Schistosoma Species - Schistosomiasis

  • Diagnosis
  • Background
  • Lab Tests
  • References
  • Related Content

Indications for Testing

  • History of exposure to fresh water in endemic area and evidence of associated hematuria

Laboratory Testing

  • Nonspecific testing
    • CBC – blood eosinophilia may be supportive evidence
      • Average of ~50 days between infection and development of eosinophilia
  • Microscopic examination for viable eggs in urine, feces, or tissue
    • 30-50 days delay between exposure to contaminated water and appearance of eggs
    • Stool exam performed when S. mansoni or S. japonicum suspected
    • Urine exam when S. haematobium suspected
  • ELISA IgG testing – may aid in diagnosis of schistosomiasis in patients from nonendemic areas
    • Unable to discriminate between active infection and past exposure
    • Generally negative at onset of clinical symptoms
      • Seroconversion occurs ~30 days after symptoms and ~6 weeks after contact with contaminated water

Differential Diagnosis

Schistosomiasis (sometimes called bilharziasis), an endemic parasitic tropical disease found especially in sub-Saharan Africa, causes substantial morbidity and mortality. In developed countries, the disease is typically seen in nonimmune travelers returning from endemic areas.


  • Prevalence – >300 million people worldwide are infected
  • Age – highest prevalence in children
  • Transmission – from water with snails, which serve as intermediate hosts
    • Common in South America, Africa, Southeast Asia, and the Middle East
    • In Europe ~2% of febrile travelers returning from abroad are eventually diagnosed with schistosomiasis


  • Common schistosomes that infect humans – snails as the intermediate host
    • S. mansoni – Africa, Latin America
    • S. haematobium – Middle East, Africa
    • S. japonicum – East Asia, Pacific
    • S. intercalatum, S. guineansis – sub-Saharan Africa
    • S. mekongi – Cambodia, Laos
  • Other schistosome spp that infect birds or aquatic mammals
    •  Schistosoma spp cercariae – common in the Great Lakes region, New England, and other parts of the U.S.; causes schistosome dermatitis (known as "swimmer’s itch")
  • Parasite has a complex life cycle and requires an intermediate-stage host 
    • Miracidia infect freshwater snails that later release cercariae back into the water
    • Cercariae then infect human and animal hosts
    • For more information on life cycle, causal agents, and geographic distribution, see CDC's information on schistosomiasis

Risk Factors

  • Rural areas with inadequate sanitation and contaminated water supplies

Clinical Presentation

  • Schistosome dermatitis (swimmer’s itch)
    • Only brief contact (1-5 minutes) with infected water is necessary
    • Itchy macular rash caused by cercariae entering the skin and dying
    • Self-limited – humans are a “dead-end” host for nonhuman-pathogenic schistosomes
  • Acute schistosomiasis (also known as schistosomiasis japonica or Katayama syndrome or fever)
    • Systemic hypersensitivity reaction – may occur 2-8 weeks after infection
    • Fever, myalgia, nonproductive cough, fatigue, abdominal pain, eosinophilia, occasionally bloody stools
    • Liver, spleen, and lymph nodes often enlarged
    • Death can occur in severe cases
  • Chronic schistosomiasis
    • Symptoms may be absent or mild, especially in patients with light or moderate egg burden
    • Peripheral blood – eosinophilia often present
    • Fatigue, abdominal pain, intermittent diarrhea, or dysentery
      • Fatigue due to anemia because of blood loss
    • Species-specific symptoms and diseases
      • Periportal fibrosis, which may lead to hepatic failureS. mansoni and S. japonicum
      • Hematuria and dysuria – S. haematobium
        • In later stages of the disease, fibrosis of the bladder may occur, which can lead to renal failure and squamous cell cancer of the bladder
      • Neurologic disease (all human-pathogenic Schistosoma)
        • Brain infection – meningitis, encephalitis
        • Myelopathy (most common sites are conus medullaris and cauda equina)

Indications for Laboratory Testing

Tests generally appear in the order most useful for common clinical situations.
Click on number for test-specific information in the ARUP Laboratory Test Directory

CBC with Platelet Count and Automated Differential 0040003
Method: Automated Cell Count/Differential

Ova and Parasite Exam, Fecal (Immunocompromised or Travel History) 2002272
Method: Qualitative Concentration/Trichrome Stain/Microscopy


Ova may not be detectable in early disease 

Ova and Parasite Exam, Body Fluid or Urine 2002277
Method: Qualitative Concentration/Microscopy

Schistosoma Antibody, IgG 0099411
Method: Semi-Quantitative Enzyme-Linked Immunosorbent Assay


Overall sensitivity 97%; specificity 92%

Sensitivity for S. japonicum <50%

Sensitivity for S. haematobium 95%

False-positive results due to cross-reactivity may occur in samples positive for malaria, filariasis, Toxocara, Leishmania, Epstein-Barr virus

Single test cannot distinguish active from past infection

Additional Tests Available

CBC with Platelet Count and Automated Differential 0040003
Method: Automated Cell Count/Differential


Nonspecific testing to determine presence of eosinophilia

General References

Colley D, Bustinduy A, Secor E, King C. Human schistosomiasis. Lancet. 2014; 383(9936): 2253-64. PubMed

Gray D, Ross A, Li Y, McManus D. Diagnosis and management of schistosomiasis. BMJ. 2011; 342: d2651. PubMed

Gryseels B, Polman K, Clerinx J, Kestens L. Human schistosomiasis. Lancet. 2006; 368(9541): 1106-18. PubMed

Jauréguiberry S, Paris L, Caumes E. Acute schistosomiasis, a diagnostic and therapeutic challenge. Clin Microbiol Infect. 2010; 16(3): 225-31. PubMed

Lewis F, Tucker M. Schistosomiasis. Adv Exp Med Biol. 2014; 766: 47-75. PubMed

Ross A, Vickers D, Olds R, Shah S, McManus D. Katayama syndrome. Lancet Infect Dis. 2007; 7(3): 218-24. PubMed

Medical Reviewers

Last Update: December 2015