Schistomiasis

Original article by Lily Stanley | Last updated on 4/6/2014
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Introduction

Schistomiasis, also known as Bilharziasis

Organisms

Blood flukes (schistosoma) 3 species most commonly affecting humans:

  • S.mansoni
  • S.haematobium
  • S.japonicum

Life Cycle

Transmission

Spread by fresh water snails
 

Epidemiology

  • Has huge socio-economic consequences in the tropics.
  • S. haematobium found in Africa and the Middle East
  • S. japonicum found in the Far East
  • S.mansoni is the most widespread, found mostly in South Americ the Caribbean, Africa the Middle East.

 

Pathogenesis

  • Fresh water snail vectors release cercariae that penetrate skin (during swimming/paddling)
  • Causes itchy popular rashàcercariae shed their tails to become schistosomulesàmigrate to the lungs and liver where they grow into adult form.
  • 2 weeks later ‘Katayma fever’ = initial immune reaction to worm maturation and shedding of eggs.
  • Approx 2 months later, flukes are mature and migrate to their resting habitats. 

 

Clinical features

Acute: Katayama fever

Complications

S.mansoni and S.japonicum

  • Both favour mesentaeric veins         
  • Lead to intestinal polyps, blood
  • Stained stools, hepatic fibrosis and portal hypertension.

S.haematobium

  • Favours bladder veins
  • Lead to urinary obstruction, polyps and
  • Bladder cancer(squamous cell) Hydronephrosis, pyelonephritis, renal failure.
  • Transverse myelitis.

Diagnosis

  • Microscopy for eggs in stool, urine or biopsy.
  • Serology in non-endemic areas
  • Eosinophilia
  • Renal tract US

 

Treatment

Praziquantel 

Prevention

Avoidance of fresh water contact in endemic areas.