Etiology and Epidemiology

Most avian species can harbor C. psittaci, but psittacine birds (e.g., parrots, parakeets) are most often infected. Human infections are uncommon and occur only as a zoonosis.

• Exposure is greatest in poultry workers and in owners of pet birds.
• Present in nasal secretions, excreta, tissues, and feathers of infected birds, C. psittaci is transmitted to humans by direct contact with infected birds or by inhalation of aerosols. Transmission from person to person has never been documented.
• As a result of quarantine of imported birds and improved veterinary-hygienic measures, outbreaks and sporadic cases of psittacosis are now rare, with fewer than 50 confirmed cases reported in the United States each year.

Clinical Manifestations

Psittacosis in humans can range in severity from asymptomatic or mild infections to acute primary atypical pneumonia (which can be fatal in 10% of untreated cases) to severe chronic pneumonia.

• After an incubation period of >5-19 days, pts present with fever, chills, muscular aches and pains, severe headaches, hepatomegaly and/or splenomegaly, and GI symptoms.
• Cardiac complications may include endocarditis and myocarditis.

Diagnosis

This diagnosis is confirmed by serologic studies.

• The gold standard is the MIF test.
• Any antibody titer >1:16 or a fourfold rise between paired acute- and convalescent-phase serum samples, in combination with a clinically compatible syndrome, can be used to diagnose psittacosis.