Which of the following causes Kala-azar disease ?

Options

A. Leishmania
B. Plasmodium
C. Entamoeba histolytica
D. Trypanosoma

Answer

**Step-by-Step Solution:**

1. **Identify the Disease**: The question asks about the causative agent of Kala-azar disease.

2. **Understand the Vector**: Kala-azar is transmitted by a specific vector, which is the sand fly.

3. **Identify the Causative Agent**: The disease is caused by a protozoan parasite known as Leishmania.

4. **Eliminate Other Options**:
- Plasmodium is associated with malaria, which is transmitted by mosquitoes, not sand flies.
- Amoebiasis is related to the digestive tract and is caused by Entamoeba histolytica, not Leishmania.
- Trypanosomiasis (sleeping sickness) is caused by Trypanosoma, which is also unrelated to Kala-azar.

5. **Conclusion**: The correct answer is Leishmania, as it is the protozoan responsible for causing Kala-azar disease.

**Final Answer**: Leishmania

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