Ornithosis

Ornithosis, also known as psittacosis, is a zoonotic infectious disease caused by the bacterium Chlamydia psittaci. The infection primarily involves birds, especially parrots, parakeets, pigeons, and other poultry, and humans acquire the disease through inhalation of dried secretions, droppings, or dust from contaminated birds. Person-to-person transmission is considered rare.

After an incubation period of about 5 to 14 days, clinical presentation usually begins with fever, headache, malaise, and myalgias, followed by a non-productive cough. Some patients develop atypical pneumonia, chest pain, or neurologic and gastrointestinal symptoms. Disease severity ranges from mild to severe, and vulnerable groups such as the elderly or immunocompromised may experience more serious illness.

Diagnosis is based on clinical suspicion supported by laboratory testing. Serology with Chlamydia psittaci–specific antibodies (such as micro-immunofluorescence or complement fixation) or nucleic acid amplification tests (PCR) on respiratory specimens can confirm the infection. Chest radiography often shows an atypical or interstitial pneumonia pattern.

Treatment typically involves doxycycline, usually 100 mg twice daily for 7 to 14 days after symptom resolution. Alternatives include macrolides (such as azithromycin or clarithromycin), particularly for those who cannot take tetracyclines (e.g., pregnant patients). Early treatment generally leads to rapid improvement; untreated disease can progress to more severe pneumonia or systemic involvement.

Prevention focuses on reducing exposure to infected birds, especially for pet bird owners, poultry workers, and veterinarians. Measures include good cage hygiene, dampening dust during cleaning, proper ventilation, and prompt veterinary care for sick birds. There is no widely used human vaccine.