Feline Herpes Viral Infection

an upper respiratory virus of cats

What is it?
One of the more common ophthalmic diseases seen in cats is herpes virus infection.  Herpes virus is suspected any time a cat has an infection on the eye surface that does not respond to antibiotics.  The virus causes conjunctivitis (inflammation of the pink tissue surrounding the eye) and/or corneal ulcerations.  The virus is a common respiratory pathogen that causes upper respiratory disease in most cats.

What are the symptoms?
Sneezing may or may not be seen.  Most often, the cat has a history of conjunctivitis and/or corneal ulcers that will not heal.  Stress is the biggest cause of relapse.  Common stress factors for cats include strangers or new animals in the home, moving to a new home, and boarding while the owner is away. Advanced age or a compromised immune system also predisposes to infection.

Who is susceptible?
Most cats are affected as kittens, contracting the infection from their mothers.  Stray cats, multi-cat households, and cats from households where new cats are constantly introduced are more likely to suffer infections.  Think of it like kids in daycare constantly being exposed to every new cold virus that comes around.

What causes it?
Bacteria are living organisms that reproduce on their own. With a bacterial infection, antibiotics are used because they directly impair the reproduction of or directly kill the bacterial organisms. Conversely, viruses are dormant until they invade and take over another cell, in order to reproduce.  Antibiotics do not kill body cells and that is why they are useless in the treatment of viral infections.  Anti-viral topical medications are indicated in active infections.  For mild cases, treatment with topical anti-viral medications must often be applied for 2-4 weeks, and for more severe cases, oral and topical medications are administered for 4-6 weeks or longer.  A daily oral supplement, L-lysine, may also be recommended to minimize risk of future flare-ups.

How is it treated?
Bacteria are living organisms that reproduce on their own. With a bacterial infection, antibiotics are used because they directly impair the reproduction of or directly kill the bacterial organisms. Conversely, viruses are dormant until they invade and take over another cell, in order to reproduce.  Antibiotics do not kill body cells and that is why they are useless in the treatment of viral infections.  Anti-viral topical medications are indicated in active infections.  For mild cases, treatment with topical anti-viral medications must often be applied for 2-4 weeks, and for more severe cases, oral and topical medications are administered for 4-6 weeks or longer.  A daily oral supplement, L-lysine, may also be recommended to minimize risk of future flare-ups.

What is the prognosis?
The key to managing the clinical signs associated with feline herpes virus is controlling the cat’s environment.  Cats exposed to multiple cats (indoor-outdoor cats), cats in multiple cat households, or introduction of new cats are very difficult to keep disease free.  Reducing stress by maintaining a routine is helpful.

Keep in mind that it is the nature of the virus to see recurrences of the disease and periodic treatment is often necessary.