Medicine & USMLE


  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. Ancylostoma 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)


Babesia is a parasite that is transmitted by the Ixodes tick, which is commonly found in the Northeastern US. The infection that Babesia causes is called Babesiosis. Babesia typically infects the red blood cells of people, causing hemolysis and anemia in patients. Other presentations of Babesiosis include non-specific flu-like symptoms, hepatomegaly, and splenomegaly. A diagnosis of Babesiosis can be supported by the finding of maltese cross inclusions inside red blood cells on the Giemsa stain. Finally, the first-line treatment for Babeiosis is a combination of atovaquone and macrolides like azithromycin.

Key Points

  • Babesia
    • Includes Babesia divergens and Babesia microti
    • Characteristics
      • Protozoan parasite
    • Transmission
      • Transmitted by Ixodes tick
        • Same tick as B. burgdorferi (Lyme disease)
          • Babesia and Borrelia often coinfect
        • Predominantly in Northeastern US
          • Seen with outdoor activities (camping, hiking, etc.)
      • Asplenia increases risk of severe disease
        • Since splenic macrophages clear infected RBCs
    • Presentation: Babesiosis
      • Non-specific flu-like symptoms
        • Fever, chills, fatigue, myalgia, headache
        • Caused by a host inflammatory response producing cytokines in the bloodstream
      • Hepatosplenomegaly
        • Icterus and jaundice may be seen
      • Anemia
        • Caused by both hemolysis and by reactive oxygen species produced by Babesia infection
    • Diagnosis
      • Blood smear with Giemsa stain
        • Ring-shaped or Maltese Cross inclusions in RBC
          • Maltese cross is less common than rings but pathognomonic for babesiosis
      • PCR may also be used
    • Treatment
      • Atovaquone + Azithromycin
        • Clindamycin and oral quinine is a second-line treatment that may be added in severe cases