Chlamydophilosis in Birds

Chlamydophilosis, also called psittacosis, chlamydiosis, and parrot fever, is a common disease of birds. It is also referred to as ornithosis in birds other than parrots. While this disease can occur in any bird, it is especially common in cockatiels, budgerigars (often referred to as budgies), 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 Chlamydophila that affects people.

What causes chlamydophilosis?

Chlamydophilosis is caused by infection with an obligate intracellular bacterial organism called Chlamydophila psittaci (C. psittaci). This organism used to be called Chlamydia psittaci. Both terms can be found in scientific literature as causing this disease in people and birds. This organism shares similarities with viruses and parasites in that it has to live inside host cells to survive and reproduce; however, it is now classified as a bacterium. Like a virus, but unlike many other bacteria, it lives right inside the cells of the bird, making it difficult to kill with treatment.

What are some common signs of chlamydophilosis in birds?

Chlamydophilosis 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, at all, and are then asymptomatic carriers. In general, birds with chlamydophilosis exhibit a decreased appetite, weight loss, lethargy, diarrhea, nasal or ocular discharge, a fluffed-up appearance, and 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, chlamydophilosis causes chronic respiratory (sneezing, coughing, runny eyes or nose) or gastrointestinal signs (diarrhea).

"Some birds can carry Chlamydophila psittaci asymptomatically."

Classically, chlamydophilosis causes lime-green or yellow-green feces and urates (the normally solid white part of the droppings) due to Chlamydophila infection of the liver. However, these changes to the droppings are not seen all the time, and other diseases that affect the liver can also cause discolored droppings. Some birds can carry C. psittaci asymptomatically, which means they carry the infection and spread it to other birds (and to people) through their droppings and respiratory tract secretions but are not sick themselves. Chlamydophilosis is most commonly 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 for testing all newly-acquired birds for chlamydiosis.

How is chlamydophilosis diagnosed?

Several tests are available for diagnosing chlamydophilosis in birds, but none are 100% reliable. Testing birds for the presence of this infection often includes a combination of tests reach a diagnosis. Typically, your veterinarian will check your bird’s complete blood count (CBC) for elevations in white blood cells, suggesting 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 chlamydophilosis. Sometimes they will also perform a polymerase chain reaction (PCR) test looking for genetic material of this bacteria in your bird’s blood and/or stool.

Veterinarians who specialize in treating birds also will commonly run a protein electrophoresis (EPH) test in birds with suspected disease. While an EPH does not specifically test for chlamydophilosis, 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 also 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 still be infected with this disease but not be actively shedding 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 C. psittaci infection.

Tests run on deceased birds are particularly useful for veterinarians who are deciding whether to treat other birds for chlamydophilosis if they have been in contact with the dead bird, even if the other birds are not showing signs of illness.

How is chlamydophilosis treated?

Treatment is usually with oral or injectable doxycycline antibiotic. Since doxycycline only kills the Chlamydophila organisms when they are active and dividing, and the lifecycle of these organisms is prolonged, with possible periods of dormancy (ceasing to be active for a period of time), drug treatment should go on continuously for the recommended period of 45 days, without interruption.

Owners may choose to give oral medication twice a day at home for 45 days or visit their veterinarians for weekly shots of long-acting doxycycline for six weeks. Since doxycycline, like other antibiotics, kills helpful, as well as harmful, bacteria in a bird’s gastrointestinal (GI) tract predisposing birds to yeast infections, many veterinarians will prescribe a probiotic medication during treatment to help promote the growth of helpful GI bacteria. After the 45-day treatment, some veterinarians will recommend repeating tests for C. psittaci to help ensure the treatment was effective.

Can chlamydophilosis affect humans?

Yes! C. psittaci is a zoonotic disease, meaning it can be passed not only from bird to bird, but also from bird to human, usually through inhalation or ingestion of contaminated fecal matter or dust containing dried respiratory tract secretions from an infected bird. In humans, this disease often causes flu-like respiratory tract signs such as fever, sweating, headache, fatigue, muscle pain, inappetence, nausea, vomiting, diarrhea, and a dry cough.  If you develop these signs, particularly if you have been around a bird, seek help from your own medical doctor. Since chlamydophilosis 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.