Scrub typhus
Scrub typhus is a mite-borne rickettsial infection caused by Orientia tsutsugamushi, predominantly acquired in Asia through the bite of larval chigger mites, and presents with a black eschar at the inoculation site followed by fever, rash, and multiorgan involvement. Doxycycline for 7 to 10 days is the treatment of choice, as it is for all rickettsial infections.
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What this article covers
- Overview
A mite-borne rickettsial infection of the genus Orientia: scrub typhus is caused by the intracellular bacterium Orientia tsutsugamushi, transmitted by the bite of larval mites (chiggers) rather than…
- Epidemiology
Endemic across most of Asia: scrub typhus is one of the most common causes of febrile illness in travelers to and residents of endemic parts of Asia.
- Risk factors
Travel or residence in an endemic area of Asia, the dominant risk factor given the concentration of Orientia tsutsugamushi transmission there.
- Pathophysiology
Mite-larva inoculation: humans acquire the disease through the bite of the larval stage of mites known as chiggers, which inoculate Orientia tsutsugamushi into the skin.
- Clinical features
Black eschar at the mite bite site, the most specific early clue: a painless black eschar, often with regional lymphadenopathy, marks the point of inoculation and should be actively searched for…
- Differential diagnosis
Rocky Mountain spotted fever (Rickettsia rickettsii): shares fever, rash, and possible eschar, but is transmitted by Dermacentor ticks in the Americas rather than mite larvae in Asia, and the rash classically begins on the wrists and ankles.
- Diagnosis
The diagnosis is confirmed by demonstrating the organism directly during the acute stage, before antibiotics are started: polymerase chain reaction (PCR), immunohistochemical analysis of tissue…
- Management
First, start doxycycline empirically in any patient with a compatible exposure history and clinical picture, without waiting for confirmatory testing, given that the treatment of choice for all…
- Complications
Shock: severe rickettsial vasculitis can progress to circulatory shock, representing the most life-threatening complication.
- Prognosis
Generally good with prompt doxycycline treatment, reflecting the reliable and rapid response of Orientia tsutsugamushi to appropriate antibiotic therapy.
- Prevention
Avoid chigger mite habitats in endemic areas (scrub vegetation, grassland, and agricultural land) whenever possible, particularly in Asia, where transmission is most concentrated.
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