Psittacosis is an infectious disease, common in many species of birds, but that can also infect mammals, including humans.  It is caused by a bacterial organism that lives within the cells of its host, called Chlamydia psittaci

It is usually spread form bird to bird or to a human by inhalation of the organism in dried bird droppings, feather dust or respiratory secretions. The organism can remain infectious for months in dried faeces. Outbreaks in pet birds can be due to contact with infected wild birds or their droppings. Cats can be infected by Chlamydia psittaci but they are unlikely to transmit it to people. The organism has been isolated from a wide variety of bird species, including pigeons, turkeys, ducks and many members of the parrot family, including budgerigars and cockatiels.

In people symptoms are usually mild and often flu-like, including coughs, fevers and headaches. Although most people recover with the correct treatment, psittacosis can occasionally be fatal, and must be taken very seriously when diagnosed in a pet bird.

The clinical signs in an affected bird can be variable and range from respiratory signs to weight loss, yellow or lime green droppings, conjunctivitis and/or poor appetite. Some infected birds show no symptoms at all and can be carriers of C. psttac, periodically shedding the organism with the potential to infect other birds and humans. They are most likely to shed the organism when stressed, for example by a change in environment, by the removal of chicks from the nest, or by another illness. Other birds may develop a chronic illness or suddenly die. Young birds are particularly susceptible.

Diagnosis is not possible on the basis of clinical signs alone, as these are so variable and similar to those caused by a variety of other diseases. However, diagnosis can be aided by a variety of tests, including blood sampling, taking samples for culture and cytology. The PCR test for chlamydial DNA and the ELISA test are two of the most reliable tests.  They are usually carried out on a faecal sample, however since the organism may only be shed intermittently from an infected bird, samples need to be collected over several days to increase the accuracy of the test. Due to this intermittent excretion, these tests may be negative, even though a bird is infected.  Repeated testing may therefore be necessary in suspected cases. Sometimes psittacosis is only diagnosed on post-mortem examination.

Treatment of birds with psittacosis is a long process and may not always be successful. Infected birds must be isolated and given long courses of antibiotics. They may need additional care such as fluids and nutritional support. Protective clothing and masks should be used when handling or cleaning out these birds. C. psttac is susceptible to most commonly used disinfectants.

The following control measures should be taken by bird keepers

• Birds should always be purchased from reputable sources – never buy a bird that seems ill. 

• All new birds should be quarantined for at least 45 days before introducing them to other birds. 

• During this period they should be examined by a vet and tested for psittacosis.