**Question:** Sandfly transmits which of the following diseases?

A. Kala-azar
B. Oriental sore
C. Relapsing fever
D. Oraya fever
E. Sleeping sickness

**Core Concept:** Sandflies are small, biting insects that are vectors for certain diseases, transmitting pathogens from one host to another. The diseases that can be transmitted by sandflies include leishmaniasis, borreliosis, and trypanosomiasis.

**Why the Correct Answer is Right:**

Sandflies are known to transmit diseases caused by parasites, specifically protozoa and bacteria. In this case, the correct answer is E. Sleeping sickness, caused by Trypanosoma brucei, is a disease transmitted by the bite of an infected tsetse fly, not sandflies. Sandflies are vectors for the transmission of the diseases listed in options A, B, C, and D.

**Why Each Wrong Option is Incorrect:**

A. Kala-azar (Leishmaniasis): This disease is caused by Leishmania parasites and transmitted by the bite of sandflies, making it correct.
B. Oriental sore: Oriental sore is caused by Rickettsia bacteria and transmitted through the bite of ticks, not sandflies.
C. Relapsing fever: This disease is caused by Borrelia bacteria and transmitted by the bite of louse and tick vectors, not sandflies.
D. Oraya fever: Oraya fever is caused by Rickettsia bacteria and transmitted through the bite of ticks, not sandflies.

**Clinical Pearl:** Understanding the vectors that transmit specific diseases is crucial for physicians to diagnose and treat patients correctly. Sandfly-borne diseases are widespread in tropical and subtropical regions and can cause significant morbidity and mortality if not diagnosed and treated promptly.

In conclusion, while sandflies play a significant role in transmitting certain diseases, the correct answer is E (Sleeping sickness). The other options are incorrect because they are associated with different vectors and transmission mechanisms.