True about scrub typhus-
**Core Concept**
Scrub typhus is a vector-borne disease caused by the bacterium *Orientia tsutsugamushi*, transmitted to humans through the bite of infected chiggers (larval mites). The pathogenesis of scrub typhus involves the infection of endothelial cells, macrophages, and other cell types, leading to a systemic inflammatory response.
**Why the Correct Answer is Right**
The correct answer is **C**. Scrub typhus is characterized by its distinctive eschar at the site of the chigger bite, which is a necrotic lesion surrounded by inflammation and hemorrhage. The eschar is a key diagnostic feature of scrub typhus and is often accompanied by fever, headache, and regional lymphadenopathy. The pathogenesis of scrub typhus involves the production of immune complexes and the activation of complement, which contribute to the development of a systemic inflammatory response.
**Why Each Wrong Option is Incorrect**
**Option A:** Incorrect because scrub typhus is not caused by a tick bite, but rather by the bite of infected chiggers.
**Option B:** Incorrect because scrub typhus is not typically associated with a rash, although a maculopapular rash may occasionally be seen.
**Option D:** Incorrect because scrub typhus is not typically associated with a high mortality rate, although it can be severe in untreated cases.
**Clinical Pearl / High-Yield Fact**
The eschar in scrub typhus is often described as a "eschar with a dimple," which is a characteristic feature that can help distinguish it from other skin lesions.
**Correct Answer:** C. Scrub typhus is characterized by its distinctive eschar at the site of the chigger bite.