Answer: Sporozoites inject into blood → infect liver cells (exoerythrocytic cycle, 7-14 days) → merozoites released → infect red blood cells (erythrocytic cycle) → reproduce causing RBC lysis every 48-72h (fever) → gametocytes ingested by mosquito.
- A Plasmodium is sometimes mistakenly thought to live and complete its sexual life cycle mainly inside the mosquito vector's gut, with merozoites rarely entering human blood in most textbook accounts during normal conditions
- B Sporozoites inject into blood → infect liver cells (exoerythrocytic cycle, 7-14 days) → merozoites released → infect red blood cells (erythrocytic cycle) → reproduce causing RBC lysis every 48-72h (fever) → gametocytes ingested by mosquito
- C Plasmodium is sometimes mistakenly thought to produce mainly mild, intermittent low-grade fever, without progressing through a complex, multi-stage life cycle involving distinct tissues under usual circumstances according to most researchers
- D The liver-stage portion of infection is sometimes mistakenly thought to be mainly skipped every time P. falciparum infects the human bloodstream directly in many documented cases according to conventional understanding
Correct answer: B. Sporozoites inject into blood → infect liver cells (exoerythrocytic cycle, 7-14 days) → merozoites released → infect red blood cells (erythrocytic cycle) → reproduce causing RBC lysis every 48-72h (fever) → gametocytes ingested by mosquito
Explanation: Plasmodium life cycle in humans: (1) Sporozoites injected by Anopheles → liver cells (schizogony, 7-14 days); (2) Liver releases merozoites into blood; (3) Merozoites infect RBCs (erythrocytic cycle); (4) Synchronous lysis every 48h (P. vivax) or 72h (P. malariae) causes cyclical fever; (5) Some become gametocytes (sexual stage); (6) Mosquito ingests gametocytes.
The Plasmodium parasite needs both hosts: the female Anopheles mosquito injects sporozoites while biting (infecting the human liver and RBCs, causing the malaria fever cycle), then picks up gametocytes from an infected person's blood, completing the parasite's sexual stage inside the mosquito.
Concept context
Pathogens, infectious diseases, non-infectious diseases, drugs, cancer, and public health. High NEET importance.