Explanation

Erythrocytic cycle of Plasmodium occurs in RBCs and beings when a cryptomerozoite or micrometacryptomerozoite enters into an RBC. After entering into RBC, a merozoite becomes, rounded disc-like young trophozoite. The accumulation of haemozoin granules (acquire trophozoite) and probably also some other toxic substances in blood causes the characteristic attack of malarial fever initially after about four erythrocytic cycles and than after each cycle.