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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 ]
Rickettsia rickettsii is a Gram-negative, intracellular, cocco-bacillus bacterium that was first discovered in 1902. [1] Having a reduced genome, the bacterium harvests nutrients from its host cell to carry out respiration, making it an organo-heterotroph.
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.
No rapid laboratory tests are available to diagnose rickettsial diseases early in the course of illness, and serologic assays usually take 10–12 days to become positive. Research is indicating that swabs of eschars may be used for molecular detection of rickettsial infections. [6] [7]
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. [4] [5] [7] In 1997, a man living in eastern France seroconverted to Rickettsia 4 weeks after onset of an unexplained febrile illness. [8]
Rickettsialpox is a mite-borne infectious illness caused by bacteria of the genus Rickettsia (Rickettsia akari). [1] Physician Robert Huebner and self-trained entomologist Charles Pomerantz played major roles in identifying the cause of the disease after an outbreak in 1946 in a New York City apartment complex, documented in "The Alerting of Mr. Pomerantz," an article by medical writer Berton ...
Treatment: Antibiotics are the treatment for relapsing fever, with doxycycline, tetracycline, or erythromycin being the treatment of choice. [32] Typhus Several diseases caused by Rickettsia bacteria (below) Rocky Mountain spotted fever. Organism: Rickettsia rickettsii; Vector: Wood tick (Dermacentor variabilis), D. andersoni; Region (US): East ...