Fluke Infections (Trematodiases): Types, Transmission & Treatment

What Are Flukes?

Trematodes (flukes) are parasitic flatworms with complex life cycles involving snails and often fish/crustaceans. Humans acquire them via contaminated water, raw/undercooked aquatic foods, or vegetation.

Major Human Fluke Infections

Disease	Species	Primary Organ	Geography	Key Symptoms
Clonorchiasis	Clonorchis sinensis	Liver/bile ducts	East/SE Asia	RUQ pain, diarrhea, cholangitis, cholangiocarcinoma risk
Opisthorchiasis	Opisthorchis viverrini	Liver/bile ducts	SE Asia	Similar; strong cancer link
Fascioliasis	Fasciola hepatica	Liver/bile ducts	Worldwide (sheep areas)	Fever, hepatomegaly, eosinophilia, biliary obstruction
Paragonimiasis	Paragonimus westermani	Lungs	Asia, Americas, Africa	Chronic cough, hemoptysis, pleural effusion
Schistosomiasis	Schistosoma spp.	Mesenteric/vesical veins	Tropics/subtropics	Hematuria, bloody stool, portal hypertension, bladder cancer

Diagnosis

• Microscopy: eggs in stool (most), urine (S. haematobium), sputum (Paragonimus).
• Serology/antigen tests for light infections.
• Imaging for complications.

Treatment

• Praziquantel – Drug of choice for most (single or divided dose).
• Triclabendazole – For fascioliasis (praziquantel ineffective).
• Corticosteroids for acute inflammatory reactions (e.g., Katayama fever).

Prevention

• Cook fish/crustaceans thoroughly (63°C).
• Avoid raw watercress, aquatic plants.
• Safe water, sanitation, snail control (schisto).
• Mass drug administration in endemic areas.