Alternative names
Ornithosis; Chlamydia psittaci

Psittacosis is an infection caused by the bacterium Chlamydia psittaci, which is spread to humans by birds, causing systemic (throughout the body) symptoms and pneumonia.

Causes, incidence, and risk factors

Psittacosis is caused by Chlamydia psittaci, a bacterium found in the droppings of birds. It is a rare disease- fewer than 50 cases have been reported in the U.S. in the past 5 years.

Bird owners, pet shop employees, workers in poultry processing plants, and veterinarians are at increased risk for acquiring this infection.


  • Fever and chills  
  • Muscle aches  
  • Headache  
  • Fatigue  
  • Dry cough  
  • Shortness of breath  
  • Rales may be present  
  • Blood-tinged sputum

Signs and tests
Abnormal lung sounds such as rales and decreased breath sounds are heard when listening to the chest with a stethoscope.

Tests include:

  • X-ray of the chest (interstitial infiltrates)  
  • CT scan of the chest  
  • Blood gas (decreased oxygen saturation)  
  • Sputum culture  
  • Blood culture (grows chlamydia)  
  • Antibody titer

The infection is treated with antibiotics, including:

  • Tetracycline  
  • Doxycycline  
  • Erythromycin  
  • Azithromycin

Note: Oral tetracycline is usually not prescribed for children until after all the permanent teeth have erupted. It can permanently discolor teeth that are still forming.

Expectations (prognosis)
Full recovery is expected.


  • Decreased pulmonary function as a result of the pneumonia  
  • Heart valve infection  
  • Hepatitis (inflammation of the liver)  
  • Brain involvement

Calling your health care provider
Antibiotics are needed to treat this infection. If you develop symptoms suggestive of psittacosis, call your health care provider.

Avoid exposure to suspect birds (often imported parakeets and similar birds carry this bacterium). Treat underlying medical problems that cause immune dysfunction and increase susceptibility to this disease.

Johns Hopkins patient information

Last revised: December 5, 2012
by Potos A. Aagen, M.D.

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