Scrub typhus is caused by Orientia tsutsugamushi. In India, the 'scrub typhus belt' includes the Himalayan foothills, Northeast India, and parts of South India. The vector-reservoir complex for scrub typhus involves:
- A Adult Ixodes tick — transovarial transmission of Orientia through all life stages
- B Culex mosquito — Orientia is an arbovirus transmitted through mosquito bites
- C Larval stage (chigger/trombiculid mite) of Leptotrombidium species — only larval stage feeds on vertebrates and transmits Orientia ✓
- D Body louse (Pediculus humanus corporis) — transmits Orientia via louse feces contaminating bite wounds
Explanation
Scrub typhus (Orientia tsutsugamushi) has a unique transmission biology. The vector is the larval stage (chigger) of trombiculid mites — specifically Leptotrombidium deliense in Asia. Only the larval mite feeds on vertebrates (humans are incidental dead-end hosts — the natural reservoir is small rodents). Adult and nymphal mites feed on plants/soil. Orientia is transmitted transovarially through mite generations, maintaining the organism in the mite population without requiring vertebrate amplifying hosts. The eschar (tache noire) forms at the chigger bite site. Weil-Felix OX-K (Proteus OX-K) is specifically reactive in scrub typhus due to Orientia-Proteus OX-K antigenic cross-reactivity. Body louse transmits Rickettsia prowazekii (epidemic typhus); Ixodes ticks transmit Lyme disease and RMSF varies.
Reference: Ananthanarayan & Paniker's Textbook of Microbiology, 11th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.