{{Short description|Species of bacterium}} {{More citations needed|date=October 2023}} {{Speciesbox | image = Chlamydophila psittaci FA stain.jpg | image_caption = Direct fluorescent antibody stain of a mouse brain impression smear showing ''C. psittaci''. | genus = Chlamydia | species = psittaci | authority = (Lillie 1930) Page 1968 (Approved Lists 1980) | synonyms = ''Chlamydophila psittaci'' {{au|(Lillie 1930) Everett et al. 1999}}<ref name="EverettBush1999">{{cite journal | vauthors = Everett KD, Bush RM, Andersen AA | title = Emended description of the order Chlamydiales, proposal of Parachlamydiaceae fam. nov. and Simkaniaceae fam. nov., each containing one monotypic genus, revised taxonomy of the family Chlamydiaceae, including a new genus and five new species, and standards for the identification of organisms | journal = International Journal of Systematic Bacteriology | volume = 49 Pt 2 | issue = 2 | pages = 415–40 | date = April 1999 | pmid = 10319462 | doi = 10.1099/00207713-49-2-415 | doi-access = free }}</ref> }}
'''''Chlamydia psittaci''''' is a lethal intracellular bacterial species that may cause endemic avian chlamydiosis, epizootic outbreaks in other mammals, and respiratory psittacosis in humans. Potential hosts include feral birds and domesticated poultry, as well as cattle, pigs, sheep, and horses. ''C. psittaci'' is transmitted by inhalation, contact, or ingestion among birds and to mammals. Psittacosis in birds and in humans often starts with flu-like symptoms and becomes a life-threatening pneumonia. Many strains remain quiescent in birds until activated by stress. Birds are excellent, highly mobile vectors for the distribution of chlamydia infection, because they feed on, and have access to, the detritus of infected animals of all sorts.
''Chlamydia psittaci'' in birds is often systemic, and infections can be inapparent, severe, acute, or chronic with intermittent shedding.<ref name="Andersen">{{cite journal |author=Andersen AA |title=Serotyping of US isolates of ''Chlamydophila psittaci'' from domestic and wild birds |journal=J. Vet. Diagn. Invest. |volume=17 |issue=5 |pages=479–82 |date=September 2005 |pmid=16312243 |doi=10.1177/104063870501700514 |doi-access=free }}</ref><ref name="Dorrestein">{{cite journal |vauthors=Dorrestein GM, Wiegman LJ |title=[Inventory of the shedding of ''Chlamydia psittaci'' by parakeets in the Utrecht area using ELISA] |language=nl |journal=Tijdschr Diergeneeskd |volume=114 |issue=24 |pages=1227–36 |date=December 1989 |pmid=2617495 }}</ref><ref name="Sareyyupoglu">{{cite journal |vauthors=Sareyyupoglu B, Cantekin Z, Bas B |title=''Chlamydophila psittaci'' DNA detection in the faeces of cage birds |journal=Zoonoses Public Health |volume=54 |issue=6–7 |pages=237–42 |year=2007 |pmid=17803512 |doi=10.1111/j.1863-2378.2007.01060.x |s2cid=9087999 }}</ref> ''C. psittaci'' strains in birds infect mucosal epithelial cells and macrophages of the respiratory tract. Septicaemia eventually develops and the bacteria become localized in epithelial cells and macrophages of most organs, conjunctiva, and gastrointestinal tracts. It can also be passed in the eggs. Stress will commonly trigger onset of severe symptoms, resulting in rapid deterioration and death. ''C. psittaci'' strains are similar in virulence, grow readily in cell culture, have 16S rRNA genes that differ by <0.8%, and belong to eight known serotypes. All should be considered to be readily transmissible to humans.
''Chlamydia psittaci'' serovar A is endemic among psittacine birds and has caused sporadic zoonotic disease in humans, other mammals, and tortoises. Serovar B is endemic among pigeons, has been isolated from turkeys, and has also been identified as the cause of abortion in herds of dairy cattle. Serovars C and D are occupational hazards for slaughterhouse workers and for people in contact with birds. Serovar E isolates (known as Cal-10, MP or MN) have been obtained from a variety of avian hosts worldwide and, although they were associated with the 1920s–1930s outbreak in humans, a specific reservoir for serovar E has not been identified. The M56 and WC serovars were isolated during outbreaks in mammals. Many ''C. psittaci'' strains are susceptible to bacteriophages.
==Life cycle and method of infection== thumb|right|200px|Lifecycle of ''C. psittaci'' ''Chlamydia psittaci'' is a small bacterium (0.5μm) that undergoes several transformations during its lifecycle. It exists as an elementary body (EB) between hosts. The EB is not biologically active, but is resistant to environmental stresses and can survive outside a host. The EB travels from an infected bird to the lungs of an uninfected bird or person in small droplets, and is responsible for infection. Once in the lungs, the EB is taken up by cells in a pouch called an endosome by phagocytosis. However, the EB is not destroyed by fusion with lysosomes, as is typical for phagocytosed material. Instead, it transforms into a reticulate body and begins to replicate within the endosome. The reticulate bodies must use some of the host's cellular machinery to complete their replication. The reticulate bodies then convert back to elementary bodies, and are released back into the lung, often after causing the death of the host cell. The EBs are thereafter able to infect new cells, either in the same organism or in a new host. Thus, the lifecycle of ''C. psittaci'' is divided between the elementary body which is able to infect new hosts, but can not replicate, and the reticulate body, which replicates, but is not able to cause new infection.
==History== The disease caused by ''C. psittaci'', psittacosis, was first characterized in 1879 when seven individuals in Switzerland were found to experience pneumonia after exposure to tropical pet birds. The causative pathogen was not known. The related bacterial species ''Chlamydia trachomatis'' was described in 1907, but was assumed to be a virus, as it could not be grown on artificial media. In the winter of 1929–1930, a psittacosis pandemic spread across the United States and Europe. Its mortality rate was 20% and as high as 80% for pregnant women. The disease's spread was eventually attributed to exposure to Amazon parrots imported from Argentina. Though ''C. psittaci'' was identified in 1930 as the agent responsible for psittacosis, it was not found to be a bacterium until examination by electron microscopy in the 1960s.<ref>{{cite journal|last=Harkinezhad|first=Taher|author2=Geens, Tom |author3=Vanrompay, Daisy |title=Chlamydophila psittaci infections in birds: A review with emphasis on zoonotic consequences|journal=Veterinary Microbiology|date=1 March 2009|volume=135|issue=1–2|pages=68–77|doi=10.1016/j.vetmic.2008.09.046|pmid=19054633|url=https://biblio.ugent.be/publication/723722/file/783389 }}</ref>
===Taxonomy=== For several decades, the family Chlamydiaceae contained a sole genus, ''Chlamydia''. ''C. psittaci'' was originally classified from the 1960s to 1999 as a species of this sole genus. In 1999, the order Chlamydiales was assigned two new families (Parachlamydiaceae and Simkaniaceae), and within the family Chlamydiaceae, the genus ''Chlamydia'' was divided into two genera, ''Chlamydia'' and the newly designated genus ''Chlamydophila'', with ''C. psittaci'' becoming ''Chlamydophila psittaci''.<ref name="EverettBush1999"/> However, this reclassification "was not wholly accepted or adopted"<ref name="Balsamo2017">{{cite journal | vauthors = Balsamo G, Maxted AM, Midla JW, Murphy JM, Wohrle R, Edling TM, Fish PH, Flammer K, Hyde D, Kutty PK, Kobayashi M, Helm B, Oiulfstad B, Ritchie BW, Stobierski MG, Ehnert K, Tully TN | display-authors = 6 | title = Compendium of Measures to Control Chlamydia psittaci Infection Among Humans (Psittacosis) and Pet Birds (Avian Chlamydiosis), 2017 | journal = Journal of Avian Medicine and Surgery | volume = 31 | issue = 3 | pages = 262–282 | date = September 2017 | pmid = 28891690 | doi = 10.1647/217-265 | url = http://www.nasphv.org/Documents/PsittacosisCompendium.pdf | doi-access = free }}</ref> among microbiologists, which "resulted in a reversion to the single, original genus ''Chlamydia'', which now encompasses all 9 species including ''C. psittaci''."<ref name="Balsamo2017"/> A new species was added to the reunited genus ''Chlamydia'' in 2013,<ref>{{cite journal | vauthors = Vorimore F, Hsia RC, Huot-Creasy H, Bastian S, Deruyter L, Passet A, Sachse K, Bavoil P, Myers G, Laroucau K | title = Isolation of a New Chlamydia species from the Feral Sacred Ibis (Threskiornis aethiopicus): Chlamydia ibidis | journal = PLOS ONE | volume = 8 | issue = 9 | article-number = e74823 | date = 20 September 2013 | pmid = 24073223 | pmc = 3779242 | doi = 10.1371/journal.pone.0074823 | bibcode = 2013PLoSO...874823V | doi-access = free}}</ref> two more were added in 2014.<ref name="Joseph2015">{{cite journal |vauthors=Joseph SJ, Marti H, Didelot X, Castillo-Ramirez S, Read TD, Dean D |title=Chlamydiaceae Genomics Reveals Interspecies Admixture and the Recent Evolution of Chlamydia abortus Infecting Lower Mammalian Species and Humans |journal=Genome Biology and Evolution |volume=7 |issue=11 |pages=3070–84 |date=October 2015 |pmid=26507799 |pmc=4994753 |doi=10.1093/gbe/evv201}}</ref>
What were once classified as the mammal-endemic ''C. psittaci'' abortion, ''C. psittaci'' feline, and ''C. psittaci'' guinea pig are since 1999 three separate species, ''C. abortus'', ''C. felis'', and ''C. caviae''.<ref name="pmid10319462">{{cite journal |vauthors=Everett KD, Bush RM, Andersen AA |title=Emended description of the order Chlamydiales, proposal of Parachlamydiaceae fam. nov. and Simkaniaceae fam. nov., each containing one monotypic genus, revised taxonomy of the family Chlamydiaceae, including a new genus and five new species, and standards for the identification of organisms |journal=Int. J. Syst. Bacteriol. |volume=49 |issue=2 |pages=415–40 |date=April 1999 |pmid=10319462 |doi=10.1099/00207713-49-2-415 |doi-access=free }}</ref> New species continue to be described from inside of what was thought to be ''C. psittaci''. Being a pathogen with a very broad host range, ''C. psittaci'' has a lot of opportunities to recombine with other ''Chlamydia''.<ref name="Joseph2015" />
Genotypes of ''C. psittaci'' are defined by the partial ompA sequence, which is immunologically relevant and can be amplified by PCR. The main types are A-F, E/B, with G, G1, G2, 1V, 6N, Mat116, R54, YP84, CPX0308, I, and J considered provisional. This has since been expanded into a seven-partial-gene MLST scheme. The MLST scheme technically yields "sequence types" distinct from genotype assignment,<ref name=Szymanska/> but it usually recovers the genotype grouping anyways.<ref name=Longbottom/>
==== Psittaci-abortus intermediate ==== Phylogenetic trees show a relatively recent branch between ''C. psittaci'' and ''C. abortus''. There are also many strains intermediate in position between strains clearly defined as belonging in either species, such as 84/2334 isolated from a parrot.<ref name=Longbottom>{{cite journal |last1=Longbottom |first1=David |last2=Livingstone |first2=Morag |last3=Ribeca |first3=Paolo |last4=Beeckman |first4=Delphine Sylvie Anne |last5=van der Ende |first5=Arie |last6=Pannekoek |first6=Yvonne |last7=Vanrompay |first7=Daisy |title=Whole genome de novo sequencing and comparative genomic analyses suggests that Chlamydia psittaci strain 84/2334 should be reclassified as Chlamydia abortus species |journal=BMC Genomics |date=6 March 2021 |volume=22 |issue=1 |doi=10.1186/s12864-021-07477-6|doi-access=free |pmid=33676404 |pmc=7937271 }}</ref>
Vafin et al. (2007) believe that this intermediate position should be its own species "''C. parapsittaci''", which includes the genotypes C (strains GD, CT1, Par1), D (NJ1, 92-1293, TT3, 7344/2), G (strains Rostinovo-70, 250, PP-87, KC-93), F (strains VS225, 7778B15), and non-grouped strains WC, 84/2334, and R54. Genotypes C, D, and F are isolated from avians; G is isolated from livestock abortions in the former Soviet Union; and WC was isolated from a mammal. For the Rostinovo-70 strain, ''omp1'', ''omp2'', 16S, 23S, plasmid (all partial) sequences are available. All G genotype strains have the same plasmid sequence as the one in 84/2334, and the same 23S sequence as the three strains from genotype C.<ref>{{cite journal |last1=Vafin |first1=R. R. |last2=Ravilov |first2=R. Kh. |last3=Gaffarov |first3=Kh. Z. |last4=Ravilov |first4=A. Z. |last5=Iskhakov |first5=G. M. |last6=Bakirov |first6=I. Kh. |last7=Kashov |first7=V. N. |title=On the nomenclature and classification of chlamydiae |journal=Molecular Genetics, Microbiology and Virology |date=December 2007 |volume=22 |issue=4 |pages=155–164 |doi=10.3103/S0891416807040040}}</ref>
Two provisional genotypes were defined in 2017: G1, G2. These too reflect an intermediate position, though because the author was unaware of Vafin's results, there was no comparison with Vafin's ompA sequences.<ref name=Szymanska>{{cite journal |last1=Szymańska-Czerwińska |first1=Monika |last2=Mitura |first2=Agata |last3=Niemczuk |first3=Krzysztof |last4=Zaręba |first4=Kinga |last5=Jodełko |first5=Agnieszka |last6=Pluta |first6=Aneta |last7=Scharf |first7=Sabine |last8=Vitek |first8=Bailey |last9=Aaziz |first9=Rachid |last10=Vorimore |first10=Fabien |last11=Laroucau |first11=Karine |last12=Schnee |first12=Christiane |title=Dissemination and genetic diversity of chlamydial agents in Polish wildfowl: Isolation and molecular characterisation of avian Chlamydia abortus strains |journal=PLOS ONE |date=28 March 2017 |volume=12 |issue=3 |article-number=e0174599 |doi=10.1371/journal.pone.0174599|doi-access=free |pmid=28350846 |pmc=5370153 |bibcode=2017PLoSO..1274599S }}</ref>
A new species was effectively published in 2019, ''C. buteonis'', which consisted of one type strain RSHA from a red-shouldered hawk. This species occupies an intermediate position.<ref>{{cite journal |last1=Laroucau |first1=K. |last2=Vorimore |first2=F. |last3=Aaziz |first3=R. |last4=Solmonson |first4=L. |last5=Hsia |first5=R.C. |last6=Bavoil |first6=P.M. |last7=Fach |first7=P. |last8=Hölzer |first8=M. |last9=Wuenschmann |first9=A. |last10=Sachse |first10=K. |title=Chlamydia buteonis, a new Chlamydia species isolated from a red-shouldered hawk |journal=Systematic and Applied Microbiology |date=September 2019 |volume=42 |issue=5 |page=125997 |doi=10.1016/j.syapm.2019.06.002|pmid=31257045 |bibcode=2019SyApM..4225997L |doi-access=free }}</ref>
Longbottom et al. (2021) sequenced the whole genome of 84/2334. They find its entire genome, alongside that of genotypes G1 and G2, to be closer to ''C. abortus'' than to ''C. psittaci'', despite the fact that it has a plasmid (typical ''C. abortus'' does not carry one). Analyses of seven MLST housekeeping gene fragments also find the same for genotype 1V, leading to the suggestion to transfer these three genotypes plus 84/2334 to ''C. abortus''. On the other hand, ''C. buteonis'' was shown to be closer to ''C. psittaci'' than to ''C. abortus'' on MSLT, and intermediate with a long branch of its own on whole-genome NeighborNet. Vafin's four strains were not analyzed. WC and genotypes C, D, F were solidly placed in ''C. psittaci''.<ref name=Longbottom/>
==Diseases== ''Chlamydia psittaci'' infection is also associated with schizophrenia. Many other kinds of infections have been associated with schizophrenia.<ref name="pmid22104141 ">{{cite journal | vauthors = Arias I | title = Infectious agents associated with schizophrenia: a meta-analysis. | journal = Schizophr. Res. | volume = 136 | issue = 1–3 | pages = 128–36 | date = April 2012 | pmid = 22104141 | doi = 10.1016/j.schres.2011.10.026 | s2cid = 2687441 | hdl = 10481/90076 | hdl-access = free }}</ref>
==Genomics== Like other ''Chlamydia'', ''C. psittaci'' is an intracellular pathogen and has thus undergone significant genome reduction. Most ''C. psittaci'' genomes encode between 1,000 and 1,400 proteins. A total of 911 core genes were found to be present in all 20 strains sequenced by Read et al., corresponding to 90% of the genes present in each genome.<ref>{{cite journal | vauthors = Read TD, Joseph SJ, Didelot X, Liang B, Patel L, Dean D | title = Comparative analysis of Chlamydia psittaci genomes reveals the recent emergence of a pathogenic lineage with a broad host range | journal = mBio | volume = 4 | issue = 2 | pages = e00604–12 | date = March 2013 | pmid = 23532978 | pmc = 3622922 | doi = 10.1128/mBio.00604-12 | doi-access = free}}</ref>
==Confirmation of diagnosis== In addition to symptoms and CHX, complement fixation, microimmunofluorescence, and polymerase chain reaction tests can be used to confirm the diagnosis.
==Treatment== Tetracycline or macrolides can be used to treat this condition. The drugs are given intravenously or orally, depending on drug choice. Treatment should continue for 10–14 days after the fever subsides. In children or pregnant women, though, tetracycline should not be used. Ibuprofen or acetominophen, and fluids are also administered. Cannabis or tobacco smoke should be avoided. While taking tetracycline, dairy products should be avoided.
==See also== * ''Chlamydia'' infection * Koala (''Phascolarctos cinereus'')
==References== {{Reflist}}
==Further reading== *{{cite book |title=Brock Biology of Microorganisms |url=https://archive.org/details/brockbiologyofmi00madi |url-access=registration |publisher=Prentice Hall |location=Upper Saddle River, NJ |year=2003 |isbn=978-0-13-049147-3 |edition=10th}}
{{Gram-negative non-proteobacterial diseases}} {{Taxonbar|from=Q134275}}
Category:Chlamydiota Category:Biological anti-agriculture weapons Category:Pathogenic bacteria