Treatment of Feline Herpesvirus-1 Associated Disease in Cats with Famciclovir and Related Drugs

Background Feline herpesvirus 1 (FHV-1) is a common cause of ocular and upper respiratory disease in cats and kittens, and a potential cause of eosinophilic dermatitis. Hypothesis The systemic anti-herpes drug, famciclovir (Famvir; Novartis), would be effective in the clinical management of disease attributable to FHV-1, including conjunctivitis, keratitis, corneal sequestra, rhinosinusitis and FHV-1 associated dermatitis. Clinical outcome Oral famciclovir was used to treat signs considered referable to FHV-1 in 10 cats: four had primary ocular disease, two had rhinosinusitis and four had FHV-1 associated dermatitis. Patients treated in Australia (five cats) and Europe (one cat) were given 62.5 mg of famciclovir once or twice daily. Four cats treated in the USA were given 125 mg three times daily. Famciclovir was uniformly well tolerated and, in all cases, had a positive impact on the patient's condition. The apparent improvement in lesions was superior to what had been achieved previously using other therapeutic strategies. One cat with severe destructive rhinosinusitis was significantly improved by a 4-month course of famciclovir in combination with antibacterials. Corneal sequestra detached in two out of three cats treated; cats with ocular signs were qualitatively more comfortable, with reduced clinical signs and an improved appearance of the eyes. Critically, oral famciclovir therapy was considered more convenient than topical ocular therapy. All four cats with FHV-1 associated dermatitis improved substantially, although relapse occurred subsequently in three patients. A further cat with presumptive FHV-1 associated dermatitis responded to topical aciclovir cream before famciclovir could be sourced. Conclusions Famciclovir appears to be a promising systemic drug for treating diseases associated with FHV-1 infection. More rigorous clinical trials are required to optimise the dosing regimen for safe and effective specific anti-herpes treatment in feline clinical medicine.