Scrub typhus is caused by-
**Core Concept**
Scrub typhus is an infectious disease caused by a specific type of bacteria. The underlying principle being tested is the knowledge of **rickettsial diseases**, which are transmitted by vectors such as ticks, fleas, and mites.
**Why the Correct Answer is Right**
The correct answer is *Orientia tsutsugamushi*, a type of **Rickettsia**. This bacterium is transmitted to humans through the bite of an infected **chigger mite**, specifically the larval stage of the mite.
**Why Each Wrong Option is Incorrect**
**Option A:** Incorrect because it is not the causative agent of scrub typhus.
**Option B:** Incorrect as it is associated with a different disease.
**Option C:** Incorrect because it is not related to scrub typhus.
**Option D:** Incorrect as it is not the correct causative agent.
**Clinical Pearl / High-Yield Fact**
Scrub typhus is characterized by symptoms such as fever, headache, and a distinctive **eschar** at the bite site.
**Correct Answer:** D. Orientia tsutsugamushi