Diagnosis of Feline Chlamydiosis
Diagnosis is usually based on clinical symptoms, as well as the cat's medical history. Several tests can detect C. psittaci in the cat's eye discharge and confirm the diagnosis. They involve using cotton or gauze to collect eye discharge samples from the conjunctiva.
Swab samples can be stained with a special dye that identifies inclusion bodies (structures inside the nucleus of bacteria-infected cells). Inclusion bodies are more numerous during the first 4 to 7 days of clinical disease.
A bacterial culture (the growth of cells in a special medium so the bacteria can be identified) can be done, though it can be difficult to distinguish C. psittaci from normal respiratory tract bacteria.
Immunofluorescent assay (IFA) uses special proteins labeled with a fluorescent chemical to locate C. psittaci antibodies (proteins that the immune system manufactures to fight the bacteria). If the antibodies are present, the bacteria are present.
Feline Chlamydiosis Differential Diagnosis
Clinical symptoms of chlamydiosis are similar to those of other feline upper respiratory infections.
Cats with feline calicivirus infection usually have ulcerative stomatitis (an inflammation of the mouth that causes ulcers on the tongue and lips) and are more likely to have pneumonia. Because it's caused by a virus and not a bacteria, calicivirus infection does not respond to antibiotics.
Cats with rhinotracheitis usually have severe sneezing (as opposed to occasional sneezing), more rapid onset of conjunctivitis, and ulcerative keratitis. Rhinotracheitis is also caused by a virus, so it doesn't respond to antibiotics.
Some cats with URI symptoms may have pneumonia caused by another type of bacteria, which should be identifiable on a lung x-ray.
Treatment for Feline Chlamydiosis
Chlamydiosis usually is mild enough to be treated with antibiotics on an outpatient basis. Tetracyline eye ointment is usually prescribed to treat the infection. Cats generally need to be treated for several weeks, sometimes as long as 6 weeks. In cases of chlamydiosis outbreaks in multicat households or pet adoption shelters, all the cats may need to be treated. Pet owners should keep their cat's eyes and nostrils clean and clear of discharge.
Infected cats should be separated from other cats and kept indoors to prevent the spread of infection, and to minimize the cat's exposure to outdoor stressors, like fights with other cats.
Some veterinarians recommend that infected cats be vaccinated. Vaccination can reduce the severity and duration of the disease. Some cats may experience a slight adverse reaction to the vaccine (i.e., a short-lived, mild, clinical disease).
Supportive nutritional therapy (e.g., feeding the cat through a tube or intravenously) generally isn't necessary unless the infection occurs with another URI, and the cat becomes anorexic.
Feline Chlamydiosis Prevention
Cats that live in multicat households or pet adoption shelters should be vaccinated. Vaccination may not prevent infection, but it can reduce the severity and duration of disease. Cats should receive one vaccination at their initial visit, and annual vaccinations thereafter.
Veterinarians generally recommend that cats that live in single-cat households not be vaccinated because the incidence of disease is so low.
Feline Chlamydiosis Prognosis
Chlamydiosis is a mild disease, and the prognosis is generally very good. It tends to be chronic unless the cat is treated with tetracycline.