Rickettsial agent of Epidemic typhus isRickettsial agent of Epidemic typhus is
**Core Concept**
Epidemic typhus, also known as louse-borne typhus, is a vector-borne disease caused by a specific rickettsial agent. This agent is transmitted to humans through the bite of an infected body louse.
**Why the Correct Answer is Right**
The correct answer is Rickettsia prowazekii, a Gram-negative, obligate intracellular bacterium. R. prowazekii is transmitted to humans through the feces of infected body lice, which contaminate the skin or mucous membranes of humans. Once inside the human host, R. prowazekii invades and replicates within endothelial cells, leading to inflammation and damage to these cells.
**Why Each Wrong Option is Incorrect**
* **Option A:** None provided.
* **Option B:** This option is incorrect because Rickettsia rickettsii is the agent responsible for Rocky Mountain spotted fever, not epidemic typhus.
* **Option C:** This option is incorrect because Coxiella burnetii is the agent responsible for Q fever, not epidemic typhus.
* **Option D:** This option is incorrect because Bartonella quintana is the agent responsible for trench fever, not epidemic typhus.
**Clinical Pearl / High-Yield Fact**
Epidemic typhus is characterized by fever, headache, and a characteristic rash, which typically appears 4-7 days after the onset of fever. The rash is often accompanied by lymphadenopathy and can be severe enough to cause death if left untreated.
**Correct Answer: C. Rickettsia prowazekii**