Q.Describe the erythrocytic (blood) cycle of Plasmodium vivax in man.

[!TLDR] The erythrocytic cycle is the repeated invasion, growth and rupture of Plasmodium inside red blood cells.

Cryptomerozoites from the liver invade RBCs, growing through ring and trophozoite stages (depositing haemozoin, producing Schuffner's dots), then undergoing schizogony to form a schizont with merozoites. The RBC ruptures, releasing merozoites (causing the fever paroxysm) that invade fresh RBCs, repeating roughly every 48 hours (benign …

The erythrocytic cycle of Plasmodium vivax begins when cryptomerozoites, released from the liver at the end of the exo-erythrocytic cycle, invade red blood cells. Inside an RBC, the parasite first appears as a small ring stage, then grows into a feeding trophozoite that actively digests the host cell's haemoglobin, depositing the insoluble brownish-black pigment haemozoin as a waste product; infected RBCs also develop a fine stippled appearance on their membrane known as Schuffner's dots, a diagnostic feature of P. vivax. The growing trophozoite's nucleus then undergoes repeated asexual division by schizogony, forming a schizont containing 12 to 24 daughter merozoites. The infected RBC eventually ruptures, releasing the merozoites, along with haemozoin pigment and cell debris, into the blood plasma; it is this synchronised rupture of many infected RBCs together that triggers the characteristic bout of chills and high fever experienced by the patient. The released merozoites immediately invade fresh, healthy RBCs, and the entire cycle repeats. Because one erythrocytic cycle of P. vivax take …

• Starting the erythrocytic cycle description with sporozoites — sporozoites act only in the liver (exo-erythrocytic) stage; the erythrocytic cycle begins with cryptomerozoites/merozoites invading RBCs. …