Table 1.

Studies of wild birds summarized in this review. Where a study included both captive and wild birds, we only report prevalence in wild birds. We have excluded case studies involving a single individual bird.

Host Species	Family	Location	Sample Source	Sample Size	Detection Method(s)	Chlamydiales Species Tested For	Key Findings	Disease Signs Reported? (Y/N/NR) **	Reference
Seabirds; 13 species, 4 orders *	Anatidae, Alcidae, Laridae, Procellaridae, Sulidae	France	Rehabilitation centre	195	PCR (cloacal swabs) Sequencing Multilocus sequence typing (MLST)	C. psittaci Chlamydiaceae	• 18.5% Chlamydiaceae prevalence (prev.) • Prev. varied between host spp.; Northern gannets Morus bassanus) had higher prev. compared to European herring gulls (Larus argentatus) and common murres (Uria aalge) • Seasonal variation in prev. (in Northern gannets) • C. psittaci identified in Northern gannets and herring gulls • Unclassified Chlamydiaceae also identified	N	Aaziz et al., 2015 [12]
48 species from 11 orders *	Psittacidae, Cacatuidae, Podargidae (…) *	Australia	Rehabilitation centre	229	PCR (live birds: choanal/cloacal swabs; dead birds: swabs from trachea and intestine/caecum) MLST	C. psittaci	• 1 crimson rosella (Platycercus elegans) and 1 superb lyrebird (Menura novaehollandiae) tested positive (0.7%) • All other wild birds tested negative	Y	Amery-Gale et al. 2020 [32]
Great white pelicans (Pelecanus onocrotalus)	Pelecanidae	South Africa	Live trapping	50	PCR (tracheal and cloacal swabs)	C. psittaci	• 0% C. psittaci prevalence	N/A	Assunção et al., 2007 [87]
Songbirds (Passeriformes); Pigeons and doves (Columbiformes) *	Paridae, Prunellidae, Turdidae (…) *	U.K.	Necropsy (selected based on clinical signs)	40	PCR (liver and spleen) Histology Immunohistochemistry	C. psittaci	• 53% C. psittaci prevalence • Nonspecific clinical signs observed (lethargy, fluffed up plumage) and emaciation • Concurrent disease in >50% cases • Genotype A present in all passerine cases	Y	Beckmann et al., 2014 [81]
16 species from 5 orders *	Cacatuidae, Psittacidae, Columbidae (…) *	Australia	Trapping and community submissions	278	Isolation (from liver) and inoculation Serology (Complement Fixation Test (CFT))	C. psittaci (methods not spp. specific)	• 10.6% prevalence (Psittaciformes) • 0.7% prevalence (all other species; 1 house sparrow (Passer domesticus) tested positive)	NR	Beech and Miles 1953 [60]
Peregrine falcons (Falco peregrinus) and white-tailed sea eagles (WTSE) (Haliaeetus albicilla)	Falconidae, Accipitridae	Sweden	Nestlings (breeding monitoring), adults (museum submissions)	319 (299 nestlings; 108 falcons and 191 WTSE, and 20 WTSE adults)	PCR (cloacal swabs) ompA sequencing	C. psittaci Chlamydia	• 1.3% C. psittaci prev. (n = 2 falcons, n = 2 eagles) • New strains of C. psittaci identified	NR	Blomqvist et al., 2012 [76]
Feral pigeons (Columbia livia domestica), ring-necked parakeets (Psittacula krameri), crows (Corvus splendens)	Psittacidae, Columbidae, Corvidae	India	Trapping	85 (55 pigeons, 19 parakeets, 11 crows)	Isolation and inoculation (faecal swabs/intestinal and visceral organs) Serology (indirect micro-immunofluorescense test (IMIFT) and ELISA)	C. psittaci (methods not spp.-specific)	• 26.3% prev. in ring-necked parakeets • 16.4% prev. in pigeons • 18.2% prev. in crows	NR	Chahota et al., 1997 [61]
Seabirds; 22 species *	Laridae, Alcidae	Bering Sea	NR	722	PCR (faeces) ompA, mpB, and 16S sequencing	C. psittaci Chlamydiales	• 0.1% C. psittaci prev. (n = 1 black-headed gull (Larus ridibundus))	NR	Christerson et al., 2010 [57]
Blue-fronted Amazon parrot (Amazona aestiva) and hyacinth macaw (Anodorhynchus hyacinthinus)	Psittacidae	Brazil	Nestlings (breeding monitoring)	77 (32 Amazon parrots nestlings, 45 macaw nestlings)	PCR (tracheal and cloacal swabs) Serology (CFT)	C. psittaci (methods not spp.-specific)	• 6.3% prevalence in Amazon parrots (cloacal swabs) • 26.7% prevalence in hyacinth macaws (cloacal swabs) 8.9% (tracheal swabs), 4.8% (CFT)	N	de Freitas Raso et al., 2006 [62]
Feral pigeons	Columbidae	Brazil	Live trapping	238	PCR (cloacal and tracheal swabs)	C. psittaci	• 16.8% C. psittaci prev. • Prev. ranged from 6.1% to 37.8% according to location	NR	de Lima et al., 2010 [69]
Blue-fronted Amazon parrot	Psittacidae	Bolivia	Live trapping	34	Serology (CFT)	C. psittaci (method not species-specific)	• 0% prevalence	N/A	Deem et al. 2005 [84]
Canada geese (Branta canadensis)	Anatidae	Belgium	Culling program	81	Serology (rMOMP-based ELISA) Inoculation and culture (pharyngeal swabs)	C. psittaci	• 93.6% seropositive • 58% of swabs were culture positive, but low culture score (low no. of viable organisms)	N	Dickx et al., 2013 [73]
Rosy-faced lovebirds (Agapornis roseicollis); 15 other species, including Passeriformes and Columbiformes *	Psittaculidae, Columbidae, Icteridae, Troglodytidae (…) *	USA	Live trapping	188 (46 lovebirds; 142 birds of other species)	PCR (conjunctival/ choanal and cloacal swabs) Serology (Elementary body agglutination (EBA))	C. psittaci	• 93% C. psittaci prev. and 76% seroprevalence in lovebirds • 10% C. psittaci prev. and 7% seroprevalence (in all other bird species combined)	NR	Dusek et al., 2018 [88]
Feral pigeons	Columbidae	Brazil	Live trapping	240	PCR (cloacal swabs)	C. psittaci	• 13% C. psittaci prevalence	NR	Ferreira et al., 2016 [68]
New Zealand bellbirds (Anthornis melanura; n = 4); rifleman (Acathisitta chloris; n = 3); hihi (Notiomyces cincta; n = 2); whitehead (Mohoua albicilla; n = 1)	Meliphagidae, Notiomystidae, Acanthisittidae, Mohouidae	New Zealand	Live trapping	10	PCR (cloacal swabs) Sequencing	C. psittaci	• 10% C. psittaci prevalence; one bird identified positive (a hihi) • First report of C. psittaci detection from a wild native bird in New Zealand	NR	Gartrell et al., 2012 [89]
Dusky-headed parakeets (Aratinga weddellii) and Tui parakeets (Brotogeris sanctithomae)	Psittacidae	Peru	Live trapping	48 (35 dusky-headed parakeets, 13 Tui parakeets)	Serology (CFT, Latex agglutination, EBA)	C. psittaci (methods not spp.-specific)	• 0% seroprevalence using any method	N/A	Gilardi et al., 1995 [85]
Fulmars (Fulmarus glacialis)	Procellaridae	Faroe Islands	Non-flying juveniles sampled	431 (juveniles)	PCR (cloacal swabs) ompA sequencing	C. psittaci	• 10% C. psittaci prevalence (range from 7% to 21% between locations) • 6BC strain identified in all positive samples	NR	Hermann et al., 2006 [74]
Great tits (Parus major; n = 318), blue tits (Parus caerulus; n = 43), marsh tits (Parus palustris; n = 32), coal tits (Parus ater; n = 3), willow tits (Parus montanus; n = 3)	Paridae	Germany	Live trapping (n = 389), necropsy (n = 6)	395	Inoculation and culture (cloacal and pharyngeal swabs) Organ tissues (necropsied birds)	Chlamydia	• 54.3% Chlamydia prevalence • Shedding varied according to swab site • Prevalence varied between host species; highest prevalence in blue tits, followed by great tits, then marsh tits • Repeated sampling of n = 38 individuals; 60.5% changed in Chlamydia status	N	Holzinger-Umlauf et al., 1997 [80]
Chinstrap penguins (Pygoscelis antarcticus) and Magellanic penguins (Scheniscus magellanicus); seabirds *	Sphenisicidae, Sterocorariidae, Laridae, Procellaridae, Chionidae	Antarctica, Chile	Live trapping (penguins), fresh faeces (seabirds)	527 (264 penguins; 263 seabirds)	PCR (cloacal swabs and faeces) Sequencing	C. psittaci Chlamydiales	• 18% Chlamydiales prevalence (Antarctica) • No C. psittaci detected in birds in Antarctica • 10% C. psittaci prevalence (Chile)	NR	Isaksson et al., 2015 [77]
43 species; 14 different orders *	Corvidae, Scolopacidae, Columbidae (…) *	South Korea	Rehabilitation centres	225	PCR (tracheal swabs and tissues) ompA sequencing	C. psittaci Chlamydiales	• 1.8% C. psittaci prev. (rook (Corvus frugilegus), Korean magpie (Pica serica), feral pigeon) • 0.9% C. gallinacea prev. (woodcock (Scolopax rusticola))	NR	Jeong et al., 2017 [36]
Raptors: osprey (Pandion haliaetus), great horned owl (Bubo virginianus), red-tailed hawk (Buteo jamaicaensis) (others not listed)	Accipitridae, Pandionidae, Strigidae (others not listed)	USA	Rehabilitation centres	82	PCR (oral and cloacal swabs) Sequencing	C. psittaci Chlamydiales	• 1 osprey was C. psittaci-positive • 1 red-tailed hawk was Ca, Rhabdochlamydia spp. positive	NR	Jouffroy et al., 2016 [75]
35 species; 15 orders *	Anatidae, Accipitridae, Passeridae (…) *	Poland	Hunting, culling programs, fishing bycatch, wildlife rehabilitation centres, community submissions	369	PCR (combined tissues and conjunctival swabs) Sequencing	Chlamydia (all species)	• 7.3% Chlamydia prevalence • C. psittaci and C. trachomatis identified • Chlamydia positive birds identified across eight orders	N	Krawiec et al., 2015 [52]
Hawks; Buteo genus	Accipitridae	USA	Live trapping	297	PCR (conjunctival, choanal, and cloacal swab) Sequencing Serology (EBA) and immunofluorescent antibody (IFA))	Chlamydiaceae	• 1.4% Chlamydia prev. (2 positive red-tailed hawks, 2 positive Swainson’s hawks (Buteo swainsoni)) • 0% seroprevalence	N	Luján-Vega et al., 2018 [37]
Feral pigeons; house sparrows	Columbidae	Iran	NR	150 (75 pigeons; 75 house sparrows)	PCR (cloacal swabs) ompA sequencing	C. psittaci	• 25.3% C. psittaci prev. in pigeons • 18.6% C. psittaci prev. in house sparrows • Genotypes A and B identified	NR	Mahzounieh et al., 2020 [90]
Feral pigeons, Eurasian collared doves (Streptopelia decaocto), wood pigeon (Columba palumbus)	Columbidae	Switzerland	Pigeon lofts, rehabilitation centres, culling programs	431	PCR (choanal/cloacal swabs and liver samples) DNA microarray assay 16S sequencing MLST	C. psittaci Chlamydiaceae	• 14.1% Chlamydiaceae prev. (feral pigeons) • 5.1% Chlamydiaceae prev. (collard dove) • 5.7% Chlamydiacaeae prev. (wood pigeon) • Prevalence in feral pigeons varied by location • 57.6% positive samples were C. psittaci, 5.4% of positive samples were C. avium	NR	Mattman et al., 2019 [47]
7 species, order Psittaciformes, Anseriformes, Passeriformes *	Cacatuidae, Anatidae, Rallidae, Artamidae	Australia	NR	124	PCR (conjunctival, choanal, and cloacal swabs) Cell culture	C. psittaci	• 0% prevalence; no wild birds tested positive	N/A	McElnea and Cross, 1999 [91]
Galapagos doves (Zenaida galapagoensis) and feral pigeons	Columbidae	The Galapagos Islands, Ecuador	Live trapping	133 (105 Galapagos doves, 28 feral pigeons)	PCR (cloacal swabs)	C. psittaci	• 6% C. psittaci prev. (Galapagos doves) • 0% C. psittaci prev. (feral pigeons) • Geographic variation in prev. (all positive cases occurred on one island)	NR	Padilla et al., 2004 [92]
Ring-necked parakeet	Psittacidae	France	Live trapping	85	PCR (cloacal swabs)	C. psittaci C. avium Chlamydiaceae	• 7.1% Chlamydiaceae prevalence • The chlamydial species was only identified to species level in one individual (C. avium)	NR	Pisanu et al. 2018 [49]
Red-tailed Amazon parrot (Amazona brasiliensis)	Psittacidae	Rasa Island, Brazil	Nestlings (breeding monitoring)	117 (nestlings)	PCR (tracheal and cloacal swabs)	C. psittaci (method not spp. specific)	• 1.2% prevalence (one positive sample identified)	N	Ribas et al. 2014 [82]
Feral pigeons	Columbidae	Germany	Management project	570	PCR (cloacal swabs and faeces) DNA microarray ompA sequencing	C. psittaci Chlamydiaceae	• 14.6% Chlamydiaceae prev. (swabs) and 10.4% C. psittaci prev. (swabs) • Faecal prev. higher than swabs • Temporal variation in Chlamydiaceae prev.; 9.3% prev. in 2009, compared to 19.3% in 2010 • C. pecorum, C. abortus, C. trachomatis, and unclassified Chlamydiaceae also identified	NR	Sachse et al., 2012 [66]
Feral pigeons	Columbidae	Thailand	NR	407	PCR (tracheal and cloacal swabs), ompA sequencing	C. psittaci	• 10.8% C. psittaci prevalence • Genotype B identified	N	Sariya et al., 2015 [71]
Raptors; 15 species *	Accipitridae, Falconidae, Tytonidae, Strigidae, Pandionidae	Germany	Veterinary submissions	39	PCR (lung and spleen)	C. psittaci	• 74% C. psittaci prevalence • No association of infection with sex, age, or year	NR	Schettler et al., 2003 [93]
Raptors; 346 diurnal birds of prey; 55 owls) *	Accipitridae, Pandionidae, Strigidae, Tytonidae, Falconidae	Germany	Rehabilitation centres	428	Serology (ELISA)	C. psittaci	• 63% seropositivity • Age association with seroprevalence; older birds more likely to test seropositive	NR	Schettler et al., 2001 [94]
10 species * majority of birds tested were Columbiformes	Columbidae, Turdidae, Anatidae (…)	U.K.	Rehabilitation centre	43	PCR (cloacal swabs)	C. psittaci	• 11.6% C. psittaci prevalence • All positive birds were Columbiformes • Positive pigeons were emaciated and anorexic, but no signs of respiratory distress	Y	Sharples and Baines, 2009 [95]
42 species *	Columbidae, Passeridae, Fringillidae (…) *	Switzerland	Rehabilitation centre	339	PCR (choanal and cloacal swabs, faecal swabs) ompA sequencing	C. psittaci Chlamydiaceae	• 0.9% Chlamydiaceae prev. (all Columbidae) • No other birds tested positive	NR	Stalder et al., 2020 [31]
Raptors (16 species); corvids (six species) *	Accipitridae, Falconidae, Strigidae, Tytonidae, Corvidae	Switzerland	Rehabilitation centres, community submissions, culling programs	594 (341 raptors, 253 corvids)	PCR (choanal and cloacal swabs, faecal swabs) ompA and 16S sequencing	C. psittaci C. buteonis Chlamydiaceae	• 23.7% Chlamydiaceae prev. (corvids) • 5.9% Chlamydiaceae prev. (raptors) • 0% C. buteonis prev.	N	Stalder et al., 2020 [34]
Feral pigeons	Columbidae	Poland	NR	101	PCR (cloacal and pharyngeal swabs) ompA sequencing	C. psittaci	• 3.9% C. psittaci prevalence • More pigeons were co-infected with C. psittaci and pigeon circovirus than with C. psittaci alone	N	Stenzel et al., 2014 [96]
Crimson rosella	Psittacidae	Australia	Live trapping	136	PCR (cloacal swabs) Serology (ELISA) 16S sequencing	C. psittaci C. gallinacea Chlamydiales	• 27.7% Chlamydiales prevalence • 6.2% C. psittaci prev. and 4.6% C. gallinacea prev. • 16% seroprevalence • Higher Chlamydiales prev. in non-breeding birds and female birds • Seroprevalence was highest in autumn and in non-breeding birds	N	Stokes et al., 2020 [46]
7 species; order Psittaciformes *	Psittacidae, Cacatuidae	Australia	Live trapping	132	PCR (cloacal swabs) Serology (ELISA) 16S and ompA sequencing	C. psittaci C. gallinacea Chlamydiales	• Overall Chlamydiales prevalence was 39.8% • C. psittaci prevalence was 9.8%, and C. gallinacea prevalence was 0.8% • Seroprevalence was 37.0% • Prevalence varied between species and location	N	Stokes et al., 2020b [33]
Long-billed corella (Cacatua tenuirostris), little corella (Cacatua sanguinea), sulfur-crested cockatoo (Cacatua galerita) and galah (Eolophus roseicapillus)	Cacatuidae	Australia	Live trapping and rehabilitation centres	55	PCR (choanal/cloacal swabs) Next-generation sequencing (NGS)	C. psittaci	• None PCR positive, but NGS identified C. psittaci in one little corella; hence, overall prevalence was 1.8%	Y	Sutherland et al. 2019 [63]
33 species; 16 families *	Accipitridae, Anatidae, Corvidae (…) *	Poland	Rehabilitation centres; some free-living birds captured	894	PCR (cloacal or faecal swabs) ompA and rrn sequencing	C. psittaci C. abortus Chlamydiaceae	• 14.8% Chlamydiaceae prev. (all birds tested) • 19.7% Chlamydiaceae prev. (Anatidae) • 13.4% Chlamydiaceae prev. (Corvidae) • C. psittaci/C. abortus intermediate isolates identified	NR	Szymańska-Czerwińska et al., 2017 [29]
Common swift (Apus apus)	Apodidae	Germany	Community veterinary submissions	243	PCR (pooled organs)	C. psittaci Chlamydia	• 0% prev. (no birds tested positive over 9 years)	N/A	Tiyawattanaroj et al. 2021 [86]
Red-tailed Amazon parrot	Psittacidae	Rasa Island, Brazil	Nestlings (breeding monitoring)	74 (nestlings)	PCR (cloacal and oropharyngeal swabs) Serology (ELISA)	C. psittaci (method not spp. specific)	• 0% prevalence	N/A	Vaz et al. 2017 [83]
African sacred ibis (Threskiornis aethiopicus)	Threskiornithidae	France	Culling program	70	PCR (cloacal swabs) Culture and inoculation	C. psittaci Chlamydiaceae	• 11% Chlamydiaceae prev. • 1.4% C. psittaci prev. and • 4.3% Ca. C. ibidis prev. • Ca. C. ibidis identified and proposed as a new species	N	Vorimore et al., 2013 [50]
Greater flamingo (Phoenicopterus roseus)	Phoenicopteridae	France	Live trapping	404	PCR (cloacal swabs) Isolation and cell culture Sequencing	C. psittaci C. avium C. gallinacean Ca. C. ibidis	• 30.9% (125/404) chlamydial positive, but not for known species • Three isolates were cultured, with two new species identified and proposed, in a new genus, Chlamydiifrater gen. nov.	N	Vorimore et al., 2021 [78]
Feral pigeons	Columbidae	Thailand	Live trapping (public locations)	150	PCR (cloacal swabs) Isolation and inoculation	C. psittaci	• 1.3% C. psittaci prevalence	N	Wannaratana et al., 2017 [70]
Songbirds (n = 527; 11 families) Pigeons (n = 84; Columbidae) Waterfowl (n = 442; 5 families) *	Columbidae, Fringillidae, Turdidae (…) *	Switzerland	Collected through avian influenza surveillance, live trapping (pigeons), and hunters (cormorants)	1091	PCR (cloacal swabs) 16S Sequencing	C. psittaci Chlamydiaceae	• 3.3% C. psittaci prev. in feral pigeons • 0.4% Chlamydiaceae prev. in songbirds (Passeriformes) • 4% Chlamydiaceae prev. in waterfowl (all were tufted ducks (Aythya fuligula) and pochards (Aythya farina))	NR	Zweifel et al., 2009 [30]

* For the list of all species and families tested, refer to the publication. ** Y indicates Yes; N indicates No; NR indicates Not Recorded.