To prevent and treat feline herpesvirus 1 (FHV-1), a veterinary visit, some TLC, and supplementing cat food with the amino acid lysine is often recommended. But a new study suggests that may not be such a good idea.

Researchers at the University of California, Riverside conducted a literature review of the National Center for Biotechnology Information (NCBI) PubMed database to identify the efficacy of using lysine supplementation to prevent and treat FHV-1. They concluded that not only is lysine ineffective; it may, in fact, increase the frequency and severity of FHV-1.

The study was published Nov. 16 in BMC Veterinary Research.

Per the study, lysine has no antiviral properties but works by lowering arginine concentrations that can impact FHV-1. However, the researchers note that not only does the literature review fail to support that but also that because cats cannot synthesize lysine, lowering arginine levels isn’t desirable.

The researchers also note that some feline clinical studies showed that not only is lysine ineffective in preventing or treating FHV-1; in some cases, it increased infection frequency and disease severity. 

Photo credit: © iStock/Valeriya

Comments (4) -

Janine Oliver, DVM
Janine Oliver, DVMUnited States
11/30/2015 6:37:38 AM #

"Lysine ineffective in treating cats with herpesvirus 1 infection" this article is irresponsible in that it is quoting a literature review study and not an actual study.  Cats with FHV-1 can run the gamut of mild to severe and life threatening. A literature review does not factor out any and all other factors that may have had an impact on the cats records that were studied.  It's quite possible there was a bias because hospitalized records are usually those of the most sick cats and therefore the worst outcomes.  We need a study comparing cats with FHV-1 where there is a double blind with placebo, lysine and nothing at all to determine the efficacy of lysine. The reason there are so many products to deliver lysine to cats is that anecdotally in just about every cat practice we have noticed that cats with lysine do seem to improve with lysine.  Our anecdotal observations are only marginally better than a literature review, so it's important that this be studied.  Please don't throw the baby out with the bathwater on the word of a literature review.  In my humble opinion literature reviews should not establish clinical practices but should be used to alert us to the need for an actual effective study of the question.

Cristina Valas
Cristina ValasUnited States
12/4/2015 4:53:47 PM #

I agree.  This is extremely irresponsible.  If they are going to say something then study how lysine works.  It not only works in cats but it also works in humans and probably other species and on many other viruses not only herpes.  One of colleagues read this and started telling my clients so one irresponsible act can lead to a misinformed opinion that harms the wellbeing of many cats. I think that after practicing over 20 years I know what works and what doesn't.  Nothing else makes URI symptoms less severe and less frequent other than lysine and I mean NOTHING! So why knock it?.  The article is also misleading as it says "It doesn't work at preventing and treating herpes" and who said anything about preventing or treating????We are ameliorating the severity of the disease which runs rampant in cats with something that is not harmful.  As far as arginine goes, my challenge is "prove it" and when you do that, prove that it somehow affects the well being or longevity of the cat! I very much doubt you ever will. I am sure that big pharma wants to sell more antivirals and I am not opposed to using those in some severe cases but in most cases they are simply not necessary and the big drug companies do not like that so they are going to try to knock more natural and inexpensive remedies until they give up and start making a product with lysine in it!!!

Caroline Montgomery, DVM
Caroline Montgomery, DVMUnited States
12/4/2015 9:40:50 AM #

I would agree that lysine supplementation on its own will not get a severe case of ocular herpes under control. but I do know from personal experience for my own cat that once I started supplementing 500 mg Lysine even just once daily that her chronic eye discharge is much less and that only rarely do I have to reach for the ocular antibiotics or famciclovir.
I can report more of these anecdotal incidences from clients too.

Sebastiaan Bol
Sebastiaan BolUnited States
1/20/2016 6:32:43 PM #

We decided to publish it in a open access journal, so everybody can read the full text version of our systematic review for free. Unfortunately some people do or did not read the complete article (11 pages).

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