Cats are frequently brought to the clinic because they have a discharge from their eyes. This problem is most often caused by an infection of the conjunctiva, the membranes around the eye. The condition can be acute, chronic or recurrent. The organisms most often involved are feline herpes virus, calicivirus, Mycoplasma spp. and Chlamydophila felis. These organisms are infectious to other cats and all the feline members of a household may be affected. Some other organisms that may cause conjunctivitis in cats are Bartonella spp. and Histoplasma capsulatum. Samples of conjunctival cells may be collected to diagnose the cause of the inflammation. Conjunctivitis may also be associated with eyelid abnormalities, ocular trauma or foreign material in the eye.

Kitten with conjunctivitis

Feline herpes virus is the most common cause of ocular discharge in cats. Generally both eyes are involved initially and sneezing may be present. Eighty percent of the cats that have this condition will remain carriers for life.  Later in life, frequently in response to stress, the virus will re-activate and may produce conjunctivitis in one or both eyes.

Cats infected with Chlamydophila generally show less signs of respiratory disease and more severe conjunctivitis than cats infected with herpes virus. The condition may be apparent in only one eye initially and it is most common in young cats. The eyelids can be very swollen and the discharge may be cloudy.

The initial treatment for all cases is symptomatic.  The eyes should be gently cleaned with warm water.  Artificial tears may be placed in the eye to make the cat more comfortable. Owners should wash their hands after cleaning the cat’s eyes. The amino acid L-lysine helps decrease the severity of herpes virus conjunctivitis in some cats.  It can be purchased at the clinic as a flavored powder, paste or treat. Kittens should receive 250mg of oral lysine twice daily and adult cats 500mg twice daily.  In mild cases supportive care may be the only treatment needed. Topical antibiotics may be prescribed to help prevent secondary bacterial infections. When the patient has moderate to severe disease, oral or topical antiviral medications may be indicated. Ophthalmic antiviral solutions must be custom made for each patient and are shipped directly to the patient. The oral antiviral medications are available and may be purchased from local pharmacies when prescribed.

Antibiotics are used topically or systemically to help control secondary bacterial infections. If the infection is severe or non-responsive, systemic antibiotics such as doxycycline or azithromycin are given over a period of three weeks. Most cases of viral conjunctivitis resolve in two weeks. Because herpes virus can be reactivated at times of stress, recurrent conjunctivitis may be seen in some patients.  Many of these patients will benefit from continual l-lysine supplementation.

Conjunctivitis is a common condition in cats and is most often associated with feline herpes virus infection. Appropriate testing can help identify the cause and treatment can limit the discomfort that is associated with this disease.