• A classic zoonotic disease caused by Chlamydophila psittaci, psittacosis is almost always contracted by contact with infected birds (e.g., parrots, cockatiels, parakeets, pigeons, doves, mynah birds, canaries, finches, birds of prey, and shore birds) and (rarely) mammals (sheep; goats).
    • Psittacosis is a systemic infectious disease of varying severity that initially causes influenza-like symptoms and primarily affects the lungs. It causes an atypical pneumonia that may spread hematogenously to other organs.
    • Psittacosis ranges in severity from a subclinical infection to fulminant sepsis with multiorgan system failure and may occur in otherwise healthy persons (1)[C].
  • Often occupation related: poultry farmers, ranchers, and zoo and pet shop employees
  • Synonym(s): ornithosis; parrot fever; bird-breeder’s disease; bird-fancier lung


  • Predominant age: adults
  • Predominant sex: male = female
  • 112 cases reported in the United States from 2003 to 2014 (2)[C]

In bird populations, prevalence of infection is estimated to be between 5% and 8%.

Pregnancy Considerations

  • Infections in late 2nd and 3rd trimesters are potentially life-threatening to mother and fetus.
  • C. psittaci can cross the placenta.
  • Pregnant women should avoid contact with birds, pregnant sheep, and goats.

Pediatric Considerations
Relatively uncommon in children

Geriatric Considerations
Mortality rates are higher in geriatric or chronically ill patients.

Etiology and Pathophysiology

  • C. psittaci is an obligate intracellular gram-negative bacterium capable of surviving on dry, inanimate surfaces for 15 days.
  • In humans, the bacterium is usually inhaled through contact with dried nasal secretions and feces from infected birds (2)[C].
  • If untreated, C. psittaci can also infect pericardium, heart, liver, kidneys, joints, and CNS.
  • C. psittaci can also be acquired through close contact with infected pets (e.g., mouth-to-beak, bites).
  • Human-to-human transmission has been documented (3)[B].

No known genetic predisposition

Risk Factors

  • Strains transmitted from turkeys and psittacine birds (parrots and similar pets) are most virulent.
  • Ranchers in contact with parturient goats, sheep, dairy cattle, and horses are at increased risk.
  • Immunosuppressed patients

General Prevention

  • Avoid exposure.
    • Maintain clean bird habitats.
    • Avoid contact with birds in confined spaces.
    • Brief, passing exposures can cause infection.
  • Infected birds may be asymptomatic.
  • Treat birds if infection is suspected.
  • Use personal protective equipment, including air-filter face masks, for occupational exposures.
  • Prophylactic antibiotics after suspected exposure to C. psittaci not usually recommended (1)[C]

Commonly Associated Conditions

  • C. psittaci occurs in ~80% of cases of ocular adnexal lymphoma. It can also occur in diffuse B-cell lymphomas.
  • Subclinical C. psittaci infection occurs in a significant percentage of patients with chronic inflammatory polyarthritis (including psoriatic arthritis), suggesting that C. psittaci may be an infectious trigger in the pathogenesis of psoriasis.
  • Other diseases related to bird exposures
    • Avian influenza
    • Viral encephalomyelitides (e.g., West Nile virus)
    • Salmonellosis, campylobacteriosis, yersiniosis
    • Mycobacterium avium and Mycobacterium tuberculosis infection
    • Q fever, histoplasmosis, cryptococcosis
    • Newcastle disease

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