Sections View Full Chapter Figures Tables Videos Annotate Full Chapter Figures Tables Videos Supplementary Content + Download Section PDF Listen ++ For further information, see CMDT Part 33-41: Chlamydophila Psittaci & Psittacosis (Ornithosis) + Key Features Download Section PDF Listen +++ +++ 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 Chlamydia 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 The incubation period is 6–19 days Exposure history may be difficult to obtain if the patient acquired infection from an illegally imported bird + Clinical Findings Download Section PDF Listen +++ +++ 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 Other cause of culture-negative endocarditis + Diagnosis Download Section PDF Listen +++ +++ 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 Studies ++ 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 Download Section PDF Listen +++ +++ Medications ++ Tetracycline, 500 mg every 12 hours intravenously or orally, or doxycycline, 100 mg every 12 hours orally, for 14–21 days Erythromycin, 500 mg every 6 hours orally, may also be effective + Outcome Download Section PDF Listen +++ +++ 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 +++ When to Refer ++ Early referral to an infectious disease specialist for severe disease may aid in management +++ When to Admit ++ Respiratory compromise Rapidly deteriorating clinical course Suspected or proven endocarditis + Reference Download Section PDF Listen +++ + +Hogerwerf L et al. Chlamydia psittaci (psittacosis) as a cause of community-acquired pneumonia: a systematic review and meta-analysis. Epidemiol Infect. 2017 Nov;145(15):3096–105. [PubMed: 28946931]