Abstract
The rickettsioses of the “Far East” or Asia–Australia–Pacific region include but are not limited to endemic typhus, scrub typhus, and more recently, tick typhus or spotted fever. These diseases embody the diversity of rickettsial disease worldwide and allow us to interconnect the various contributions to this special issue of Tropical Medicine and Infectious Disease. The impact of rickettsial diseases—particularly of scrub typhus—was substantial during the wars and “police actions” of the last 80 years. However, the post-World War II arrival of effective antibiotics reduced their impact, when recognized and adequately treated (chloramphenicol and tetracyclines). Presently, however, scrub typhus appears to be emerging and spreading into regions not previously reported. Better diagnostics, or higher population mobility, change in antimicrobial policies, even global warming, have been proposed as possible culprits of this phenomenon. Further, sporadic reports of possible antibiotic resistance have received the attention of clinicians and epidemiologists, raising interest in developing and testing novel diagnostics to facilitate medical diagnosis. We present a brief history of rickettsial diseases, their relative importance within the region, focusing on the so-called “tsutsugamushi triangle”, the past and present impact of these diseases within the region, and indicate how historically, these often-confused diseases were ingeniously distinguished from each another. Moreover, we will discuss the importance of DNA-sequencing efforts for Orientia tsutsugamushi, obtained from patient blood, vector chiggers, and rodent reservoirs, particularly for the dominant 56-kD type-specific antigen gene (tsa56), and whole-genome sequences, which are increasing our knowledge of the diversity of this unique agent. We explore and discuss the potential of sequencing and other effective tools to geographically trace rickettsial disease agents, and develop control strategies to better mitigate the rickettsioses.
Highlights
Of all infectious diseases the world has experienced, few have truly altered human history
From an ill-defined mixture of fevers, the typhus fevers became clearly defined, including epidemic and murine typhus, with agents R. prowazekii and R. typhi, and scrub typhus and its agent O. tsutsugamushi representing the overwhelming proportion of cases in the AAP geographic region
The WF reaction is based on the cross-reaction of patient antibodies with SFGR, typhus group rickettsiae (TGR), and scrub typhus group orientiae (STGO) to antigenic epitopes of species of the genus Proteus, a member of the gamma proteobacteria
Summary
Of all infectious diseases the world has experienced, few have truly altered human history. Scrub and murine typhus represent the two most common forms of rickettsial diseases in these regions Other rickettsioses such as tick-borne rickettsioses and spotted fever, though relatively infrequent in the AAP, are, endemic in the region [5]. Improved recognition of the disease syndromes by clinicians within the endemic regions and improved more accurate, easy-to-use diagnostics have led in recent years to enhanced recognition Rickettsioses such as scrub typhus are being reported within an ever-growing, geographically disparate region [6,7]. The years from 1910 to 1915 proved to be important for rickettsia-associated typhus research, with a number of substantial discoveries made around the world to determine the causative agents, their vectors, and the identification of hosts and reservoirs This resulted in the recognition of rickettsial diseases as distinct diseases and the creation of “Rickettsiology” as a discipline. During the war and post war-time period between 1917 and 1923, 30 million cases and 3 million deaths were recorded in European Russia alone, where combatants were returning home [1]
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