Whole genome sequencing and phylogenetic analysis of the equine infectious anemia virus associated with 2017 Spain outbreaks.
Abstract: In 2017, Spain reported its first equine infectious anemia virus (EIAV) outbreak in 34 years, affecting three horses in two unrelated holdings in Candeleda (Ávila) and Serradilla (Cáceres), with no apparent epidemiological link between premises. Phylogenetic analysis of whole genome and the gene revealed that the Spanish EIAV strains form a distinct monophyletic clade, sharing more than 99% nucleotide identity, suggesting a common contamination event. Interestingly, these three viral strains seem to cluster with North American strains, sharing up to 80.12% nucleotide identity, notably with the Wyoming strain, marking the first such association for European strains. These findings raise important questions regarding the potential routes of EIAV introduction into Spain and highlight the need for enhanced surveillance and genomic characterization to better understand viral transmission dynamics. The online version contains supplementary material available at 10.1186/s12917-025-05100-4.
Publication Date: 2025-12-04 PubMed ID: 41340062PubMed Central: PMC12781545DOI: 10.1186/s12917-025-05100-4Google Scholar: Lookup
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- Journal Article
Summary
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Overview
- This study sequenced and analyzed the entire genome of the equine infectious anemia virus (EIAV) from outbreaks in Spain in 2017.
- The research identified a close genetic relationship between the Spanish EIAV strains and certain North American strains, suggesting a common source and raising questions about virus introduction routes into Spain.
Background and Context
- Equine infectious anemia virus (EIAV) is a retrovirus that infects horses, causing a potentially fatal disease.
- Spain experienced an EIAV outbreak in 2017, which was significant as it was the first outbreak in 34 years in this country.
- The outbreak affected three horses located in two geographically distinct holdings with no known epidemiological connection, located in Ávila and Cáceres regions.
Research Objectives
- To perform whole genome sequencing of the EIAV strains isolated from the 2017 Spanish outbreaks.
- To conduct phylogenetic analyses to understand the genetic relationship between these new Spanish strains and other known EIAV strains worldwide.
- To investigate the possible sources and transmission routes of EIAV into Spain.
Methods
- Whole genome sequencing techniques were used to obtain the complete viral genetic data from the infected horses.
- Phylogenetic analysis was performed using both the whole genome and specific viral genes (notably the env gene) to assess genetic relatedness.
- The sequences were compared with global EIAV reference strains, including those from North America.
Key Findings
- The three Spanish EIAV strains closely clustered together, forming a distinct monophyletic clade, indicating a shared contamination or introduction event.
- The strains showed over 99% nucleotide identity among themselves, supporting the idea of a common source within Spain.
- Interestingly, phylogenetic comparisons revealed that these Spanish strains are most closely related to North American EIAV strains, particularly the Wyoming strain.
- The nucleotide identity between the Spanish and North American strains was around 80.12%, which is notable for European viral strains, marking the first reported genetic link of this nature.
Implications
- The close relationship between Spanish and North American EIAV strains points to possible introduction pathways, such as importation of horses or equine products, though these remain to be definitively identified.
- There may be a need to review and enhance the surveillance protocols for EIAV, especially monitoring animal movement and international trade connections.
- Genomic characterization of EIAV is crucial for improving understanding of viral epidemiology and transmission patterns in Europe and globally.
- The findings suggest that EIAV might be more widespread or have a higher risk of spread via international routes than previously considered.
Conclusion
- This research provides the first complete genome sequences of EIAV from Spain and identifies a close genetic link with North American strains.
- The study highlights the importance of genomic surveillance and phylogenetic analysis in tracing the origins of viral outbreaks and informing disease prevention strategies.
- Further investigations are needed to clarify how EIAV was introduced into Spain and to strengthen control measures to prevent future outbreaks.
Cite This Article
APA
(2025).
Whole genome sequencing and phylogenetic analysis of the equine infectious anemia virus associated with 2017 Spain outbreaks.
BMC Vet Res, 22(1), 10.
https://doi.org/10.1186/s12917-025-05100-4 Publication
Researcher Affiliations
Grant Funding
- CPER 2015-2020 / French Ministry of Higher Education
- 21E1168/ 00061963 / Regional Council of Normandie - Chaire d'Excellence
- European Commission through DG SANTÉ funding for the Reference Laboratory for Equine Diseases other than African Horse Sickness / European Commission through DG SANTÉ
Conflict of Interest Statement
Declarations. Ethics approval and consent to participate: No ethical approval was required since this study deals with naturally infected horses. EIA is a notifiable disease in Spain; as such, the Spanish legislation enforces euthanasia of EIA positive horses as stated in the Royal Decree 1347/92. In this context, blood and organ collection from EIA positive horse was performed following strictly the Spanish authority regulation regarding Equine infectious anemia which approved the collection of samples from EIA infected horses. Consent for publication: Not applicable. Competing Interests: The authors declare no competing interests.
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