Chlamydiosis in Birds

By Gregory Rich, DVM; Laurie Hess, DVM; Rick Axelson, DVM

Amazon parrot with nasal discharge; a sign of chlamydiosis.Chlamydiosis, also called psittacosis or parrot fever, is a common disease of parrots. The disease is caused by the organism Chlamydia psittaci. It is also referred to as ornithosis in birds other than parrots, like canaries, doves, and pigeons. While this disease can occur in any bird, it is more common in cockatiels, budgerigars (often referred to as budgies), amazon parrots, macaws, and lorikeets.

The disease can cause chronic infections, asymptomatic infections, or sudden death. The disease can also be transmitted to people, particularly if they are immunosuppressed. It is not associated with the venereal form of Chlamydia that affects people.

What causes chlamydiosis?

Chlamydiosis is caused by infection with a bacterial organism called Chlamydia psittaci, also referred to as C. psittaci. This organism shares similarities with viruses and parasites in that it must live inside host cells to survive and reproduce; however, it is classified as a bacterium. Like a virus, but unlike many other bacteria, it lives inside the cells of the bird’s internal organs, making it difficult to kill with standard antibiotic treatment. (Photo courtesy of Gregory Rich, DVM.)

What are some common signs of chlamydiosis in birds?

Chlamydiosis can cause many different clinical signs, and therefore it should be suspected in any sick bird with generalized signs of illness. Some birds are infected with this disease without any signs, and are considered asymptomatic carriers.

"Some birds are infected with this disease without any signs."

In general, birds with chlamydiosis exhibit a decreased appetite, weight loss, lethargy, diarrhea, nasal or ocular discharge, a fluffed-up appearance, and/or breathing difficulties. C. psittaci may affect some or all of a bird's organ systems, most commonly the liver, spleen, respiratory tract, and digestive tract. Commonly, chlamydiosis causes chronic respiratory symptoms, such as sneezing, coughing, runny eyes or nose or gastrointestinal signs (diarrhea).

Classically, chlamydiosis causes lime-green or yellow-green feces and urates (the normally solid, white part of the droppings) due to the Chlamydia organism infecting the liver, causing a form of hepatitis. However, these changes to the droppings are not always seen, and other diseases that affect the liver can also cause discolored droppings.

As mentioned, some birds can be asymptomatic carriers of C. psittaci, which means they may harbor the organism in their liver or intestines and spread it to other birds (and to people) through their droppings and respiratory tract secretions, but they are not sick themselves. Chlamydiosis is most often spread from bird to bird when birds are housed in close quarters, such as in a pet store or breeding facility. This is a good reason to test all newly acquired birds for chlamydiosis.

How is chlamydiosis diagnosed?

Several tests (serology, PCR, culture) are available for diagnosing chlamydiosis in birds, but none are 100% reliable. A combination of tests is often required to reach a diagnosis.

  • Typically, your veterinarian will check your bird’s complete blood count (CBC) for an elevation in white blood cells, which suggests infection. 
  • They also will look at the results of a chemistry profile analysis to see whether your bird’s liver enzymes are elevated – a common finding with chlamydiosis. 
  • Sometimes, they will also perform a polymerase chain reaction (PCR) test looking for genetic material of the Chlamydia bacteria in your bird’s blood, swabs of the oral cavity, or fecal material. The presence of Chlamydia genetic material only identifies that the bird in question has been exposed to the organism. Clinical signs and other testing will be necessary to see if the organism is the cause of the illness.
  • Veterinarians who are knowledgeable in treating birds will also commonly run a protein electrophoresis (EPH) test on birds with suspected disease. While an EPH does not specifically test for chlamydiosis, it looks for patterns of change in a bird’s antibody levels, suggesting an immune response and that the bird is fighting infection.

There are other blood tests available that look for specific antibodies to this organism, but these tests cannot distinguish previous exposure to the bacteria from ongoing, active infection. Your veterinarian may also check your bird’s feces for the presence of this organism; however, birds can be infected with this disease but not actively shed the bacteria in their stool. Therefore, tests relying on the presence of the organism in the stool to diagnose active infection are unreliable and not commonly run.

Finally, special tests can be performed on the liver, spleen, heart, and air sacs of birds that have died. These tests check for the presence of C. psittaci organisms in tissues of internal organs. Tests run on deceased birds are particularly useful for veterinarians who are deciding whether to treat other birds for chlamydiosis if they have been in contact with the dead bird, even if the other birds are not showing signs of illness.

How is chlamydiosis treated?

Chlamydiosis is usually treated with oral or injectable doxycycline antibiotic. Drug treatment should go on continuously for the recommended period of 45 days, without interruption, because doxycycline only kills the Chlamydia organisms when they are active and dividing, and the life cycle of these organisms is prolonged, with possible periods of dormancy (ceasing to be active for a period of time).

You may choose to give oral medication at home, twice a day, for 45 days, or you may visit your veterinarian for weekly shots of long-acting doxycycline for six weeks. Since doxycycline, like other antibiotics, kills helpful and harmful bacteria in a bird’s gastrointestinal (GI) tract, long-term antibiotic treatment may predispose the bird to yeast infections. Many veterinarians prescribe probiotic medication during treatment to help promote the growth of helpful GI bacteria. After the 45-day treatment, some veterinarians recommend repeating tests for C. psittaci to ensure the treatment was effective.

Can chlamydiosis affect humans?

Yes, C. psittaci can infect humans. C. psittaci is a zoonotic disease, meaning it can be passed from bird to human as well as bird to bird. Infection in humans usually occurs through inhalation or ingestion of contaminated fecal matter or dust that contains dried respiratory tract secretions from an infected bird. In humans, this disease often causes flu-like respiratory signs such as fever, sweating, headache, fatigue, muscle pain, inappetence, nausea, vomiting, diarrhea, and a dry cough.

If left unattended, chlamydiosis in humans may progress to pneumonia. If you develop these signs, particularly if you have been around a bird, seek help from your medical doctor. Since chlamydiosis is a zoonotic disease, all new pet birds should be examined by a bird-savvy veterinarian and have some form of testing for this disease. But to be clear, this is not the venereal form of Chlamydia.

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