The Chlamydia family is large and made up of many different strains. Just like any family, some of its members are more of a nuisance than others, and this is very true of the condition chlamydia.
Cats may be infected by a strain called Chlamydia felis, which, as the name implies, infects cats but doesn’t usually bother people.
Although there is no link between Chlamydia felis and serious problems in people, there are anecdotal reports of people getting conjunctivitis from cats with chlamydial conjunctivitis — therefore, always wash your hands after petting a cat, especially one with sticky eyes.
The signs are usually restricted to the eyes but also include sneezing or other respiratory symptoms.
Most commonly, kittens around 8 weeks old are affected. This is because they get some immunity from their mother’s milk, but this starts to wane between 6 and 8 weeks of age.
The kitten’s immune system is still weak, and so she isn’t good at fighting off any infections yet. As the cat grows older and the immune system gets stronger, she is better equipped to fight off any chlamydia she encounters in the environment.
Chlamydia felis is widespread in the environment, but infection in mature cats is rare. This is because their immune systems mount a defense and prevent bacteria from causing clinical infection.
There are different ways of diagnosing chlamydia, but because of the distinctive symptoms, the veterinarian may go ahead and use a trial treatment rather than rack up the expense of diagnostic tests. The tests are usually reserved for cats who do not respond to treatment as expected.
A blood test can show exposure to chlamydia, but this does not prove illness (the test measures the body’s immune response, so a positive test could mean the cat has fought off infection).
Swabs taken by rolling a special cotton tip over the surface of the eye can demonstrate the presence of chlamydia, which in the presence of clinical signs is equivalent to a “smoking gun.”
Chlamydia felis is killed by antibiotics belonging to the tetracycline family.
If the symptoms are limited to the eye, a treatment applied directly into the eye (such as a medicated eye drop containing tetracycline) may be effective, but it must be a long course (at least 2 weeks is necessary).
Many experts advise topping up treatment with oral antibiotics, even if the cat is not showing signs other than sore eyes. This helps prevent the cat from shedding chlamydia and makes it less likely that the cat will go on to become a carrier that may shed chlamydia when stressed.
Good hygiene is crucial in preventing the spread of chlamydia between cats. Stop infected cats from coming into contact with healthy animals, and always wash your hands after touching an infected cat.
A vaccine is available against Chlamydia felis, but whether it should be used widely is debatable. Because of the limited nature of the infection and its response to antibiotics, it could be argued as unnecessary, except in high-risk places such as catteries or rescue centers.
- “Diagnosing and treating chlamydia conjunctivitis in cat.” Dorin & Goodwin. Vet Med, 158: 932–938.
- “Chlamydophilia felis infection.” Gruffy-Jones, Addie & Belak. J Fel Med Surg, 11: 605–609.
This pet health content was written by a veterinarian, Dr. Pippa Elliott, BVMS, MRCVS. It was last reviewed Oct. 13, 2018.