USMLE

Schistosoma

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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

Schistosoma are fluke or flatworm parasites that naturally live in freshwater snails. Humans get infected by swimming, bathing, or doing other activities in infected freshwater containing these snails. Schistosoma infections present in different ways, depending on the specific species of schistosoma implicated. These species can be differentiated by the appearance of their eggs on microscopy. The first species , S. mansoni, has eggs with a lateral spine. S. mansoni lives in the blood vessels of the intestines and liver and clinically presents with hepatomegaly and diarrhea. The second species, S. jasponicum, is similar to S. masoni in that it contains a lateral spine and can also cause hepatomegaly and diarrhea. The last species , S. haematobium, has eggs with a terminal spine. S. haematobium lives in the blood vessels around the bladder and presents with bladder injury or hematuria that can progress to bladder cancer. All strains of Schistosoma can live in the pulmonary vessels of the lung, causing pulmonary hypertension. Diagnosis for a S. mansoni or S. japonicum infection can be done through visualization of eggs in stool. A S. haematobium infection can be diagnosed by the presence of eggs in the urine. Finally, the main treatment option for all Schistosoma infections is praziquantel.

Key Points

  • Schistosoma spp.
    • Characteristics
      • Types of trematode (fluke) parasites
    • Transmission
      • Exposure to infected freshwater via snails
    • Presentation: Schistosomiasis
      • Acute
        • Swimmer’s itch
        • Katayama fever (acute schistosomiasis syndrome)
      • Chronic
        • S mansoni
          • Egg has lateral spine
            • Hepatomegaly
            • Diarrhea
        • S haematobium
          • Egg has terminal spine
          • Painless hematuria
            • Can lead to bladder cancer
        • S japonicum (MB)
          • Egg has vestigial (faint) lateral spine
            • Hepatomegaly
            • Diarrhea
        • All strains
          • Pulmonary hypertension
    • Diagnosis
      • Eggs seen in stool (S. mansoni, S. japonicum) or urine (S. haematobium)
    • Treatment
      • Praziquantel