Trematodes (Flukes)

Question 1

Schistosomiasis (Schistosoma mansoni, S. japonicum, S. haematobium)

Answer 1

• Most important human helminthic infection, very disabling.
• S. haematobium: Intense inflammatory response, damage to nearby tissue, usually Liver, GI, or bladder, where it causes granulomas and dysregulated growth (polyps in colon, sq cell carcinoma in bladder).
• Portal hypertension (Desposit egg in venules), esophageal varices (S. Mansoni +S. japonicum)
• Asexual reproduction in snail.
• Penetrates human skin as schistosomula.
• Lays eggs: These cause the inflammatory response.
• Diagnosed based on eggs in feces.
• Generally self-limited

Question 2

Clonorchiasis / Liver fluke (Clonorchis sinensis)

Answer 2

• Asia, Vietnam, Korea
• spread by ingesting inadequately cooked freshwater fish
• flat and transparent adult
• lethal due to complications: biliary obstruction, bacterial cholangitis, pancreatitis, cholangiocarcinoma

Question 3

Paragonimiasis / Lung fluke (Paragonimus westermani)

Answer 3

• spread through ingestion of uncooked crab
• Korea, Philippines, Taiwan, China
• peripheral eosinophilia-distinguishing factor against TB + eggs in sputum or stools
• frequently misdiagnoses as tuberculosis

Question 4

Fascioliasis

Answer 4

• spread by eating contaminated vegetation (watercress) with cysts from sheep
• cysts liberate metacecariae that pass into peritoneal cavity–live in intrahepatic and extrahepatic bile ducts
• hepatic abscesses and granulomas
• induce hyperplasia of bile duct epithelium, portal and periductal fibrosis, and biliary obstruction
• Symptoms: eosinophilia, vomiting, acute gastric pain
• Fatal if untreated
• diagnosis: recovering eggs from stool or biliary tract