Psittacosis is infection caused by Chlamydia psittaci. The most common presentation is as a cause of atypical pneumonia. Psittacosis should be suspected in a combination of typical fever with a history of bird contact (reported in 84%) or a presentation with pneumonia and severe headache or organomegaly and failure to respond to penicillin-based antibiotics.


  • Incidence: 0.25 cases per 100,000 person-years
  • Peak incidence: 30-40 years
  • Sex ratio: 1:1
<1 1-5 6+ 16+ 30+ 40+ 50+ 60+ 70+ 80+


  • Chlamydia psittaci is an obligate intracellular bacterium
  • Transmission is typically from birds or bird secretions including urine and faeces, typically occurring after cleaning bird cages
  • Many birds have been implicated in transmission, including pet birds and wild birds
  • Transmission from other animals or humans is possible but very rare and no strong female or male predisposition has been noted
  • It is rare; in the US there are roughly 10 cases reported annually

Clinical features

Patients typically present with a subacute onset of:

  • Chest: unilateral crepitations and vesicular breathing (common), evidence of pleural effusion (uncommon)
  • Abdomen: hepatomegaly and splenomegaly (rare)




  • 1st-line: tetracyclines e.g. doxycycline
  • 2nd-line: macrolides e.g. erythromycin