Which of the following diseases is caused by Leishmania, a protozoan organism?

Kala-azar

The correct answer is Option (2) → Kala-azar

Out of the listed options, the disease caused by Leishmania, a protozoan organism, is Kala-azar.

Leishmania is a parasite that infects humans through the bite of sandflies. It causes a group of diseases called leishmaniasis, with Kala-azar being the most serious form. Symptoms of Kala-azar include fever, weight loss, enlargement of the spleen and liver, and anemia.

Here's a breakdown of the other options:

• Sleeping sickness is caused by a trypanosome parasite transmitted by tsetse flies.
• Malaria is caused by a plasmodium parasite transmitted by mosquitoes.
• Acne is a non-infectious skin condition caused by clogged pores and hormonal changes.