Rickettsiales

Rickettsiales is an order of Gram-negative bacteria. This order includes important human pathogens such as Rickettsia rickettsii, which causes Rocky Mountain spotted fever, and Orientia tsutsugamushi, the causative agent of scrub typhus.

Taxonomy

The order Rickettsiales is divided into four families: Anaplasmataceae, Rickettsiaceae, Holosporaceae, and Candidatus Midichloriaceae. The family Anaplasmataceae includes the genera Anaplasma, Ehrlichia, Neorickettsia, and Wolbachia. The family Rickettsiaceae includes the genera Rickettsia and Orientia. The family Holosporaceae includes the genera Holospora, Caedibacter, and Paracaedibacter. The family Candidatus Midichloriaceae includes the genus Candidatus Midichloria.

Pathogenesis

Rickettsiales are obligate intracellular parasites, meaning they can only survive and reproduce inside host cells. They are typically transmitted to humans through the bite of an infected tick, flea, or louse. Once inside the host, they invade the endothelial cells lining the blood vessels, causing vasculitis and leading to symptoms such as fever, rash, and headache.

Diagnosis and Treatment

Diagnosis of Rickettsiales infections is usually based on clinical symptoms and confirmed by laboratory tests such as serology or PCR. Treatment typically involves antibiotics such as doxycycline or chloramphenicol.

Prevention

Prevention of Rickettsiales infections primarily involves avoiding contact with the vectors that transmit these bacteria. This can be achieved through the use of insect repellents, wearing long sleeves and pants when in tick-infested areas, and checking for and removing ticks promptly after outdoor activities.

See Also

• Rickettsia rickettsii
• Orientia tsutsugamushi
• Anaplasma
• Ehrlichia
• Wolbachia

Rickettsiales Resources
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