Psittacosis (Ornithosis)

Key Features

Essentials of Diagnosis

• Fever, chills, and cough; headache common

• Atypical pneumonia with slightly delayed appearance of signs of pneumonitis

• Contact with infected psittacine bird 7–15 days previously

• Isolation of chlamydiae or rising titer of complement-fixing antibodies

General Considerations

• Etiologic agent is Chlamydophila psittaci, a bacterium

• Infection is acquired by inhaling dried secretions from infected psittacine birds (parrots, parakeets, pigeons, chickens, ducks, and many others), which may or may not appear ill

• Exposure history may be difficult to obtain if the patient acquired infection from an illegally imported bird

Clinical Findings

Symptoms and Signs

• The onset is usually rapid, with fever, chills, myalgia, dry cough, and headache

• Signs include temperature-pulse dissociation, dullness to percussion, and rales

• Pulmonary findings may be absent early

• Dyspnea and cyanosis may occur later

• Culture-negative endocarditis

Differential Diagnosis

• Other atypical pneumonia (eg, viral pneumonia, Mycoplasma pneumoniae, Chlamydophila pneumoniae)

• Unusual presentations of typical bacterial pneumonia

• Hypersensitivity pneumonitis

Diagnosis

Laboratory Tests

• The diagnosis is usually made serologically by a rise in titer of complement-fixing antibody in convalescent versus acute serum

• Antibodies appear during the second week

• Antibody response may be suppressed by early chemotherapy

Imaging

• The radiographic findings are those of atypical pneumonia, which tends to be interstitial and diffuse in appearance, though consolidation can occur

• Psittacosis is indistinguishable from other bacterial or viral pneumonias by radiography

Treatment

Medications

• Doxycycline, 100 mg orally twice daily for 10–21 days

• Erythromycin, 500 mg orally every 6 hours may be effective

• Azithromycin, 500 mg orally on day 1 then 250 mg orally once daily for 4 days may also be effective

Outcome

Complications

• Endocarditis, hepatitis, and neurologic complications may occasionally occur

• Severe pneumonia requiring intensive care support may also occur

• Fatal cases have been reported

Prevention

• Traceback of infected birds to distributors and breeders often is not possible because of limited regulation of the pet bird industry

Prognosis

• Excellent with early treatment

Reference