Exo-erythrocytic phase of the life cycle of malaria parasite occurs in the

Analyze the question: "Exo-erythrocytic" means "outside the red blood cells." So we need the stage of the Plasmodium life cycle that happens in the human body but not inside red blood cells.

Concept: Life cycle of the malaria parasite

1. An infected female Anopheles mosquito bites a human and injects sporozoites.
2. The sporozoites travel in the blood to the liver, where they enter liver cells (hepatocytes). They multiply there and form merozoites. This is the exo-erythrocytic (pre-erythrocytic) phase.
3. The merozoites are released into the blood and invade red blood cells. This is the erythrocytic phase, which causes fever and chills when the cells burst.
4. Some parasites develop into gametocytes, which are taken up by a mosquito. Fertilisation and sporogony then occur in the mosquito's gut and gut wall.

Checking the options:

• A. Liver of humans: Correct. The exo-erythrocytic phase happens in the liver cells.
• B. Reticuloendothelial cells of humans: The parasite can also be found in these cells in some descriptions, but the classic textbook answer is the liver. The liver is the main site of the phase, and in JAMB the expected answer is the liver.
• C. Malpighian tubules of mosquito: These are excretory organs in insects. The parasite does not develop here, and this is not part of the human phase.
• D. Brain of humans: This is involved only in cerebral malaria, which is a complication of the erythrocytic phase, not the exo-erythrocytic phase.

Exam tip: Remember "Exo = Exit from blood, so it's in the Liver" or simply: sporozoites go to the liver first, then to the red blood cells. Whenever you see "exo-erythrocytic" or "pre-erythrocytic," think liver.