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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]
A 2021 systematic review of 32 confirmed and 45 probable cases of human infection with R. parkeri determined that 94% of the confirmed cases had fever, 91% an eschar, 72% a rash, 56% headache, and 56% myalgia, with similar percentages among the probable cases. [8] The rash was most frequently described as papular or macular. [8]
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.
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 spread by ticks [4] Diagnostic method: Based on symptoms [5] Differential diagnosis: Zika fever, dengue, chikungunya, Rickettsia parkeri rickettsiosis, Pacific Coast tick fever, rickettsialpox [6] [7] Treatment: Doxycycline [8] Prognosis: 0.5% risk of death [6] Frequency < 5,000 cases per year (USA) [6]
Rickettsia typhi is a small, aerobic, obligate intracellular, rod shaped gram negative bacterium. [1] It belongs to the typhus group of the Rickettsia genus, along with R. prowazekii . [ 2 ] R. typhi has an uncertain history, as it may have long gone shadowed by epidemic typhus ( R. prowazekii ). [ 3 ]
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]
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 ...