Strongyloides stercoralis (threadworm)

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Parasites

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)