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Diseases

Psittacosis

OVERVIEW

  • Highlights & Basics
  • Images

DIAGNOSIS

  • Diagnostic Approach
  • Risk Factors
  • History & Exam
  • Tests
  • Differential Diagnosis
  • Criteria
  • Screening

TREATMENT

  • Tx Approach
  • Tx Options
  • Emerging Tx
  • Prevention

FOLLOW-UP

  • Overview
  • Complications

REFERENCES

  • Citations
  • Guidelines
  • Credits

PATIENT RESOURCES

  • Patient Instructions

Highlights & Basics

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Key Highlights
  • Psittacosis is a notifiable condition. Patient isolation is usually not required as human-to-human transmission is rare.

  • Pneumonia due to Chlamydia psittaci cannot be clinically differentiated from other community-acquired, atypical pneumonias. Molecular testing and/or serology is required to confirm the diagnosis.

  • Tetracycline antibiotics are the preferred treatment; however, other antibiotics may be used as an alternative in select patients.

  • Patients generally respond well to antibiotics, with resolution of symptoms within 24 to 48 hours, although there is the potential for relapse from persistent infection.

Chlamydia psittaci-infected HEp-2 cells stained with a fluorescein isothiocyanate-conjugated monoclo
Chlamydia psittaci-infected HEp-2 cells stained with a fluorescein isothiocyanate-conjugated monoclonal antibody against the lipopolysaccharide of Chlamydia (1000X)
From the collection of Professor Deborah Dean; used with permission

Quick Reference

  • History & Exam

    • Key Factors

      • Other Factors

        More information...
      • Diagnostics Tests

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        • Treatment Options

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          Definition

          Epidemiology

          Etiology

          Pathophysiology

          content by BMJ Group
          Last updated

          Images

          • Chlamydia psittaci-infected HEp-2 cells stained with a fluorescein isothiocyanate-conjugated monoclo

            Chlamydia psittaci-infected HEp-2 cells stained with a fluorescein isothiocyanate-conjugated monoclonal antibody against the lipopolysaccharide of Chlamydia (1000X)

          Citations

            Key Articles

            • National Association of State Public Health Veterinarians (NASPHV). Compendium of measures to control Chlamydia psittaci infection among humans (psittacosis) and pet birds (avian chlamydiosis). 2017 [internet publication].[Full Text]

            Other Online Resources

            • NASPHV: psittacosis human case surveillance report
            • CDC: psittacosis​

            Referenced Articles

            • 1. Bennett JE, Dolin R, Blaser MJ. Mandell, Douglas, and Bennett's principles and practice of infectious diseases. 9th ed. Philadelphia, PA: Elsevier; 2019.

            • 2. Dean D, Kandel RP, Adhikari HK, et al. Multiple Chlamydiaceae species in trachoma: implications for disease pathogenesis and control. PLoS Med. 2008 Jan 3;5(1):e14.[Abstract][Full Text]

            • 3. Dean D, Shama A, Schachter J, et al. Molecular identification of an avian strain of Chlamydia psittaci causing severe keratoconjunctivitis in a bird fancier. Clin Infect Dis. 1995 May;20(5):1179-85.[Abstract]

            • 4. Lietman T, Brooks D, Moncada J, et al. Chronic follicular conjunctivitis associated with Chlamydia psittaci or Chlamydia pneumoniae. Clin Infect Dis. 1998 Jun;26(6):1335-40.[Abstract][Full Text]

            • 5. Harkinezhad T, Geens T, Vanrompay D. Chlamydia psittaci infections in birds: a review with emphasis on zoonotic consequences. Vet Microbiol. 2009 Mar 16;135(1-2):68-77.[Abstract]

            • 6. Shaw KA, Szablewski CM, Kellner S, et al. Psittacosis outbreak among workers at chicken slaughter plants, Virginia and Georgia, USA, 2018. Emerg Infect Dis. 2019 Nov;25(11):2143-5.[Abstract][Full Text]

            • 7. Ito I, Ishida T, Mishima M, et al. Familial cases of psittacosis: possible person-to-person transmission. Intern Med. 2002 Jul;41(7):580-3. [Abstract][Full Text]

            • 8. Wallensten A, Fredlund H, Runehagen A. Multiple human-to-human transmission from a severe case of psittacosis, Sweden, January-February 2013. Euro Surveill. 2014 Oct 23;19(42):20937.[Abstract][Full Text]

            • 9. Hughes C, Maharg P, Rosario P, et al. Possible nosocomial transmission of psittacosis. Infect Control Hosp Epidemiol. 1997 Mar;18(3):165-8.[Abstract]

            • 10. Zhang Z, Zhou H, Cao H, et al. Human-to-human transmission of Chlamydia psittaci in China, 2020: an epidemiological and aetiological investigation. Lancet Microbe. 2022 Jul;3(7):e512-20.[Abstract][Full Text]

            • 11. Tantengco OAG. Gestational psittacosis: an emerging infection. Lancet Microbe. 2022 Oct;3(10):e728.[Full Text]

            • 12. Centers for Disease Control and Prevention. CDC Stacks: ​National Notifiable Diseases Surveillance System (NNDSS) [internet publication].[Full Text]

            • 13. World Health Organization. Psittacosis - European region. Mar 2024 [internet publication].​[Full Text]

            • 14. Hogerwerf L, DE Gier B, Baan B, 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. [Abstract][Full Text]

            • 15. Spoorenberg SM, Bos WJ, van Hannen EJ, et al. Chlamydia psittaci: a relevant cause of community-acquired pneumonia in two Dutch hospitals. Neth J Med. 2016 Feb;74(2):75-81.[Abstract]

            • 16. Vanrompay D, Harkinezhad T, van de Walle M, et al. Chlamydia psittaci transmission from pet birds to humans. Emerg Infect Dis. 2007 Jul;13(7):1108-10.[Abstract][Full Text]

            • 17. Hogerwerf L, Roof I, de Jong MJK, et al. Animal sources for zoonotic transmission of psittacosis: a systematic review. BMC Infect Dis. 2020 Mar 4;20(1):192.[Abstract][Full Text]

            • 18. National Association of State Public Health Veterinarians (NASPHV). Compendium of measures to control Chlamydia psittaci infection among humans (psittacosis) and pet birds (avian chlamydiosis). 2017 [internet publication].[Full Text]

            • 19. Magnino S, Haag-Wackernagel D, Geigenfeind I, et al. Chlamydial infections in feral pigeons in Europe: review of data and focus on public health implications. Vet Microbiol. 2009 Mar 16;135(1-2):54-67.[Abstract]

            • 20. Health and Safety Executive. Construction micro-organisms: psittacosis and other diseases from work involving bird droppings [internet publication]​.​[Full Text]

            • 21. Harris RL, Williams TW Jr. "Contribution to the question of pneumotyphus": a discussion of the original article by J. Ritter in 1880. Rev Infect Dis. 1985 Jan-Feb;7(1):119-22.[Abstract]

            • 22. Jelocnik M, Branley J, Heller J, et al. Multilocus sequence typing identifies an avian-like Chlamydia psittaci strain involved in equine placentitis and associated with subsequent human psittacosis. Emerg Microbes Infect. 2017 Feb 15;6(2):e7.[Full Text]

            • 23. Washington State Department of Health. Psittacosis: reporting and surveillance guideline. January 2018 [internet publication].[Full Text]

            • 24. Verminnen K, Duquenne B, De Keukeleire D, et al. Evaluation of a Chlamydophila psittaci infection diagnostic platform for zoonotic risk assessment. J Clin Microbiol. 2008 Jan;46(1):281-5.[Abstract][Full Text]

            • 25. Telfer BL, Moberley SA, Hort KP, et al. Probable psittacosis outbreak linked to wild birds. Emerg Infect Dis. 2005 Mar;11(3):391-7.[Abstract][Full Text]

            • 26. Queensland Department of Health, Australia. Animal contact guidelines - reducing the risk to human health 2014. August 2014 [internet publication].[Full Text]

            • 27. Laroucau K, de Barbeyrac B, Vorimore F, et al. Chlamydial infections in duck farms associated with human cases of psittacosis in France. Vet Microbiol. 2009 Mar 16;135(1-2):82-9.[Abstract]

            • 28. Heddema ER, van Hannen EJ, Duim B, et al. Genotyping of Chlamydia psittaci in human samples. Emerg Infect Dis. 2006 Dec;12(12):1989-90.[Abstract][Full Text]

            • 29. Koene R, Hautvast J, Zuchner L, et al. Local cluster of psittacosis after bird show in the Netherlands, November 2007. Euro Surveill. 2007 Dec 13;12(12):E071213.1.[Abstract][Full Text]

            • 30. Heddema ER, van Hannen EJ, Duim B, et al. An outbreak of psittacosis due to Chlamydia psittaci genotype A in a veterinary teaching hospital. J Med Microbiol. 2006 Nov;55(Pt 11):1571-5.[Abstract][Full Text]

            • 31. Chan J, Doyle B, Branley J, et al. An outbreak of psittacosis at a veterinary school demonstrating a novel source of infection. One Health. 2017 Feb 24;3:29-33.[Abstract][Full Text]

            • 32. Centers for Disease Control and Prevention. Psittacosis: clinical overview of psittacosis. Sep 2025 [internet publication].​[Full Text]

            • 33. Binet R, Maurelli AT. Frequency of development and associated physiological cost of azithromycin resistance in Chlamydia psittaci 6BC and C. trachomatis L2. Antimicrob Agents Chemother. 2007 Dec;51(12):4267-75.[Abstract][Full Text]

            • 34. Ran O, Liang M, Yu J, et al. Recombinant protein CPSIT_0846 induces protective immunity against Chlamydia psittaci infection in BALB/c mice. Pathog Dis. 2017 Apr 1;75(3).[Abstract]

            • 35. Xu L, Zhao Z, Mai H, et al. Clinical and chest computed tomography features associated with severe Chlamydia psittaci pneumonia diagnosed by metagenomic next-generation sequencing: a multicenter, retrospective, observational study. Medicine (Baltimore). 2022 Dec 16;101(50):e32117.[Abstract][Full Text]

            • 36. Katsura D, Tsuji S, Kimura F, et al. Gestational psittacosis: a case report and literature review. J Obstet Gynaecol Res. 2020 May;46(5):673-7.[Abstract]

            • 37. Cunha BA. The atypical pneumonias: clinical diagnosis and importance. Clin Microbiol Infect. 2006 May;12 Suppl 3:12-24.[Abstract]

            • 38. Dean D. Pathogenesis of chlamydial ocular infections. In: Tasman W, Jaeger EA, eds. Duane's foundations of clinical ophthalmology. Philadelphia, PA. Lippincott Williams & Wilkins, 2010.

            • 39. McGovern OL, Kobayashi M, Shaw KA, et al. Use of real-time PCR for Chlamydia psittaci detection in human specimens during an outbreak of psittacosis - Georgia and Virginia, 2018. MMWR Morb Mortal Wkly Rep. 2021 Apr 9;70(14):505-9.[Abstract][Full Text]

            • 40. Centers for Disease Control and Prevention. Psittacosis: laboratory testing for psittacosis. Sep 2025 [internet publication].​[Full Text]

            • 41. Ni Y, Zhong H, Gu Y, et al. Clinical features, treatment, and outcome of psittacosis pneumonia: a multicenter study. Open Forum Infect Dis. 2023 Feb;10(2):ofac518.[Abstract][Full Text]

            • 42. Zhu N, Zhou D, Yuan R, et al. Identification and comparison of Chlamydia psittaci, Legionella and Mycoplasma pneumonia infection. Clin Respir J. 2023 May;17(5):384-93.[Abstract][Full Text]

            • 43. Centers for Disease Control and Prevention. Case data implementation resources: psittacosis/ornithosis (Chlamydophila psittaci) 2010 case definition. Apr 2021 [internet publication].[Full Text]

            • 44. UK Health Security Agency. Guidance on psittacosis​. Nov 2024 [internet publication].​[Full Text]

            • 45. Muanda FT, Sheehy O, Bérard A. Use of antibiotics during pregnancy and the risk of major congenital malformations: a population based cohort study. Br J Clin Pharmacol. 2017 Nov;83(11):2557-2571.[Abstract][Full Text]

            • 46. Jorgensen DM. Gestational psittacosis in a Montana sheep rancher. Emerg Infect Dis. 1997 Apr-Jun;3(2):191-4.[Abstract]

            • 47. Khatib R, Thirumoorthi MC, Kelly B, et al. Severe psittacosis during pregnancy and suppression of antibody response with early therapy. Scand J Infect Dis. 1995;27(5):519-21.[Abstract][Full Text]

            • 48. Lim WS, Baudouin SV, George RC, et al; Pneumonia Guidelines Committee of the BTS Standards of Care Committee. BTS guidelines for the management of community acquired pneumonia in adults: update 2009. Thorax. 2009 Oct;64 Suppl 3:iii1-55.[Abstract][Full Text]

            • 49. Wong KF, Chan JK, Chan CH, et al. Psittacosis-associated hemophagocytic syndrome. Am J Med. 1991 Aug;91(2):204-5.[Abstract]

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