Rickettsioses

Rickettsioses are mild to life-threatening zoonoses caused by obligate intracellular bacteria of the order Rickettsiales (family Rickettsiaceae). Arthropods, including ticks, fleas, and mites, are implicated as their vectors, reservoirs, or amplifiers. With an increasing number of new pathogens and recognition of new pathogenicity and affected geographical areas over the past few decades, there is a better understanding of the scope and importance of these pathogens, particularly as a paradigm to understanding emerging and remerging infections. The taxonomy has undergone numerous changes, with now three main groups classified as rickettsioses according to morphological, antigenic and metabolic characteristics: (1) Rickettsioses due to the bacteria of the genus Rickettsia, including the spotted fever group, typhus groups (Rickettsiaceae), (2) Ehrlichioses and Anaplasmoses due to bacteria of the Anaplasmataceae and (3) scrub typhus due to Orientia tsutsugamushi.