🐦 Psittacosis (Chlamydia psittaci infection) is a zoonotic atypical pneumonia transmitted from birds.
Always ask about exposure to parrots, pigeons, or poultry in a febrile patient with pneumonia. Untreated disease can be severe or fatal.
🔎 About
- Zoonotic infection caused by Chlamydia psittaci.
- Often underdiagnosed – may present as “atypical pneumonia” with systemic features.
🧬 Characteristics
- Obligate intracellular bacterium – requires host ATP and amino acids.
- Does not stain well on Gram stain.
- Life cycle:
- Elementary body (EB): Extracellular, infectious, resistant to drying.
- Reticulate body (RB): Intracellular, metabolically active, divides inside host cells.
🐦 Source
- Direct or indirect contact with infected birds (pet shop parrots, pigeons, poultry, zoo birds).
- Transmission via inhalation of dried faeces, feather dust, or secretions.
🫁 Clinical Features
- Atypical pneumonia: non-productive cough, CXR opacities.
- Systemic illness: fever, chills, headache, myalgia.
- Can mimic typhoid → relative bradycardia, constipation.
- Extra-pulmonary features: hepatitis, splenomegaly, aseptic meningitis, endocarditis, macular rash.
- Severe untreated disease may progress to respiratory failure and death.
🧪 Investigations
- Diagnosis is usually clinical + confirmed by serology (fourfold rise in titres).
- Other tests: NAAT / PCR (if available).
- CXR: patchy consolidation, sometimes diffuse infiltrates.
💊 Sensitivities
- First line: Doxycycline (most effective).
- Alternatives: Azithromycin, Erythromycin.
- Tetracyclines contraindicated in children, pregnancy, breastfeeding.
🛠️ Management
- Doxycycline 100 mg BD for 10–14 days (continue at least 7 days after fever subsides).
- Azithromycin or Erythromycin for patients where doxycycline is unsuitable.
- Supportive care: fluids, oxygen, antipyretics.
- Severe cases may need IV antibiotics and hospital admission.
📚 Key Notes
- Think of psittacosis in an atypical pneumonia with bird exposure.
- Can mimic viral illness, typhoid, or hepatitis → exposure history is crucial.
- Notify public health authorities for confirmed cases (zoonotic disease reporting).
