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Chlamydial Conjunctivitis in Cats (Feline Pneumonitis)

By Kirk N. Gelatt, VMD, DACVO, Emeritus Distinguished Professor, Department of Small Animal Clinical Sciences, College of Veterinary Medicine, University of Florida ; David G. Baker, DVM, MS, PhD, DACLAM, Director and Professor, Division of Laboratory Animal Medicine, School of Veterinary Medicine, Louisiana State University ; A. K. Eugster, DVM, PhD, Director and Head, Diagnostic Services, Texas Veterinary Medical Diagnostic Laboratory

Also see professional content regarding chlamydial conjunctivitis.

Chlamydial conjunctivitis is an infection of the membranes around the eye. Different strains of Chlamydophila psittaci and Chlamydia pecorum bacteria cause significant eye infections in cats. The disease in cats is also known as feline pneumonitis, which can be misleading because these bacteria rarely cause pneumonia in cats. The infection usually involves the eye and the upper respiratory tract (the nose, sinuses, and throat).

Signs in cats range from watery to mucus- and pus-filled inflammation of the conjunctiva and inflammation of the mucous membranes of the nose. Early signs are reddened, slightly swollen conjunctivae in one eye. Conjunctivitis in both eyes develops after a few days, and the conjunctivae become full of blood and swollen around the cornea. The signs are most severe 9 to 13 days after onset and then subside over 2 to 3 weeks. In some cats, however, signs can last for weeks despite treatment, and recurrence is not uncommon.

Your veterinarian can confirm the diagnosis by taking a smear from the conjunctiva and finding the chlamydial organism under a microscope. It is important to identify the organism causing conjunctivitis in order to provide effective treatment.

There are various medications and ointments your veterinarian can prescribe after infection occurs. Be sure to follow directions carefully and for the full period prescribed by your veterinarian. To reduce recurrence, treatment in cats is usually continued for 7 to 10 days after signs disappear. So, even though your cat looks better, be sure to follow the treatment program for the full length of time prescribed.

Vaccines are available for chlamydiosis in cats. The vaccine does not completely protect the cat from infection, but it can significantly reduce the severity and likelihood of infection. You may want to discuss with your veterinarian whether vaccination is appropriate for your cat.

There have been occasional reports of transmission of the Chlamydia bacteria from cats to people, so frequent hand-washing and other good hygiene measures are recommended when treating a sick cat to reduce the chance of infection in people.