Trematodiases

Trematodiases are infections caused by trematodes, or flukes, a group of parasitic flatworms. In humans they cause a wide range of diseases depending on the species and site of infection, most commonly affecting the liver and biliary tract, the intestine, the lungs, or the urinary tract.

Most trematodes require snails as the first intermediate host; humans are infected after ingesting metacercariae on aquatic plants or by consuming undercooked fish or crustaceans. Schistosoma species differ in that infection occurs when free-swimming cercariae penetrate intact skin in freshwater. The life cycle includes definitive hosts and release of eggs; some eggs cause pathology by granulomatous reaction.

Clinical features vary by organism. Hepatic and biliary infections may cause cholangitis, biliary obstruction, and fibrosis; intestinal infections can cause diarrhea and abdominal pain; paragonimiasis presents with cough and lung involvement; urinary schistosomiasis causes hematuria and bladder pathology. Diagnosis relies on finding eggs in stool or urine, serology or molecular tests, and imaging; repeated sampling or concentration techniques may be needed. Treatments include praziquantel for many trematodiases; triclabendazole for fascioliasis; regimen depends on species and severity.

Prevention focuses on reducing transmission: safe drinking water, proper sanitation, snail control, cooking or adequately processing freshwater fish and plants, and health education. Public health measures and surveillance reduce endemicity in affected areas.