Chlamydiosis (Psittacosis, Ornithosis)

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.

    With respect to birds, the organism is most commonly recovered from psittacine birds, pigeons and doves. Were it not for the potential for this organism to occasionally be passed from birds to humans, it is probable that C. psittaci would be viewed as any other treatable bacteria in birds. Chlamydia infections can cause varied problems and/or clinical changes depending on the strain and quantity of organism to which a bird is exposed and the species, age and condition of the bird.

    The fact that many healthy birds have antibodies against this organism suggests that most birds exposed to chlamydia mount an appropriate immune response that prevents the organism from causing progressive disease. Some infected birds will die shortly after clinical changes are first noted, while others can develop a mild disease and shed the organism for an extended period.

    Chlamydiosis causes symptoms that are similar to those associated with many bacterial, fungal or viral infections. Mycobacteriosis, aspergillosis and mycoplasmosis cause particularly similar clinical changes. Toxins that affect the liver or digestive tract can also cause clinical signs similar to chlamydiosis. Chlamydiosis should be considered in any bird with clinical signs that suggest damage to the respiratory or digestive tracts. These include difficult breathing, depression, weight loss, loss of appetite, diarrhea, nasal discharge, swelling of the tissues around the eyes or discharge from the eyes. Yellowish or greenish discoloration of the urates and urine is a common symptom. This discoloration is not specific to Chlamydia, however, since it can be seen anytime cells in the liver are damaged.

    Chlamydia is most frequently transmitted through direct contact with feces, or ocular or nasal secretions from an actively infected bird. This organism can remain infectious in dried feces for several months, and contaminated enclosures, toys, perches and food bowels can serve as a source for indirect exposure to the organism. The most severe outbreaks of disease typically occur in crowded conditions where numerous birds congregate. It has been suggested that chlamydia may be shed in the feces for several days to a week before a bird develops obvious signs of disease. The reported incubation period ranges from 5 to 42 days.

    Diagnosis In-depth

    Your veterinarian may use radiographs (X-rays) or changes in the types of blood cells (CBC) or enzymes found in the blood (blood chemistry) to evaluate the overall health status of a sick bird. Results of these tests may raise the index of suspicion that chlamydia may be involved in the disease process.


    The most common radiographic changes associated with chlamydiosis include an enlarged liver, enlarged spleen and inflammation of the air sacs. However, all of these changes can also occur from other causes.

    Complete Blood Count

    The most common changes in the blood are a substantial increase in the number of white blood cells, particularly heterophils and monocytes. A decrease in the number of red blood cells (anemia) is common in birds with chronic forms of the disease.

    Serum Biochemistry Profile

    The most common change is an increase in liver enzyme activity. All of these blood changes can also occur from other causes. Therefore, specialized testing of swabs from the choana and feces, whole blood and/or serum, will be necessary to determine if an active chlamydial infection is present.

  • Confirming an active case of chlamydiosis is best achieved by combining tests that detect antibodies against the organism with tests that demonstrate that chlamydia, or pieces of the chlamydia organism, are present in a sample. Currently available antibody assays include complement fixation, elementary body agglutination and indirect fluorescent antibody. Tests to detect the presence of the organism in living birds include culture, ELISA and DNA probe-based assays (PCR).
  • Tests like culture and DNA probe-based assays are most valuable in birds with suggestive clinical signs, since these birds are most likely to be shedding chlamydia from the respiratory and/or gastrointestinal tract. Culture remains the gold standard for documenting the presence of chlamydia in a clinical sample. However, culture is problematic, time consuming and expensive in comparison to other tests. Samples for culture should be refrigerated but not frozen. Because the quantity of chlamydia shed by an actively infected bird appears to vary from day to day, collecting a pooled sample of excrement for 3 to 5 days may improve the sensitivity of culture. During the pooling process, the samples should be kept in a sealed container in a refrigerator that is not used to store food. If a swab for DNA probe-based testing or culture is not slimy after sampling the choana and not coated with excrement after sampling the feces, then it is a poor quality sample.
  • Tests that detect antibodies to chlamydia are best for determining if birds have previously been infected. A single positive antibody titer only indicates that a bird was infected with C. psittaci in its immunologic definable past, but it does not indicate that a bird is actively infected. Currently, antibody tests can only be used to confirm an active infection if there is a significant increase in the antibody titer in serum samples that are collected several weeks apart and tested with the same type of assay.
  • Antibody tests are of least value during the earliest phases of an infection when a bird might be clinically ill, shedding the organism, but antibody negative. Additionally, early treatment with antibiotics may alter the normal immune response and thus cause false negative or lower than expected antibody results.
  • A positive result from a DNA probe-based assay is more likely to be the result of an active infection with Chlamydia.
  • Currently, there is no test that can be used to confirm that a bird does not have chlamydia. However, a lack of detectable antibodies in serum coupled with an inability to detect the organism at a portal of exit provides supportive evidence. 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).

    Therapy In-depth

  • Because C. psittaci can infect humans and occasionally cause disease, many states require that confirmed cases must be reported to local health officials. The requirements for what constitutes a confirmed diagnosis vary from state to state. Once the disease has been reported, a state official may dictate the treatment protocol or may leave treatment to the discretion of your veterinarian. If given a choice, your veterinarian will use doxycycline to treat your bird for chlamydiosis. Other therapies that may be needed include fluids to correct dehydration and supportive nutrition if the bird has not eaten for several days or has lost considerable weight.
  • Depending on ease of administration, your veterinarian may suggest an injectable or oral form of doxycycline. The injectable preparation is given in the muscle once each week. The oral medication is administered several times a day. If a large number of birds must be treated, your veterinarian is likely to suggest adding doxycycline to a specially prepared mixture of rice, beans and corn. Research conducted at North Carolina State University suggests that doxycycline will reach therapeutic blood levels when added to the drinking water of some birds. Irrespective of the route of administration, your veterinarian will probably recommend that treatment continue for 45 days.

    Optimal treatment for your companion bird requires a combination of home and professional veterinary care. Follow-up can be critical, especially if your bird does not rapidly improve. Follow-up care consists of the following:

  • Make certain you administer all prescribed medications at the appropriate times. Contact your veterinarian immediately if you are having difficulties treating your bird as prescribed. If you are having problems, it may be best to hospitalize your bird to assure that a proper course of treatment is administered.
  • Keep your bird isolated from other birds to prevent transmission.
  • Wear a dust mask when handling the waste of your infected bird. To reduce dust, use a misting bottle filled with disinfectant to moisten excrement and feather debris before handling.
  • If your bird is diagnosed with chlamydia and you or any family members have flu-like symptoms, have your physician talk directly with your veterinarian.
  • The clinical changes associated with chlamydiosis should improve dramatically within 12 to 24 hours after starting doxycycline therapy. If your bird does not respond within this time period, you should contact your veterinarian.
  • Some birds will regurgitate or have discolored excrement when given the oral form of doxycycline. If your bird is regurgitating, contact your veterinarian.
  • Birds that recover from chlamydiosis are subject to reinfection. Thorough cleaning and disinfection of the contaminated environment is necessary to reduce the chance of reinfection. Thus, birds being treated for chlamydia should be maintained in an isolated area that is easy to clean and disinfect.
  • Chlamydia can be inactivated with household bleach, isopropyl alcohol, quaternary ammonium compounds or chlorophenols.
  • If you are a bird breeder, ask your veterinarian about starting a chlamydial screening program for your aviary. To find an avian veterinarian in your area who can test for chlamydia, contact the Infectious Disease Laboratory at the University of Georgia College of Veterinary Medicine (706-542-8092).

    Testing for chlamydia may help to control spread of the disease by identifying those birds possibly infected. However, given that free-ranging birds can serve as a reservoir for chlamydia, testing does not restrict organism spread within a group of birds. And the fact that many breeders of smaller less expensive birds are not likely to attempt to control chlamydia through testing, a vaccine will ultimately be needed to reduce the uncontrolled spread of chlamydia among companion birds.

    A research team at Louisiana State University is actively involved in developing and testing a vaccine to help reduce the unrestricted spread of C. psittaci among companion birds. In the future, it is likely that you will be able to vaccinate your bird to prevent chlamydiosis.

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