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They are obligate intracellular parasites, and some are notable pathogens, including Rickettsia, which causes a variety of diseases in humans, and Ehrlichia, which causes diseases in livestock. Another genus of well-known Rickettsiales is the Wolbachia , which infect about two-thirds of all arthropods and nearly all filarial nematodes. [ 2 ]
[4] [5] [7] In 1997, a man living in eastern France seroconverted to Rickettsia 4 weeks after onset of an unexplained febrile illness. [8] In 2010, a case report indicated that tick-borne R. helvetica can also cause meningitis in humans. [9] Molecular evidence suggests that in Croatia, as many as 10% of D. reticulatus ticks are infected with R ...
Rickettsia is a genus of nonmotile, gram-negative, nonspore-forming, highly pleomorphic bacteria that may occur in the forms of cocci (0.1 μm in diameter), bacilli (1–4 μm long), or threads (up to about 10 μm long).
Some well-known rickettsial diseases include: Rickettsialpox - caused by Rickettsia akari, this disease is transmitted by mite bites and is generally milder than other rickettsial infections. Rocky Mountain spotted fever - caused by Rickettsia rickettsii, this disease is transmitted by tick bites and is prevalent in the Americas.
Rickettsia rickettsii can be transmitted to human hosts through the bite of an infected tick. As with other bacterium transmitted via ticks, the process generally requires a period of attachment of 4 to 6 hours. However, in some cases a Rickettsia rickettsii infection has been contracted by contact with tick tissues or fluids. [19]
However, scrub typhus is still considered a rickettsiosis, even though the causative organism has been reclassified from Rickettsia tsutsugamushi to Orientia tsutsugamushi. [ citation needed ] Examples of rickettsioses include typhus , both endemic and epidemic, Rocky Mountain spotted fever , and Rickettsialpox .
Rickettsia parkeri (abbreviated R. 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 .
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.