Understanding Psittacosis

by Bob Doneley BVSc FANZCVS (Avian Medicine) CMAV

Chlamydiosis, also known as ornithosis, psittacosis, or parrot fever, is a common disease of many bird species and is caused by the organism Chlamydophila psittaci. Bird owners need to be fully informed of the implications of chlamydiosis and the potential for transmission to humans.


Transmission of Chlamydophila is primarily through inhalation of contaminated dust from droppings or feathers. Risk of infection is increased by close contact with infected birds that are shedding the organism. For this reason, the disease is more common in stressed birds (shipping, overcrowding, or malnutrition) since birds tend to shed the organism when stressed. Infected birds do not have to show specific signs of the illness in order to transmit the disease.


The visible signs of chlamydiosis are typically respiratory or gastrointestinal in nature. Lime-green diarrhoea is not an uncommon sign in many species. Some birds may show general signs of illness: lack of appetite, weight loss, depression, diarrhoea, discharge from the eyes or nostrils, or even death. However, birds may exhibit only a few visible signs of illness and those signs they do show may also be present in a number of other diseases. This is why testing is needed to narrow down the possibilities and identify the disease. Some birds that are actively infected with chlamydophila may show no signs of illness. An infected bird may carry the organism and not become identifiably ill until some stressful incident brings it out, if at all. Breeding birds can pass the organism to their young. Baby birds are more susceptible to severe infection than adult birds and may die in the nest or soon after weaning.


A confirmed diagnosis of chlamydiosis in a live bird is sometimes difficult and depends on the species, length of time since exposure, and general condition of the bird. Currently available diagnostic tests include: antibody tests (Immunocomb), antigen detection test (Clearview), or polymerase chain reaction (DNA-PCR) assay. A positive test indicates the presence of organism but not necessarily disease. A negative test may only reflect a bad sample and may need to be redone. Current recommendations are that a suspect bird be given more than one type of test and that these results be considered, along with the bird’s condition and history, to achieve a diagnosis. Some veterinarians recommend treatment of all suspected cases with or without a positive test result.


If chlamydiosis has been diagnosed, or if treatment has been recommended by your veterinarian, all exposed birds in the household should be treated at the same time to reduce the spread or recurrence of the disease. It is imperative that infected birds be isolated during treatment and that certain sanitary measures be employed to prevent spread or reinfection of the disease.

The biggest problem with treatment is the lack of compliance by the bird owner in completing the recommended course of medication. The success of treatment depends on all of the medication being given in the recommended dosage and time frame. Antibiotic dosage and feeding should be directed by us to ensure each bird gets the correct dose. There are several ways to administer medication: by mouth, by injection, or by mixing the antibiotic in drinking water. Depending on the condition of the patient, other supportive treatment may be recommended as well. We will discuss the most appropriate treatment for your bird. Treatment must be continued for a minimum of 45 days to be effective.

During treatment you must:

  • clean the premises with an appropriate disinfectant (ask us which one to use);
  • use caution when handling droppings and cage debris, take care not to stir up dust while cleaning, keep dust and feather circulation to a minimum (e.g. lightly spraying the area with disinfectant before sweeping);
  • separate/isolate and seek medical care for other birds showing signs of disease;
  • avoid contact with the birds by elderly, pregnant, sick or very young persons, immunosuppressed persons, or persons on chemotherapy;
  • remove all mineral supplements containing calcium as calcium interferes with the medication;
  • reduce stress in the bird’s environment as much as possible; and
  • follow all treatment instructions as prescribed by us.


Chlamydiosis is transmissible from birds to humans, although this doesn’t happen very often – especially considering common this infection is in birds. If anyone in the household with an infected bird develops persistent flu-like symptoms, breathing difficulties, fever, chills, headache, weakness, or fatigue, that person should seek the advice of a physician as soon as possible. Treatment is simple and most often successful in humans, but neglect of the symptoms or delayed diagnosis may result in serious illness, especially in compromised persons. Chlamydophila psittaci is not the same organism that causes venereal Chlamydia infection in humans.


The following recommendations help reduce the incidence of chlamydiosis in flocks or companion birds:

  • immediately after purchase, take all newly-acquired birds to the West Toowoomba Vet Surgery for Chlamydophila screening tests;
  • buy birds from suppliers who routinely screen their birds for the presence of Chlamydophila psittaci or who are willing to stand behind the health of their birds in some manner (health guarantee);
  • isolate and quarantine all newly acquired birds for a minimum of six weeks;
  • maintain appropriate preventative health management as recommended by us.