 | This articleneeds additional citations forverification. Please helpimprove this article byadding citations to reliable sources. Unsourced material may be challenged and removed. Find sources: "Chlamydia psittaci" – news ·newspapers ·books ·scholar ·JSTOR(October 2023) (Learn how and when to remove this message) |
| Chlamydia psittaci | |
|---|---|
 | |
| Direct fluorescent antibody stain of amouse brain impression smear showingC. psittaci. | |
Scientific classification | |
| Domain: | Bacteria |
| Kingdom: | Pseudomonadati |
| Phylum: | Chlamydiota |
| Class: | Chlamydiia |
| Order: | Chlamydiales |
| Family: | Chlamydiaceae |
| Genus: | Chlamydia |
| Species: | C. psittaci |
| Binomial name | |
| Chlamydia psittaci (Lillie 1930) Page 1968 (Approved Lists 1980) | |
| Synonyms | |
Chlamydophila psittaci(Lillie 1930) Everett et al. 1999[1] | |
Chlamydia psittaci is a lethalintracellular bacterial species that may causeendemicavian chlamydiosis,epizooticoutbreaks in othermammals, and respiratorypsittacosis inhumans. Potential hosts include feral birds and domesticated poultry, as well ascattle,pigs,sheep, andhorses.C. psittaci is transmitted by inhalation, contact, or ingestion among birds and to mammals. Psittacosis in birds and in humans often starts withflu-like symptoms and becomes a life-threateningpneumonia. Many strains remainquiescent in birds until activated by stress. Birds are excellent, highly mobilevectors for the distribution ofchlamydia infection, because they feed on, and have access to, thedetritus of infected animals of all sorts.
Chlamydia psittaci in birds is oftensystemic, and infections can be inapparent, severe, acute, or chronic with intermittent shedding.[2][3][4]C. psittaci strains in birds infectmucosalepithelial cells andmacrophages of therespiratory tract.Septicaemia eventually develops and the bacteria become localized inepithelial cells and macrophages of mostorgans,conjunctiva, andgastrointestinal tracts. It can also be passed in theeggs. Stress will commonly trigger onset of severe symptoms, resulting in rapid deterioration and death.C. psittaci strains are similar in virulence, grow readily incell culture, have16S rRNAgenes that differ by <0.8%, and belong to eight knownserotypes. All should be considered to be readily transmissible to humans.
Chlamydia psittaci serovar A is endemic amongpsittacine birds and has caused sporadiczoonotic disease in humans, other mammals, andtortoises. Serovar B is endemic amongpigeons, has been isolated fromturkeys, and has also been identified as the cause of abortion in herds ofdairy cattle. Serovars C and D areoccupational hazards forslaughterhouse 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 specificreservoir for serovar E has not been identified. The M56 and WC serovars were isolated during outbreaks in mammals. ManyC. psittaci strains are susceptible tobacteriophages.
Chlamydia psittaci is a small bacterium (0.5μm) that undergoes several transformations during its lifecycle. It exists as anelementary body (EB) betweenhosts. The EB is not biologically active, but is resistant toenvironmental stresses and can survive outside a host. The EB travels from aninfected bird to thelungs of an uninfected bird or person in smalldroplets, and is responsible for infection. Once in the lungs, the EB is taken up bycells in a pouch called anendosome byphagocytosis. However, the EB is not destroyed by fusion withlysosomes, as is typical for phagocytosed material. Instead, it transforms into areticulate 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 ofC. 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.
The disease caused byC. 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 speciesChlamydia 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 toAmazon parrots imported from Argentina. ThoughC. 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.[5]
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 genusChlamydia was divided into two genera,Chlamydia and the newly designated genusChlamydophila, withC. psittaci becomingChlamydophila psittaci.[1] However, this reclassification "was not wholly accepted or adopted"[6] among microbiologists, which "resulted in a reversion to the single, original genusChlamydia, which now encompasses all 9 species includingC. psittaci."[6] A new species was added to the reunited genusChlamydia in 2013,[7] two more were added in 2014.[8]
What were once classified as the mammal-endemicC. psittaci abortion,C. psittacifeline, andC. psittaciguinea pig are since 1999 three separate species,C. abortus,C. felis, andC. caviae.[9] New species continue to be described from inside of what was thought to beC. psittaci. Being a pathogen with a very broad host range,C. psittaci has a lot of opportunities to recombine with otherChlamydia.[8]
Genotypes ofC. 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,[10] but it usually recovers the genotype grouping anyways.[11]
Phylogenetic trees show a relatively recent branch betweenC. psittaci andC. 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.[11]
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 exact same plasmid sequence as the one in 84/2334, and the exact same 23S sequence as the three strains from genotype C.[12]
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.[10]
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.[13]
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 toC. abortus than toC. psittaci, despite the fact that it has a plasmid (typicalC. 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 toC. abortus. On the other hand,C. buteonis was shown to be closer toC. psittaci than toC. 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 inC. psittaci.[11]
Chlamydia psittaci infection is also associated with schizophrenia. Many other kinds of infections have been associated with schizophrenia.[14]
Like otherChlamydia,C. psittaci is anintracellular pathogen and has thus undergone significantgenome reduction. MostC. psittaci genomes encode between 1,000 and 1,400proteins. 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.[15]
In addition to symptoms and CHX,complement fixation,microimmunofluorescence, andpolymerase chain reaction tests can be used to confirm the diagnosis.
Tetracycline ormacrolides 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.