Malaria

Basics

Description

  • Protozoan infection transmitted through the Anopheles mosquito
  • Incubation period 7–30 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 most likely cause of severe malaria and deaths
    • Usually presents as an acute, febrile 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 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
  • P. vivax and P. ovale:
    • May present with an acute febrile illness
    • Dormant liver stages (hypnozoites) that may cause relapse months to years after initial infection
  • P. malariae:
    • May persist in the bloodstream at low levels up to 30 yr
  • P. knowlesi:
    • Primarily nonhuman malaria parasite, but can infect humans

Etiology

  • Transmission usually occurs from the bite of infected female Anopheles mosquito
  • North American transmission possible:
    • 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, should be considered in all children presenting with febrile illness

Pregnancy Considerations

Pregnant patients, especially primigravida, at higher risk for infection and severe disease

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