Detection, molecular characterization and phylogenetic analysis of full-length equine infectious anemia (EIAV) gag genes isolated from Shackleford Banks wild horses.

The study examines and characterizes the gene sequences related to Equine Infectious Anemia Virus (EIAV) in the wild horse population of Shackleford Banks, North Carolina. It discovers that the horses are infected with a distinct strain of EIAV, which can lay dormant for years before leading to severe illness.

Research Context and Objectives

• This research was conducted against the backdrop of a notable prevalence of Equine Infectious Anemia Virus (EIAV) among the wild horses of Shackleford Banks, North Carolina. In a 1996 survey, 41% of the gathered horses tested positive for EIAV.
• The main objectives of the research were to detect the presence of the EIAV gag gene, perform molecular characterization and carry out phylogenetic analysis to understand the nature and origin of the virus strain prevalent among these horses.

Observations and Findings

• Two horses that had been in quarantine for 10 and 11 years respectively, showed late clinical signs of EIA. One of these cases was so critical that euthanasia was the only relief. The other survived but experienced another episode of EIA within a month.
• A third horse also developed severe clinical EIA after an extended period in quarantine.
• This provided evidence that the EIAV strain prevalent in these horses can remain dormant and undetected for years, potentially causing severe health episodes much later after the initial exposure.

Phylogenetic Analysis and Conclusion

• The researchers carried out a phylogenetic analysis of the complete EIAV gag gene sequences obtained from the three horses. This was to understand the relationship of this strain with other forms of the virus.
• They found that although very closely related amongst themselves, the virus strains present in these horses were distinct from all others examined in the study. This distinct group primarily comprised isolates from the New World and is significantly different from some recently characterized Central European EIAV strains.
• This suggests that these wild horses, believed to be the direct descendants of the Spanish stock, carry a unique strain of EIAV which belongs to a distinct monophyletic group essentially from New World isolates.