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International journal of molecular sciences2025; 26(17); 8298; doi: 10.3390/ijms26178298

Genetic Diversity of Equid Herpesvirus 5 in Temporal Samples from Mares and Their Foals at Three Polish National Studs.

Abstract: Equid herpesvirus 5 (EHV-5) comprises a group of heterogeneous viruses with a worldwide distribution. Primary infection typically occurs early in life, which is followed by latency and periodic recrudescence of the virus. The aim of this study was to determine the genetic variation of EHV-5 in individual animals over time and to determine the dynamics of EHV-5 spread among selected mare-foal pairs at three horse studs. The partial glycoprotein B () gene was amplified from archival nasal swab samples. Sequences from 3-5 clones from each PCR product were compared using identity matrix, phylogeny, and median-joining haplotype networks. Overall, 328 clones were sequenced from long PCR products amplified from 84 EHV-5 PCR-positive swabs. The sequences were heterogeneous (89.4% to 100% nucleotide identity). The EHV-5 sequences from mares and their foals most often clustered separately, although similar EHV-5 sequences from the same mare-foal pair were also recovered. For some animals, the EHV-5 sequences from multiple sampling times clustered together, while sequences from other animals were distributed throughout the networks. Clones from the same PCR product were most often similar to each other, but divergent clones from the same PCR product were also apparent. In conclusion, the foals were likely to acquire EHV-5 infection from sources other than their dams, but some exchange of EHV-5 between mares and their foals also occurred. Some foals likely acquired EHV-5 from a single source, while others from multiple sources. These data contribute to our understanding of EHV-5 variability and the dynamics of infection in individual horses.
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Publication Date: 2025-08-27 PubMed ID: 40943220PubMed Central: PMC12428152DOI: 10.3390/ijms26178298Google Scholar: Lookup
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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 genetic diversity of Equid herpesvirus 5 (EHV-5) in mares and their foals over time at three Polish national horse studs.
  • The research aimed to understand how EHV-5 spreads between mares and foals and within individual horses, using genetic sequencing of viral samples collected longitudinally.

Background on Equid Herpesvirus 5 (EHV-5)

  • EHV-5 is a group of genetically diverse viruses found worldwide that infect horses.
  • Infection usually happens early in life and is characterized by a latent phase, where the virus remains dormant, and periodic reactivation (recrudescence).
  • Understanding EHV-5’s genetic variation is important for tracking infection dynamics and potential impacts on horse health.

Objectives of the Study

  • To determine the genetic variation of EHV-5 within individual horses over time.
  • To analyze how EHV-5 spreads among mares and their foals at three different Polish national horse studs.
  • To see if foals acquire the virus primarily from their dams or from other sources within the stud environment.

Methodology

  • Archival nasal swab samples were collected from mares and their foals that tested positive for EHV-5 by PCR.
  • The partial glycoprotein B (gB) gene of EHV-5 was amplified from these samples using long PCR.
  • From each PCR product, 3-5 clones were sequenced to capture genetic diversity within the sample.
  • A total of 328 clones from 84 PCR-positive swabs were sequenced.
  • Sequence comparison techniques included identity matrices to measure nucleotide similarity, phylogenetic tree construction, and median-joining haplotype network analysis.

Key Findings

  • The EHV-5 sequences showed high heterogeneity, with nucleotide identity ranging from 89.4% to 100%, indicating substantial viral genetic diversity.
  • Sequences from mares and their foals generally clustered separately in genetic analyses, suggesting limited direct transmission from mare to foal.
  • However, some mare-foal pairs shared highly similar viral sequences, indicating occasional transmission between them.
  • In some individual horses sampled multiple times, viral sequences from different time points clustered tightly together, implying persistent infection with a stable viral population.
  • Other horses showed viral sequences that were scattered across the networks, suggesting either multiple infection events or ongoing viral evolution within the host.
  • Within individual PCR samples, clones usually were genetically similar, but divergent clones co-occurred, demonstrating mixed viral populations in a single swab.

Conclusions and Implications

  • Foals appear to acquire EHV-5 infections primarily from sources other than their dams, likely from other horses or the environment within the stud.
  • Some mare-foal viral exchange occurs, but it is not the dominant transmission route.
  • Infection sources vary between foals – some are infected by a single viral strain, while others carry multiple genetically distinct EHV-5 variants.
  • The research enhances understanding of EHV-5 genetic diversity and infection dynamics, providing insight into viral persistence and transmission in horse populations.
  • These findings could inform biosecurity and infection control strategies at horse breeding facilities to limit spread of EHV-5.

Cite This Article

APA
Stasiak K, Dunowska M, Rola J. (2025). Genetic Diversity of Equid Herpesvirus 5 in Temporal Samples from Mares and Their Foals at Three Polish National Studs. Int J Mol Sci, 26(17), 8298. https://doi.org/10.3390/ijms26178298

Publication

International journal of molecular sciences
ISSN: 1422-0067
NlmUniqueID: 101092791
Country: Switzerland
Language: English
Volume: 26
Issue: 17
PII: 8298

Researcher Affiliations

Stasiak, Karol
  • Department of Virology and Viral Animal Diseases, National Veterinary Research Institute, Al. Partyzantow 57, 24-100 Pulawy, Poland.
Dunowska, Magdalena
  • School of Veterinary Science, Massey University, Palmerston North 4442, New Zealand.
Rola, Jerzy
  • Department of Virology and Viral Animal Diseases, National Veterinary Research Institute, Al. Partyzantow 57, 24-100 Pulawy, Poland.

MeSH Terms

  • Animals
  • Horses / virology
  • Genetic Variation
  • Phylogeny
  • Herpesviridae Infections / veterinary
  • Herpesviridae Infections / virology
  • Poland
  • Female
  • Horse Diseases / virology

Conflict of Interest Statement

The authors declare no conflicts of interest.

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