Scrub typhus

Definition

An acute, febrile rickettsial disease of humans and rodents caused by the obligate intracellular bacterium Orientia tsutsugamushi (formerly Rickettsia tsutsugamushi), transmitted through the bite of infected larval trombiculid mites (chiggers), principally of the genus Leptotrombidium. Endemic across a broad 'tsutsugamushi triangle' spanning South and Southeast Asia, northern Australia, and the western Pacific, the disease presents with eschar at the bite site, fever, headache, and lymphadenopathy; severe cases may progress to multi-organ failure. The mite vector acquires the pathogen transovarially or by feeding on infected small mammals, maintaining a zoonotic cycle in scrub vegetation, grasslands, and transitional forest edges.

Etymology

From 'scrub' for the scrubland and transitional vegetation habitats where transmission occurs, and 'typhus' from Greek tuphos (fever, stupor), the historic name for louse-borne epidemic typhus; the disease was distinguished from louse-borne typhus by its mite vector and ecological setting.

Example

Field entomologists conducting small-mammal trapping in Thailand often find high Leptotrombidium deliense chigger burdens on Rattus rodents in grassy field margins; PCR screening of these mites for Orientia tsutsugamushi helps map scrub typhus risk and identify transmission hotspots for public health intervention.

Synonyms

• bush typhus
• tsutsugamushi disease
• mangrove typhus
• Kedani fever
• Shimamushi disease

Related Terms

• Orientia tsutsugamushi
• trombiculid mite
• Chigger
• Leptotrombidium
• rickettsiosis
• typhus
• eschar
• Zoonosis
• Transovarial transmission
• tsutsugamushi triangle

Usage Notes

Distinguished from epidemic (louse-borne) typhus caused by Rickettsia prowazekii and endemic (flea-borne) murine typhus caused by Rickettsia typhi by vector, agent, and geographic range. The term 'scrub' refers to habitat, not medical scrubbing. Serological cross-reactivity with other rickettsiae can complicate diagnosis; molecular methods (PCR, sequencing) are preferred for definitive identification. Antibiotic treatment with doxycycline or azithromycin is effective, but no licensed vaccine exists.