Medicine & USMLE

Plasmodium Disease (Malaria)

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Parasites
  1. Giardia lamblia
  2. Toxoplasma gondii
  3. Entamoeba histolytica
  4. Cryptosporidium
  5. Naegleria fowleri
  6. Trypanosoma brucei
  7. Plasmodium Overview
  8. Plasmodium Disease (Malaria)
  9. Babesia
  10. Trypanosoma cruzi
  11. Leishmania
  12. Trichomonas vaginalis
  13. Enterobius vermicularis (pinworm)
  14. Ascaris lumbricoides (giant roundworm)
  15. Strongyloides stercoralis (threadworm)
  16. Ancyclostoma and Necator
  17. Trichinella spiralis
  18. Trichuris trichiura (whipworm)
  19. Toxocara canis
  20. Onchocerca volvulus
  21. Loa loa
  22. Wuchereria bancrofti
  23. Taenia solium
  24. Diphyllobothrium latum
  25. Echinococcus granulosus
  26. Schistosoma
  27. Clonorchis sinensis
  28. Sarcoptes scabiei (Scabies)
  29. Pediculus humanis and Phthirus pubis (Lice)

Summary

Malaria refers to a clinical syndrome caused by various parasites of the Plasmodium family.  The classic presentation of presentations of malaria is recurrent, or relapsing , fevers that occur at regular intervals, like every second or third day. Other clinical findings for malaria related to the parasite infecting red blood cells include splenomegaly and hemolysis. Also, the parasitized red blood cells can adhere to capillaries, causing infarcts by blocking blood flow. To diagnose a malaria infection, you should do a Giemsa stain on a blood smear to visualize the parasite. The Giemsa stain can reveal ring-shaped trophozoites inside the red blood cells.

Treatment for malaria is complicated due to the widespread development of resistance. The archetypal treatment preferred in all sensitive strains is chloroquine. However, many strains of plasmodium are now fully resistant to chloroquine, so other combination therapies are used to kill the parasites and prevent development of further resistance. 
For these chloroquine-resistant strains, a combination of artemisinins and mefloquine like artesunate-mefloquine is the first- line therapy. The second line therapy for chloroquine-resistant species is the combination of atovaquone and proguanil. Finally, in Plasmodium vivax and P.ovale, primaquine must be added in order to kill the dormant hypnozoites.

Key Points

  • Plasmodium Disease: Malaria
    • Presentation
      • Malaria
        • Etymology: “mal aire” = bad air (swamp air, where mosquitos were prevalent)
        • Relapsing (episodic) fevers
          • Headache, tachycardia, sweating also seen
          • Caused by RBC lysis in life cycle of malaria
          • 48 hour cycles (every other day)
            • seen with P. falciparum (may be irregular), P. vivax/ovale
          • 72 hour cycles (every third day)
            • Seen with P. malariae
        • Splenomegaly
          • Occurs in acute malaria, due to splenic sequestration of infected RBCs
        • Hemolysis
          • Anemia may be seen
          • Jaundice is fairly common
        • Parasitized RBCs can adhere to capillaries, causing infarcts
          • Altered mentation (CNS ischemia)
          • Cardiovascular collapse (microinfarcts in heart)
          • Renal failure (“blackwater fever”)
            • dark colored urine due to hemoglobin presence
          • Hepatic failure
          • Respiratory distress
    • Diagnosis
      • Blood smear with Giemsa staining
        • Trophozoite (ring-shaped parasites) visualized within RBC
        • Schizont containing merozoites may also be seen
      • Rapid diagnostic tests (RDTs) for malaria are becoming more widespread
    • Treatment
      • Chloroquine is first-line (for sensitive species)
      • For chloroquine-resistant species:
        • Artemisinins
          • First-line for chloroquine-resistant P. falciparum malaria
          • Given in artemisinin combination therapies (ACT)
            • Combinations include artesunate–mefloquine, artemether–lumefantrine, and dihydroartemisinin–piperaquine
        • Atovaquone-Proguanil
          • Second-line for chloroquine-resistant P. falciparum malaria
        • Mefloquine
          • Generally not administered as a monotherapy; instead combined with artesunate
      • Primaquine is needed (to kill hypnozoites) in P. vivax/ovale