Conjunctivitis is a swelling and irritation of the supportive structures in the eyes. In our experience, roughly 25% of cats suffer from conjunctivitis at some point in their lives. Conjunctivitis occurs in cats as the result of some other disease that is affecting the whole body. Conjunctivitis can occur alone or with upper respiratory signs. The top three causes of conjunctivitis in cats are chlamydia psittaci, feline rhinotracheitis (herpes virus), and feline influenza (calicivirus). Vaccination, spaying and neutering to prevent risky behaviors, and controlling cat-to-cat interaction will all help prevent the transfer of these diseases. Cats and kittens can have a single or mixed infection. Presenting with only mild to moderate symptoms, feline influenza requires treatment, but doctors typically do not consider it a significant problem.
Herpes Virus: The conjunctiva consists of membranes that line the eyelid and eyebulb. Feline rhinotracheitis is a herpes virus that causes conjunctivial disease and systemic respiratory disease. This disease is a common disease of kittens and cats. Once this disease infects a cat, it becomes a lifelong problem. Once infected, eighty percent of cats will carry the virus for life, but will only have occasional flare ups. Most cats will only be able to spread the virus while showing symptoms, but forty-five percent of cats will spread the virus even while apparently healthy. Kittens and cats will experience clinical symptoms during periods of stress and anxiety, such as new introductions into the household, change of environment, and periods of sickness.
The clinical symptoms of feline rhinotracheitis are marked conjunctival swelling, red eyes, sensitivity to light, increased blinking, and increased eye discharge that can be clear fluid or pus. If the conjunctivitis is left untreated, the disease can progress to excruciatingly painful ulcers in the eyes. The course of the disease can last 2 weeks to three months if untreated or seven days if treated.
The treatment regimen usually includes topical antibiotics, antivirals, and treating the ulcer. Antiviral drugs are expensive and are available in a topical and systemic form. Anti-inflammatories such as Metacam can help reduce inflammation in the eyes and the upper respiratory system. Studies have shown that steroids and cyclosporine A can suppress clinical symptoms, but they do not remove the virus. A cat’s or kitten’s response to treatment will depend on its immune status and general health.
Chlamydia: Chlamydia psittaci is similar to herpes virus but is less severe in clinical symptoms. The clinical symptoms of chlamydia psittaci are similar: conjunctival swelling, red eyes, increased eye drainage, and squinting. The symptoms can be seen in one eye or both eyes. This disease can have a respiratory component, or it can just cause symptoms in the eye. Typically, kittens acquire the disease from their mothers. This disease can last months if untreated or 3-7 days if treated.
The treatment of choice is a topical ophthalmic antibiotic tetracycline. Doctors will avoid using steroids in the eyes if there is the possibility of mixed infections or if the eye has an ulcer. If the kitten or cat has respiratory symptoms, oral tetracycline is the antibiotic of choice. Anti-inflammatories such as Metacam can help reduce inflammation in the eyes and the upper respiratory system.