Updated: 1/22/2019

Flukes (Trematodes)

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Snapshot
  • A 15-year-old boy presents to the emergency room for a 2-month history of shortness of breath on exertion and cough. He recently moved from Laos to the United States for school. He reports having an unintentional 8-lb weight loss in the past few months, occasional fevers, and night sweats. He also reports having occasional hemoptysis. Prior to immigrating, he had a normal tuberculin skin test. A chest radiograph shows a linear streak and right-sided consolidation. A sputum sample is procured and sent for microscopy, which demonstrates oval-shaped eggs. (Paragonimiasis)
Introduction
  • Introduction
    • flukes are parasitic trematodes
      • characteristics
        • possess 2 suckers (trematos = “pierced with holes”)
        • unsegmented and flattened worms
      • blood fluke
        • Schistosoma species
      • liver fluke
        • Clonorchis sinensis
      • lung fluke
        • Paragonimus species
  • Treatment
    • praziquantel
Schistosoma
  • Schistosoma species (blood flukes)
    • organisms
      • Schistosoma haematobium (Africa and Middle East)
        • causes genitourinary tract disease
      • Schistosoma mansoni (Africa and South America)
        • causes intestinal tract and hepatosplenic disease
      • Schistosoma japonicum (East Asia)
        • causes intestinal tract and hepatosplenic disease
    • epidemiology
      • most occur in sub-Saharan Africa
    • transmission
      • snails are intermediate hosts
      • via penetration of skin
    • risk factors
      • exposure to fresh water
      • farming
  • Presentation
    • Katayama fever
      • fevers, hives, weight loss, and cough
      • acute illness after initial infection
    • chronic infections
      • S. mansoni and S. japonicum
        • hepatosplenomegaly with fibrosis and inflammation
          • portal hypertension
        • intestinal tract infection
          • abdominal pain
          • diarrhea
      • S. haematobium
        • squamous cell bladder cancer
          • hematuria (classic symptom)
          • dysuria
  • Studies
    • microscopy of urine or stool
      • S. haematobium
        • eggs with terminal spine
      • S. mansoni and S. japonicum
        • eggs with lateral spine
    • serology or PCR within 2 months of exposure
    • eosinophilia
  • Complications
    • portal hypertension
    • bladder stones
    • squamous cell bladder cancer
Clonorchis
  • Clonorchis sinensis (liver flukes)
    • epidemiology
      • east Asia
      • Russia
    • transmission
      • via ingestion of undercooked, dried, or pickled fish
    • pathogenesis
      • causes biliary tract inflammation
  • Presentation
    • chronic symptoms
      • right upper quadrant abdominal pain
      • anorexia
      • weight loss
      • diarrhea
      • jaundice
    • cholecystitis
    • ascending cholangitis
    • cholelithiasis with pigmented gallstones
  • Studies
    • microscopy of stool
      • flask-shaped C. sinensis eggs
    • eosinophilia
    • elevated alkaline phosphatase
  • Complications
    • cholangiocarcinoma
Paragonimus
  • Paragonimus species (lung flukes)
    • organisms
      • Paragonimus westermani (east Asia, Africa, and South America)
      • Paragonimus heterotremus (India)
    • transmission
      • via ingestion of undercooked crabs or crayfish
    • pathogenesis
      • inhabits lung parenchyma by penetrating through intestinal wall and peritoneal cavity to diaphragm
  • Presentation
    • tuberculosis-like illness
      • pleural effusion
      • pleuritic chest pain
      • recurrent bacterial pneumonia
      • hemoptysis
      • shortness of breath
      • fever, weight loss, and night sweats
  • Imaging
    • chest radiograph
      • consolidations
      • “ring shadow” of an oval thin-walled cyst
      • linear streak or fluke tract
  • Studies
    • microscopy of sputum or stool
      • ovoid and thick-shelled Paragonimus eggs
  • Complications
    • pulmonary abscess
 

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