eMedicine Specialties > Infectious Diseases > Lower Respiratory Tract Infections

Psittacosis: Differential Diagnoses & Workup

Author: Klaus-Dieter Lessnau, MD, FCCP, Clinical Associate Professor of Medicine, New York University School of Medicine; Medical Director, Pulmonary Physiology Laboratory; Director of Research in Pulmonary Medicine, Department of Medicine, Section of Pulmonary Medicine, Lenox Hill Hospital
Coauthor(s): Farhad Arjomand, MD, Pulmonary Fellow, Department of Internal Medicine, Division of Pulmonary and Critical Care, Brooklyn Hospital Center, Cornell University School of Medicine
Contributor Information and Disclosures

Updated: Jun 27, 2008

Differential Diagnoses

Brucellosis
Pneumonia, Fungal
Chlamydial Pneumonias
Pneumonia, Viral
Infective Endocarditis
Q Fever
Legionnaires Disease
Tuberculosis
Mycoplasma Infections
Tularemia
Pneumonia, Bacterial
Typhoid Fever

Other Problems to Be Considered

Coxiella burnetii infection
Francisella tularensis infection
Atypical pneumonia (all causes)

Workup

Laboratory Studies

  • 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.

Imaging Studies

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

More on Psittacosis

Overview: Psittacosis
Differential Diagnoses & Workup: Psittacosis
Treatment & Medication: Psittacosis
Follow-up: Psittacosis
References
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References

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Further Reading

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Keywords

psittacosis, ornithosis, parrot fever, Chlamydia psittaci, C psittaci, avian-acquired psittacosis

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Contributor Information and Disclosures

Author

Klaus-Dieter Lessnau, MD, FCCP, Clinical Associate Professor of Medicine, New York University School of Medicine; Medical Director, Pulmonary Physiology Laboratory; Director of Research in Pulmonary Medicine, Department of Medicine, Section of Pulmonary Medicine, Lenox Hill Hospital
Klaus-Dieter Lessnau, MD, FCCP is a member of the following medical societies: American College of Chest Physicians, American College of Physicians, American Medical Association, American Society for Artificial Internal Organs, American Thoracic Society, Physicians for Social Responsibility, and Society of Critical Care Medicine
Disclosure: Nothing to disclose.

Coauthor(s)

Farhad Arjomand, MD, Pulmonary Fellow, Department of Internal Medicine, Division of Pulmonary and Critical Care, Brooklyn Hospital Center, Cornell University School of Medicine
Disclosure: Nothing to disclose.

Medical Editor

Kenneth C Earhart, MD, Deputy Head, Disease Surveillance Program, United States Naval Medical Research Unit #3
Kenneth C Earhart, MD is a member of the following medical societies: American College of Physicians, American Society of Tropical Medicine and Hygiene, Infectious Diseases Society of America, and Undersea and Hyperbaric Medical Society
Disclosure: Nothing to disclose.

Pharmacy Editor

Francisco Talavera, PharmD, PhD, Senior Pharmacy Editor, eMedicine
Disclosure: Nothing to disclose.

Managing Editor

Richard B Brown, MD, FACP, Chief, Division of Infectious Diseases, Baystate Medical Center; Professor, Department of Internal Medicine, Tufts University School of Medicine
Richard B Brown, MD, FACP is a member of the following medical societies: Alpha Omega Alpha, American College of Chest Physicians, American College of Physicians, American Medical Association, American Society for Microbiology, Infectious Diseases Society of America, and Massachusetts Medical Society
Disclosure: Nothing to disclose.

CME Editor

Eleftherios Mylonakis, MD, Clinical and Research Fellow, Department of Internal Medicine, Division of Infectious Diseases, Massachusetts General Hospital
Eleftherios Mylonakis, MD is a member of the following medical societies: American Association for the Advancement of Science, American College of Physicians, American Society for Microbiology, and Infectious Diseases Society of America
Disclosure: Nothing to disclose.

Chief Editor

Burke A Cunha, MD, Professor of Medicine, State University of New York School of Medicine at Stony Brook; Chief, Infectious Disease Division, Winthrop-University Hospital
Burke A Cunha, MD is a member of the following medical societies: American College of Chest Physicians, American College of Physicians, and Infectious Diseases Society of America
Disclosure: Nothing to disclose.

 
 
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