: Causal Agents

Blood parasites of the genus Plasmodium.  There are approximately 156 named species of Plasmodium which infect various species of vertebrates.  Four are known to infect humans: P. falciparum, P. vivax , P. ovale  and P. malariae.

:Life Cycle

The malaria parasite life cycle involves two hosts.  During a blood meal, a malaria-infected female Anopheles mosquito inoculates sporozoites into the human host .

Sporozoites infect liver cells and mature into schizonts , which rupture and release merozoites .(Of note, in P. vivax and P. ovale a dormant stage [hypnozoites] can persist in the liver and cause relapses by invading the bloodstream weeks, or even years later.)  After this initial replication in the liver (exo-erythrocytic schizogony ),

the parasites undergo asexual multiplication in the erythrocytes (erythrocytic schizogony ).  Merozoites infect red blood cells .  The ring stage trophozoites mature into schizonts, which rupture releasing merozoites .  Some parasites differentiate into sexual erythrocytic stages (gametocytes) .  Blood stage parasites are responsible for the clinical manifestations of the disease. 
 

The gametocytes, male (microgametocytes) and female (macrogametocytes), are ingested by an Anopheles mosquito during a blood meal .  The parasites’ multiplication in the mosquito is known as the sporogonic cycle .  While in the mosquito's stomach, the microgametes penetrate the macrogametes generating zygotes .  The zygotes in turn become motile and elongated (ookinetes) which invade the midgut wall of the mosquito where they develop into oocysts .  The oocysts grow, rupture, and release sporozoites , which make their way to the mosquito's salivary glands.  Inoculation of the sporozoites into a new human host perpetuates the malaria life cycle . 

برگرفته ازسايت:  DPDX  وابسته به مرکز کنترل و پيشگيری از بيماريها ( CDC )