17 March 2013

Cats: Herpes

Just like humans, cats can get herpes.  But with cats, the herpes can cause more than a bothersome cold sore.  In fact, herpes can cause anything from runny eyes to rupturing of the eyes, or even death.

Herpes in cats is caused by feline herpesvirus 1, which is obviously a herpes virus.  In cats and especially kittens, it causes feline viral rhinotracheitis (FVR).  This a common upper respiratory infection (about 50% of all cats have had it) and is one of the leading causes of conjunctivitis in cats. Most cats get the virus and get over it.  Some cats get the virus and have major problems because of it -- conjunctivitis, pneumonia, corneal ulcers, etc.  A few cats get the virus, and because their immune system is weak, are never able to totally clear the virus and so they become chronically infected with it.

The virus is spread by nasal discharge, tears, and saliva.  The normal incubation period is 2-5 days.  A cat with FVR will have thick nasal discharge (usually yellowish), a fever, maybe coughing, and sneezing.  Antibiotics will not cure it but are used to prevent secondary infections.  Vitamin C and vitamin A and fasting are my treatment of choice in most cases.  After the cat flu stage, the cat will shed the virus for 1-3 weeks, or in the cat which become chronically infected, for the life of the cat.

Anya, who likely lost one eye to herpes
Until advances were made with DNA, there was no reliable test for herpes in a cat.  Now, there is a PCR test which is very sensitive and moderately expensive.

There is a vaccine which will lessen the symptoms, but not prevent the infection.

Unfortunately, the virus has an affinity for eyes, especially the cornea.  When a cat with a weakened immune system is exposed to the herpes virus, the virus enters the body and causes the typical symptoms.  Because the body can not fight off the herpes virus, like a healthy cat does, the virus escapes the digestive and pulmonary tracts and becomes chronic.  It can take up residence in a number of locations, such as the nose but especially the eyes.  With the eyes, the herpes virus causes eye ulcers which may lead to the rupturing and removal of one or both eyes.  My dear Anya came to me with one eye, but the other eye shows clear signs of previous ulcerations.  Without constant treatment with lysine, her eye and nose both quickly develop mucus and I would expect her remaining eye to ulcerate.

Isabel with staining due to excessive tearing
But there is also another form of herpes, or so I am convinced -- a subclinical chronically infected version.  A couple of researchers are looking at these cats, but so far, nothing major has come of their research other than to say the pool of chronic carriers may be larger.  Anya is a classic chronically infected cat -- ulcers in the eye(s), mucus, etc.  The other form is less obvious.  It's almost like a subclinical chronic infection, with periods of mild symptoms.  The symptoms, such as increased nasal discharge, could be caused by other things such as allergies or even dust.  These cats would not be considered to have herpes by most vets and without a PCR test, they would go diagnosed.  But they do have herpes.  My Isabel is one such cat.  Normally, her nose and eyes are fine.  But when she feels stressed (and then her immunity would be down), she starts having excessive nasal drainage as if she had a sinus infection.  Antibiotics do not clear it up, so it's not bacterial.  There's no pattern to it, so I doubt it's allergies.  But give her large doses of lysine (which helps to control herpes) and a bit of echinacea (which boosts her immune system), and she quickly returns to normal. 

In any case, for the chronically infected, while there are some antiviral medication that shows some promise, the herpes virus can't be removed even by interferon, but it can be controlled to a large degree.  Most owners rely on l-lysine, an amino acid, to control the herpes and to prevent flair-ups.

I will post about lysine in a day or two...

1 comment:

Anonymous said...

Excellent information Linda and thank you so much for posting this. I look forward to your follow up information regarding lysine as well. Joane