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)


Cryptosporidium is a parasite transmitted through the fecal-oral route, via ingestion of parasite eggs or oocysts in contaminated water sources. Most healthy people are unaffected, but the parasite may end up causing disease in  immunocompromised patients. The most common finding of an infection by Cryptosporidium is profuse watery diarrhea. Diagnosis of a Cryptosporidium infection is done through a stool microscopy test, which can reveal acid-fast oocysts inside the stool.  Finally, the first line treatment for a cryptosporidium infection is nitazoxanide.

Key Points

  • Cryptosporidium spp.
    • Characteristics
      • Intracellular protozoan parasite
      • Transmission
        • Fecal-oral
          • Ingestion of oocysts in contaminated water
        • Affects immunocompromised patients
      • Presentation: Cryptosporidiosis
        • Watery diarrhea
      • Diagnosis
        • Stool microscopy (O&P)
          • Oocysts may be seen with acid-fast stains
      • Treatment
        • Nitazoxanide