Lysine supplementation appears to be a popular intervention for feline herpes virus-1 (FHV-1) infection, recommended by ~90 % of feline veterinarians as based on a survey made in this report. The survey included cat clinics in the United States, United Kingdom, and Australia. Since lysine supplementation is commonly recommended, researchers from University of California, Riverside performed a systematic review of published data pertaining to using lysine to treat human herpes virus-1 (HHV-1) in humans and FHV-1 infections in cats. HHV-1 publications were included because lysine supplementation in cats was initially based on supposed benefits in humans with HHV-1 infections. Nine publications pertaining to lysine supplementation and FHV-1 and 32 publications pertaining to lysine supplementation and HHV-1 were identified. From these publications, 7 FHV-1 and 10 HHV-1 studies met a stringent research quality eligibility requirement.
Lysine supplementation was concluded not to be effective in preventing cats from becoming infected with FHV-1, in decreasing the chance of developing clinical signs related to active FHV-1 infection, nor in providing a positive effect on the clinical course of its disease manifestations. In fact, results from two clinical trials with cats suggest that excess dietary lysine may have an enhancing effect on FHV-1 replication.
In conclusion, despite all efforts and after more than half a century of research, the precise mechanism of lysine-arginine antagonism remains poorly understood. Furthermore, there is no evidence for lysine-arginine antagonism in the cat. Based on the complete lack of scientific evidence for the efficacy of lysine supplementation, the researchers of this article recommend an immediate stop of lysine supplementation for cats. (GO)
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Drazenovich TL, Fascetti AJ, et al. Effects of dietary lysine supplementation on upper respiratory and ocular disease and detection of infectious organisms in cats within an animal shelter. Am J Vet Res. 2009 Nov;70(11):1391-400.