Evaluation of compounded cidofovir, famciclovir, and ganciclovir for the treatment of feline herpesvirus ocular surface disease in shelter‐housed cats

Abstract

Objective To assess the efficacy of compounded cidofovir, famciclovir, and ganciclovir for the treatment of feline herpesvirus type 1 (FHV‐1) ocular surface disease. Animals studied 132 shelter‐housed cats qPCR positive for FHV‐1. Procedures A masked placebo‐controlled study design was utilized. Animals were enrolled in one of four treatment groups: topical ocular placebo + oral placebo (n = 32), compounded cidofovir 0.5% ophthalmic solution + oral placebo (n = 32), compounded famciclovir oral solution (90 mg/kg) + topical ocular placebo (n = 32), and compounded ganciclovir 0.15% ophthalmic solution + oral placebo (n = 36). Cats were treated with each medication twice daily for 7 days and were evaluated on Day 1 and Day 8 using an ocular scoring system, body weight, and qPCR for FHV‐1 viral load. Results Cidofovir significantly decreased viral load from Day 1 to Day 8 compared with placebo (p = .024). Neither famciclovir nor ganciclovir decreased viral load compared with placebo (p = .14, p = .41). There was no significant improvement of ocular scores for any drug group compared with placebo (p = .62). In all groups, 65%–75% of cats improved from Day 1 to Day 8. Juvenile cats had a significant increase in weight gain compared with placebo for cidofovir (p = .025) and ganciclovir (p = .023). All corneal ulcers in placebo animals failed to heal whereas 77% of ulcers in antiviral group animals healed. Conclusions Topical ophthalmic cidofovir significantly decreased ocular FHV‐1 viral shedding and increased weight gain in juvenile cats. Ganciclovir increased weight gain in juvenile cats. Compounded famciclovir demonstrated limited efficacy for the treatment of FHV‐1 ocular surface disease in shelter‐housed cats.

A review of evidence‐based management of infectious ocular surface disease in shelter‐housed domestic cats

“…Concurrent URI clinical signs are common in FHV-1 infected cats in the shelter environment. 4,21 While dermatologic clinical signs 22 and pneumonia [23][24][25] have also been described in domestic cats, these are uncommon in the authors' experience.…”

“…Although not rigorously assessed in a shelter setting, molecular methods of pathogen quantification have been widely used in experimental assessments of feline IOSD. 4,[74][75][76][77][78] In addition, novel methods of pathogen quantification such as digital droplet PCR 76 are now available. The preferred anatomic sampling locations for feline IOSD are the inferior conjunctival fornix and/or the oropharyngeal mucosa.…”

“…79,80 qPCR is an effective tool for determination of FHV-1 viral load 76,81 and has been utilized in numerous experimental studies for this purpose. 4,[74][75][76][77][78] While it is widely understood that clinically normal cats may shed FHV-1, 82 early evidence suggests that qPCR can successfully differentiate between latently infected animals and actively infected animals shedding large quantities of virus. 81,83,84 While interpretation of cycle threshold (Ct) values varies by laboratory, Ct values are strongly correlated with FHV-1 viral titer in acute infections.…”

“…Famciclovir, an orally administered prodrug of penciclovir, has been the subject of numerous investigations for the treatment of FHV-1 in cats. 4,5,8,74,78,[101][102][103][104] Several of these studies specifically utilized shelter-housed cats with IOSD 4,5,8,101 or animals in a 'foster' environment (temporary private residence). 102 Studies using experimental animals in a highly controlled laboratory setting have shown that famciclovir is an effective treatment for FHV-1 and that, at appropriate doses, anti-herpetic concentrations of penciclovir are achievable in the tear film.…”

“…One of the motivations for this focus is apparent variability between results of experimental studies and clinical trials involving shelter-housed cats, which are discussed herein. [4][5][6][7][8][9] Prevention and treatment strategies which are practical in an experimental setting or in privately owned cats may be wholly unfeasible in the shelter setting for various reasons. Likewise, clinical trial data generated using shelterhoused cats may not be applicable to privately-owned animals with IOSD.…”