Fasciola hepatica (liver fluke)
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Epidemiology
- distribution: may parts of the world
- animal hosts: cattle, sheep, goats, other herbivores
- intermediate host: snail
- cercaria shed from snails encyst on aquatic vegetation
- infectious metacercariae present on aquatic vegetation
- humans most often acquire infection by eating watercress
- infection may occur by eating infected cattle or sheep liver
Pathology
- ingested larvae penetrate intestinal wall
- larvae migrate through peritoneal cavity to the liver
- they burrow through the capsule & parenchyma to become adults in the bile ducts
- egg-laying is initiated in about 2 months
- migration of the larvae through the liver elicits a painful inflammatory reaction
- bile ducts eventually become fibrotic
Clinical manifestations
- colic
- jaundice
- abdominal pain & tenderness
- cholelithiasis
- fever
- nausea
- diarrhea
- cough
- urticaria
Laboratory
- complete blood count: eosinophilia
- liver function tests
- abnormal liver function tests (LFTs)
- increased conjugated bilirubin
- diagnosis made by finding unembryonated eggs in feces
- yellowish-brown, operculate eggs
- 130-150 by 63-90 um
- not easily distinguish from eggs of Fasciolopsis
- Fasciola hepatica serology
Management
- bithionol 30-50 mg/kg on alternate days for 10-15 doses
- albendazole may be useful
- praziquantel is not very effective