Psittacosis is a disease caused by the intracellular bacterium Chlamydia psittaci. This bacterium is zoonotic, which means that it can be transmitted to people from birds and vice versa. This is why it is important for all bird owners to know about this disease and how to keep your birds and yourself safe.
So how do birds get the disease? This organism can be shed in large numbers in the feces, urine, and from the oral cavity and/or from respiratory secretions of affected birds. It can also be found in the crop milk of pigeons and doves. The particles can be aerosolized when the birds beat their wings. This infects others, which includes birds and people who breathe in the dander. Infection then takes place quickly as the organisms replicate rapidly in the lungs, air sacs, and pericardium about 24 hours after inhaling or ingesting them. Within 48 hours, the organisms can be detected in the blood and they are able to shed or release the organism at about 72 hours post-infection. This means that disease spreads quickly in a flock.
It appears that when the organisms enter the respiratory tract, the infection spreads to other adjacent organs like the liver and spleen. When the organisms enter by the oral route, the signs are often less and can lead to a chronic non-symptomatic form of the disease. There has been transmission through the egg in some species of birds including the budgie. Cockatiels can be frequent carriers of the disease and can shed C. psittaci in their feces for more than a year.
What are the symptoms of the disease in birds? The disease varies based on the strain of the organism; some produce severe symptoms while others cause very mild symptoms. They also vary based on the species of birds affected. Often, birds have respiratory signs along with GI signs. Psittacines can have signs ranging from dyspnea (trouble breathing) to oculonasal discharge to anorexia to bright green feces to regurgitation and/or vomiting. The bird may also have neurologic signs, especially in cockatiels, which may suffer tremors or twisting of the head, body, and neck. In other situations, particularly in lovebirds, there may be no signs previous to the bird being found dead.
In birds, the incubation time or the time from infection to development of signs is about 3 days to several weeks up to a month. However, birds can develop signs without an identifiable risk factor. This is most likely the consequence of being in a carrier state.
How do you know if your bird is free of this disease? The quickest and preferred method of detecting the Chlamydia organism is a PCR, polymerase chain reaction, test. This reliable, sensitive test does not rely on the organism being viable, as with a culture. Chlamydia is very difficult to grow. Because it is zoonotic, not all labs will attempt to grow the organism. There are some serologic tests of the blood available, but those tests can have more interpretive problems.
Clinicians may determine that an avian patient has the disease if the bird fits the clinical picture based on CBC (Complete Blood Count) and profile blood tests along with X-rays. On X-rays there may be an enlarged liver and/or spleen with changes in the lungs (pneumonia) and air sacs (air sacculitis, or inflammation of the air sacs). These may then be part of the diagnostic plan. The clinician may then take swabs of the oropharynx, fresh feces of the cloaca, and blood for testing by PCR. These testing sites can also be used by PCR to test a well bird to make sure that the bird does not carry the disease; such tests are often recommended during the first visit to the avian veterinarian.
From this information, you as a good bird owner then know that you should not take your bird to functions with other birds unless all are tested and negative for C. psittaci. Also because the organism can be aerosolized, I recommend against purchasing food from bulk bins.
Treatment For Psittacosis
The traditional treatment of this bacterium is the use of doxycycline for 45 days. The reason that the course of therapy is so long is that the C. psittaci organism can hide out in the macrophage — a type of white blood cell in the bloodstream. Unfortunately, doxycycline cannot reach the organism in the macrophage when it is in its non-replicative cycle. But during its cellular division, which occurs at least two times during a 45-day treatment period, the organisms are released from the macrophage, which provides a time that the doxycycline can kill them. For this reason, the bird or birds must be retested after the end of the treatment period to make sure that the birds are free from disease and are not clinical carriers.
Several forms of the drug can be administered, so options should be discussed with your veterinarian. Doxycycline can be administered in the water, and the dose depends on the species of bird. It can also be coated on specified seeds with oil or administered directly by mouth. The doses vary based on the species of birds.
Dangers of Psittacosis
Psittacosis is a zoonotic disease that can affect people, so it receives a higher level of attention than other diseases. How it is reported and treated varies among countries and even among U.S. states. In humans, the signs occur about 5 to 14 days after incubation but can take up to a month to appear. Typically, the symptoms are non-specific and include headache and muscle aches, and flu-like symptoms with upper respiratory signs. People tend to have swollen lymph nodes with high fevers, particularly at night. The symptoms worsen without proper treatment of the organism. Azithromycin is commonly used for humans and is an effective form of treatment.
Since the disease can be deadly for birds as well as humans, we as bird owners need to understand this disease so that we can all be safe!