The distribution of the pathogen is worldwide. The disease is notifiable as soon as psittacosis is detected in parrots and parakeets (Psittaciformes). If birds of other species are infected with C. psittaci, this infection is called ornithosis. However, infection by other chlamydiae such as C. avium bez. C. gallinacea is referred to as avian chlamydiosis according to the WOAH.Psittacosis is a zoonosis (i.e., a disease that can be transmitted from animals to humans) but is rare overall.
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.
For prevention, birds must be quarantined and tested for Chlamydia after purchase. The usual hygiene measures for handling animals must be observed. Caution should be taken when coming into direct contact with bird excreta. It is recommended to wear protective mask, gloves and protective clothing when handling infected birds. Psittacosis is a notifiable animal disease according to the Animal Diseases Act. Direct vaccination against the pathogen is not possible.
Situation in Austria
In 2023, 103 molecular biological examinations of various birds (chickens, pigeons, parakeets, parrots, other ornamental birds, etc.) were performed - 1 of them tested positive for C. psittaci.
In Austria, psittacosis (in parrots and parakeets) is subject to compulsory notification according to § 16 of the Animal Diseases Act (TSG). Suspicion of psittacosis must be reported to the official veterinarian. In case of corresponding clinical symptoms and diagnostic evidence of C. psittaci, the official veterinarian decides whether blocking/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, tularaemia.
All secretions and excretions are infectious. The pathogen is usually ingested by droplet infection through inhalation and inhalation of infectious feces, dust, or aerosols. In this mode of transmission, the upper respiratory tract is the most likely port of entry. Transmission can also occur by contact infection or smear infection, whereby almost exclusively people with close contact to infectious animals are infected. In humans, infection usually occurs aerogenically via inhalation of infectious faecal particles and dust. There are usually febrile general symptoms and subsequent pneumonia (lung inflammation). The incubation period is 3-29 days, but can also be up to 100 days.
Symptoms in birds include pneumonia, coughing, emaciation, ruffled feathers, diarrhea, eye and nasal discharge. The disease leads to death within a few days to weeks or changes into a chronic form in which the animals seem to recover but continue to excrete pathogens. In humans, it usually results in febrile general symptoms and subsequent pneumonia.
Suitable specimen material:
- 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 by molecular biological methods (PCR). When birds are necropsied, swelling of the spleen and liver in particular are important indications of psittacosis, so this must always be considered for differential diagnosis in the event of corresponding changes. The cultivation of C. psittaci is difficult and is reserved for a few specialised laboratories. Diagnosis in birds by detection of specific antibodies in serum is not possible, only in ruminants, pigs, horses or small animals.
Institut für veterinärmedizinische Untersuchungen Mödling
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Robert Koch-Gasse 17
Last updated: 31.05.2023