What are the presentation, diagnostic approach, and first-line therapy for Fasciola hepatica infection (fascioliasis)?

Fasciola Hepatica: Clinical Approach

First-Line Treatment

Triclabendazole 10 mg/kg as a single oral dose is the definitive treatment for Fasciola hepatica infection, as recommended by the World Health Organization. 1

• Triclabendazole demonstrates high efficacy with rapid clinical response and is the only recommended medical treatment 1, 2, 3
• Bithionol serves as an alternative agent when triclabendazole is unavailable 3
• Critical caveat: Triclabendazole is not widely available in many countries, and emerging resistance has been reported 2, 4
• In resource-limited settings where triclabendazole cannot be obtained, metronidazole 1.5 g/day for 3 weeks has shown success in isolated case reports, though this is not standard therapy 4

Clinical Presentation

Acute Phase (Hepatic Migration)

• Abdominal pain, fever, and fatigue develop within days to weeks after ingestion of contaminated watercress or aquatic plants 1, 5, 6
• Nausea is common during this invasive stage 5
• Symptoms typically appear approximately 22 days post-exposure 6

Chronic Phase (Biliary)

• Biliary obstruction, cholecystitis, and hepatic abscess occur in untreated cases as adult flukes establish in bile ducts 1, 5
• Chronic hepatobiliary disease with inflammation and fibrosis develops over time 2

Diagnostic Approach

Initial Clinical Suspicion

The triad of peripheral eosinophilia, abdominal pain, and elevated liver enzymes should immediately raise suspicion for F. hepatica infection. 1

Imaging Studies

• CT scan showing subcapsular tubular and nodular hypodense lesions is highly suggestive 1
• Microabscess-like multiple nodular lesions may be visible on hepatic imaging 1
• Ultrasound, CT, and MRI can reveal biliary complications but lack specificity 2, 3

Laboratory Confirmation

• Serological testing must be positive for definitive diagnosis 1, 5
• ELISA is the primary serological method 3
• Important limitation: Cross-reactivity with other parasites can cause false positives 2

Stool Examination

• Detection of Fasciola eggs in stool is diagnostic, particularly in the chronic biliary phase 1, 3
• Major limitation: Unreliable due to inconsistent egg shedding patterns 2

Emerging Diagnostics

• PCR offers higher sensitivity and specificity with earlier detection capability 2
• Not yet widely available, especially in endemic low-resource areas 2

Diagnostic Algorithm Priority

1. Recognize the clinical triad: eosinophilia + abdominal pain + elevated liver enzymes 1
2. Order CT imaging to identify characteristic hypodense hepatic lesions 1
3. Obtain serological testing for confirmation 1, 3
4. Perform stool examination for eggs, particularly if chronic phase suspected 1, 3
5. Consider invasive procedures (ERCP, percutaneous cholangiography) only for complicated biliary disease, not for routine diagnosis 3

Epidemiological Context

• Infection occurs through consumption of raw or undercooked watercress and aquatic vegetation contaminated with metacercariae 6, 7
• The endemic cycle exists in the United States involving local snails and aquatic vegetation 7
• Most U.S. cases are imported from travelers or immigrants, though autochthonous transmission occurs 6, 7
• Commercially grown watercress cultivated in controlled settings (e.g., Hawaii) appears safe 6

Treatment Monitoring

• Clinical abnormalities typically resolve after triclabendazole treatment 6
• Follow-up imaging should demonstrate resolution of hepatic lesions 1
• Eosinophilia should normalize during recovery 6