Vernau KM, Kim S, Thomasy SM, Lucyshyn DR, Purpura J, Montgomery E, Surmick JD, Dubelko AR, Moussavi A, Kass PH, Maggs DJ. Doxycycline with or without famciclovir for infectious ophthalmic and respiratory disease: a prospective, randomized, masked, placebo-controlled trial in 373 kittens. J Feline Med Surg. 2024 Nov;26(11):1098612X241278413. doi: 10.1177/1098612X241278413. PMID: 39485362; PMCID: PMC11531040.
Infectious upper respiratory tract disease (IURD) is a common and serious condition caused by various pathogens, with feline herpesvirus type 1 (FHV-1) being a primary culprit.
Traditional treatments for IURD, such as doxycycline, primarily target secondary bacterial infections. While effective for these, they do not address the underlying viral infections. This paper investigates the potential benefits of combining doxycycline with famciclovir, an antiviral with some evidence for efficacy against FHV-1 in adult cats. Famciclovir alone has previously been shown to be of minimal value in treating feline IURD, however combination therapy with doxycycline has been minimally investigated. The study aims to evaluate the efficacy of this combination therapy in kittens with IURD, focusing on disease duration and severity.
This study enrolled kittens from animal shelters and rescue organizations in Northern California. Kittens were randomized to receive either doxycycline and famciclovir or doxycycline and a placebo. Kittens were monitored daily for 21 days, with caregivers recording body weight and clinical signs of IURD. At the beginning and end of the study, veterinarians performed a comprehensive physical examination and slit-lamp biomicroscopy to assess ocular health. The primary objective of the study was to compare the efficacy of the combination therapy to doxycycline alone in reducing the duration and severity of IURD in kittens.
Caregiver data was collected daily for 21 days, while veterinary data was collected only on days 1 and 21. Veterinary data was more detailed, especially for ocular examinations. The primary outcome for caregiver data was the rate of improvement in clinical signs, measured using various definitions of resolution and recovery. Overall, the analysis aimed to assess the efficacy of the combination therapy in improving clinical signs and reducing the duration of IURD in kittens.
For kittens with mild disease, those treated with doxycycline alone were slower than those treated with both drugs to achieve clinical recovery and clinical resolution, but not ophthalmic recovery or ophthalmic resolution. Kittens with mild disease and receiving famciclovir achieved 75% clinical resolution 4–5 days earlier than kittens with mild disease and receiving doxycycline alone. Fewer kittens treated with both drugs developed corneal disease than those with doxycycline alone.
Contrary to some previous work, this study found that the addition of famciclovir to doxycycline for cats with IURD helped to reduce the severity of symptoms. If it important to remember that this is a specific population of cats, both temporally and geographically, and as such these findings may not be generalizable. The daily dose of famciclovir was also relatively large, meaning that the costs in limited resource (ie shelter) setting may be significant. However, the benefits may be worth the increased costs. ~MK
See Also
Lappin MR, Blondeau J, Boothe D, et al. Antimicrobial use guidelines for treatment of respiratory tract disease in dogs and cats: Antimicrobial Guidelines Working Group of the International Society for Companion Animal Infectious Diseases. J Vet Intern Med 2017; 31: 279–294. PMCID: PMC5354050. PMID: 28185306. DOI: 10.1111/jvim.14627
Thomasy SM, Shull O, Outerbridge CA, et al. Oral administration of famciclovir for treatment of spontaneous ocular, respiratory, or dermatologic disease attributed to feline herpesvirus type 1: 59 cases (2006–2013). J Am Vet Med Assoc 2016; 249: 526–538. DOI: https://doi.org/10.2460/javma.249.5.526
Thomasy SM, Lim CC, Reilly CM, et al. Evaluation of orally administered famciclovir in cats experimentally infected with feline herpesvirus type-1. Am J Vet Res 2011; 72: 85–95. PMID: 21194340. DOI: 10.2460/ajvr.72.1.85