Clinical course of ophthalmic findings and potential influence factors of herpesvirus infections: 18 month follow-up of a closed herd of lipizzaners.
Authors: Rushton James O, Kolodziejek Jolanta, Tichy Alexander, Nowotny Norbert, Nell Barbara
Journal: PloS one
Summary
# Editorial Summary Equine herpesvirus types 2 and 5 (EHV-2 and EHV-5) have long been suspected in ocular disease, yet the true causal relationship remained unclear. Researchers conducted a longitudinal study of 266 Lipizzaners across Austrian studs, performing ophthalmological examinations and collecting blood, nasal and conjunctival samples every six months over 18 months, with herpesvirus detection via PCR and qPCR analysis alongside statistical modelling to identify associations with ocular findings. Younger horses showed significantly higher rates of herpesvirus detection, though corneal pathologies paradoxically increased with age; notably, whilst 45–57% of horses with conjunctival or corneal lesions tested positive for EHV-2 and/or EHV-5, a substantial proportion (13–32%) of clinically normal animals also carried the virus at each assessment point. The inability to definitively prove causation—given the high rate of viral detection in disease-free horses—suggests that herpesvirus infection alone does not reliably predict or explain ocular disease in this population, highlighting the importance of considering multifactorial causes and the distinction between viral shedding and clinical pathology when managing equine eye problems in stabled herds.
Read the full abstract on PubMed
Practical Takeaways
- •EHV-2 and EHV-5 are commonly detected in horses with ocular disease but also in clinically normal animals, making causation difficult to assign on PCR results alone
- •Young horses are more likely to test positive for these herpesviruses, so age context is important when interpreting test results in your herd
- •Corneal pathology appears to increase with age independent of herpesvirus status, suggesting other factors (environmental, nutritional, management) should be investigated in cases of recurrent eye problems
Key Findings
- •Probability of positive EHV-2/EHV-5 PCR results decreased with progressing age in the 266 Lipizzaners followed over 18 months
- •Corneal findings increased over time despite decreasing herpesvirus PCR positivity, suggesting multifactorial etiology
- •Between 45-57% of horses with conjunctival or corneal findings tested positive for EHV-2/EHV-5, but 13-32% of clinically sound horses also tested positive
- •No unequivocal causal relationship could be established between herpesvirus detection and ocular pathology