Insights:
    • The association between prior EHV-1 vaccination and higher fatality suggests complex interactions affecting disease severity that warrant further research.
  • Clinical Usefulness:
    • These identified variables can help veterinarians and trainers with prognosis counseling and decision-making after EHM outbreaks.
    • Early assessment of ataxia grade and monitoring for vascular and urinary complications are critical for guiding treatment and expectations.

Cite This Article

APA
de la Cuesta-Torrado M, Velloso Alvarez A, Neira-Egea P, Cuervo-Arango J. (2024). Long-term performance of show-jumping horses and relationship with severity of ataxia and complications associated with myeloencephalopathy caused by equine herpes virus-1. J Vet Intern Med, 38(3), 1799-1807. https://doi.org/10.1111/jvim.17070

Publication

Journal of veterinary internal medicine
ISSN: 1939-1676
NlmUniqueID: 8708660
Country: United States
Language: English
Volume: 38
Issue: 3
Pages: 1799-1807

Researcher Affiliations

de la Cuesta-Torrado, María
  • Department of Animal Medicine and Surgery, Universidad CEU-Cardenal Herrera, CEU Universities, Valencia, Spain.
  • Veterinary Teaching Hospital, Universidad Cardenal Herrera CEU, Valencia, Spain.
Velloso Alvarez, Ana
  • Department of Animal Medicine and Surgery, Universidad CEU-Cardenal Herrera, CEU Universities, Valencia, Spain.
  • Veterinary Teaching Hospital, Universidad Cardenal Herrera CEU, Valencia, Spain.
Neira-Egea, Patricia
  • Veterinary Teaching Hospital, Universidad Cardenal Herrera CEU, Valencia, Spain.
Cuervo-Arango, Juan
  • Department of Animal Medicine and Surgery, Universidad CEU-Cardenal Herrera, CEU Universities, Valencia, Spain.
  • Veterinary Teaching Hospital, Universidad Cardenal Herrera CEU, Valencia, Spain.

MeSH Terms

  • Animals
  • Horses
  • Herpesvirus 1, Equid
  • Horse Diseases / virology
  • Ataxia / veterinary
  • Ataxia / virology
  • Retrospective Studies
  • Herpesviridae Infections / veterinary
  • Herpesviridae Infections / virology
  • Herpesviridae Infections / complications
  • Male
  • Female
  • Physical Conditioning, Animal
  • Sports

Conflict of Interest Statement

The authors declare no conflict of interest.

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Citations

This article has been cited 4 times.
  1. Musoles-Cuenca B, Padilla-Blanco M, Vitale V, Lorenzo-Bermejo T, de la Cuesta-Torrado M, Ballester B, Maiques E, Rubio-Guerri C, Velloso Alvarez A. First Molecular Evidence of Equine Herpesvirus Type 1 (EHV-1) in Ocular Swabs of Clinically Affected Horses. Viruses 2025 Jun 18;17(6).
    doi: 10.3390/v17060862pubmed: 40573453google scholar: lookup
  2. de la Cuesta-Torrado M, Vitale V, Velloso Alvarez A, Neira-Egea P, Diss C, Cuervo-Arango J. The Effect of Vaccination Status on Total Lymphocyte Count in Horses Affected by Equine Herpes Virus-1 Myeloencephalopathy. Animals (Basel) 2025 Apr 1;15(7).
    doi: 10.3390/ani15071019pubmed: 40218411google scholar: lookup
  3. de la Cuesta-Torrado M, Velloso Alvarez A, Santiago-Llorente I, Armengou L, Nieto F, Ríos J, Cruz-López F, Jose-Cunilleras E. Risk Factors and Long-Term Outcomes in Horses After the 2021 Outbreak of Equine Herpesvirus 1 Myeloencephalopathy, Valencia, Spain. J Vet Intern Med 2025 Mar-Apr;39(2):e70040.
    doi: 10.1111/jvim.70040pubmed: 40055829google scholar: lookup
  4. de la Cuesta-Torrado M, Velloso Alvarez A, Cárdenas-Rebollo JM, Neira-Egea P, Vitale V, Cuervo-Arango J. Comparison of clinical variables and outcome of 2 natural equine herpesvirus myeloencephalopathy outbreaks induced by equine herpesvirus-1 A2254/N752 strain in sport horses. J Vet Intern Med 2025 Jan-Feb;39(1):e17287.
    doi: 10.1111/jvim.17287pubmed: 39778904google scholar: lookup
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