• Protozoan infection transmitted through the Anopheles mosquito
  • Incubation period 8–16 d
  • Periodicity of the disease is due to the life cycle of the protozoan:
    • Exoerythrocytic phase: Immature sporozoites migrate to liver, where they rapidly multiply into mature parasites (merozoites)
    • Erythrocytic phase: Mature parasites are released into circulation and invade RBCs
    • Replication within RBCs followed 48–72 hr later by RBC lysis and release of merozoites into circulation, repeating cycle
    • Fever corresponds to RBC lysis
  • Plasmodium falciparum:
    • Cause of most cases and almost all deaths
    • Usually presents as an acute, overwhelming infection
    • Able to infect red cells of all ages:
      • Results in greater degree of hemolysis and anemia
    • Causes widespread capillary obstruction:
      • Results in end-organ hypoxia and dysfunction
    • More moderate infection in people who are on or who have recently stopped prophylaxis with an agent to which the P. falciparum is resistant
    • Post-traumatic immunosuppression may cause relapse of malaria in patients who have lived in endemic areas
  • Plasmodium vivax and Plasmodium ovale:
    • May present with an acute febrile illness
    • Dormant liver stages (hypnozoites) that may cause relapse 6–11 mo after initial infection
  • Plasmodium malariae:
    • May persist in the bloodstream at low levels up to 30 yr


  • Transmission usually occurs from the bite of infected female Anopheles mosquito
  • North American transmission possible:
    • Anopheles mosquitoes on east and west coasts of the U.S.
    • Transmission may also occur through infected blood products and shared needles

Pediatric Considerations
  • Sickle cell trait protective
  • Cerebral malaria more common in children
  • In highly endemic areas with minimal lab capability, all children presenting with febrile illness may be treated

Pregnancy Considerations
Pregnant patients, especially primigravida, at higher risk

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