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Michael J Richards, MD, FRACP
Section Editor
John G Bartlett, MD
Deputy Editor
Sheila Bond, MD


Psittacosis, also known as ornithosis, is usually a disease with prominent systemic manifestations and some respiratory symptoms. This infection, caused by Chlamydia psittaci, is transmitted to humans predominantly from birds.

The epidemiology, clinical features, diagnosis, and treatment of psittacosis will be discussed here. Pneumonia caused by Chlamydia spp is discussed separately. (See "Pneumonia caused by Chlamydia pneumoniae in adults" and "Pneumonia caused by Chlamydia species in children".)


C. psittaci is an obligate intracellular bacterium. There are 10 known genotypes based on sequencing of the major outer protein gene, ompA [1]. Each genotype has host preferences and virulence characteristics, although these overlap. Knowledge of the pathogenesis at a cellular and molecular level is growing [2].


Psittacosis has been recognized throughout the world, including the United States, the United Kingdom, Europe, the Middle East, and Australia. Birds are the primary reservoir, but transmission from other animals has also been reported. The disease usually occurs sporadically, but outbreaks caused by contact with an infected bird are not uncommon [3]. Outbreaks related to pet shops, aviaries, a veterinary hospital, poultry flocks [4], and turkey and duck processing have been described [5-9].

Birds — Most patients with psittacosis have a history of contact with birds. C. psittaci has been documented in at least 460 species from 30 bird orders, including turkeys, pheasants, chickens, and even ostriches and penguins [10]. Migratory birds, including geese, may carry this pathogen [11]. Most humans are infected from birds of the order psittaciformes, which includes budgerigars, cockatiels, cockatoos, and parrots. In France, mule ducks are associated with human disease through heavy shedding, although the ducks are asymptomatic [12]. Each bird order tends to be infected by a predominant genotype of C. psittaci.

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Literature review current through: Nov 2017. | This topic last updated: Jun 27, 2017.
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  1. Wolff BJ, Morrison SS, Pesti D, et al. Chlamydia psittaci comparative genomics reveals intraspecies variations in the putative outer membrane and type III secretion system genes. Microbiology 2015; 161:1378.
  2. Knittler MR, Sachse K. Chlamydia psittaci: update on an underestimated zoonotic agent. Pathog Dis 2015; 73:1.
  3. Saeki S, Hirata I, Fukusako T, et al. [A case of psittacosis with psychiatric symptoms, abnormal EEG, and abnormal SPECT]. No To Shinkei 1996; 48:1141.
  4. Gaede W, Reckling KF, Dresenkamp B, et al. Chlamydophila psittaci infections in humans during an outbreak of psittacosis from poultry in Germany. Zoonoses Public Health 2008; 55:184.
  5. Mohan R. Epidemiologic and laboratory observations of Chlamydia psittaci infection in pet birds. J Am Vet Med Assoc 1984; 184:1372.
  6. Schlossberg D, Delgado J, Moore MM, et al. An epidemic of avian and human psittacosis. Arch Intern Med 1993; 153:2594.
  7. Hedberg K, White KE, Forfang JC, et al. An outbreak of psittacosis in Minnesota turkey industry workers: implications for modes of transmission and control. Am J Epidemiol 1989; 130:569.
  8. Hinton DG, Shipley A, Galvin JW, et al. Chlamydiosis in workers at a duck farm and processing plant. Aust Vet J 1993; 70:174.
  9. Heddema ER, van Hannen EJ, Duim B, et al. An outbreak of psittacosis due to Chlamydophila psittaci genotype A in a veterinary teaching hospital. J Med Microbiol 2006; 55:1571.
  10. Kaleta EF, Taday EM. Avian host range of Chlamydophila spp. based on isolation, antigen detection and serology. Avian Pathol 2003; 32:435.
  11. Dickx V, Kalmar ID, Tavernier P, Vanrompay D. Prevalence and genotype distribution of Chlamydia psittaci in feral Canada geese (Branta canadensis) in Belgium. Vector Borne Zoonotic Dis 2013; 13:382.
  12. Vorimore F, Thébault A, Poisson S, et al. Chlamydia psittaci in ducks: a hidden health risk for poultry workers. Pathog Dis 2015; 73:1.
  13. Trávnicek M, Cisláková L, Deptuła W, et al. Wild pigeons and pheasants--a source of Chlamydophila psittaci for humans and animals. Ann Agric Environ Med 2002; 9:253.
  14. Halsby KD, Walsh AL, Campbell C, et al. Healthy animals, healthy people: zoonosis risk from animal contact in pet shops, a systematic review of the literature. PLoS One 2014; 9:e89309.
  15. 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; 135:82.
  16. Dickx V, Geens T, Deschuyffeleer T, et al. Chlamydophila psittaci zoonotic risk assessment in a chicken and turkey slaughterhouse. J Clin Microbiol 2010; 48:3244.
  17. Petrovay F, Balla E. Two fatal cases of psittacosis caused by Chlamydophila psittaci. J Med Microbiol 2008; 57:1296.
  18. Cong W, Huang SY, Zhang XX, et al. Chlamydia psittaci exposure in pet birds. J Med Microbiol 2014; 63:578.
  19. Branley JM, Weston KM, England J, et al. Clinical features of endemic community-acquired psittacosis. New Microbes New Infect 2014; 2:7.
  20. Williams J, Tallis G, Dalton C, et al. Community outbreak of psittacosis in a rural Australian town. Lancet 1998; 351:1697.
  21. Kampinga GA, Schröder FP, Visser IJ, et al. [Lambing ewes as a source of severe psittacosis in a pregnant woman]. Ned Tijdschr Geneeskd 2000; 144:2500.
  22. Compendium of measures to control Chlamydia psittaci infection among humans (psittacosis) and pet birds (avian chlamydiosis), 1998. Center for Disease Control and Prevention. MMWR Recomm Rep 1998; 47:1.
  23. Sprague LD, Schubert E, Hotzel H, et al. The detection of Chlamydophila psittaci genotype C infection in dogs. Vet J 2009; 181:274.
  24. Maffei C, Marracino A, Di Stanislao F, et al. Psittacosis in a highly endemic area in Italy. Epidemiol Infect 1987; 99:413.
  25. Wallensten A, Fredlund H, Runehagen A. Multiple human-to-human transmission from a severe case of psittacosis, Sweden, January-February 2013. Euro Surveill 2014; 19.
  26. Yung AP, Grayson ML. Psittacosis--a review of 135 cases. Med J Aust 1988; 148:228.
  27. Sahn SA. Pleural effusions in the atypical pneumonias. Semin Respir Infect 1988; 3:322.
  28. Hughes C, Maharg P, Rosario P, et al. Possible nosocomial transmission of psittacosis. Infect Control Hosp Epidemiol 1997; 18:165.
  29. Moroney JF, Guevara R, Iverson C, et al. Detection of chlamydiosis in a shipment of pet birds, leading to recognition of an outbreak of clinically mild psittacosis in humans. Clin Infect Dis 1998; 26:1425.
  30. Adams DA, Thomas KR, Jajosky RA, et al. Summary of Notifiable Infectious Diseases and Conditions - United States, 2014. MMWR Morb Mortal Wkly Rep 2016; 63:1.
  31. Adams DA, Jajosky RA, Ajani U, et al. Summary of notifiable diseases--United States, 2012. MMWR Morb Mortal Wkly Rep 2014; 61:1.
  32. Grayston JT, Thom DH. The chlamydial pneumonias. Curr Clin Top Infect Dis 1991; 11:1.
  33. Hughes P, Chidley K, Cowie J. Neurological complications in psittacosis: a case report and literature review. Respir Med 1995; 89:637.
  34. Verweij PE, Meis JF, Eijk R, et al. Severe human psittacosis requiring artificial ventilation: case report and review. Clin Infect Dis 1995; 20:440.
  35. Taniguchi H, Mukae H, Ihiboshi H, et al. [A case of fulminant psittacosis necessitating mechanical ventilation diagnosed by chlamydial isolation form BALF]. Kansenshogaku Zasshi 1995; 69:1396.
  36. Garo B, Garre M, Boles JM, et al. [Severe pneumopathy and acute renal insufficiency disclosing Chlamydia psittaci infection: resistance to the treatment with erythromycin]. Ann Med Interne (Paris) 1987; 138:296.
  37. Hamilton DV. Psittacosis and disseminated intravascular coagulation. Br Med J 1975; 2:370.
  38. Laidlaw E, Mulligan RA. Letter: Psittacosis and disseminated intravascular coagulation. Br Med J 1975; 2:688.
  39. Wong KF, Chan JK, Chan CH, Lim WW. Psittacosis-associated hemophagocytic syndrome. Am J Med 1991; 91:204.
  40. Mason AB, Jenkins P. Acute renal failure in fulminant psittacosis. Respir Med 1994; 88:239.
  41. Jeffrey RF, More IA, Carrington D, et al. Acute glomerulonephritis following infection with Chlamydia psittaci. Am J Kidney Dis 1992; 20:94.
  42. Timmerman R, Bieger R. Haemolytic anaemia due to cold agglutinins caused by psittacosis. Neth J Med 1989; 34:306.
  43. Samra Z, Pik A, Guidetti-Sharon A, et al. Hepatitis in a family infected by Chlamydia psittaci. J R Soc Med 1991; 84:347.
  44. Carella G, Marra L, Vallot T. [Hepatic psittacosis: a case of liver abnormality diagnosed by ultrasonography]. Presse Med 1996; 25:197.
  45. Anonymous. More psittacosis. BMJ 1973; 3:704.
  46. Adachi K, Hosokawa T, Watanabe Y, et al. [A case of psittacosis meningitis complicated with uveitis]. Rinsho Shinkeigaku 1989; 29:122.
  47. Walder G, Schönherr H, Hotzel H, et al. Presence of Chlamydophila psittaci DNA in the central nervous system of a patient with status epilepticus. Scand J Infect Dis 2003; 35:71.
  48. Newton P, Lalvani A, Conlon CP. Psittacosis associated with bilateral 4th cranial nerve palsies. J Infect 1996; 32:63.
  49. Brewis C, McFerran DJ. 'Farmer's ear': sudden sensorineural hearing loss due to Chlamydia psittaci infection. J Laryngol Otol 1997; 111:855.
  50. Crook T, Bannister B. Acute transverse myelitis associated with Chlamydia psittaci infection. J Infect 1996; 32:151.
  51. Lanham JG, Doyle DV. Reactive arthritis following psittacosis. Br J Rheumatol 1984; 23:225.
  52. Tsapas G, Klonizakis I, Casakos K, Koncouris L. Psittacosis and arthritis. Chemotherapy 1991; 37:143.
  53. Bhopal RS, Thomas GO. Psittacosis presenting with Reiter's syndrome. Br Med J (Clin Res Ed) 1982; 284:1606.
  54. Davison S. Reactive arthritis and psittacosis. Am J Med 1987; 82:385.
  55. Kawamura S, Ikematsu H, Ogimoto H. [Two cases of psittacosis accompanied with rhabdomyolysis]. Kansenshogaku Zasshi 1990; 64:1239.
  56. Macheta MP, Ackrill P, August PJ. Psittacosis, panniculitis and clofazimine. J Infect 1994; 28:69.
  57. Lietman T, Brooks D, Moncada J, et al. Chronic follicular conjunctivitis associated with Chlamydia psittaci or Chlamydia pneumoniae. Clin Infect Dis 1998; 26:1335.
  58. Dean D, Shama A, Schachter J, Dawson CR. Molecular identification of an avian strain of Chlamydia psittaci causing severe keratoconjunctivitis in a bird fancier. Clin Infect Dis 1995; 20:1179.
  59. Fernández-Guerrero ML. Zoonotic endocarditis. Infect Dis Clin North Am 1993; 7:135.
  60. Levison DA, Guthrie W, Ward C, et al. Infective endocarditis as part of psittacosis. Lancet 1971; 2:844.
  61. Lamáury I, Sotto A, Le Quellec A, et al. Chlamydia psittaci as a cause of lethal bacterial endocarditis. Clin Infect Dis 1993; 17:821.
  62. Walker LJ, Adgey AA. Successful treatment by doxycycline of endocarditis caused by ornithosis. Br Heart J 1987; 57:58.
  63. Schinkel AF, Bax JJ, van der Wall EE, Jonkers GJ. Echocardiographic follow-up of Chlamydia psittaci myocarditis. Chest 2000; 117:1203.
  64. Falces Salvador C, Moleiro Oliva A, Barcons Vergés M, et al. [Acute pericarditis with effusion as a form of presentation of psittacosis]. Rev Esp Cardiol 1999; 52:727.
  65. Gherman RB, Leventis LL, Miller RC. Chlamydial psittacosis during pregnancy: a case report. Obstet Gynecol 1995; 86:648.
  66. Jorgensen DM. Gestational psittacosis in a Montana sheep rancher. Emerg Infect Dis 1997; 3:191.
  67. Hyde SR, Benirschke K. Gestational psittacosis: case report and literature review. Mod Pathol 1997; 10:602.
  68. Raderer M, Kiesewetter B, Ferreri AJ. Clinicopathologic characteristics and treatment of marginal zone lymphoma of mucosa-associated lymphoid tissue (MALT lymphoma). CA Cancer J Clin 2016; 66:153.
  69. Crosse BA. Psittacosis: a clinical review. J Infect 1990; 21:251.
  70. Kuwabara M, Tanemori N, Kawaguti Y, et al. [Clinical features of 36 cases of psittacosis]. Kansenshogaku Zasshi 1990; 64:498.
  71. Yamato H, Segawa K, Tsuda T, et al. [A case of psittacosis with migratory infiltrates]. Nihon Kyobu Shikkan Gakkai Zasshi 1992; 30:100.
  72. Hochhegger B, Marchiori E, Irion KL, et al. Psittacosis presenting as a halo sign on high-resolution computed tomography. J Thorac Imaging 2009; 24:136.
  73. Corrin B, Nicholson AG. Pathology of the Lungs, 2nd Ed, Churchill Livingstone, New York, New York 2005. p.185.
  74. Procop GW, Tazelaar HD. Bacterial infections of the lungs and upper airways. In: Thurlbeck's Pathology of the Lung, 3rd Ed, Churg AM, Myers JL, Tozelaar HD, Wright JC (Eds), Thieme, New York, New York 2005. p.204.
  75. Compendium of measures to control Chlamydophila psittaci infection among humans (psittacosis) and pet birds (avian chlamydiosis), 2010. National Association of State Public Health Veterinarians (NASPHV). http://www.nasphv.org/Documents/Psittacosis.pdf (Accessed on April 05, 2011).
  76. Wreghitt T. Chlamydial infection of the respiratory tract. Commun Dis Rep CDR Rev 1993; 3:R119.
  77. Persson K, Treharne J. Diagnosis of infection caused by Chlamydia pneumoniae (strain TWAR) in patients with "ornithosis" in southern Sweden 1981-1987. Scand J Infect Dis 1989; 21:675.
  78. Bruu AL, Haukenes G, Aasen S, et al. Chlamydia pneumoniae infections in Norway 1981-87 earlier diagnosed as ornithosis. Scand J Infect Dis 1991; 23:299.
  79. Oldach DW, Gaydos CA, Mundy LM, Quinn TC. Rapid diagnosis of Chlamydia psittaci pneumonia. Clin Infect Dis 1993; 17:338.
  80. Messmer TO, Skelton SK, Moroney JF, et al. Application of a nested, multiplex PCR to psittacosis outbreaks. J Clin Microbiol 1997; 35:2043.
  81. Madico G, Quinn TC, Boman J, Gaydos CA. Touchdown enzyme time release-PCR for detection and identification of Chlamydia trachomatis, C. pneumoniae, and C. psittaci using the 16S and 16S-23S spacer rRNA genes. J Clin Microbiol 2000; 38:1085.
  82. Toyokawa M, Kishimoto T, Cai Y, et al. Severe Chlamydophila psittaci pneumonia rapidly diagnosed by detection of antigen in sputum with an immunochromatography assay. J Infect Chemother 2004; 10:245.
  83. Heddema ER, Beld MG, de Wever B, et al. Development of an internally controlled real-time PCR assay for detection of Chlamydophila psittaci in the LightCycler 2.0 system. Clin Microbiol Infect 2006; 12:571.
  84. Branley JM, Roy B, Dwyer DE, Sorrell TC. Real-time PCR detection and quantitation of Chlamydophila psittaci in human and avian specimens from a veterinary clinic cluster. Eur J Clin Microbiol Infect Dis 2008; 27:269.
  85. 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; 74:75.
  86. BioFire Diagnostics. FilmArray Respiratory Panel. http://www.biofiredx.com/pdfs/FilmArray/InfoSheet,%20FilmArray%20Respiratory%20Panel-0229.pdf (Accessed on October 21, 2014).
  87. Hammers-Berggren S, Granath F, Julander I, Kalin M. Erythromycin for treatment of ornithosis. Scand J Infect Dis 1991; 23:159.
  88. Khatib R, Thirumoorthi MC, Kelly B, Grady KJ. Severe psittacosis during pregnancy and suppression of antibody response with early therapy. Scand J Infect Dis 1995; 27:519.
  89. Leroy O, Beuscart C, Chidiac C, et al. [Treatment of pneumonia caused by Legionella, Mycoplasma, Chlamydiae and Rickettsia using ofloxacin]. Pathol Biol (Paris) 1989; 37:1137.
  90. 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; 75.
  91. 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; 226:532.
  92. Lederer P, Müller R. [Ornithosis--studies in correlation with an outbreak]. Gesundheitswesen 1999; 61:614.
  93. Williams CJ, Sillis M, Fearne V, et al. Risk exposures for human ornithosis in a poultry processing plant modified by use of personal protective equipment: an analytical outbreak study. Epidemiol Infect 2013; 141:1965.
  94. Van Droogenbroeck C, Van Risseghem M, Braeckman L, Vanrompay D. Evaluation of bioaerosol sampling techniques for the detection of Chlamydophila psittaci in contaminated air. Vet Microbiol 2009; 135:31.