The Veterinary Record 157:254-257 (2005)
© 2005 British Veterinary Association
Efficacy of topical aciclovir for the treatment of feline herpetic keratitis: results of a prospective clinical trial and data from in vitro investigations
D. L. Williams, MA, VetMB, PhD, CertVOphthal, MRCVS1,
J. C. Robinson, MA, VetMB, MRCVS1,
E. Lay, BSc1 and
H. Field, DSc, FRCPath1
1 Department 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.
Copyright © 2005 British Veterinary Association
