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:


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:

Home Care

There are several things you should do at home:

Preventive Care

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

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.

Therapy In-depth

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:

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.