Kala-azar is transmitted by –
**Core Concept**
Kala-azar, also known as visceral leishmaniasis, is a severe form of leishmaniasis caused by protozoan parasites of the Leishmania genus. The disease is transmitted through the bite of infected female phlebotomine sandflies, which ingest the parasites while feeding on the blood of infected individuals.
**Why the Correct Answer is Right**
The correct answer is related to the life cycle of Leishmania parasites. Sandflies act as the primary vector for the transmission of Leishmania parasites from one host to another. When an infected sandfly feeds on a host's blood, it regurgitates the parasites into the wound, allowing them to infect the host's macrophages and other cells. This process is known as the "sandfly-borne" transmission route.
**Why Each Wrong Option is Incorrect**
**Option A:** Incorrect because Kala-azar is not transmitted through contaminated water or food.
**Option B:** Incorrect because while mosquitoes are vectors for other diseases, such as malaria and dengue fever, they are not responsible for transmitting Leishmania parasites.
**Option C:** Incorrect because Kala-azar is not transmitted through direct contact with an infected person or animal.
**Clinical Pearl / High-Yield Fact**
It's essential to note that the risk of Kala-azar transmission can be reduced by avoiding areas with high sandfly populations and using protective measures such as insecticide-treated bed nets and clothing.
**Correct Answer:** D. Sandfly.