What is the nature of haemozoin?

The correct answer is Option (3) → Haemozoin is a toxin released from Plasmodium-infected cells.

Malaria is caused by Plasmodium, which enters the human body through the bite of an infected female Anopheles mosquito. The parasites first multiply in the liver cells and then attack the red blood cells (RBCs), which rupture. The rupture of RBCs releases a toxic substance, haemozoin. Haemozoin is responsible for the chill and high fever that recur every three to four days.

Option (1) Haemozoin is a precursor of haemoglobin. — Incorrect. Haemozoin is not a building block of haemoglobin. It is a toxin released when RBCs infected by Plasmodium burst.

Option (2) Haemozoin acts as a toxin released from Wuchereria-infected cells. — Incorrect. Wuchereria is the filarial worm that lives in the lymphatic vessels and causes filariasis. It does not infect RBCs, and haemozoin is not linked to it.

Option (3) Haemozoin is a toxin released from Plasmodium-infected cells. — Correct. Haemozoin is released when the Plasmodium-infected RBCs rupture, and it causes the recurring chill and high fever of malaria.

Option (4) Haemozoin is a toxin released from Trichophyton-infected cells. — Incorrect. Trichophyton is a fungus that causes ringworm of the skin, nails and scalp. It does not infect blood cells or release haemozoin.

NCERT Extract:
Common Diseases in Humans – “… Plasmodium enters the human body as sporozoites (infectious form) through the bite of infected female Anopheles mosquito. The parasites initially multiply within the liver cells and then attack the red blood cells (RBCs) resulting in their rupture. The rupture of RBCs is associated with release of a toxic substance, haemozoin, which is responsible for the chill and high fever recurring every three to four days.”