Malaria

Life cycle

Malaria replication

Sexual multiplication: Mosquito (starts in the human and finishes in the mosquito)

Two types of Asexual multiplication:

• Sporogony: Mosquito → Sporozoites (infective)

• Schizogony: Human → Schizonts (Merozoites)

  - Liver: Exo-erythrocytic or pre-erythrocytic

  - Red blood cells: Erythrocytic

Exo-erythrocytic or pre-erythrocytic schizogony (liver asexual cycle)

1. After inoculation of sporozoites (mosquito) dermis → blood in ~30 min → transverse hepatic sinusoids → invade hepatocytes

2. Immediate multiplication to Schizonts containing Merozoites

3. If enter a latent phase → Hipnozoites (only P. vivax and P. ovale)

4. Mature schizont → budding of parasite-filled vesicles (Merosomes) → merozoites into liver sinusoids → in plasma ~15 min → invade RBC

5. Hipnozoite (weeks, months) → Schizonts → Relapse

Erythrocytic schizogony (RBC asexual cycle)

RBC:

1. Merozoites → invade RBCs ~30 seconds → Trophozoite

2. Immature trophozoites (ring form) → mature schizonts → rupture releasing merozoites → RBC invasion cycle

3. Some parasites develop into sexual erythrocytic stages (Gametocytes)

4. Gametocytes, male (microgametocytes) and female (macrogametocytes), are ingested by an Anopheles mosquito → zygote → ookinete (mosquito stage)

Erythrocytes developmental stages of trophozoites

• Ring trophozoite

• Ameboid trophozoite / Band trophozoite (P.malariae, P. knowlesi)

• Immature schizont (nucleus replication)

• Mature schizont (8-24 merozoites)

• Gametocytes

Rings of P. falciparum in a thin blood smear

Ring-form trophozoites of P. falciparum in a thin blood smear, exhibiting Maurer's clefts.

Trophozoite of P. ovale in a thin blood smear.

Note the fimbriation and Schüffner's dots.

Trophozoite of P. vivax in a thin blood smear.

Note the amoeboid appearance, Schüffner's dots and enlarged infected RBCs.

Ring-form trophozoites of P. vivax in a thin blood smear.

Note enlarged infected RBCs

Band-form trophozoite of P. malariae in a thin blood smear.