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Efficacy of topical aciclovir for the treatment of feline herpetic keratitis: results of a prospective clinical trial and data from in vitro investigations
  1. D. L. Williams, MA, VetMB, PhD, CertVOphthal, MRCVS1,
  2. J. C. Robinson, MA, VetMB, MRCVS1,
  3. E. Lay, BSc1,1 and
  4. H. Field, DSc, FRCPath1,1
  1. 1Department of Clinical Veterinary Medicine, University of Cambridge, Madingley Road, Cambridge CB3 0ES


This study aimed to evaluate the efficacy of topical ophthalmic aciclovir applied five times daily as a treatment for feline herpesvirus type 1 (FHV-1) keratitis in a group of cats in a first-opinion practice setting. Cats with ocular signs indicative of FHV-1 or Chlamydophila species infection, predominantly conjunctivitis and keratitis, were tested for FHV-1 antigen using an immunofluorescent technique on air-dried conjunctival swabs. They were first treated with topical chlortetracycline with efficacy against Chlamydophila species and then, in cases positive for FHV-1, with topical aciclovir. The time to recovery was determined and illustrated using a Kaplan-Meier plot. Three cats were infected with Chlamydophila species and showed a median time to recovery of 14 days (95 per cent confidence interval [CI] 10 to 18 days), while 30 cats infected with FHV-1 showed a median time to recovery of 12 days (95 per cent CI 10 to 14 days). The drug dose at which 50 per cent plaque reduction (ED50) occurred in a standard plaque reduction assay was determined in an in vitro study. This showed a mean (sd) ED50 of aciclovir of 25 (3·5) mg/ml compared with 0·4 (0·05) mg/ml for trifluorothymidine, a drug known to be efficacious against FHV-1. The study shows that even though aciclovir is generally considered to lack efficacy against ocular FHV-1 infection, when used frequently it can have a beneficial effect in FHV-1 conjunctivitis and keratitis

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