Schistosomiasis
Epidemiology and Etiology:
- Schistosoma
mansoni Latin America,
Africa, Middle East
- Schistosoma
japonicum East Asia
- Schistosoma
mekongi East Asia
- Schistosoma
haematobium Africa
(bladder)
- Habitat:
- Fresh water snails
- Slow-moving water
of tropical rivers, lakes, irrigation ditches
- Lifecycle:
- Larvae (cercariae)
swim in fresh water
- Penetrate through
human skin
- Migrate into the
peripheral vasculature
- Travel to the lung
- Settle in the
portal or pelvic venous system
- Develop into adult
schistosomes
- Females produce eggs
into venous blood
- Some eggs travel
through intestinal wall into colonic lumen and are shed in the feces
- Eggs infect
freshwater snails
- Develop into
larvae in the snails
Common sites:
- Liver immune response
- Colon
inflammatory patches and pseudopolyps (severe disease)
- Bladder (S.
haematobium)
Gross features:
- Mild:
- White, pinhead
sized granulomas scattered throughout the gut and liver
- Severe:
- Hepatic fibrosis
- Bumpy surface
- Cut surface fibrous
portal enlargement and fibrosis (pipe-stem fibrosis) without distortion
of the intervening parenchyma by regenerative nodules
- Splenomegaly secondary
to portal hypertension
- Bladder (S.
haematobium):
- Inflammatory patches
- sandy appearance
of bladder wall
- inflammation and
fibrosis of ureteral walls may lead to obstruction, hydronephrosis,
chronic pyelonephritis
Histologic features:
- Eosinophilic granulomas
and fibrosis form around eggs
- Eosinophilic granulomatous
inflammation particularly in the liver
- Fibrotic portal
tracts often lacking portal vein
- Lung (if portal
hypertension):
- Granulomatous pulmonary
arteritis
- Kidneys:
- Mesangioproliferative
or membranous glomerulopathy (immunoglobulin and complement deposition)
- Rarely schistosome
antigen present
Immunophenotype:
Marker:
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Sensitivity:
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Specificity:
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Molecular features:
Other features:
References: