Detection and molecular characterisation of equine infectious anaemia virus from field outbreaks in Slovenia.

Reasons For Performing This Study: In 2009, a surprisingly high number of animals seropositive for equine infectious anaemia virus (EIAV; 26 horses from 13 farms) were detected in Slovenia.

Objectives: To develop a polymerase chain reaction (PCR) assay for the detection of the proviral nucleic acid, to phylogenetically characterise the Slovenian EIAV strains and to investigate whether transmission in utero occurred.

Study Design: Cross-sectional clinical study.

Methods: In total, 26 horses (including 2 foals and 4 pregnant mares) and 4 fetuses were examined in this study. A PCR assay using the EIAV F1 and EIAV R1 primers was designed and tested using genomic DNA extracted from 28 spleen samples, 18 whole blood samples and 17 peripheral blood leucocyte samples. Amplicons of 22 PCRs obtained from the spleen samples were subjected to direct DNA sequencing and phylogenetic analysis.

Results: All spleen samples from 22 adult animals were positive for EIAV by PCR, whereas whole blood and the peripheral blood leucocyte samples were positive from only 4 animals. Spleen samples from foals and fetuses were negative by PCR. The Slovenian EIAV sequences could be mapped to 9 different branches of the phylogenetic tree.

Conclusions: The PCR was able to detect different EIAV strains from spleen samples of seropositive animals detected in Slovenia. Phylogenetic analysis revealed high genetic diversity of the EIAV strains detected in Slovenia, with their closest relatives being European strains. In utero transmission in pregnant mares did not occur.