Strongyloides stercoralis (threadworm)

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Key Points

  • Strongyloides stercoralis
    • Characteristics
      • Also known as a threadworm
      • Type of nematode (roundworm) parasite
    • Transmission
      • Found in soil contaminated with human feces
        • Larvae invade the skin of barefoot walkers
        • Usually in tropics of SE Asia
    • Pathogenesis and Presentation: Strongyloidiasis
      • Skin irritation at site of skin invasion
        • Urticaria and swelling
      • After entering the foot, migrate via blood to the lungs
        • Early pneumonitis
          • Pulmonary signs of worm infection known as Loeffler syndrome
          • Presents with dry cough, bloody sputum, wheezing
      • Larvae migrate through trachea and are swallowed
        • GI symptoms
          • Intermittent abdominal cramps and diarrhea/constipation
        • Mature larvae may reinvade intestinal walls, causing autoinfection
      • Larvae may migrate subcutaneously from perianal region
        • Raised pruritic skin streaks along lower trunk, thighs, buttocks
          • Also known as larva currens
      • Eosinophilia
        • Observed in >60% of cases
        • Non-specific; seen in many parasitic diseases
      • Immunodeficient patients prone to developing hyperinfection (multiorgan damage and sepsis)
    • Diagnosis
      • Stool microscopy (O&P)
        • Rhabditiform larvae seen in feces
      • Serologic testing is gold-standard
        • Anti-strongyloides antibodies measured by ELISA
    • Treatment
      • Ivermectin
        • Bendazoles are second-line (less efficacious)