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Keratitis: viral
Synonym(s): Herpetic keratitis
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.
Presenting signs
- Superficial, white, punctate to more generalized, corneal opacities Vitreous: opacities .
- Blepharospasm.
- Increased tear production.
- Conjunctivitis.
- Iridocyclitis.
- Keratitis (ulcerative or non-ulcerative).
- Mucopurulent ocular discharge.
- Corneal ulceration.
Age predisposition
- Foals, but all ages affected.
Breed/Species predisposition
- None suspected at this time.
Cost considerations
- Topical antiviral medication Therapeutics: eye is generally recommended at a moderate cost - to be applied TID and may take 4 weeks for clinical symptoms to resolve.
- Frequency may vary with treatment, eg drops higher frequency than ointments. TF3 may be used as much as q2 h until fluorescein negative.
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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Prevention
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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.