Psittacosis (Parrot Fever) Workup

Updated: Jul 24, 2019
  • Author: Klaus-Dieter Lessnau, MD, FCCP; Chief Editor: Michael Stuart Bronze, MD  more...
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Laboratory Studies

The following are potential laboratory findings associated with psittacosis:

  • White blood cell counts are normal to mildly decreased.
  • Liver function test values are usually mildly increased.
  • The erythrocyte sedimentation rate (ESR) may be elevated.
  • Urinalysis may show mild proteinuria (< 3500 mg/d).
  • Culturing of C psittaci is possible, but this practice is avoided because it can be hazardous to laboratory personnel.
  • Test acute-phase serum and convalescent-phase serum 2 weeks after onset to confirm a 4-fold or greater rise in the titer. Complement fixation (CF) is not a specific test and may cross-react with other chlamydial species.
  • Physicians use microimmunofluorescence (MIF) and polymerase chain reaction (PCR) studies to detect different chlamydial species. PCR may develop into an early and specific detection test.
  • Enzyme-linked immunosorbent assay (ELISA) and direct immunofluorescence (DIF) are experimental in this setting, but physicians have used them to help diagnose C psittaci infection.
  • Serologic tests are the mainstays of diagnosis; however, because of the delayed appearance of specific antibodies, these tests are not helpful in emergent clinical management.
  • Most diagnoses are established by clinical presentation and positive antibodies against C psittaci in paired sera using microimmunofluorescence (MIF) methods. [1]

Imaging Studies

Chest radiographic findings are abnormal in up to 90% of cases of psittacosis.

The most common finding is unilateral, lower-lobe dense infiltrate/consolidation. Psittacosis may present in a bilateral, nodular, miliary, or interstitial pattern.

Rarely, patients develop pleural effusion.

Chest radiograph abnormalities resolve within an average of 6 weeks (range, 3-20 wk).


Other Tests

Few patients with psittacosis have CSF abnormalities.

CDC criteria for C psittaci infection include the following:

  • Confirmed cases produce a positive culture result for C psittaci from respiratory secretions, a 4-fold increase in antibody titer in 2 serum samples obtained via CF or MIF 2 weeks apart, or immunoglobulin M (IgM) antibodies against C psittaci, as detected by MIF to a reciprocal titer of 16.
  • Possible cases show the presence of antibodies against C psittaci with titers of 1:32 by CF or MIF.

Histologic Findings

Findings of psittacosis may include tracheobronchitis and interstitial pneumonitis with air-space involvement and predominant mononuclear cell infiltration. Findings may also include macrophages that contain cytoplasmic inclusion bodies (ie, Levinthal-Coles-Lillie [LCL] bodies), focal necrosis of hepatocytes along with Kupffer cell hyperplasia in the liver, and hepatic noncaseating granulomata.