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Written by Lee-Anne, Birdmad Girl

What Is Psittacosis?

A Scarlet Macaw recovering from psittacosis

Psittacosis is a disease caused by a bacterium called Chlamydophila psittaci. This disease is also referred to as Chlamydiosis, Parrot Fever, and Orthithosis. The genus Chlamydia consists of two groups of bacteria; groups A and B. Group A is represented by Chlamydia trachomatis, which is responsible for trachoma and genital infections in humans. Group B comprises strains of Chlamydophila psittacil. Psittacosis is the term most commonly used to describe the disease in psittacine birds (parrots, parakeets) and in humans. This disease is also seen in pigeons, doves and domestic poultry, but is more commonly referred to as Ornithosis in these circumstances, because these are non-psittacine birds. The term Chlamydiosis is used to describe the infection of any animal with any species of chlamydia.

The organism Chlamydophila psittaci has some typical characteristics of bacteria, like it is sensitive to antibiotics, but it also resembles a virus because it can only grow and multiply within the cells of its host.

How is it transmitted?

In birds, Chlamydophila psittaci is endemic in many wild parrots. Infected birds can carry this disease throughout its life without showing any clinical symptoms, and can continue to spread the disease continuously via excretions of infected particles. Birds that harbor the disease can develop clinical symptoms when placed in a stressful environment, for example, being captured and placed with many other birds for transit. Infection from carrier birds to other susceptible birds in these environments is a huge opportunity for spread of infection. Because originally the ancestors of our captive pet birds were potential carriers, any captive bred bird can still be a carrier from having the disease passed down through the generations.

If you have never tested your birds for psittacosis, it is possible that you may have a carrier bird in your flock. Birds can be carriers for years until some stress, such as a change of diet, moving of the cage etc, triggers the shedding of the organism, and then an outbreak can occur in a closed population, even if you have not bought in any new birds. Carrier birds can spread the disease to other susceptible pet birds via dust, nasal or fecal secretions. It is therefore very important that any new pet bird you intend to add to your existing flock should have a period of at least 30 days quarantine and an avian vet check up that includes a psittacosis test, before being introduced to your birds.

If you do have an uninfected bird that does come into contact with a carrier bird, and the uninfected bird is weak and susceptible due to stress or a poor diet, that bird can easily contract the disease quickly, and immediately fall sick with it. Sometimes a bird owner will add a seemingly healthy new bird to their flock, only to watch their older birds fall sick, with the new bird showing no symptoms. This is because the new bird is a carrier, and the older birds were more susceptible to the disease.

The incubation period of the disease is extremely variable, and this can cause confusion when attempting to source the infection. The minimum interval is usually documented at 42 days, but only 10 days is possible. At the same time an infected bird will start shedding Chlamydophila, therefore becoming contagious, 10 days before it shows signs of illness itself, thus being a risk to other birds while it still appears "healthy." The maximum incubation period is pretty much open ended. Periods from nine months to one and half years have been recorded.

In humans, we are most likely to catch psittacosis from contact with infected birds. We can catch it from breathing in Chlamydophila, when an infected bird releases fine droplets or dust particles containing urine, feces or respiratory secretions into the air. It can also be caught via direct contact with infected bird feathers, feces or from bite wounds. Human to human spread is vary rare, but not impossible. Even an infected bird that appears clinically healthy can he a hazard to anyone in the same room, and the disease can be contracted even from a very brief contact with an infected bird.

Clinical Symptoms

Cockatiel presenting with nasal and eye discharge, and feather picking

As I have mentioned previously, it is possible for carrier birds to not present any clinical symptoms, and appear to be clinically healthy. It is only when a bird becomes sick with the disease that symptoms will start to become apparent. The clinical signs are not really specific to the disease, and the symptoms that are shown can also be symptoms of other diseases. Psittacosis should always be ruled out as the possible cause of any non-specific disease, especially in a recently purchased bird that might be susceptible from the stress of moving home.

There are a wide range of clinical signs. In the early stages of the disease, symptoms can include tiredness, loss of appetite, weight loss, shivering, sneezing and nasal discharge, and watery droppings. In more acute stages, there is usually severe depression, loss of appetite, ruffled feathers, watery droppings, thick nasal and eye discharge, respiratory distress with rapid breathing, diarrhea and sudden death. The diarrhea is typically bright fluorescent green. Affected birds may show any combinations of these symptoms, which can vary from mild to severe. Psittacosis can also be present as a localized conjunctivitis without any other signs of the disease. Birds with psittacosis may also present with feather picking.

In humans, the symptoms are often flu-like at the beginning and can include high temperatures, head and neck pain, fever, aching joints, chest tightness and pain, and a dry cough. If left untreated it can progress very seriously and can cause death.

How serious is it?

If your bird becomes sick with psittacosis, and does not receive treatment, it can lead to the death of your bird. Sometimes symptoms are so mild and non-specific that owners do not always notice that there is something wrong. Birds are especially skilled at hiding their symptoms, because in the wild a sick bird will be seen as a risk to the flock, and will either picked on by the flock so that they eliminate the weakness amongst them, or will be picked off by predators. The natural response of a bird to hide symptoms until they are very sick is called the preservation response.

It is therefore advisable to get all new birds tested for psittacosis as soon as you get them. If the disease is present, it can be treated before the bird becomes too sick, and the quarantine period will ensure that the disease is controlled before any other birds come into contact with the infected bird.


There are a few different tests that vets use to test for the presence of psittacosis. Clinically it can be a difficult disease to diagnose accurately, which is why there are various different methods of testing that are used, all of which have their benefits and disadvantages.

Usually, various tests can only detect Chlamydophila psittacid during an active infection. When Chlamydophila psittaci bacteria become active, they reproduce by breaking out of their host cells (they live withing the cells of tissue) and invade other cells. It is during this time, when the bacteria are in transit, between cells, that various test can detect their genetic material and when medicine can destroy them. They are active during an infection, and in carrier birds when they transport from one cell to another, hence the disease is shed intermittently in carrier birds.

Some tests work by testing for the presence of Chlamydophila psittaci the organism that causes psittacosis. There is a test called a PCR test, that can be done from either blood of fecal samples, and it identifies the organism from small amounts of its genetic material. The fecal samples should be collected each day, over a period of 5 days, and then tested. This is because a carrier bird sheds the organism intermittently, so a single fecal sample alone may test negative, when in fact the bird is positive, because the bird may not have been shedding the disease at the time of the sample.

There is also a test that involves taking a cloacal swab and/or a fecal sample and sending it for a cultural examination. The problem with this test is again that the bird may be shedding the disease intermittently, and also this particular organism can be quite difficult to grow. The organism could have died in transit to the laboratory if not packaged properly, therefore the test outcome may show a false negative.

There is another test called The Immunocomb (IC) ELISA test. This works by testing the level of Chlamydophia psittaci antibodies within the blood of the infected bird. One of the benefits of this test is the speed at which a result can be known. These test kits can be kept in-house at veterinary clinics and can give a result in just a few hours.

Treatment can also affect these tests. A bird that is undergoing treatment for psittacosis should stop actively shedding the disease 48 hours after treatment has started. Therefore, if a bird that is already on the same antibiotic used to treat psittacosis, and has a fecal or cloacal swab taken, the result may show a false negative.

The Immunocomb test can also show up a false negative if the test is done on a bird during the acute stage of infection before a detectable antibody titre has been produced or in the terminal stage. Antibiotics can also affect this test result, especially following treatment. After treatment, this test may show a false positive because of the high levels of antibodies in the blood from fighting the infection. However, after successful treatment, the antibody level should half more or less every three months, so the strength of the positive result must be assessed each time to make sure that the positive is becoming weaker.


The author with a Molluccan Cockatoo, still feather plucking following treatment

Tetracyclines are considered the most suitable antibiotics for treat psittacosis, with Doxycycline being the most popular choice. Treatment usually involved a series of 9 Doxycycline injections given 5 days apart, therefore lasting over a 45 day period. The volume of such injections can make the breast quite sore, so some people prefer to opt for a water soluble alternative called Ornicure. This is not as effective because you can never be sure that a bird gets the correct dosage with water administered medication, because you cannot determine how much the bird will drink. Due to varying nutritional requirements and appetites, it can be difficult to ensure that a bird takes in sufficient concentrations of the drug for the required period. Therefore this method of treatment will usually be suggested only if injections are a problem, or if frequent visits to the clinic are difficult.

Whilst it is possible to totally free the bird of this disease with treatment, it is also possible that the bird will remain a carrier following treatment, therefore it is advisable to have an annual psittacosis test done if your bird has been treated for psittacosis.

Treating the infecting bird is just one part of the battle against psittacosis. The Chlamydophila psittaci organism can survive outside the host for approximately one month if protected by cell debris and protein material, like droppings and nasal discharges. Therefore, when considering disease prevention and control, cleanliness, cage hygiene and good disinfection are very important, and the birds environment (ie, your home) must also be made free of any lurking Chlamydophia psittaci organisms. Ask your avian vet for disinfectant like F10 or Tri-Gene, that is effective against this disease.

I would like to thank the following people for their information and help:
Retief W Ehlers B.Vet.Med, MRCVS (article verification)
Alan K Jones B.Vet.Med, MRCVS (references)

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