Psittacosis (Parrot Fever)

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Background

Psittacosis, also known as parrot fever, is an infection caused by the obligatory intracellular bacterium Chlamydia psittaci. The term psittacosis is derived from the Greek word for parrot, psittakos, and was first used by Morange in 1892.

This bacterium can infect parrots, parakeets, canaries, and other avian species (eg, turkeys, pigeons, ducks). Another term for this infection is ornithosis, which describes the infection caused by nonpsittacine birds.

The largest epidemic occurred in 1930 and affected 750-800 individuals. This epidemic led to the isolation of C psittaci in several laboratories in Europe and the United States.

Psittacosis is an occupational disease of zoo and pet-shop employees, poultry farmers, and ranchers. Human-to-human transmission is rare, but possible. These cases may cause more severe disease than avian-acquired psittacosis.

Psittacosis is probably underdiagnosed because patients with milder cases may not seek medical attention or may not be reported.[1]

Pathophysiology

The primary route for infection is through the respiratory system. Infection develops after organisms from aerosolized dried avian excreta or respiratory secretions from sick birds are inhaled. C psittaci attaches to the respiratory epithelial cells. After the initial inoculation, the organism spreads via the blood stream to the reticuloendothelial system. Subsequently, secondary bacteremia causes lung infection.

Humans may acquire disease by handling sick birds. Mouth-to-beak resuscitation has also been implicated in transmission. Transient exposure to infected birds may cause symptomatic infection, even in visitors to pet shops.

Epidemiology

Frequency

United States

Reports show up to 200 cases of psittacosis annually. From 1988-97, the US Centers for Disease Control and Prevention (CDC) received 766 reports of psittacosis, which is probably an underestimate of the actual number of cases because psittacosis is difficult to diagnose, is covered by macrolide antimicrobials (which may be used empirically for therapy of community-acquired pneumonia), and often goes reported.

From 1988-2003, 935 human cases of psittacosis were reported to the CDC.[2] From 2005-2009, 66 human cases of psittacosis were reported (mean, 13; range, 8-21) to the CDC through the Nationally Notifiable Diseases Surveillance System.[1, 3]

International

Psittacosis is found worldwide. The incidence seems to be increasing in developed countries, which is correlated to the import of exotic birds.

Mortality/Morbidity

The mortality rate of psittacosis prior to the advent of antimicrobial treatment was approximately 15-20%. The mortality rate is less than 1% with appropriate antibiotic therapy.

Race

Psittacosis has no observed racial predilection.

Sex

Psittacosis has no observed sexual predilection.

Age

Psittacosis occurs in all age groups, including children. The infection is more common among individuals in the middle decades of life.

Breed

Certain strains of C psittaci infect sheep, goats, and cows and may cause chronic infection and abortion.

Wild birds such as falcons have caused disease through nasal or fecal secretions.

Mowing lawns without a grass catcher has been found to be a risk factor.

Most diseases resulted from exposure to infected pet birds, usually cockatiels, parakeets, parrots, and macaws.

Prognosis

With appropriate antibiotic therapy, the mortality rate of psittacosis is less than 1%.

Hypoxemia and renal failure portend a poor prognosis.

Patient Education

Warn pet owners and pet-shop and poultry workers to be aware of possible respiratory symptoms and fever.

For excellent patient education resources, visit eMedicineHealth's Sexual Health Center. Also, see eMedicineHealth's patient education article Chlamydia.

History

The incubation period of psittacosis is generally 5-14 days. The longest observed incubation time was 54 days. The predominant presentation is respiratory tract infection with constitutional symptoms. Clinical findings vary.

Physical

Psittacosis may range from mild insidious presentations to severe pneumonia that requires mechanical ventilation.

Causes

Psittacosis is an infectious disease caused by the obligatory intracellular bacterium C psittaci.

C psittaci is associated with psittacine birds and poultry.

Psittacosis is an occupational disease of poultry farmers, pet-shop workers, and veterinarians.

Relapses may occur.

Because psittacosis is a bacterial disease, major protective immunity is unlikely to develop after a single episode of disease. The exact risk of recurrence upon reexposure is unknown. It is reasonable to advise avoidance of infected birds.

Laboratory or laboratory-related infections are possible. These are particularly underreported for several reasons, particularly because of fear for reprisal and stigma associated with such events. In addition, it would be difficult to prove that the infection is indeed laboratory related.[5]

Complications

Potential complications of psittacosis include the following:

Laboratory Studies

The following are potential laboratory findings associated with psittacosis:

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:

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.

Medical Care

Consider the diagnosis of psittacosis in patients with community-acquired pneumonia who have been exposed to birds. The mainstay of medical care is antibiotic therapy.

Standard infection-control practices and droplet transmission precautions are sufficient for the medical management of humans with psittacosis, and specific isolation procedures (eg, private room, negative-pressure air flow, masks) are not indicated.[1, 6]

Consultations

Notify public health authorities about cases of psittacosis.

Obtain a consultation with an infectious disease specialist.

Diet

Patients require no specific diet.

Activity

Patients do not require activity restrictions.

Prevention

Instruct high-risk individuals to avoid handling newly imported or sick birds.

Further Outpatient Care

Instruct patients with psittacosis to see a physician if symptoms recur (ie, relapse).

Patients with relapses may need prolonged retreatment (eg, 3-4 wk).

Further Inpatient Care

Severe psittacosis requires intravenous antibiotics and hospital admission.

Isolation is not indicated during hospital stay.

Inpatient & Outpatient Medications

Patients with psittacosis may require doxycycline, usually 100 mg IV; alternatively, consider PO administration with the same dose twice a day.

Chloramphenicol is the third drug of choice but is rarely used in the United States.

Consider changing erythromycin from intravenous to oral administration (eg, 500 mg qid).

Chloramphenicol is rarely used in the United States because it may cause agranulocytosis.

Consider changing quinolones from intravenous to oral administration.

Transfer

Transfer patients with psittacosis who have acute respiratory failure to an intensive care unit.

Medication Summary

The goals of pharmacotherapy are to reduce morbidity and to prevent complications.

Azithromycin (Zithromax)

Clinical Context:  Anecdotal reports suggest that it is effective. Acts by binding to 50S ribosomal subunit of susceptible microorganisms and blocks dissociation of peptidyl tRNA from ribosomes, causing RNA-dependent protein synthesis to arrest. Nucleic acid synthesis is not affected.

Concentrates in phagocytes and fibroblasts as demonstrated by in vitro incubation techniques. In vivo studies suggest that concentration in phagocytes may contribute to drug distribution to inflamed tissues.

Treats mild-to-moderate microbial infections.

Plasma concentrations are very low, but tissue concentrations are much higher, giving it value in treating intracellular organisms. Has a long tissue half-life.

Doxycycline (Vibramycin)

Clinical Context:  DOC; inhibits protein synthesis and thus bacterial growth by binding to 30S and possibly 50S ribosomal subunits of susceptible bacteria. Continue treatment for at least 2 wk to prevent relapse.

Erythromycin (E-Mycin, Ery-Tab, E.E.S.)

Clinical Context:  Macrolide antibiotic; second DOC. Inhibits bacterial growth, possibly by blocking dissociation of peptidyl t-RNA from ribosomes, causing RNA-dependent protein synthesis to arrest. For treatment of staphylococcal and streptococcal infections. In children, age, weight, and severity of infection determine proper dosage. When bid dosing is desired, administer half total daily dose q12h. For more severe infections, double the dose.

Chloramphenicol (Chloromycetin)

Clinical Context:  Third DOC but rarely used in the US. Binds to 50S bacterial-ribosomal subunits and inhibits bacterial growth by inhibiting protein synthesis. Effective against gram-negative and gram-positive bacteria.

Moxifloxacin (Avelox)

Clinical Context:  Inhibits the A subunits of DNA gyrase, resulting in inhibition of bacterial DNA replication and transcription. Anecdotal reports suggest that this drug is effective.

Class Summary

Empiric antimicrobial therapy must be comprehensive and should cover all likely pathogens in the clinical setting. Tetracycline and doxycycline are the antibiotics of choice. Treating patients for 2-3 weeks usually prevents relapse. Clinical response occurs within 24-72 hours. Use erythromycin in children younger than 9 years and in pregnant women. Chloramphenicol is a third alternative antibiotic.

Doxycycline remains the drug of choice. Macrolide and quinolone failures have been observed.

Author

Klaus-Dieter Lessnau, MD, FCCP, Former 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

Disclosure: Nothing to disclose.

Coauthor(s)

Dora E Izaguirre Anariba, MD, MPH, Physician, Department of Medicine, Wyckoff Heights Medical Center

Disclosure: Nothing to disclose.

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.

Jesus Lanza, MD, Fellow in Pulmonary and Critical Care Medicine, Department of Medicine, Section of Pulmonary Medicine, Lenox Hill Hospital

Disclosure: Nothing to disclose.

Specialty Editors

Francisco Talavera, PharmD, PhD, Adjunct Assistant Professor, University of Nebraska Medical Center College of Pharmacy; Editor-in-Chief, Medscape Drug Reference

Disclosure: Received salary from Medscape for employment. for: Medscape.

Richard B Brown, MD, FACP, Chief, Division of Infectious Diseases, Baystate Medical Center; Professor, Department of Internal Medicine, Tufts University School of Medicine

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

Disclosure: Nothing to disclose.

Acknowledgements

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.

References

  1. Smith KA, Campbell CT, Murphy J, et al. Compendium of measures to control Chlamydophila psittaci infection among humans (psittacosis) and pet birds (avian chlamydiosis), 2010. J Exotic Pet Med. 2011 Jan. 20 (1):32-45.
  2. Smith KA, Bradley KK, Stobierski MG, et al. Compendium of measures to control Chlamydophila psittaci (formerly Chlamydia psittaci) infection among humans (psittacosis) and pet birds, 2005. J Am Vet Med Assoc. 2005 Feb 15. 226(4):532-9. [View Abstract]
  3. Centers for Disease Control and Prevention. Notifiable Diseases and Mortality Tables. Available at http://www.cdc.gov/mmwr/preview/mmwrhtml/mm5906md.htm. Accessed: March 4, 2013.
  4. Matsushima H, Takayanagi N, Ubukata M, et al. [A case of fulminant psittacosis with rhabdomyolysis]. Nihon Kokyuki Gakkai Zasshi. 2002 Jul. 40(7):612-6. [View Abstract]
  5. Dickx V, Van Droogenbroeck C, Van Vaerenbergh B, Herman P, Braeckman L, Vanrompay D. Chlamydia psittaci, causative agent of avian chlamydiosis and human psittacosis: risk assessment and biosafety recommendations for laboratory use. Applied Biosafety. 2012. 17(2):82-8.
  6. Siegel JD, Rhinehart E, Jackson M, Chiarello L, and the Healthcare Infection Control Practices Advisory Committee. 2007 Guideline for Isolation Precautions: Preventing Transmission of Infectious Agents in Healthcare Settings. Available at http://www.cdc.gov/hicpac/pdf/isolation/isolation2007.pdf. Accessed: March 4, 2013.
  7. Committee of the National Association of State Public Health Veterinarians. Compendium of measures to control Chlamydia psittaci infection among humans (psittacosis) and pet birds (avian chlamydiosis), 2000. Centers for Disease Control and Prevention. Morbidity Mortality Weekly Reports. 2000. 49:3-17. [View Abstract]
  8. Coutts II, Mackenzie S, White RJ. Clinical and radiographic features of psittacosis infection. Thorax. 1985 Jul. 40(7):530-2. [View Abstract]
  9. Crosse BA. Psittacosis: a clinical review. J Infect. 1990 Nov. 21(3):251-9. [View Abstract]
  10. Cunha BA. Atypical pneumonias. Clinical diagnosis and empirical treatment. Postgrad Med. 1991 Oct. 90(5):89-90, 95-8, 101. [View Abstract]
  11. Cunha BA. Atypical pneumonias. Conn RB, Borer WZ, Snyder JW, eds. Current Diagnosis. WB Saunders Co; 1996.
  12. Cunha BA. The atypical pneumonias: clinical diagnosis and importance. Clin Microbiol Infect. 2006 May. 12 Suppl 3:12-24. [View Abstract]
  13. Cunha BA. The chlamydial pneumonias. Drugs Today (Barc). 1998 Dec. 34(12):1005-12. [View Abstract]
  14. Cunha BA, Ortega AM. Atypical pneumonia. Extrapulmonary clues guide the way to diagnosis. Postgrad Med. 1996 Jan. 99(1):123-8, 131-2. [View Abstract]
  15. De Schrijver K. A psittacosis outbreak in Belgian customs officers. Euro Surveillance. 1995. Sep:3. [View Abstract]
  16. Elliott JH. Psittacosis. A flu like syndrome. Aust Fam Physician. 2001 Aug. 30(8):739-41. [View Abstract]
  17. Entrican G, Brown J, Graham S. Cytokines and the protective host immune response to Chlamydia psittaci. Comp Immunol Microbiol Infect Dis. 1998 Jan. 21(1):15-26. [View Abstract]
  18. Gherman RB, Leventis LL, Miller RC. Chlamydial psittacosis during pregnancy: a case report. Obstet Gynecol. 1995 Oct. 86(4 Pt 2):648-50. [View Abstract]
  19. Gregory DW, Schaffner W. Psittacosis. Semin Respir Infect. 1997 Mar. 12(1):7-11. [View Abstract]
  20. Heddema ER, Kraan MC, Buys-Bergen HE, et al. A woman with a lobar infiltrate due to psittacosis detected by polymerase chain reaction. Scand J Infect Dis. 2003. 35(6-7):422-4. [View Abstract]
  21. Hughes C, Maharg P, Rosario P, Herrell M, Bratt D, Salgado J, et al. Possible nosocomial transmission of psittacosis. Infect Control Hosp Epidemiol. 1997 Mar. 18(3):165-8. [View Abstract]
  22. Hughes P, Chidley K, Cowie J. Neurological complications in psittacosis: a case report and literature review. Respir Med. 1995 Oct. 89(9):637-8. [View Abstract]
  23. Jaton K, Greub G. [Chlamydia: diagnostic and treatment]. Rev Med Suisse. 2005 Mar 30. 1(13):895-8, 901-3. [View Abstract]
  24. Johnson DH, Cunha BA. Atypical pneumonias. Clinical and extrapulmonary features of Chlamydia, Mycoplasma, and Legionella infections. Postgrad Med. 1993 May 15. 93(7):69-72, 75-6, 79-82. [View Abstract]
  25. Kirchner JT. Psittacosis. Is contact with birds causing your patient's pneumonia?. Postgrad Med. 1997 Aug. 102(2):181-2, 187-8, 193-4. [View Abstract]
  26. MacLaren G, Pellegrino V, Butt W, et al. Successful use of ECMO in adults with life-threatening infections. Anaesth Intensive Care. 2004 Oct. 32(5):707-10. [View Abstract]
  27. Matsui T, Nakashima K, Ohyama T, et al. An outbreak of psittacosis in a bird park in Japan. Epidemiol Infect. 2008 Apr. 136(4):492-5. [View Abstract]
  28. Nash TW, Murray HW. The atypical pneumonias. Fishman AP, ed. Pulmonary diseases and disorders. 2nd ed. New York, NY: McGraw-Hill; 1998. Vol 2: 1619-24.
  29. Oldach DW, Gaydos CA, Mundy LM, et al. Rapid diagnosis of Chlamydia psittaci pneumonia. Clin Infect Dis. 1993 Sep. 17(3):338-43. [View Abstract]
  30. Raso Tde F, Godoy SN, Milanelo L, et al. An outbreak of chlamydiosis in captive blue-fronted Amazon parrots (Amazona aestiva) in Brazil. J Zoo Wildl Med. 2004 Mar. 35(1):94-6. [View Abstract]
  31. Schlossberg D. Chlamydia psittaci (psittacosis). Mandell GL, Bennett JE, Dolin R, eds. Mandell, Douglas, and Bennett's Principles and Practice of Infectious Diseases. 5th ed. Philadelphia, Pa: Churchill Livingstone; 2000. 2004-6.
  32. Schlossberg D, Delgado J, Moore MM, et al. An epidemic of avian and human psittacosis. Arch Intern Med. 1993 Nov 22. 153(22):2594-6. [View Abstract]
  33. Stamm WE. Chlamydial infection: psittacosis. Braunwald E, et al, eds. Harrison's Principles of Internal Medicine. 14th ed. New York, NY: McGraw Hill; 1998. 1055-64.
  34. Telfer BL, Moberley SA, Hort KP, et al. Probable psittacosis outbreak linked to wild birds. Emerg Infect Dis. 2005 Mar. 11(3):391-7. [View Abstract]
  35. The latest from the IVD industry December 2004. Chlamydia--pathogens that are still often underestimated. Clin Lab. 2005. 51(3-4):225-9. [View Abstract]
  36. Tong CY, Sillis M. Detection of Chlamydia pneumoniae and Chlamydia psittaci in sputum samples by PCR. J Clin Pathol. 1993 Apr. 46(4):313-7. [View Abstract]
  37. Verweij PE, Meis JF, Eijk R, et al. Severe human psittacosis requiring artificial ventilation: case report and review. Clin Infect Dis. 1995 Feb. 20(2):440-2. [View Abstract]
  38. Wong KH, Skelton SK, Daugharty H. Utility of complement fixation and microimmunofluorescence assays for detecting serologic responses in patients with clinically diagnosed psittacosis. J Clin Microbiol. 1994 Oct. 32(10):2417-21. [View Abstract]
  39. Psittacosis. Available at http://www.cdc.gov/pneumonia/atypical/psittacosis.html. Accessed: February 7, 2014.
  40. Psittacosis. Available at http://www.health.ny.gov/diseases/communicable/psittacosis/fact_sheet.htm. October 2011; Accessed: 8/2/2015.