A Review on Pathogenesis, Clinical Spectrum, Diagnosis and Therapeutic Management of Orientia tsutsugamushi Infection

Review Article

Abstract

Scrub typhus, an acute febrile illness caused by the obligate intracellular bacterium Orientia tsutsugamushi, is a major zoonotic threat primarily distributed across the Asia-Pacific region and increasingly recognized in non-endemic territories. Transmission occurs through the bite of larval trombiculid mites (chiggers), which serve as both vector and reservoir via transovarial and transstadial propagation. Upon inoculation into human skin during stylostome formation, O. tsutsugamushi targets dermal dendritic cells and monocytes before disseminating through blood and lymphatic channels to infect endothelial cells across major organ systems. Cellular entry is mediated by surface proteins interacting with host fibronectin, integrins, and heparan sulfate proteoglycans, followed by clathrin-mediated endocytosis, rapid endosomal escape into the cytosol, cytosolic replication, and cell exit via budding. Pathologically, systemic vasculitis and perivascular inflammation precipitate diverse clinical outcomes, ranging from self-limiting febrile illness characterized by pathognomonic eschar formation and regional lymphadenopathy to severe multi-organ dysfunction involving acute respiratory distress syndrome, meningoencephalitis, myocarditis, and renal failure. Diagnosis have evolved from classical serology toward molecular amplification assays, such as real-time polymerase chain reaction and loop-mediated isothermal amplification targeting conserved target genes including the 56-kDa outer membrane protein. First-line antimicrobial management relies on doxycycline or azithromycin, with early intervention preventing severe mortality. Mitigating the disease burden requires strict vector control, public health surveillance, and expanded access to rapid diagnostic tools in resource-limited endemic zones.