MICROBIOLOGY

• Helminthic parasite, common worldwide but especially in warmer climes.
  • S. stercoralis is the major human pathogen.
  • S. fuelleborni occasional human pathogen, described in Papua New Guinea and Africa.
• Larvae live in soil. Human infection occurs through contact with contaminated soil.
• Filariform larvae penetrate the skin and enter lymphatics → can go to lung alveoli or straight to the small intestine.
  • Adult female deposits eggs in the intestinal mucosa, larvae hatch and are excreted in stool, or may become filariform (infective) in the large intestine and cause auto-infection.
  • Cycle yields long-term infection in humans (years-decades, may be considered lifelong).
• Immunosuppression can yield increased organisms as a result of auto-infection → hyperinfection [see life cycle Fig. 1], a potentially fatal condition.
• Larvae are typically seen ~1 month after exposure.