Overview

Conjunctivitis refers to the inflammation of the mucus membranes that lines the eyelids. When infected, they become swollen, dry, and itchy. The inflammation can spread to the cornea, and lead to permanent damage of the eye or even blindness. In cats, this condition is commonly seen in kittens and is usually caused by the feline herpesvirus. Outdoor kittens, feral kittens, and kittens living in shelters are especially at risk of conjunctivitis, whereas adult cats with healthy immune systems may become carriers of the virus and do not develop symptoms themselves.

The feline and human varieties of the herpesvirus are not capable of cross-species infection, but they do have similar traits. The feline herpesvirus, much like the human herpesvirus, can never be truly eliminated from the body and symptoms may recur many times during an animal’s lifetime. Therefore, it is possible for an adult cat with prior exposure to the feline herpes virus to develop conjunctivitis later in life, especially in times of stress when its immune system is compromised. The symptoms can readily be observed and prompt treatment can restore the animal’s health with minimal impact on vision.

Symptoms and Diagnosis

Symptoms of conjunctivitis include excessive squinting, redness of the eye, and increased discharge. In kittens the symptoms can be particularly severe, with large amounts of discharge so that the eyelids may be sealed shut. Infected kittens can also show upper respiratory symptoms such as runny nose, wheezing, and congestion. In very young kittens these respiratory symptoms can develop into pneumonia, which is a life-threatening disease.

Diagnosis can usually be reached if the above symptoms are present. PCR (polymerase chain reaction) testing from an eye swab can be used if one needs to be absolutely sure that the infection is caused by herpesvirus.

Treatment

The infection can be treated with anti-viral eyedrops; oral interferon may also be helpful as it boosts the immune system, which can curb the symptoms of the viral infection. If there are risks of secondary bacterial infections, topical antibiotics may be used. It is important to allow the excessive secretion to drain, and to allow proper application of topical medication, by manually opening the swollen eyelids. The amino acid Lysine might also help when given as an oral supplement, since it interferes with the virus’ ability to replicate. Lysine is readily available in health food stores, however when used on cats one should choose a formula without the preservative propylene glycol as it is harmful for cats. In most cases the symptoms respond to treatment rapidly, and the infection quickly subsides with topical medication.

Feline herpesvirus is transmitted through air and direct contact, and is highly contagious, especially in a multiple-cat situation such as catteries or shelters. While there is a vaccine for feline herpesvirus, it only reduces the severity of the infection and cannot prevent a cat from contracting the disease. Luckily, the virus can easily be destroyed in the environment by most household cleaners.