Psittacosis | Laboratory Findings, Diagnosis and Management

Laboratory Findings

The leukocyte count is usually normal or slightly elevated or depressed. Isolation of C. psittaci is possible from sputum, pleural fluid, and pericardial fluid or autopsy specimens of lung, spleen, and liver.

Psittacosis Diagnosis

Clinically, psittacosis is characterized by fever, chills, headache, photophobia, lower or upper respiratory tract disease, and myalgias.

Laboratory Criteria
Isolation of C. psittaci from a clinical specimen or a fourfold or greater increase in psittacosis complement- fixation antibody (CFA) titer (> 1:32) between specimens obtained more than 2 weeks apart. This CFA test is specific for the genus Chlamydia only and is used most commonly for serologic testing with specimens collected at least 2 weeks apart. A single or stable titer of 1:64 or more suggests a recent infection. The CFA response may be blunted or prevented by prompt treatment of the patient with tetracycline.

Case Classification
Probable is defined as a clinically compatible illness linked to a confirmed case or with supportive serologic test results (a CFA titer of 1:32 or more from one or more specimens after the onset of symptoms). Confirmed is defined as a clinically compatible illness that is laboratory- confirmed.

Psittacosis Management

Pharmacologic therapy includes tetracycline 500 mg PO q6h or doxycycline 100 mg PO ql2h for 2 to 3 weeks. Erythromycin is the best alternative for pregnant women and children. The macrolide antibiotics clarithromycin and azithromycin, are effective as well. Initial infection does not confer lifelong immunity.14

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