Chlamydiosis (Psittacosis, Ornithosis)


Chlamydiosis is a disease caused by the bacteria-like organism Chlamydia psittaci. This is a similar bacteria to Chlamydia trachomatis, a cause of venereal disease in people, but behaves much differently. Other names for the disease include psittacosis, parrot fever, and ornithosis.

Chlamydiosis can be spread to people. Usually, the very young and very old, people on immunosuppressive medications or with immunosuppressive diseases are most at risk. Proper precautions must be taken when treating a bird with chlamydiosis.

The bacteria is spread from an infected bird in its droppings and respiratory secretions (ie. sneezing and coughing). A bird is infected by ingesting contaminated material or by inhaling the bacteria.
Chlamydial infections can cause varied clinical signs in birds. Birds with symptoms suggestive of chlamydiosis are most often birds that have been recently purchased or recently exposed to large groups of other birds.

Watch for general signs of disease like lethargy, loss or appetite and weight loss. Look also for signs of respiratory tract disease like difficulty in breathing, discharge from the nostrils, swelling of the tissues around the eyes or discharge from the eyes.

Watch also for signs of digestive tract or liver problems such as loss of appetite, diarrhea or yellowish or greenish discoloration of the urates and urine.

Veterinary Care


The bird's history and physical examination can provide clues as to whether your bird may be infected. There are several tests available to the avian veterinarian that can better diagnose the disease. Chlamydia lives inside cells, and for this reason the disease can be difficult to diagnose. No test is 100 percent accurate for diagnosing chlamydiosis. Therefore, your veterinarian must decide the best way of testing your bird. Diagnostic tests might include:

  • Complete blood count (CBC)
  • Blood chemistries
  • Cytology (microscopic evaluation of cells)
  • Radiographs (X-rays)
  • Serology (testing for antibodies)
  • Culture for chlamydia
  • DNA probe-based test (PCR) on a choanal and fecal swab.
  • DNA probe-based test (PCR) on whole blood.
  • In clinic ELISA for detecting chlamydia


    Treatment must be supervised by an avian veterinarian. Treatment usually takes 30 to 45 days, or longer. Your veterinarian will advise you on the best way to treat your bird. The most common treatments are:

  • Injectable doxycycline
  • Oral doxycycline
  • Doxycycline medicated food or water
  • Fluids and supportive nutrition

    Home Care

    There are several things you should do at home:

  • Keep your infected bird in isolation during treatment.
  • Thoroughly clean and disinfect your bird's enclosures, food bowls and non-porous toys and perches. Discard porous (wood, natural fibers, rope, etc.) objects that cannot be thoroughly cleaned and disinfected and do not replace them until treatment is completed.
  • On a daily basis, monitor fecal output to insure proper food consumption and digestion.
  • Monitor weight daily.

    Preventive Care

    There are several things you can do to prevent your bird from chlamidiosis.

  • Establish the chlamydia status of your bird using a combination of an antibody test and a DNA probe-based test. To find an avian veterinarian in your area that can test for chlamydia, contact the Infectious Disease Laboratory at the University of Georgia College of Veterinary Medicine (706-542-8092).
  • Keep your bird out of direct or indirect contact with other birds.
  • Enjoy the bird you have. If you decide to add a new bird, it should be quarantined for at least 90 days and be examined by an avian veterinarian at the beginning and end of quarantine.
  • Have any new bird tested using a combination of an antibody test and a DNA probe-based test during quarantine.
  • Purchase young birds from sources that provide documentation that each chick is tested for chlamydia prior to sale.
  • Never return a neonate to the nursery if it has been exposed to other birds.
  • Use biosecure-shipping containers to prevent exposure to chlamydia during transport.

    Chlamydia psittaci is the causative agent of psittacosis. It is classified as a bacteria even though it can only replicate when inside a cell, which is characteristic of a virus. Most species of free-ranging and domestic birds are considered to be susceptible to some strain of C. psittaci, and some strains of C. psittaci have also been associated with disease in humans, cats, koala bears, marine mammals, sheep and many other mammals.

    Humans are susceptible to at least three different species of chlamydia (C. psittaci, C. pneumonia and C. trachomatis). Until the 1980s, C. psittaci was considered a relatively common cause of upper respiratory tract disease in humans. In the 1980s, researchers found that most cases of suspected C. psittaci in humans were actually caused by C. pneumonia. Thus, literature concerning C. psittaci infections in humans prior to the 1980s is of limited value. C. psittaci and C. pneumonia both cause a flu-like illness in humans.

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