In birds, parrot disease causes coughing, emaciation, ruffled feathers, diarrhoea, eye and nasal discharge and is often fatal. In humans, it can cause pneumonia. The pathogen is the bacterium Chlamydia psittaci from the Chlamydia group.

The disease is notifiable as soon as psittacosis is detected in parrots and parakeets (Psittaciformes). Psittacosis is a zoonosis (i.e. a disease that can be transmitted from animals to humans), but overall it is very rare. If birds of other species are infected with C. psittaci, this is known as ornithosis. An infection caused by other chlamydiae, such as C. avium or C. gallinacea, is referred to as avian chlamydiosis.

The pathogen is spread worldwide.

All birds (parrots, pigeons, seagulls, ducks, turkeys, chickens...)

The pathogen is usually ingested by droplet infection through inhalation and inhalation of infectious faeces and dust or aerosols.

3 to 29 days

Symptoms in the bird include pneumonia, coughing, emaciation, ruffled feathers, diarrhea, ocular and nasal discharge. Death may occur after a few days to several weeks, or the disease may progress to a chronic form in which the birds appear to recover but continue to shed pathogens. In humans, febrile general symptoms and subsequent pneumonia usually occur.

The drugs of choice for therapy are tetracyclines (oxytetracyclines), which must be given long-term

As a preventative measure, birds must be quarantined and tested for Chlamydia after purchase. The usual hygiene measures for handling animals must be observed. Be careful with direct contact with bird faeces. It is recommended to wear a protective mask, gloves and protective clothing when handling infected birds. Psittacosis is a notifiable animal disease under the Animal Health Act. Direct vaccination against the pathogen is not possible.

In 2023, 11 cases of human infection were reported in Austria (as at 15 April 2024, see annual statistics on notifiable infectious diseases).

In 2023, 287 molecular biological tests were carried out on various birds (chickens, pigeons, parakeets, parrots, other ornamental birds, etc.) - 68 of which tested positive for C. psittaci.

In Austria, psittacosis (in parrots and parakeets) must be reported in accordance with Section 36 of the Animal Health Act (TGG). Suspicion of psittacosis must be reported to the official veterinarian. In the case of corresponding clinical symptoms and diagnostic evidence of C. psittaci, the official veterinarian decides whether isolation/treatment is necessary - depending on the course of the disease.

Chlamydia psittaci is obligate intracellular and occurs in different forms: as elementary corpuscles (infectious form), as intermediate corpuscles and as initial corpuscles. The individual species of Chlamydia show a high degree of host adaptation: C. psittaci occurs mainly in psittacids, small ruminants and humans, C. abortus in sheep and goats, C. trachomatis in humans.

Differential diagnoses include infections such as avian influenza, mycoplasma pneumonia, Q fever, brucellosis and tularaemia.

Transmission

All secretions and faeces are infectious. The pathogen is usually ingested by droplet infection through inhalation and inhalation of infectious faeces, dust or aerosols. The upper respiratory tract is the most likely entry point for this type of transmission. Transmission can also occur through contact infection or smear infection, whereby almost exclusively people with close contact to infectious animals are infected. In humans, infection is usually aerogenic via the inhalation of infectious faecal particles and dust. This usually results in feverish general symptoms and subsequent pneumonia.

The incubation period is 3-29 days, but can also be up to 100 days.

Symptoms

Symptoms in birds are pneumonia, coughing, emaciation, ruffled plumage, diarrhoea, eye and nasal discharge. The disease leads to death within a few days to weeks or changes to a chronic form in which the animals appear to recover but continue to excrete pathogens. In humans, the disease usually leads to feverish general symptoms and subsequent pneumonia.

Suitable sample materials are

• Organs
• faeces, faecal swabs
• cloacal swabs

Laboratory diagnosis is made by direct detection of Chlamydia DNA and, in positive cases, Chlamydia psittaci differentiation from other species using molecular biological methods (PCR). At necropsy of birds, swelling of the spleen and liver in particular are important indications of psittacosis, so this must always be considered in the differential diagnosis in the event of corresponding changes. The cultivation of C. psittaci is difficult and is reserved for a few specialised laboratories. It is not possible to make a diagnosis in birds by detecting specific antibodies in serum; this is only possible in ruminants, pigs, horses or small animals.