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A. Epidemiologynavigator

  1. Blood fluke infection formerly called bilharzia
  2. Infects humans directly through the skin
    1. Group of closely related flukes
    2. Migrate to and inhabit (portal) vascular system
  3. Over 200 million persons are infected worldwide
    1. 120 million symptomatic
    2. 20 million severely ill

B. Characteristicsnavigator

  1. Description
    1. Adult schistosomes are white-greyish worms of 7-20mm in length
    2. Cylindrical bodies with 2 terminal suckers, blind digestive tracdt, reproductive organs
    3. Females produce hundreds (African species) to thousands (oriental species) of eggs / day
    4. Eggs excreted in urine or feces, viable for up to 7 days
  2. Schistosoma mansoni - most widespread; only species in Western Hemisphere; Africa, others
  3. S. haematobium - mainly in Africa and Middle East
  4. S. japonicum - Japan, China, Phillipines, Celebes
  5. S. mekongi - Mekong and Mun River Valleys in Vietnam, Thailand, Laos, Cambodia
  6. S. intercalatum - restricted to specific areas of Africa

C. Clinical Stagesnavigator

  1. Three stages
    1. Early (Immediate) Stage
    2. Intermediate Stage
    3. Chronic Stage
  2. Early (Immediate) Stage
    1. Most organisms which penetrate the skin are killed by skin reaction
    2. Intensely pruritic papular skin rash develops within hours of invasion
    3. Organisms which escape migrate to liver causing fever, headache, abdominal pain
    4. Rash subsides within 1-2 days; other symptoms last 1-2 weeks
  3. Intermediate Stage
    1. Symptoms begin ~1.5 months (range 14-84 days) after primary exposure
    2. Serum-sickness like reaction with fever and chills
    3. Syndrome is called Katayama Fever
    4. Cough, urticaria, arthralgia, adominal pain and diarrhea occur
    5. Splenomegaly and lymphoadenopathy common
    6. Leukocytosis
    7. Peripheral eosinophilia, often with elevated immunoglobulin levels
    8. Aseptic meningitis and interstitial pneumonitis are uncommon
    9. Symptoms last up to three months
    10. Death is rare
  4. Chronic Schistosomiasis
    1. Schistosome eggs which reach lumen of bladder or bowel cause intense inflammation
    2. T cell dependent, eosinophilic granulomas are common
    3. Fibroblasts are stimulated and scar tissue forms
    4. Bowel and bladder fibrosis, sometimes with obstruction, are most commonly found
    5. Colicky hypogastric pain or left iliac fossa pain may occur
    6. Chronic liver disease with fibrosis can occur
    7. Hepatitis B (HBV) or hepatitis C (HCV) virus coinfection accelerates hepatic failure
    8. Pulmonary vascular lodging may occur leading to pulmonary hypertension
    9. Central nervous system (CNS) infection, including mass lesions, can develop [3]
    10. Flailing or flinging movements (balismus) may occur with CNS involvement [3]
    11. Increased incidence of salmonella bacteremia in S. mansoni infections
    12. Nephropathy due to chronic infections can also develop

D. Diagnosisnavigator

  1. Demonstration of characteristic eggs in urine, stool or biopsy
  2. Serological tests available but cannot distinguish active from inactive disease

E. Therapy [2] navigator

  1. Praziquantel (Biltricide®)
    1. Quinolone pyrazine active against all species
    2. Acts on adults with little or no effect on eggs or immature worms
    3. Available typically in 600mg tablets
    4. Usuual dose is 40mg/kg ingestion single dose
    5. Drug acts within 1 hour and paralyzes worms
    6. Side effects are mild: nausea, vomiting, malaise, abdominal pain
  2. Active Disease
    1. Proglonged praziquantel 20mg/kg/day is preferred
    2. Oxamniquine or metrifonate may be useful
    3. Praziquantel + glucocorticoids for CNS lesions [3]
  3. No specific therapy is available for dermatitis or Katayama Syndrome
  4. For Katayama fevere, glucocorticoids and/or antihistamines may be helpful
  5. Artemether
    1. Oral artemether prophylactically reduces new infections by ~50% [4]
    2. Artemether combined with praziquantel is synergistic
    3. Active against immature stages of most species
  6. Vaccines are currently being developed

References navigator

  1. Ross AGP, Bartley PB, Sleigh AC, et al. 2002. NEJM. 346(1):1212
  2. Gryseels B, Polman K, Clerinx J, Kestens L. 2006. Lancet. 368(9541):1106 abstract
  3. Ropper AH and Stemmer-Rachamimov A. 2001. NEJM. 345(2):126 (Case Record)
  4. Utzinger J, N'Goran EK, N'Dri A, et al. 2000. Lancet. 355(9212):1320 abstract