Cause
Plasmodium species (P. falciparum, P. vivax, P. ovale, P. malariae)
Vector
Female Anopheles mosquito
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Cause
Plasmodium species (P. falciparum, P. vivax, P. ovale, P. malariae)
Vector
Female Anopheles mosquito
At risk
Children (immature immunity)
Travelers from non-endemic → endemic areas (no immunity)
P. vivax, P. ovale
48 hour cycle (tertian)
Forms hypnozoites → relapse (Dormant liver stage)
P. malariae
72 hour cycle (quartan)
Chronic infection
P. falciparum
48 hour cycle (tertian)
Most severe, fatal, cerebral malaria
Life Cycle of Plasmodium: In Human (Asexual)
1. Exo-erythrocytic (Liver) Stage
2. Erythrocytic Cycle (Blood Stage)
Exo-erythrocytic (Liver) Stage
Mosquito injects sporozoites
Sporozoites travel via bloodstream to liver
Invade hepatocytes → multiply → form schizont
Schizont ruptures → merozoites released
2. Erythrocytic Cycle (Blood Stage)
Merozoites invade RBCs
Develop:
Ring stage (immature trophozoite) → trophozoite → schizont
Schizont ruptures → more merozoites
Some trophozoites → gametocytes
Life Cycle of Plasmodium: In the Mosquito (Sexual Phase)
Gametocytes (from human blood) ingested
Male gametocyte produces 8 microgametes
Fusion of male + female gametes → zygote (only diploid stage)
Zygote → ookinete (motile)
Ookinete → oocyst on midgut wall
Oocyst → sporozoites (1000+ each)
Sporozoites migrate to salivary glands
Pathophysiology & Symptoms
Fever: from synchronized RBC rupture
Anaemia: due to RBC destruction and suppressed erythropoiesis
Hypoglycaemia: due to parasite glucose consumption
ARDS: in severe malaria
Organ effects:
Hepatomegaly (liver enlargement)
Splenomegaly (spleen enlargement)
Blackwater fever: haemoglobinuria
Capillary blockage: via cytoadhesion of iRBCs to endothelium
Immunosuppression: increased risk of sepsis
Diagnosis
Blood smear (Giemsa-stained) to detect and identify Plasmodium species
Treatment: Chemotherapy
Chloroquine:
Enters parasite’s food vacuole (FV)
Acidified FV traps CQ → inhibits haemozoin formation
Free haem is toxic → kills parasite
Chloroquine resistance is widespread
Treatment: Vaccination
RTS,S/AS01: approved for use in children in high-P. falciparum transmission regions
Prevention
Take antimalarials for a few weeks after leaving endemic area
Use of mosquito nets, repellents, and vector control
Transmission routes
Mosquito bite (most common)
Airport malaria: mosquito travels by plane
Blood transfusion
Shared needles
Congenital (mother → baby)
Introduced malaria: local mosquitoes bite infected traveler