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Nucleic acid detection and molecular traceability of equine herpesvirus 1 in imported horses.
Abstract: Equid alphaherpesvirus 1 is a major pathogen threatening the global equine industry, causing respiratory disease, abortion, and neurological disease. Unassigned: In April 2024, during routine pathogen screening of a batch of imported quarantine horses from the Netherlands, four out of 20 nasal swab samples tested positive for EHV-1 nucleic acid. Unassigned: The affected horses exhibited only mild respiratory signs. ORF30 SNP typing at nucleotide position 2254 and Sanger sequencing confirmed that all positive samples belonged to the N752 non-neuropathogenic genotype. As virus isolation was unsuccessful, the ORF30, ORF33, and ORF34 gene fragments were amplified and sequenced directly from the positive samples. The complete identity of these gene sequences across all four samples indicated that they were caused by the same strain. Bayesian phylogenetic analysis based on concatenated multi-sequence alignment revealed that all reference strains first divided into two distinct clades according to host range: Clade A encompassed , , and , whereas Clade B was strictly restricted to . The strain identified in this study (EHV-1/China/2024) was located within the broadly host-adapted Clade A and formed a monophyletic group with an -derived strain isolated in Ireland in 2017 (MZ318706) with high posterior probability, which subsequently clustered with a sister group comprising another Irish -derived strain and a UK -derived strain, collectively constituting a predominantly European-derived evolutionary cluster. Unassigned: While the horses were imported from the Netherlands, the evolutionary background of the virus pointed to the Ireland/British Isles region, suggesting that the strain may have entered the Netherlands via the European equine trade network before being introduced. This study reveals the molecular characteristics and phylogenetic position of EHV-1 carried by imported horses and uncovers a geographic discordance between the evolutionary background of the virus and its direct country of origin, providing molecular evidence for understanding the international transmission dynamics of EHV-1 and pathogen surveillance in cross-border equine movements.
Copyright © 2026 Wang, Gao, Bai, Pu, Shi, Zhang, Xu and Li.
Publication Date: 2026-08-03 PubMed ID: 42609401PubMed Central: PMC13478101DOI: 10.3389/fmicb.2026.1900100Google Scholar: Lookup The Equine Research Bank provides access to a large database of publicly available scientific literature. Inclusion in the Research Bank does not imply endorsement of study methods or findings by Mad Barn.
- Journal Article
Summary
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Nucleic acid from equine herpesvirus 1 (EHV-1), a virus affecting horses worldwide, was detected in imported horses, and genetic analysis revealed the virus’s likely evolutionary origin in the British Isles despite the horses’ direct import from the Netherlands.
Introduction to Equine Herpesvirus 1 (EHV-1)
- EHV-1 is a significant infectious virus in horses causing respiratory illness, abortions, and neurological disorders.
- It poses a serious threat to the global equine industry due to its contagious nature and severe clinical outcomes.
Detection of EHV-1 in Imported Horses
- In April 2024, routine screening of nasal swabs from 20 imported horses from the Netherlands identified EHV-1 nucleic acid in 4 samples.
- The horses with positive tests showed mild respiratory symptoms, indicative of a non-severe infection.
Genotypic and Molecular Analysis of the Virus
- ORF30 gene sequencing identified the virus as the N752 genotype, which is known to be non-neuropathogenic (less likely to cause neurological disease).
- Virus isolation attempts failed, so direct amplification and sequencing of viral gene fragments (ORF30, ORF33, ORF34) were performed from the samples.
- All sequences from the four positive samples were identical, suggesting infection by a single viral strain.
Phylogenetic and Evolutionary Insights
- Using Bayesian phylogenetic analysis on concatenated gene sequences, the study categorized EHV-1 strains into two distinct clades based on host range:
- Clade A: Broad host range including different equine species
- Clade B: Restricted to a specific host group
- The detected strain (labeled EHV-1/China/2024) belonged to Clade A.
- This strain showed a close evolutionary relationship with a strain isolated in Ireland in 2017 and clustered further with other Irish and UK strains, forming a predominantly European evolutionary group.
Geographic and Epidemiological Significance
- Although the infected horses were imported directly from the Netherlands, the virus strain’s evolutionary background points to the British Isles region (Ireland and the UK).
- This finding implies that the EHV-1 strain may have spread from the British Isles to the Netherlands via intra-European equine trade before entering China.
- There is a geographic discordance between the virus’s genetic origin and the immediate source country of the horses.
Implications for Disease Surveillance and Control
- The study provides molecular evidence on the cross-border transmission dynamics of EHV-1 within Europe and internationally.
- It stresses the importance of molecular tracing and pathogen surveillance in managing international horse trade to monitor and control the spread of infectious diseases like EHV-1.
- Understanding viral phylogeny helps in tracking virus movement patterns and can inform biosecurity practices and quarantine protocols.
Cite This Article
APA
Wang L, Gao Z, Bai Z, Pu J, Shi X, Zhang W, Xu Z, Li Z.
(2026).
Nucleic acid detection and molecular traceability of equine herpesvirus 1 in imported horses.
Front Microbiol, 17, 1900100.
https://doi.org/10.3389/fmicb.2026.1900100 Publication
Researcher Affiliations
- Science and Technology Research Center of China Customs, Beijing, China.
- Science and Technology Research Center of China Customs, Beijing, China.
- Science and Technology Research Center of China Customs, Beijing, China.
- Science and Technology Research Center of China Customs, Beijing, China.
- Science and Technology Research Center of China Customs, Beijing, China.
- Science and Technology Research Center of China Customs, Beijing, China.
- Science and Technology Research Center of China Customs, Beijing, China.
- Science and Technology Research Center of China Customs, Beijing, China.
Conflict of Interest Statement
The author(s) declared that this work was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.
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