Lung Flukes

• Paragonimus westermani

  • Common Name: Oriental Lung Fluke
  • Disease: Paragonimiasis (Pulmonary Distomiasis)
  • Habitat: Lungs
  • Intermediate Hosts:

  1. Snails (Antemelania asperata, Brotia asperata)
  2. Mountain crabs (Sundathelphusa philippina)

  • Final Hosts: Humans, dogs, cats
  • Reservoir Host: Rats
  • Diagnostic Stage: Eggs in stool or sputum
  • Infective Stage: Metacercaria
  • Mode of Transmission: Eating raw or undercooked crabs
  • Treatment: Praziquantel (DOC), bithionol
• Paragonimus westermani Morphology

  Egg

  • Shape: Oval with slightly thinner posterior end
  • Color: Golden to dark brown
  • Size: 80-120 µm × 45-70 µm
  • Features: Operculated with thick shell and abopercular thickening

  Adult

  • Size: 7.5-12 mm long, 4.6 mm wide
  • Color: Reddish-brown, coffee bean-shaped
  • Reproductive Organs: Opposite lobed testes, 6-lobed ovary, extensive vitellaria
• Larval Stages

  • Miracidium – Hatches in water, infects 1st IH (snail)
  • Sporocyst – Develops inside snail
  • Redia – Further larval stage in snail
  • Cercaria – Free-swimming stage, infects 2nd IH (crab/crayfish)
  • Metacercaria – Infective stage found in crabs
• Pathogenesis Stages

  • Invading & Migrating Stage – Larvae penetrate intestines, enter peritoneal cavity, then migrate to lungs
  • Suppurative Stage – Inflammatory reaction, necrosis, abscess formation
  • Cystic Stage – Cyst formation in lungs, rusty-brown fluid with eggs & Charcot-Leyden crystals
  • Fibrous Scar Stage – Cysts rupture, fibrosis and chronic lung damage
• PARAGONIMUS: CLINICAL MANIFESTATIONS

  Paragonimiasis may be classified into 4 types:

  • Pulmonary type (CHRONIC)
  • symptoms resemble pulmonary TB.
  • Low fever
  • Night sweating
  • Chest pain
  • Loss of appetite and weight
  • Rusty sputum
  • Brain type (CHRONIC)
  • neurological symptoms resembling cerebal cysticercosis 
  • Epilepsy
  • Aphasia
  • Visual disturbances
  • Abdominal type (ACUTE) 
  • Abdominal pain
  • Diarrhea
  • Dysentery with mucus and ova in stool
  • Subcutaneous type (ACUTE)
  • Painless subcutaneous nodules
• PARAGONIMUS: LABORATORY DIAGNOSIS

  Basic Techniques

  • Microscopic examination for Paragonimus eggs in sputum smear using sedimentation technique with 3% NaOH

  Other/Specialized Techniques

  • Intradermal Test
  • ELISA

  Sputum Examination

  • Alkali Digestive Method (10% NaOH)
  • Direct Sputum Smear (eggs may not be present for 2-3 months)

  Stool Examination

  • Alkali Digestion
  • Water Sedimentation Method
  • Direct Fecal Smear (DFS)
• Other Diagnostic Methods for P. westermani

  1. Biopsy for Subcutaneous type
  2. CT for Brain Type
  3. Blood test for neutrophils and eosinophils (Charcot-Leyden crystals)
  4. Immunological test for reference
• Paragonimus westermani Egg


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• P. westermani

  Metacercaria and Adult Image