Plasmodium vivax is the most common species of the malaria parasite affecting humans. It belongs to the Kingdom Protista and has a complex life cycle that involves two hosts: the Anopheles mosquito (primary/definitive host) and the Human (intermediate host).
Only the female Anopheles mosquito transmits malaria — male mosquitoes feed only on plant nectar. The female needs blood for egg production.
India launched the National Framework for Malaria Elimination with the goal of eliminating malaria by 2030.
Step 1 — Sporozoite Injection: When an infected female Anopheles mosquito bites a human, it injects thousands of thread-like sporozoites into the bloodstream.
Step 2 — Liver Phase (Pre-erythrocytic): Sporozoites travel to the liver and invade liver cells, multiplying asexually to form merozoites (this phase takes 8-17 days in P. vivax).
Step 3 — Blood Phase (Erythrocytic): Merozoites are released into the blood and invade Red Blood Cells (RBCs). Inside the RBC, they multiply further, eventually rupturing the RBC and releasing more merozoites. This RBC rupture releases toxins that cause the characteristic fever, chills, and shivering of malaria — occurring every 48 hours in P. vivax (tertian malaria).
Step 4 — Gametocyte Formation: Some merozoites develop into sexual forms called gametocytes (male microgametocytes and female macrogametocytes) in the blood.
Step 5 — Ingestion: When a healthy Anopheles mosquito bites an infected person, it ingests gametocytes.
Step 6 — Fertilization: Inside the mosquito's gut, male and female gametocytes fuse to form a zygote, which develops into an ookinete and then an oocyst.
Step 7 — Sporozoite Formation: The oocyst multiplies to produce thousands of sporozoites, which migrate to the mosquito's salivary glands, ready to be injected into the next human.
The periodic fever in malaria is caused by the simultaneous rupture of infected Red Blood Cells (RBCs). When RBCs burst, they release merozoites AND toxic metabolic waste products into the bloodstream, triggering the immune response (fever and chills). In P. vivax, this happens every 48 hours.
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