Prophylactic and therapeutic effects of twice-daily famciclovir administration on infectious upper respiratory disease in shelter-housed cats

Abstract

Objectives: In humans with herpetic disease, early or pre-emptive famciclovir therapy reduces disease duration and severity. This prospective, masked, placebo-controlled study tested therapeutic and prophylactic effects of two famciclovir doses given to cats for 7 days following shelter entry.

Methods: Cats were assigned to prophylactic or therapeutic study arms based on clinical evidence of herpetic disease at study entry. Cats in the therapeutic arm received no treatment (n = 19), placebo (lactose; n = 18) or famciclovir at ~30 (n = 21) or ~90 mg/kg (n = 20) PO q12h for 7 days. Cats in the prophylactic arm received no treatment (n = 25) or famciclovir at ~30 (n = 28) or ~90 mg/kg (n = 27) PO q12h for 7 days. Disease scores, body weight, conjunctival feline herpesvirus 1 (FHV-1) shedding, and adoption rates were recorded on days 1 (admission), 8 (end of therapy) and 15 (1 week after cessation of therapy).

Results: No significant differences in clinical scores were observed among groups in the prophylactic or therapeutic arms at any of the three time points. However, within the therapeutic arm, viral shedding on day 8 was significantly higher in cats receiving no treatment than in those receiving ~30 or ~90 mg/kg famciclovir, and this effect persisted 1 week after famciclovir was stopped (day 15) only in cats receiving ~30 mg/kg, although this approached significance in cats receiving ~90 mg/kg. No significant differences in adoption rates were detected among groups in either arm throughout the study.

Conclusions and relevance: Although we did not demonstrate a statistically or clinically significant effect of famciclovir administration upon clinical signs of infectious upper respiratory disease or adoption, when it was administered at ~30 or ~90 mg/kg q12h for 1 week famciclovir reduced conjunctival FHV-1 shedding. This suggests a potential role in interrupting the infectious cycle within a shelter population; however, cost in time and resources, and stress and pathogen transmission induced by oral administration should be considered.

Keywords: Antiviral therapy; feline herpesvirus; ocular disease; penciclovir; population health; viral prophylaxis.

Figure 1

Study design by which cats were selected for entry and randomly assigned to one of seven treatment groups within the prophylactic or therapeutic study arm of a clinical trial assessing the efficacy of famciclovir administered at one of two doses for 1 week following shelter entry. FeLV = feline leukemia virus; FIV = feline immunodeficiency virus; BCS = body condition score; IURD = infectious upper respiratory disease; CS = clinical score

Figure 2

Clinical disease scores for 158 cats entered into a clinical trial assessing the efficacy of famciclovir administered at one of two doses for 1 week following shelter entry. (a) Cats without clinical signs of infectious upper respiratory disease (IURD) at study entry were assigned to the prophylactic study arm and stratified to receive famciclovir at ~30 mg/kg (n = 28; yellow) or ~90 mg/kg (n = 27; red) PO q12h or were untreated (n = 25; blue). (b) Cats with signs of IURD at study entry were assigned to the therapeutic study arm and received famciclovir at ~30 mg/kg (n = 21; yellow) or ~90 mg/kg (n = 20; red) PO q12h, placebo PO q12h (n = 18; green) or were untreated (n = 19; blue). No significant differences in clinical disease scores were observed among any groups within the (a) prophylactic or (b) therapeutic arms at the end of the period of famciclovir/placebo administration (day 8) or 1 week after cessation of therapy (day 15)

Figure 3

Proportions of cats in which feline herpesvirus type 1 (FHV-1) DNA was detected in the conjunctival fornix of either eye on days 1, 8 or 15 of a clinical trial assessing the efficacy of famciclovir administered at one of two doses for 1 week following shelter entry. (a) Cats without clinical signs of infectious upper respiratory disease (IURD) at study entry were assigned to the prophylactic study arm and stratified to receive famciclovir at ~30 mg/kg (n = 28; yellow) or ~90 mg/kg (n = 27; red) PO q12h or were untreated (n = 25; blue). Within the prophylactic arm of the study, the proportion of cats in which FHV-1 DNA was detected in the conjunctival fornices did not significantly differ at any time point statistical analysis was possible. (b) Cats with signs of IURD at study entry were assigned to the therapeutic study arm and received famciclovir at ~30 mg/kg (n = 21; yellow) or ~90 mg/kg (n = 20; red) PO q12h, placebo PO q12h (n = 18; green) or were untreated (n = 19; blue). At baseline (day 1), FHV-1 DNA was detected in the conjunctival fornices of a significantly greater proportion of cats in the untreated group than in the placebo or ~30 mg/kg groups but not the ~90 mg/kg groups. For placebo-treated cats, this difference was no longer evident on day 8 but had returned by day 15. For cats receiving ~30 mg/kg famciclovir, significantly fewer shed virus after 1 week of therapy and this effect persisted until day 15. For cats receiving ~90 mg/kg famciclovir, significantly fewer shed virus after 1 week of therapy and this effect approached significance on day 15