Clinical Overview of Psittacosis

Key points

  • Chlamydia psittaci, which commonly infect birds, causes psittacosis in people.
  • Psittacosis most often presents as an upper respiratory tract infection.
  • Diagnosis of psittacosis can be difficult.
  • Prompt antibiotic treatment increases the chances of a quick recovery.
A healthcare worker listens to a patient's lungs.


C. psittaci are intracellular gram-negative bacteria that commonly infect birds. These bacteria were previously called Chlamydophila psittaci.

Unique developmental cycle affects culture methods

C. psittaci have a unique developmental cycle with growth taking place within host cells. Laboratorians can't grow the organism using typical bacterial culture media.

Electron micrograph of Chlamydia psittaci cells.
An electron micrograph of Chlamydia psittaci cells.

Wolff BJ. Whole genome sequences of Chlamydophila psittaci genotypes. UGA, 2012.

Risk factors

Exposure to birds or poultry

People can get infected from transient exposure to infected birds or their droppings. However, many people with psittacosis have exposure through their hobbies, pets, or occupation.

This can include workers at:

  • Avian quarantine stations
  • Farms
  • Laboratories
  • Pet shops
  • Poultry processing plants
  • Veterinarian offices
  • Zoos

Incubation period

The incubation period is typically 5 to 14 days. Less commonly, symptoms may begin later.

How it spreads

Most common: People inhale dust that contains dried droppings or respiratory secretions from infected birds.

Less commonly: Birds infect people through bites and beak-to-mouth contact.

How the bacteria don't spread

There's no evidence that the bacteria spread by handling or eating poultry products.

There are no documented cases involving human-to-human transmission.

Clinical features

Clinical presentations can vary widely. The predominant presentation is upper respiratory tract infection with constitutional symptoms.

Typically, symptomatic infections present as:

  • Abrupt onset of fever and chills
  • Headache
  • Myalgia
  • Nonproductive cough

Less frequently, patients may present with:

  • Pulse-temperature dissociation (fever without increased pulse rate)
  • Rash
  • Splenomegaly

For patients with pneumonia, it's often evident on chest x-ray. Radiographic findings may include lobar or interstitial infiltrates.


A man cleans a bird cage
Educate bird owners on the importance of wet cleaning.


Educate patients about the importance of handling birds and cleaning bird cages safely.

Refer birds suspected as the source of human infection to veterinarians for evaluation and treatment.

Not recommended

Patient isolation and prophylaxis of contacts aren't recommended.

Testing and diagnosis

Generally, laboratories use several methods to detect C. psittaci infection:

  • Culture
  • Serology
  • Nucleic acid amplification techniques

Specimens needed for testing‎

Healthcare providers should confirm the recommended specimen types with the testing laboratory.

Treatment and recovery

Use tetracyclines, unless contraindicated, due to reported macrolide failures. Treat people with more severe presentation with doxycycline right away if psittacosis is suspected.

Children younger than 8 years

Use macrolides for children; generally, avoid tetracyclines in children aged younger than 8 years. Tetracyclines could be considered when the benefits outweigh the risks, such as in life-threatening conditions or when macrolide failure is suspected.


Severe complications can result in hospitalization. Reported complications include:

  • Severe pneumonia requiring intensive-care support
  • Respiratory failure
  • Arthritis
  • Encephalitis
  • Endocarditis or myocarditis
  • Hepatitis
  • Sepsis

Death occurs in less than 1% of properly treated patients.

Severe clinical outcomes have been reported in people who become infected with C. psittaci during pregnancy.

Surveillance and trends

Psittacosis is an uncommon but reportable condition in most states.