Whole genome sequencing and phylogenetic analysis of the equine infectious anemia virus associated with 2017 Spain outbreaks.
Authors: Wiernasz N, Deshiere A, Agüero M, Garcia E, de la Haza R, Cáceres G, Touzain F, Blanchard Y, Lecouturier F, Froger D, Berthet N, Hans A, Valle-Casuso J C
Journal: BMC veterinary research
Summary
Spain's re-emergence of equine infectious anemia virus (EIAV) in 2017—the first documented outbreak in 34 years—prompted genomic investigation into three affected horses across two geographically and epidemiologically unrelated holdings in Ávila and Cáceres provinces. Whole genome sequencing and phylogenetic analysis revealed that all three Spanish strains shared >99% nucleotide identity, indicating they likely originated from a single contamination event rather than independent introductions. Most significantly, these European strains clustered closely with North American isolates (particularly the Wyoming strain, sharing 80.12% identity), representing the first documented association between EIAV strains from these continents and raising critical questions about potential vectors of viral introduction into Spain—whether through imported horses, contaminated equipment, or other transmission routes. For equine professionals, these findings underscore the importance of rigorous biosecurity protocols and traceability systems, especially given EIAV's ability to persist undetected; enhanced genomic surveillance capacity will be essential for early detection and epidemiological investigation of future cases. The unexpected phylogenetic relationship also warrants investigation into whether this represents an isolated incursion or signals broader viral movement patterns that could affect other European populations.
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Practical Takeaways
- •EIAV remains a biosecurity risk in Europe despite decades without reported cases; enhanced surveillance and testing protocols are critical for early detection
- •The genetic link between Spanish and North American EIAV strains suggests potential international transmission routes (possibly through imported animals or contaminated equipment); review your source verification and quarantine procedures for new acquisitions
- •Even unrelated premises can be infected from a common source; investigate potential shared risk factors such as shared farriers, veterinary equipment, or bloodborne transmission when EIAV is suspected
Key Findings
- •Three horses in Spain tested positive for EIAV in 2017, the first outbreak in 34 years, occurring in two unrelated holdings with no apparent epidemiological link
- •Spanish EIAV strains shared >99% nucleotide identity, indicating a common contamination event despite geographic separation
- •Spanish EIAV strains clustered with North American strains (80.12% identity with Wyoming strain), the first such association documented for European strains