Feline chlamydiosis is a highly contagious bacterial disease that mainly affects the eyes and upper respiratory system of cats. It is caused by obligate intracellular gram negative bacteria of the genus Chlamydophila that are not very resistant in the environment. The disease is transmitted by direct contact with nasal and ocular secretions and affects cats of all ages, but more frequently young cats (from 5 weeks to 3 months of age) and cats living in communities. Very rarely the infection is transmitted from cat to man.

About 30% of conjunctivitis cases in cats appear to be caused by Chlamydophila.

It is not a fatal disease in itself, but its persistence can become chronic and insidious.

The incubation period is 3-10 days with symptoms represented by serous or muco-purulent conjunctivitis generally unilateral which subsequently becomes bilateral with hyperemia and folliculitis inside the third eyelid, associated with rhinitis with nasal discharge and sneezing, only rarely involving the lungs. Symptoms can last for weeks with other associated symptoms such as fever, fatigue, loss of appetite and weight and corneal ulcers or around the eyes and relapses are common. The differential diagnosis should include herpesvirus and calicivirus conjunctivitis.