Keratoconjunctivitis in a group of Icelandic horses with suspected γ-herpesvirus involvement.
Authors: Rushton J O, Kolodziejek J, Nell B, Weissenböck H, Nowotny N
Journal: Equine veterinary journal
Summary
# Editorial Summary: Keratoconjunctivitis and γ-Herpesvirus in Icelandic Horses A cluster outbreak of severe keratoconjunctivitis affecting 15 Icelandic horses prompted investigation into the aetiological role of equine γ-herpesviruses (EHV-2 and EHV-5), which had previously been difficult to confirm in ocular disease due to reliance on clinical diagnosis alone. Real-time PCR analysis of pooled ocular and nasal swabs, peripheral blood mononuclear cells, and necropsy specimens from the most severely affected horse revealed that all clinically symptomatic animals tested positive for EHV-2 and/or EHV-5 nucleic acid; critically, in situ hybridisation and histopathological examination identified viral nucleic acid within intraocular anatomical locations for the first time, providing stronger evidence of direct herpesviral involvement in the disease process. Most cases responded favourably to symptomatic treatment, though one horse deteriorated sufficiently to warrant euthanasia. These findings strengthen the evidence base linking γ-herpesviruses to equine keratoconjunctivitis and suggest that practitioners encountering severe, resistant corneal inflammation—particularly in group situations—should consider herpesviral aetiology and implement appropriate biosecurity measures, whilst recognising that symptomatic treatment alone may be sufficient for most affected individuals.
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Practical Takeaways
- •Suspect γ-herpesvirus involvement in outbreaks of severe keratoconjunctivitis in horse populations and consider PCR testing for definitive diagnosis
- •Recognition that EHV-2 and EHV-5 can affect intraocular structures expands understanding of disease pathology and potential complications
- •Most cases respond well to symptomatic treatment, though severe cases may require euthanasia if clinical deterioration occurs
Key Findings
- •All 15 horses with clinical keratoconjunctivitis tested positive for EHV-2 and/or EHV-5 nucleic acid using real-time PCR
- •Necropsy examination of the most severely affected case revealed EHV-2 and/or EHV-5 nucleic acid in multiple ocular and extraocular anatomical locations
- •Equid γ-herpesviruses were detected in intraocular anatomical locations for the first time
- •The majority of affected horses responded favorably to symptomatic treatment alone