Abstract
BackgroundFeline herpesvirus 1 is a highly contagious virus that affects many cats. Virus infection presents with flu-like signs and irritation of ocular and nasal regions. While cats can recover from active infections without medical treatment, examination by a veterinarian is recommended. Lysine supplementation appears to be a popular intervention (recommended by > 90 % of veterinarians in cat hospitals). We investigated the scientific merit of lysine supplementation by systematically reviewing all relevant literature.MethodsNCBI’s PubMed database was used to search for published work on lysine and feline herpesvirus 1, as well as lysine and human herpesvirus 1. Seven studies on lysine and feline herpesvirus 1 (two in vitro studies and 5 studies with cats), and 10 publications on lysine and human herpesvirus 1 (three in vitro studies and 7 clinical trials) were included for qualitative analysis.ResultsThere is evidence at multiple levels that lysine supplementation is not effective for the prevention or treatment of feline herpesvirus 1 infection in cats. Lysine does not have any antiviral properties, but is believed to act by lowering arginine levels. However, lysine does not antagonize arginine in cats, and evidence that low intracellular arginine concentrations would inhibit viral replication is lacking. Furthermore, lowering arginine levels is highly undesirable since cats cannot synthesize this amino acid themselves. Arginine deficiency will result in hyperammonemia, which may be fatal. In vitro studies with feline herpesvirus 1 showed that lysine has no effect on the replication kinetics of the virus. Finally, and most importantly, several clinical studies with cats have shown that lysine is not effective for the prevention or the treatment of feline herpesvirus 1 infection, and some even reported increased infection frequency and disease severity in cats receiving lysine supplementation.ConclusionWe recommend an immediate stop of lysine supplementation because of the complete lack of any scientific evidence for its efficacy.Electronic supplementary materialThe online version of this article (doi:10.1186/s12917-015-0594-3) contains supplementary material, which is available to authorized users.
Highlights
Feline herpesvirus 1 is a highly contagious virus that affects many cats
Lysine-arginine antagonism has not been well-studied in humans, but patients with hyperlysinemia, due to a mutation in a gene coding for a protein involved in the breakdown of lysine, do not show lowered plasma arginine levels [31], suggesting that humans may not be affected by an antagonism between these amino acids
Taking all results discussed in this systematic review together, we conclude that lysine supplementation does not have an inhibitory effect on Feline herpesvirus 1 (FHV-1) replication in the cat
Summary
Feline herpesvirus 1 is a highly contagious virus that affects many cats. While cats can recover from active infections without medical treatment, examination by a veterinarian is recommended. Lysine supplementation appears to be a popular intervention (recommended by > 90 % of veterinarians in cat hospitals). Feline herpesvirus 1 (FHV-1) infection is a common problem in cats, with reports of active infection rates ranging from 5 to 20 % [1,2,3]. Cats may present with frequent sneezing, inflammation of the eyes and nasal mucous membranes, congestion, ocular and nasal discharge, facial or nasal dermatitis and may suffer from depression, lethargy and loss of appetite. The virus can be transmitted to other cats via ocular, oral and nasal secretions. Viral reactivation can be induced by a compromised immune system as the result of comorbidity, or by mental stress caused by for example moving the cat
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