Rickettsial disease

This chapter focuses on Rickettsiae that are pathogenic for humans. Rickettsiae are intracellular alpha proteobacteria associated with eucaryotic hosts. Based on antigenic and genetic data, Rickettsiae are divided into three groups: the spotted fever group, which accounts for most tick-borne rickettsioses; the typhus group, which includes Rickettsia prowazekii, the agent of epidemic typhus, transmitted by body louse, and Rickettsia typhi, the agent of murine typhus, transmitted by rat and cat fleas; and Orientia tsutsugamushi. Symptomatic evidence of central nervous system involvement is a frequent feature in rickettsial infections. Murine typhus is typically a mild illness associated with rat and opossum fleas. The onset of illness is usually abrupt, with non-specific symptoms such as fever, headache, chills, and myalgias. Scrub typhus is extremely common in Asia and specifically in Southeast Asia. The most useful treatment in children and in adults is doxycycline.