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Fascioliasis
Fascioliasis is
infection by Fasciola hepatica, the sheep liver fluke. Humans
may acquire the infection wherever sheep are raised.
The eggs, passed
by the sheep in their faeces, require 2 weeks in fresh water before a miracidium emerges.
Miracidia infect a molluscan intermediate host (lymnaeid
snails), after which infective cercariae emerge from the snail, and
encyst on submerged vegetation, such as watercress, that is
contaminated by the cysts.
Metacercariae excyst in the duodenum, pass
through the wall into the peritoneal cavity, penetrate the liver, and
migrate through the hepatic parenchyma into the bile ducts.
The larvae
mature to adults and live in both the intrahepatic and extrahepatic
bile ducts.
Later the adult flukes penetrate the wall of the bile
ducts and wander back into the liver parenchyma, where they feed on
liver cells and deposit their eggs.
The eggs lead to abscess
formation, followed by a granuloma.
The worms induce hyperplasia of
the lining epithelium of the bile ducts, portal and periductal
fibrosis, proliferation of bile ductules, and varying degrees of
biliary obstruction.
Eosinophilia, vomiting and acute epigastrict pain
are features.
Severe untreated infections may be fatal.
Early
diagnosis and aggressive treatment with praziquantel prevents
irreparable damage to liver.
Diagnosis is
made by recovering eggs from stools or from the biliary tract.
Fasciolopsiasis
Fasciolopsiasis,
an infection by Fasciolopsis buski, the giant intestinal fluke
prevails throughout most of the Orient.
Humans, the definitive hosts,
acquire fasciolopsiasis by eating uncooked aquatic vegetables
contaminated with the encysted cercariae of F. buski .
The worm is
huge (3 x 7cm) and attaches to the duodenal or jejunal wall.
The
point of attachment may ulcerate and become infected, causing pain
that resembles that of a peptic ulcer.
Acute symptoms may be caused by
intestinal obstruction or by toxins released by large numbers of
worms.
The diagnosis is made by identifying the eggs of F. buski, which are similar to those of F. hepatica, in the stool.
Treatment is with praziquantel.
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