Scrub Typhus Serologic Testing with the Indirect Immunofluorescence Method as a Diagnostic Gold Standard: A Lack of Consensus Leads to a Lot of Confusion

Abstract

Scrub typhus infection is caused by the intracellular bacterium Orientia tsutsugamushi [1]. This miteborne infection is endemic across much of Asia and the Western Pacific region, and it causes substantial morbidity in an area stretching from Pakistan [2] and India [3, 4] to Indonesia [5] and Australia [6, 7] and to Japan [8] and Korea [9, 10]. According to the World Health Organization, “Scrub typhus is probably one of the most underdiagnosed and under-reported febrile illnesses requiring hospitalisation in the region” [11, p. 123]. There is substantial variation in reported seroprevalence and mortality rates that may arise from differences in the methodologies used to diagnose scrub typhus infection and to detect past exposure to the organism, differences in patient characteristics, differences in endemicity rates, and geographical differences. The hypothesized variation in pathogenicity between O. tsutsugamushi strains may also play a role [12, 13].