Whole genome sequencing and phylogenetic analysis of the equine infectious anemia virus associated with 2017 Spain outbreaks.

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 gag 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.