FASCIOLA HEPATICA (LIVER FLUKE)

 

3. FASCIOLA HEPATICA (LIVER FLUKE)

 

Morphology of Fasciola hepatica

  • Commonly known as the liver fluke.
  • Shape: Flattened, leaf-like, and broad.
  • Size:
    • Adults: ~2–3 cm in length and ~1 cm in width.
    • Eggs: Oval and ~130–150 µm in size with an operculum (lid-like structure).
  • Color: Flesh-colored or slightly brown in appearance.
  • Anatomical Features:
    • Oral sucker: Present at the anterior end, used for attachment.
    • Ventral sucker: Located on the ventral side, aiding in movement.
    • Digestive system: Incomplete, with a bifurcated gut.
    • Hermaphroditic: Contains both male and female reproductive organs.

Diagram of Fasciola hepatica

2. Life Cycle of Fasciola hepatica

The life cycle of Fasciola hepatica involves two hosts: a definitive host (e.g., humans, sheep, cattle) and an intermediate host (snail). It also includes several larval stages.

A. In the Definitive Host (Human or Ruminants)

  1. Ingestion of Metacercariae:
    • Humans or animals become infected by ingesting metacercariae (encysted larvae) present on contaminated water plants (e.g., watercress).
  2. Excystation and Migration:
    • The cysts hatch in the duodenum, releasing immature flukes.
    • The larvae penetrate the intestinal wall and migrate through the peritoneum to reach the liver.

 

  1. Maturation in the Liver:
    • In the liver, immature flukes feed on hepatocytes and bile, causing tissue damage.
    • They mature into adult flukes within 3-4 months and settle in the bile ducts, where they start producing eggs.
  2. Egg Release:
    • Eggs are released into the bile and eventually passed in the feces of the host.

 

 

B. In the Environment and Intermediate Host (Snail)

  1. Eggs Hatch into Miracidia:
    • When the eggs reach freshwater, they hatch into free-swimming larvae called miracidia within 2-4 weeks.
  2. Infection of Snail:
    • The miracidia infect a snail (intermediate host) and undergo multiple developmental stages:
      • Sporocysts → Rediae → Cercariae (motile larval form).
  3. Release of Cercariae:
    • The cercariae leave the snail and encyst as metacercariae on water plants.

 

C. Infection Recap Timeline

  • Egg to Miracidium: ~2-4 weeks in freshwater.
  • Development in Snail: ~5-7 weeks.
  • Maturation in Human Host: 3-4 months from ingestion to adult form in bile ducts.
  • Total Life Span of Adult Fluke: Up to 10 years.

Life cycle of Fasciola

 

3. Clinical Manifestations

In humans, fascioliasis presents in acute and chronic phases.

A. Acute Phase (Larval Migration Phase):

  • Occurs during the migration of immature flukes through the liver tissue.
  • Symptoms:
    • Fever, nausea, vomiting, diarrhea.
    • Right upper quadrant abdominal pain (due to liver involvement).
    • Hepatomegaly (enlarged liver) with tenderness.
    • Eosinophilia (high eosinophil count) is common during this phase.

B. Chronic Phase (Adult Fluke in Bile Ducts):

  • Occurs when adult flukes settle in the bile ducts and cause chronic inflammation.
  • Symptoms:
    • Biliary colic (intense pain due to obstruction of bile ducts).
    • Cholangitis or cholecystitis (inflammation of bile ducts or gallbladder).
    • Obstructive jaundice in severe cases.
    • Fibrosis and cirrhosis may develop with prolonged infections.

 

4. Laboratory Diagnosis

  1. Microscopy:
    • Identification of eggs in stool samples using sedimentation techniques.
    • Eggs are oval with an operculum at one end, differentiating them from other parasites.
  2. ELISA and Serological Tests:
    • Detect anti-Fasciola antibodies in serum, especially useful in the early acute phase when eggs are absent from stool.
  3. Liver Ultrasound or CT Scan:
    • Helps detect liver lesions, bile duct thickening, or dilation.
    • Useful for identifying the location of adult flukes.
  4. PCR:
    • Molecular methods for detecting Fasciola DNA in stool or serum samples, providing high sensitivity.

 

5. Treatment of Fascioliasis

  1. Triclabendazole:
    • The drug of choice for Fasciola hepatica infection.
    • Dosage: 10-12 mg/kg, given in two divided doses within 12 hours.
    • Effective against both larval and adult stages.
  2. Bithionol:
    • An alternative drug in cases where triclabendazole is not available.
    • Given as 30-50 mg/kg every other day for 10-15 days.
  3. Supportive Care:
    • Analgesics and antipyretics to manage pain and fever.
    • Liver function monitoring to assess damage.
  4. Surgical Intervention:
    • In rare cases of biliary obstruction, endoscopic or surgical intervention may be required to remove flukes or relieve blockages.

 

6. Prevention and Control

  1. Avoid Raw Water Plants:
    • Avoid consumption of uncooked watercress or other water plants from contaminated areas.
  2. Snail Control:
    • Reduce snail populations in freshwater bodies to interrupt the parasite’s life cycle.
  3. Public Health Education:
    • Awareness programs about the dangers of consuming raw aquatic vegetation.
  4. Mass Treatment Campaigns:
    • In endemic areas, mass administration of triclabendazole to control the spread of infection.

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