Detection and molecular characterisation of equine infectious anaemia virus from field outbreaks in Slovenia.
Authors: Kuhar U, Završnik J, Toplak I, Malovrh T
Journal: Equine veterinary journal
Summary
# Editorial Summary: Detection and molecular characterisation of equine infectious anaemia virus from field outbreaks in Slovenia A 2009 outbreak in Slovenia resulted in the unexpected identification of 26 seropositive horses across 13 farms, prompting Kuhar and colleagues to develop a sensitive PCR assay for detecting EIAV proviral DNA and to characterise the genetic diversity of circulating strains in the region. Using tissue samples from infected animals including pregnant mares and foals, the researchers tested spleen, whole blood and peripheral blood leucocyte samples with custom-designed PCR primers, followed by direct sequencing and phylogenetic analysis of positive amplicons. The PCR demonstrated superior sensitivity in spleen tissue, with 22 of 22 adult samples positive compared to only 4 positive peripheral blood samples; notably, all foetal and foal samples tested negative, indicating that intrauterine transmission had not occurred despite four pregnant mares being infected. Phylogenetic mapping revealed substantial genetic heterogeneity among the Slovenian isolates, distributed across nine distinct branches and clustering most closely with other European EIAV strains rather than forming a single outbreak lineage. These findings underscore the importance of tissue sampling strategy when screening for EIAV in carrier animals, whilst the high genetic diversity suggests either long-standing endemic circulation or multiple independent introductions, with significant implications for regional surveillance and understanding transmission routes in infected populations.
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Practical Takeaways
- •Spleen samples are significantly more reliable than blood samples for PCR detection of EIAV in seropositive horses, improving diagnostic accuracy in field outbreaks
- •High genetic diversity of EIAV strains circulating in Slovenia suggests multiple independent introductions or substantial viral evolution, requiring strain-specific surveillance protocols
- •In utero transmission does not appear to be a significant transmission route for EIAV, suggesting foals born to infected mares may not be at direct risk through vertical transmission
Key Findings
- •PCR assay successfully detected EIAV proviral nucleic acid in spleen samples from 22 of 22 adult seropositive horses, but only 4 of 26 whole blood and peripheral blood leucocyte samples were positive
- •Slovenian EIAV strains mapped to 9 different phylogenetic branches with high genetic diversity and closest relationships to European strains
- •In utero transmission did not occur in 4 pregnant mares or 2 foals examined, with all foal and fetus samples testing negative by PCR