**Core Concept**
Kyasanur Forest Disease (KFD) is a tick-borne viral hemorrhagic fever endemic to the Indian subcontinent. It is a zoonotic disease, transmitted to humans through the bite of an infected tick, primarily the Haemaphysalis spinigera.

**Why the Correct Answer is Right**
KFD is caused by a flavivirus, specifically the Kyasanur Forest Disease virus (KFDV), which is transmitted to humans through the bite of an infected tick. The virus replicates in the tick's salivary glands and is then transmitted to humans through the tick's saliva during feeding. KFDV is characterized by its ability to cause fever, hemorrhaging, and thrombocytopenia in infected humans.

**Why Each Wrong Option is Incorrect**
**Option A:** Not relevant, as KFD is not caused by a rickettsial infection.
**Option B:** Not correct, as KFD is not caused by a Leptospira species.
**Option C:** Not relevant, as KFD is not caused by a protozoan parasite like Plasmodium species.

**Clinical Pearl / High-Yield Fact**
KFD is a zoonotic disease, and its transmission can be prevented by wearing protective clothing and using tick repellents when working in endemic areas.

**Correct Answer:** C. Kyasanur Forest Disease virus (KFDV).