Which of the following toxic substance is responsible for the chill and high fever recurring every three to four days in malaria?

Options

A. Haemotoxin
B. Haemoglobin
C. Haemozoin
D. Sporozoites

Explanation

### Step-by-Step Solution:

1. **Understanding the Question**: The question asks for the toxic substance responsible for the chills and high fever that recur every three to four days in malaria.

2. **Identifying the Options**: The options provided include hemotoxin, hemoglobin, hemozoin, and sporozoites. We need to analyze each option to determine which one is related to malaria.

3. **Analyzing Hemotoxin**: Hemotoxin is a toxic substance found in animal venoms, such as snake venom. It is not associated with malaria, so this option can be eliminated.

4. **Analyzing Hemoglobin**: Hemoglobin is an iron-containing protein found in red blood cells (RBCs) that carries oxygen throughout the body. It is not a toxic substance responsible for fever in malaria, so this option can also be eliminated.

5. **Analyzing Hemozoin**: Hemozoin is a biocrystal formed by the malarial parasite, Plasmodium. It is produced to avoid the toxicity of free heme derived from hemoglobin during the parasite's invasion of erythrocytes (RBCs). Hemozoin is indeed linked to the high fever experienced during malaria, making this option a strong candidate.

6. **Analyzing Sporozoites**: Sporozoites are the infectious stage of the malarial parasite, Plasmodium. While they are involved in the life cycle of the parasite, they are not responsible for the fever symptoms, so this option can be eliminated.

7. **Conclusion**: After analyzing all the options, the correct answer is **hemozoin**, as it is the toxic substance responsible for the chills and high fever that recur every three to four days in malaria.

### Final Answer:
The toxic substance responsible for the chill and high fever recurring every three to four days in malaria is **hemozoin**.

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