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.

Epidemiology

• Psittacosis is present throughout the world, including the United Kingdom
• It is more common in young adults

Pathology

• 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

PC

Patients typically present with a subacute onset of:

• Flu-like symptoms (90%): fever, headache and myalgia
• Respiratory symptoms (82%): dyspnoea, dry cough and chest pain

Signs:

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