Equis ISSN 2398-2977

Keratitis: viral

Synonym(s): Herpetic keratitis

Contributor(s): David Donaldson, Paul Gerding, Robert Lowe, Graham Munroe

Introduction

  • A disorder in horses that presents with increased lacrimation, conjunctivitis, superficial keratopathy and rarely, upper respiratory infection.
  • Infrequently occurring disorder in the USA. 
  • Most common specific corneal disease in the UK.
  • Cause: most commonly attributed to EHV-2.
  • Signs: punctate to more generalized, corneal opacities, blepharospasm, lacrimation.
  • Diagnosis: characteristic ophthalmological appearance, virus isolation.
  • Treatment: antiviral agents/systemic therapy.
  • Prognosis: good, although recurrences may occur.

Pathogenesis

Etiology

  • Suspected to be due mainly to EHV-2   Equine herpesvirus  although EHV-5 may cause similar symptoms.

Predisposing factors

General
  • Previous topical or systemic use of corticosteroids   Therapeutics: eye   may compromise naturally occurring ocular immunity responsiveness.

Pathophysiology

  • A possible predilection for viral replication and shedding within conjunctival tissue cells.
  • Virus has been detected in ocular and nasal secretions, ganglion of the trigeminal nerve and circulating lymphocytes.

Timecourse

  • Slow; may take up to 2 weeks or longer to develop cytopathic effects in incubated cell cultures.
  • After experimental inoculation, infectious virus was isolated up to day 12 post-infection.

Epidemiology

  • Reported to affect multiple foals in one herd.
  • The ocular disease is not necessarily concurrent with the systemic disease.
  • The ocular disease is not contagious to in-contact horses.

Diagnosis

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Treatment

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Outcomes

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Further Reading

Publications

Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Borchers K, Wolfinger U et al (1998) Virological and molecular biological investigations into equine herpes virus type 2 (EHV-2) experimental infection. Virus Res 55 (1), 101-106 PubMed.
  • Reubel G H, Crabb B S & Fluddart M J (1995) Diagnosis of equine gammaherpesvirus 2 and 5 by PCR. Arch Virol 140 (6), 1049-1060 PubMed.
  • Collinson P N, ORielly J L, Ficorilli N et al (1994) Isolation of equine herpesvirus type 2 (equine gammaherpesvirus 2) from foals with keratoconjunctivitis. JAVMA 205 (2), 329-331 PubMed.

Other sources of information

  • Barnett K C, Crispin S M, Lavach J D & Matthews A G (2004) Equine Ophthalmology - An Atlas and Text. 2nd edn. W B Saunders.
  • Lavach J D (1990) Cornea. In: Large Animal Ophthalmology. Mosby, USA. pp 133-134. ISBN: 0801627737.


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