Chlamydia in Cats: Signs, Treatment, and Prevention

How it spreads

The bacterium passes between cats through close contact, mostly through discharge from the eyes. Cats pick it up when they groom each other, share bedding, or sleep curled up together. Young kittens are partly protected by antibodies from their mother for the first month or two. After that, they can catch it from the cats they live with. The bacterium can also live in the gut and the reproductive tract, but eye discharge is the main source.

Chlamydia felis does not survive long outside the body. Shared bowls, bedding, and hands play a smaller role, though they can matter in crowded places. Normal detergents and common household disinfectants kill it easily.

Signs usually appear two to ten days after a cat is infected. Some cats carry the bacterium without looking ill, and they can still pass it on. Without treatment, a cat often keeps shedding it for about two months, and sometimes much longer.

Signs to watch for

The infection usually starts in one eye and often spreads to the other eye later. These are the signs owners notice most often.

• Red, swollen tissue around the eye, including the third eyelid in the inner corner
• Puffy, jelly-like swelling of the pink lining of the eye
• Squinting or keeping the eye half closed
• Watery discharge that later turns thick and yellow or green
• Occasional sneezing or a mild runny nose
• A short spell of fever, a smaller appetite, or weight loss in some cats

Many cats stay bright and keep eating even when their eyes look very sore. Without treatment, the eye problems can drag on for weeks or months. When a cat also has a respiratory virus, such as feline herpesvirus or calicivirus, or other bacteria, the illness is often more severe.

When to see a vet quickly

Chlamydia itself is rarely an emergency. Other eye diseases can look similar at first, though, and some of them can damage the eye quickly. It is best to call your vet the same day if the eye looks cloudy or bluish, if you see a spot or dent on the clear surface of the eye, or if the cat cannot open the eye at all or keeps pawing at it. Ulcers on the surface of the eye are unusual with chlamydia, so these signs may point to another cause, such as feline herpesvirus.

A young kitten that stops eating, becomes weak, or breathes with effort also needs to be seen the same day. Small kittens can get worse fast.

How vets diagnose it

Many different germs cause sore, runny eyes in cats, and they often look alike. Feline herpesvirus, feline calicivirus, and Mycoplasma bacteria are common examples. Your vet will look at the eyes closely and may use a special eye stain to check the surface for damage.

The most reliable test for chlamydia is PCR, which looks for the genetic material of the bacterium. The vet gently rubs a small swab on the lining of the eye and sends it to a laboratory. Antibiotics given before the test can affect the result, so tell your vet about any medicine your cat has already had. Blood tests for antibodies can add information in cats that have not had the chlamydia vaccine.

Treatment and home care

Chlamydia is treated with antibiotics. Vets usually choose one from the tetracycline family, given by mouth. Treatment by mouth works better than eye drops or ointment alone, because the bacterium can live in other parts of the body too. For very young kittens, the vet may choose a different antibiotic that is safer at that age. Your vet will decide which medicine and dose suit your cat.

The course is long. Treatment usually lasts at least four weeks and often continues for a while after the eyes look normal. Cats in some multi-cat groups need an even longer course. Most cats look better within two days, so it can be tempting to stop early. Stopping too soon can let the infection come back, so vets advise finishing the full course.

Some tablets in this group can irritate the esophagus, the tube that carries food to the stomach, if they stick on the way down. Vets often advise giving a little food or water straight after the tablet. Ask your vet to show you how to give it if you are unsure.

Some cats carry the infection without signs, and cats in the same home can pass it back and forth. For this reason, vets often recommend treating every cat in the household at the same time. At home, gently wipe away discharge with a clean, damp cotton pad, using a fresh pad for each eye. Wash your hands afterward. Keep bowls and bedding clean, and go back to your vet if the eyes do not improve.

Prevention and the vaccine

A vaccine against chlamydia is available. It comes as part of some combination cat vaccines and is not one of the core vaccines that every cat needs. Vets usually suggest it for cats at higher risk, such as cats in multi-cat homes or in homes and shelters where chlamydia has already been diagnosed. It lowers the chance of illness, though a vaccinated cat can still become infected. Kittens can start at around eight to nine weeks of age, with a second dose a few weeks later. Cats that stay at risk usually get a booster every year. Your vet can tell you whether it makes sense for your cat.

Hygiene and housing matter too. In shelters and rescue homes, housing cats separately and cleaning on a set routine help stop the infection moving from cat to cat. At home, it helps to give a new cat its own room for a while before it meets your other cats, and to have any eye discharge checked before introductions.

Risk to people and other pets

Chlamydia felis spreads mainly between cats. Other cats in the home are at the highest risk, so watch their eyes closely while one cat is being treated.

The risk to people is very low. Only a few cases of long-lasting eye infection in people have been linked to infected cats. Wash your hands after cleaning your cat's eyes or giving medicine, and avoid touching your own eyes until you have. If you have a weakened immune system, or you develop a red or sore eye while caring for an infected cat, ask your doctor for advice and mention the cat's diagnosis.

Rescued and newly adopted cats

Studies find chlamydia more often in stray and shelter cats than in pet cats. It spreads where cats live close together, so it is worth knowing about if you adopt a young rescued cat.

At Paw Squadron, the first stops after every rescue are the vet and a bath. Each animal gets a checkup, deworming, and treatment against fleas and other parasites. Before adoption, every animal has a checkup, treatment, vaccinations, and a microchip. Some cats carry the bacterium without showing it, though, so signs can still appear after the move to a new home.

In the first weeks, watch your new cat's eyes closely. Book a vet visit if you see redness, squinting, or discharge, and mention that the cat came from a rescue or a multi-cat setting. If you have other cats, it helps to keep the newcomer in a separate room until your vet is happy with its health. For more health guides, browse PawPedia, and for questions about adopting, see our FAQ.