The Effect of Vaccination Status on Total Lymphocyte Count in Horses Affected by Equine Herpes Virus-1 Myeloencephalopathy

Equine herpesvirus 1-induced myeloencephalopathy has a significant impact on the equine industry. Nevertheless, the clinical variables that may affect the severity of the disease are still under investigation. The objective of this research is studying the relationship between the level of lymphopen...

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Main Authors: María de la Cuesta-Torrado, Valentina Vitale, Ana Velloso Alvarez, Patricia Neira-Egea, Clairianne Diss, Juan Cuervo-Arango
Format: Article
Language:English
Published: MDPI AG 2025-04-01
Series:Animals
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Online Access:https://www.mdpi.com/2076-2615/15/7/1019
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author María de la Cuesta-Torrado
Valentina Vitale
Ana Velloso Alvarez
Patricia Neira-Egea
Clairianne Diss
Juan Cuervo-Arango
author_facet María de la Cuesta-Torrado
Valentina Vitale
Ana Velloso Alvarez
Patricia Neira-Egea
Clairianne Diss
Juan Cuervo-Arango
author_sort María de la Cuesta-Torrado
collection DOAJ
description Equine herpesvirus 1-induced myeloencephalopathy has a significant impact on the equine industry. Nevertheless, the clinical variables that may affect the severity of the disease are still under investigation. The objective of this research is studying the relationship between the level of lymphopenia and vaccination status with the severity of the disease in horses at an event, considering whether they had been correctly vaccinated or not prior to exposure to EHV-1. Ten horses were admitted to a veterinary teaching hospital following an equine herpesvirus myeloencephalopathy outbreak during an international show jumping competition in Spain. Data were collected from passport vaccination records, daily analyses, and the clinical histories of the affected horses. Correctly vaccinated horses had a significantly longer hospitalization duration (6/10, 15.5 ± 1.2 days) compared to incorrectly vaccinated horses (4/10, 12.5 ± 1.2 days; <i>p</i> = 0.01). Lymphopenia (<1.6 × 10<sup>3</sup> lymphocytes/µL) was the most common leukogram abnormality. Correctly vaccinated horses demonstrated a higher lymphocyte count compared to incorrectly vaccinated horses within 24 h of admission (<i>p</i> < 0.01). This difference remained significant from days 1 to 4 and on day 6 post-admission (<i>p</i> =0.03). This study found that lymphopenia is a common leukogram alteration in equine herpesvirus 1-infected horses, and horses correctly vaccinated prior to an equine herpesvirus myeloencephalopathy outbreak tend to have a longer hospitalization time. Correctly vaccinated horses exhibited higher lymphocyte counts during the first 24 h and throughout hospitalization compared to incorrectly vaccinated horses. The immune system could play a relevant role in influencing the severity of equine herpesvirus myeloencephalopathy outbreaks, highlighting the need for further studies in this area.
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publishDate 2025-04-01
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spelling doaj-art-b972c78fef4f4bea97b5b713a211385a2025-08-20T02:09:18ZengMDPI AGAnimals2076-26152025-04-01157101910.3390/ani15071019The Effect of Vaccination Status on Total Lymphocyte Count in Horses Affected by Equine Herpes Virus-1 MyeloencephalopathyMaría de la Cuesta-Torrado0Valentina Vitale1Ana Velloso Alvarez2Patricia Neira-Egea3Clairianne Diss4Juan Cuervo-Arango5Department of Animal Medicine and Surgery, Universidad Cardenal Herrera-CEU, CEU Universities, 46115 Alfara del Patriarca, Valencia, SpainDepartment of Animal Medicine and Surgery, Universidad Cardenal Herrera-CEU, CEU Universities, 46115 Alfara del Patriarca, Valencia, SpainDepartment of Animal Medicine and Surgery, Universidad Cardenal Herrera-CEU, CEU Universities, 46115 Alfara del Patriarca, Valencia, SpainVeterinary Teaching Hospital, Universidad Cardenal Herrera-CEU, CEU Universities, 46115 Alfara del Patriarca, Valencia, SpainDepartment of Animal Medicine and Surgery, Universidad Cardenal Herrera-CEU, CEU Universities, 46115 Alfara del Patriarca, Valencia, SpainDepartment of Animal Medicine and Surgery, Universidad Cardenal Herrera-CEU, CEU Universities, 46115 Alfara del Patriarca, Valencia, SpainEquine herpesvirus 1-induced myeloencephalopathy has a significant impact on the equine industry. Nevertheless, the clinical variables that may affect the severity of the disease are still under investigation. The objective of this research is studying the relationship between the level of lymphopenia and vaccination status with the severity of the disease in horses at an event, considering whether they had been correctly vaccinated or not prior to exposure to EHV-1. Ten horses were admitted to a veterinary teaching hospital following an equine herpesvirus myeloencephalopathy outbreak during an international show jumping competition in Spain. Data were collected from passport vaccination records, daily analyses, and the clinical histories of the affected horses. Correctly vaccinated horses had a significantly longer hospitalization duration (6/10, 15.5 ± 1.2 days) compared to incorrectly vaccinated horses (4/10, 12.5 ± 1.2 days; <i>p</i> = 0.01). Lymphopenia (<1.6 × 10<sup>3</sup> lymphocytes/µL) was the most common leukogram abnormality. Correctly vaccinated horses demonstrated a higher lymphocyte count compared to incorrectly vaccinated horses within 24 h of admission (<i>p</i> < 0.01). This difference remained significant from days 1 to 4 and on day 6 post-admission (<i>p</i> =0.03). This study found that lymphopenia is a common leukogram alteration in equine herpesvirus 1-infected horses, and horses correctly vaccinated prior to an equine herpesvirus myeloencephalopathy outbreak tend to have a longer hospitalization time. Correctly vaccinated horses exhibited higher lymphocyte counts during the first 24 h and throughout hospitalization compared to incorrectly vaccinated horses. The immune system could play a relevant role in influencing the severity of equine herpesvirus myeloencephalopathy outbreaks, highlighting the need for further studies in this area.https://www.mdpi.com/2076-2615/15/7/1019equine herpesvirus 1myeloencephalopathyseveritylymphocytesvaccination
spellingShingle María de la Cuesta-Torrado
Valentina Vitale
Ana Velloso Alvarez
Patricia Neira-Egea
Clairianne Diss
Juan Cuervo-Arango
The Effect of Vaccination Status on Total Lymphocyte Count in Horses Affected by Equine Herpes Virus-1 Myeloencephalopathy
Animals
equine herpesvirus 1
myeloencephalopathy
severity
lymphocytes
vaccination
title The Effect of Vaccination Status on Total Lymphocyte Count in Horses Affected by Equine Herpes Virus-1 Myeloencephalopathy
title_full The Effect of Vaccination Status on Total Lymphocyte Count in Horses Affected by Equine Herpes Virus-1 Myeloencephalopathy
title_fullStr The Effect of Vaccination Status on Total Lymphocyte Count in Horses Affected by Equine Herpes Virus-1 Myeloencephalopathy
title_full_unstemmed The Effect of Vaccination Status on Total Lymphocyte Count in Horses Affected by Equine Herpes Virus-1 Myeloencephalopathy
title_short The Effect of Vaccination Status on Total Lymphocyte Count in Horses Affected by Equine Herpes Virus-1 Myeloencephalopathy
title_sort effect of vaccination status on total lymphocyte count in horses affected by equine herpes virus 1 myeloencephalopathy
topic equine herpesvirus 1
myeloencephalopathy
severity
lymphocytes
vaccination
url https://www.mdpi.com/2076-2615/15/7/1019
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