Effect of topical ophthalmic application of cidofovir on experimentally induced primary ocular feline herpesvirus-1 infection in cats

Objective-To evaluate the efficacy of twice-daily ophthalmic application of 0.5% cidofovir solution in cats with experimentally induced primary ocular feline herpesvirus-1 (FHV-1) infection. Animals-Twelve 6-month-old sexually intact male cats. Procedures-Cats were randomly assigned to either a treatment or control group. Ocular infection with FHV-1 was induced (day 0) in all cats via inoculation of both eyes with 101 plaque-forming units of a plaque-purified FHV-1 field strain. Twice daily for 10 days beginning on day 4 after virus inoculation, the treatment group received 1 drop of 0.5% cidofovir in 1% carboxymethyl cellulose in both eyes, and the control group received 1 drop of 1% carboxymethylcellulose in both eyes. A standardized scoring method was used to evaluate clinical signs of FHV-1 infection in each cat once daily for 24 days. The amount of ocular viral shedding was assessed by use of a quantitative real-time PCR procedure every 3 days during the study period. Clinical scores and viral quantification were averaged over the pretreatment (days 0 to 3), treatment (days 4 to 14), and posttreatment (days 15 to 24) periods for each cat. Results-During the treatment period, clinical scores and amount of viral ocular shedding were significantly lower in the treatment group, compared with findings in the control group. Conclusions and Clinical Relevance-Twice-daily application of 0.5% cidofovir solution in both eyes significantly decreased the amount of viral shedding and the severity of clinical disease in cats with experimentally induced ocular FHV-1 infection.