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Questions and Answers
What type of anemia is commonly associated with fascioliasis due to blood-sucking activity of the adult worm?
What type of anemia is commonly associated with fascioliasis due to blood-sucking activity of the adult worm?
Which complication associated with chronic fascioliasis is characterized by severe bleeding from the bile duct?
Which complication associated with chronic fascioliasis is characterized by severe bleeding from the bile duct?
Which of the following forms of fascioliasis is considered the classic type?
Which of the following forms of fascioliasis is considered the classic type?
What is the infective stage of true fascioliasis?
What is the infective stage of true fascioliasis?
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Which symptom is NOT typically associated with hemobilia as a complication of fascioliasis?
Which symptom is NOT typically associated with hemobilia as a complication of fascioliasis?
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What is the main morphological difference between Fasciola hepatica and Fasciola gigantica?
What is the main morphological difference between Fasciola hepatica and Fasciola gigantica?
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Which stage is considered the diagnostic stage of Fasciola hepatica and gigantica infection?
Which stage is considered the diagnostic stage of Fasciola hepatica and gigantica infection?
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What is the infective stage of Fasciola hepatica upon ingestion?
What is the infective stage of Fasciola hepatica upon ingestion?
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Which of the following statements is true regarding the lifecycle of Fasciola species?
Which of the following statements is true regarding the lifecycle of Fasciola species?
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Which snail species serves as the intermediate host for both Fasciola hepatica and Fasciola gigantica?
Which snail species serves as the intermediate host for both Fasciola hepatica and Fasciola gigantica?
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Study Notes
Morphology
- Fasciola hepatica and Fasciola gigantica differ primarily in size, with F. hepatica being smaller (2.5-3 cm) and F. gigantica being larger (7 cm).
- The cephalic cone of F. hepatica is more prominent and larger than in F. gigantica.
- The suckers in F. hepatica are nearly equal in size, while in F. gigantica the ventral sucker is larger than the oral sucker.
- The intestinal ceca of F. hepatica are converging and poorly developed, while in F. gigantica they are parallel and highly developed.
- The median branches in F. hepatica are poorly developed, while in F. gigantica they are highly developed.
- F. hepatica infects Lymnaea truncatule, while F. gigantica infects Lymnaea natalesis.
- F. giganica eggs are larger than F. hepatica eggs.
- F. gigantica metacercaria are more liable to desiccation than F. hepatica metacercaria.
Life Cycle
- The definitive host (DH) is typically herbivorous animals, with accidental infection in humans.
- The intermediate host (IH) is a snail of the genus Lymnaea.
- The infective stage is the encysted metacercaria, which appears microscopically as white spherical structures.
- Metacercaria become encysted on vegetation after losing their tail.
- Infection occurs through ingestion of encysted metacercaria in aquatic plants or contaminated water.
- Immature eggs pass in the stool and mature in freshwater, hatching into miracidia.
- Miracidia enter the snail and undergo developmental stages (sporocyst, redia, cercaria).
Pathogenesis and Pathology
- After ingestion of infective stage, cercaria escapes in the stomach.
- Eosinophilia is common (40%).
- Fascioliasis causing anemia is a type of normocytic normochromic anemia that can change to microcytic hypochromic anemia.
- The cause of anemia is believed to be from blood-sucking activity of the adult fluke, migration through the bile duct causing bleeding, and toxic substances released by the worm.
- Hemobilia is a rare complication characterized by arterial bleeding associated with ulcers caused by a dead parasite in the common bile duct.
Types of Fascioliasis
- True Fascioliasis (classic) caused by encysted metacercaria in unwashed vegetables.
- False fascioliasis (spurious) caused by adult and eggs of Fasciola in cooked liver.
- Halzoun fascioliasis (pharyngeal) caused by adult Fasciola attached to the mucosa of the pharynx, larynx, or esophagus.
- Ectopic fascioliasis caused by encysted metacercaria in unwashed vegetables, but the worm migrates to other organs.
Diagnosis
-
Clinical
- History of exposure to endemic areas, eating raw vegetables
- Symptoms such as abdominal pain, fever, hepatomegaly, and high eosinophilia.
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Laboratory
- Direct: Stool analysis for immature eggs (in chronic phase), duodenal aspiration in the early stages.
- Indirect: Immunological tests such as IHAT, IFAT, ELISA, gel electrophoresis, counter immunoelectrophoresis, metacercaria precipitin test, and copro-antigen ELISA in stool.
- CBC: Eosinophilia (40-80%), leukocytosis, anemia.
- Liver function tests: ALT, AST, GGT, alkaline phosphatase, bilirubin.
- Radiological: Ultrasound, CT, MRI showing hypodense areas in the liver and abnormalities in the bile tract. ERCP for diagnosis and treatment, MRCP for diagnosis.
Differential Diagnosis
- Causes of hepatomegaly (schistosomiasis, hydatid cyst, VLM, viral hepatitis, amoebic hepatitis).
- Causes of cholangitis and recurrent jaundice (gallbladder stones, Gilbert disease).
Treatment
-
Medical
- Triclabendazole (10 mg/kg single dose after a meal or 20 mg/kg in two divided doses for heavy infections)
- Merazide (2 tablets daily before breakfast for 6 days)
- Nitazoxanide (500 mg twice daily for 7 days)
- Surgical: Cholecystectomy
- Endoscopic Therapy: ERCP to open sphincter and extract worms followed by medical treatment.
Prevention and Control
- Health education
- Good washing of vegetables with vinegar or potassium permanganate for 5-10 minutes
- Control of snails using molluscicides
- Treatment of infected humans and animals.
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