Chlamydiosis is a bacterial infection that affects cats. It causes the inside of the eyelid and the white part of the eye to become inflamed. Though it’s often relatively mild at first, affecting only one eye, this disease can progress to both eyes, leading to heavy discharge and such painful swelling that infected cats keeps their eyes half closed. The bacterium that causes Chlanydiosis is spread directly through cat to cat contact. The cats that are most susceptible are kittens and older cats that live in close proximity to lots of other felines. Pet medication such as antibiotics are very affective against this infection and a vaccine may also be useful in minimizing its affects. Left untreated, Chlanydiosis can become a chronic problem.