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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 (0.1 μm in diameter), bacilli (1–4 μm long), or threads (up to about 10 μm long).
Within the Rickettsia species, these bacteria are divided into four clades. The clades include the ancestral group, spotted fever group (SFG), typhus group, and transitional group, and the determining factors for classifying into each group depends on phenotypic characteristics, phylogenetic organization, or the type of vector host they inhabit.
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]
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 ...
Rickettsia typhi is a small, gram-negative intracellular bacterium that establishes the murine typhus infection in mammals and fleas. [30] Murine typhus was once one of the most prevalent rickettsial diseases in the world, [ 8 ] [ 9 ] [ 10 ] having isolated the R. typhi causative agent from nearly every continent around the globe except for ...
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 (red dots) in the cell of a deer tick Scientific classification; Domain: Bacteria: Phylum: Pseudomonadota: Class: Alphaproteobacteria: Order: Rickettsiales: Family: Rickettsiaceae Pinkerton 1936 (Approved Lists 1980) Tribes and genera "Candidatus Arcanobacter" Martijn et al. 2015 "Candidatus Cryptoprodota" corrig ...