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Rickettsia is a genus of nonmotile, gram-negative, nonspore-forming, highly pleomorphic bacteria that may occur in the forms of cocci, bacilli, or threads. The genus was named after Howard Taylor Ricketts in honor of his pioneering work on tick-borne spotted fever.
Boutonneuse fever is a fever as a result of a rickettsial infection caused by the bacterium Rickettsia conorii and transmitted by the dog tick Rhipicephalus sanguineus. Boutonneuse fever can be seen in many places around the world, although it is endemic in countries surrounding the Mediterranean Sea. This disease was first described in Tunisia in 1910 by Conor and Bruch and was named boutonneuse due to its papular skin-rash characteristics.
Scrub typhus or bush typhus is a form of typhus caused by the intracellular parasite Orientia tsutsugamushi, a Gram-negative α-proteobacterium of family Rickettsiaceae first isolated and identified in 1930 in Japan.
Rickettsia rickettsii is a Gram-negative, intracellular, coccobacillus bacterium that was first discovered in 1902. Having a reduced genome, the bacterium harvests nutrients from its host cell to carry out respiration, making it an organoheterotroph. Maintenance of its genome is carried out through vertical gene transfer where specialization of the bacterium allows it to shuttle host sugars directly into its TCA cycle.
The Weil–Felix test is an agglutination test for the diagnosis of rickettsial infections. It was first described in 1916. By virtue of its long history and of its simplicity, it has been one of the most widely employed tests for rickettsia on a global scale, despite being superseded in many settings by more sensitive and specific diagnostic tests. The Weil–Felix antibody was recently found to target the rickettsial lipopolysaccharide O-antigen.
Orientia is a genus of bacteria in family Rickettsiaceae. They are obligate intracellular, gram-negative bacteria found in insects and mammals. They are spread through the bites or feces of infected insects.
Orientia tsutsugamushi is a mite-borne bacterium belonging to the family Rickettsiaceae and is responsible for a disease called scrub typhus in humans. It is a natural and an obligate intracellular parasite of mites belonging to the family Trombiculidae. With a genome of only 2.0–2.7 Mb, it has the most repeated DNA sequences among bacterial genomes sequenced so far. The disease, scrub typhus, occurs when infected mite larvae accidentally bite humans. This infection can prove fatal if prompt doxycycline therapy is not started.
Rickettsia conorii is a Gram-negative, obligate intracellular bacterium of the genus Rickettsia that causes human disease called boutonneuse fever, Mediterranean spotted fever, Israeli tick typhus, Astrakhan spotted fever, Kenya tick typhus, Indian tick typhus, or other names that designate the locality of occurrence while having distinct clinical features. It is a member of the spotted fever group and the most geographically dispersed species in the group, recognized in most of the regions bordering on the Mediterranean Sea and Black Sea, Israel, Kenya, and other parts of North, Central, and South Africa, and India. The prevailing vector is the brown dog tick, Rhipicephalus sanguineus. The bacterium was isolated by Emile Brumpt in 1932 and named after A. Conor, who in collaboration with A. Bruch, provided the first description of boutonneuse fever in Tunisia in 1910.
Rickettsia typhi is a small, aerobic, obligate intracellular, rod shaped gram negative bacterium. It belongs to the typhus group of the Rickettsia genus, along with R. prowazekii. R. typhi has an uncertain history, as it may have long gone shadowed by epidemic typhus. This bacterium is recognized as a biocontainment level 2/3 organism. R. typhi is a flea-borne disease that is best known to be the causative agent for the disease murine typhus, which is an endemic typhus in humans that is distributed worldwide. As with all rickettsial organisms, R. typhi is a zoonotic agent that causes the disease murine typhus, displaying non-specific mild symptoms of fevers, headaches, pains and rashes. There are two cycles of R. typhi transmission from animal reservoirs containing R. typhi to humans: a classic rat-flea-rat cycle that is most well studied and common, and a secondary periodomestic cycle that could involve cats, dogs, opossums, sheep, and their fleas.
Leptotrombidium is a genus of mites in the family Trombiculidae, that are able to infect humans with scrub typhus through their bite. The larval form feeds on rodents, but also occasionally humans and other large mammals. They are related to the harvest mites of the North America and Europe.
African tick bite fever (ATBF) is a bacterial infection spread by the bite of a tick. Symptoms may include fever, headache, muscle pain, and a rash. At the site of the bite there is typically a red skin sore with a dark center. The onset of symptoms usually occurs 4–10 days after the bite. Complications are rare but may include joint inflammation. Some people do not develop symptoms.
Rickettsia australis is a bacterium that causes a medical condition called Queensland tick typhus. The probable vectors are the tick species, Ixodes holocyclus and Ixodes tasmani. Small marsupials are suspected reservoirs of this bacterium.
North Asian tick typhus also known as Siberian tick typhus, is a condition characterized by a maculopapular rash.
Flinders Island spotted fever is a condition characterized by a rash in approximately 85% of cases.
Rickettsia parkeri is a gram-negative intracellular bacterium. The organism is found in the Western Hemisphere and is transmitted via the bite of hard ticks of the genus Amblyomma. R. parkeri causes mild spotted fever disease in humans, whose most common signs and symptoms are fever, an eschar at the site of tick attachment, rash, headache, and muscle aches. Doxycycline is the most common drug used to reduce the symptoms associated with disease.
Rickettsia helvetica, previously known as the Swiss agent, is a bacterium found in Dermacentor reticulatus and other ticks, which has been implicated as a suspected but unconfirmed human pathogen. First recognized in 1979 in Ixodes ricinus ticks in Switzerland as a new member of the spotted fever group of Rickettsia, the R. helvetica bacterium was eventually isolated in 1993. Although R. helvetica was initially thought to be harmless in humans and many animal species, some individual case reports suggest that it may be capable of causing a nonspecific fever in humans. In 1997, a man living in eastern France seroconverted to Rickettsia 4 weeks after onset of an unexplained febrile illness. In 2010, a case report indicated that tick-borne R. helvetica can also cause meningitis in humans.
Rickettsia felis is a species of bacterium, the pathogen that causes cat-flea typhus in humans, also known as flea-borne spotted fever. Rickettsia felis also is regarded as the causative organism of many cases of illnesses generally classed as fevers of unknown origin in humans in Africa.
Rickettsia honei is a species of Rickettsia.
Rickettsia sibirica is a species of Rickettsia. This bacterium is the etiologic agent of North Asian tick typhus, which is also known as Siberian tick typhus. The ticks that transmit it are primarily various species of Dermacentor and Haemaphysalis.
Rickettsia japonica is a species of Rickettsia. It can cause Japanese spotted fever.
References
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- ↑ Raoult D, Roux V (October 1997). "Rickettsioses as paradigms of new or emerging infectious diseases". Clin. Microbiol. Rev. 10 (4): 694–719. doi:10.1128/CMR.10.4.694. PMC 172941 . PMID 9336669.
- ↑ Paddock CD, Finley RW, Wright CS, et al. (November 2008). "Rickettsia parkeri rickettsiosis and its clinical distinction from Rocky Mountain spotted fever". Clin. Infect. Dis. 47 (9): 1188–96. doi: 10.1086/592254 . PMID 18808353.
- ↑ Parola P, Paddock CD, Raoult D (October 2005). "Tick-Borne Rickettsioses around the World: Emerging Diseases Challenging Old Concepts". Clin. Microbiol. Rev. 18 (4): 719–56. doi:10.1128/CMR.18.4.719-756.2005. PMC 1265907 . PMID 16223955.
- ↑ Unsworth NB, Stenos J, Faa AG, Graves SR (July 2007). "Three Rickettsioses, Darnley Island, Australia". Emerging Infect. Dis. 13 (7): 1105–7. doi:10.3201/eid1307.050088. PMC 2878210 . PMID 18214193.
- ↑ Angelakis, Emmanouil; Richet, Hervé; Rolain, Jean-Marc; La Scola, Bernard; Raoult, Didier (2012). "Comparison of real-time quantitative PCR and culture for the diagnosis of emerging Rickettsioses". PLOS Neglected Tropical Diseases. 6 (3): e1540. doi: 10.1371/journal.pntd.0001540 . ISSN 1935-2735. PMC 3295807 . PMID 22413026.
- ↑ Giulieri, Stefano; Jaton, Katia; Cometta, Alain; Trellu, Laurence T.; Greub, Gilbert (February 2012). "Development of a duplex real-time PCR for the detection of Rickettsia spp. and typhus group rickettsia in clinical samples". FEMS Immunology and Medical Microbiology. 64 (1): 92–97. doi: 10.1111/j.1574-695X.2011.00910.x . ISSN 1574-695X. PMID 22098502.
- ↑ "Rickettsial Infection: Background, Pathophysiology, Etiology". reference.medscape.com.
