Infectious Disease Online
Pathology of Fascioliasis and Fasciolopsiasis
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, 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 Fasciolopsis 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 Fasciolopsis buski, which are similar to those of Fasciola hepatica, in the stool.
Treatment is with praziquantel.
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