If your handsome Maine coon winks at you from across the room and doesn't stop, it's probably not saying, "Hey baby, can I buy you a drink?" In all likelihood it's squinting because its eye hurts. By definition, conjunctivitis is an inflammation of the inner eyelid and the superficial layer of the eye.
Dr. Mitzi Zarfoss is an ophthalmology resident at the University of Illinois Veterinary Teaching Hospital in Urbana. She says, "early/mild conjunctivitis may go unnoticed by some cat owners, and may progress if untreated." Frequent squinting may go overlooked and tearing or red eye might be attributed to allergies, which are a relatively uncommon cause of eye disease in cats. Veterinary attention is indicated whenever eye symptoms are noted.
The most common cause of the conjunctivitis in our feline friends is a herpesvirus. "Feline-specific herpesvirus is a very important cause of eye disease in cats," says Dr. Zarfoss. She also notes that this same feline herpesvirus frequently causes respiratory diseases, too (sneezing and nasal discharge).
Although most veterinarians blame the feline herpesvirus when they see a cat with conjunctivitis, confirming the real cause of the disorder is very challenging. "We believe that most cats are positive for herpes," says Dr. Zarfoss, "and just because they have it doesn't mean it is necessarily causing the conjunctivitis." In short, testing is not always practical for the diagnosis and treatment of conjunctivitis in cats.
Feline herpes, a virus that is easily passed from cat to cat and common in the environment, is almost impossible to prevent. Although herpesvirus protection is a component of a commonly administered feline vaccine, the vaccine doesn't fully protect every cat. In addition, there are several other causes of conjunctivitis in cats including chlamydia and mycoplasma, both of which are bacterial species, not viruses.
As far as treating the herpes problem, oral L-lysine, an amino acid nutraceutical that inhibits virus replication, is often used. Depending on how serious the eye looks, your veterinarian may also choose to treat with antibiotics or antiviral medications. If you notice that your cat has frequent bouts of conjunctivitis, Dr. Zarfoss says that, "some cats with chronic conjunctivitis may benefit from long-term L-lysine under the supervision of a veterinarian." She goes on to note that the drug is very safe in cats and comes in many formulations with or without flavoring for cats' individual tastes.
Just like certain herpes viruses in humans, stress can cause flare-ups. A cat that previously had a bout of conjunctivitis may become stressed by a new animal in the house, or an owner leaving for vacation. That amount of anxiety may be enough to suppress its immune system, allowing for the virus to take hold once again.
For more information on conjunctivitis in cats contact your local veterinarian or visit the American College of Veterinary Ophthalmologists' Web site at: http://www.acvo.org/frames/publicframe.htm.
An archive of Pet Columns from the University of Illinois College of Veterinary Medicine is available online at www.vetmed.illinois.edu/petcolumns/. Requests for reprints of this article may be directed to Mandy Barth, email@example.com.
Veterinary Extension/Office of Public Engagement
University of Illinois College of Veterinary Medicine