Chlamydiosis in Cats


Chlamydiosis is a common infection caused by an intracellular bacterium (a bacterium which lives inside the host’s cells) with a global distribution. The family Chlamydiae is now divided into two genera, Chlamydia and Chlamydophila. The genus Chlamydophila contains four speciesC. pneumoniae, C. felis (formerly C. psittaci var felis), C. pecorum and C. trachomatis. C. felis is the causative in cats.

C. felis predominantly affects the conjunctiva (the tissue that lines the inside of the eyelids and covers the sclera), leading to conjunctivitis (inflammation of the conjunctiva). Some cats may also develop upper respiratory symptoms.


The incubation period is between 3 to 10 days.

The eyes initially develop a watery discharge, as the infection progresses, the conjunctiva becomes reddened and swollen and the discharge becomes thicker. It may start out with discharge from one eye but usually, spreads to both eyes. Symptoms usually appear around 5 days after exposure.

Mild upper respiratory symptoms such as low-grade fever, nasal discharge, and sneezing may also be present.

Some cats are asymptomatic, but can still infect other cats via bacteria shed in the ocular discharge.

What does chlamydophilia do?

C. felis attaches to the mucosal cells of the conjunctiva, gastrointestinal and genital tracts. The eyes become red, inflamed and develop a discharge.

In young kittens, chlamydiosis may cause pneumonia.


The primary mode of transmission is direct contact with the nasal or ocular discharges from an infected cat. Kittens may become infected during birth.

Indirect contact is unlikely as C. felis doesn’t survive well in the environment, however, it is always advisable to exercise caution when dealing with infected cats and practice routine hand washing and disinfecting in order to minimise the risks of infecting other cats.

Risk factors

Chlamydiosis can affect cats of all ages, however, it occurs most often in kittens between 5 and 9 months of age or cats in overcrowded or stressful environments such as animal shelters and breeding catteries.


A tentative diagnosis can be made based on presenting symptoms. However, a definitive diagnosis will require testing as several pathogens can produce similar symptoms.

There are several tests to diagnose chlamydia, including PCR (polymerase chain reaction), immunofluorescent assay (IFA) or bacterial culture.


Antibiotic eye ointment (usually tetracycline), steroid-based antibiotic ointment or oral antibiotics.

Supportive care:

  • Nutritional support and fluid therapy to maintain hydration.
  • Remove discharge from the eyes with a warm, damp cloth.


Fortunately, C. Felis does not remain active in the environment for long. The following disinfectants are effective.

  • Bleach (sodium hypochlorite, calcium hypochlorite or sodium dichloroisocyanurate)
  • Trifectant or Virkon-Potassium peroxomonosulfate
  • Virox, Accel – Accelerated hydrogen peroxide
  • Ethanol 70%


Vaccination: There is a vaccination available for Chlamydophila felis. It can reduce the severity of symptoms but doesn’t prevent infection in the first place. A small percentage of cats can develop side effects such as lethargy, lameness, depression, loss of appetite and fever. Therefore the vaccine is only recommended for high-risk cats. The use of this vaccine and as such the American Association of Feline Practitioners don’t recommend routine use of this vaccination.

Separate infected cats from healthy cats and practice safety protocols to reduce the risk of infection. Wash hands with soapy water for twenty seconds after contact with infected cats.

Julia Wilson is a cat expert with over 20 years of experience writing about a wide range of cat topics, with a special interest in cat health, welfare and preventative care.Julia lives in Sydney with her family, four cats and two dogs. She enjoys photography, gardening and running in her spare time.Full author bio Contact Julia