 |
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.
Page last modified : February 17, 2006
Content source: Division of Parasitic Diseases
National Center for Zoonotic, Vector-Borne, and Enteric Diseases (ZVED)
|
|
|
