(Strongyloides stercoralis)

Because most infections with Strongyloides stercoralis are asymptomatic, strongyloidiasis should be considered in any patient with unexplained eosinophilia and potential risk of exposure. When symptoms occur, they are most often related to larval skin invasion, tissue migration, and/or the presence of adult worms in the intestine. Infective (filariform) larvae are acquired from skin contact with contaminated soil, producing transient pruritic papules at the site of penetration. Larvae migrate to the lungs and can cause a transient pneumonitis or Loeffler-like syndrome. After ascending the tracheobronchial tree, larvae are swallowed and mature into adults within the gastrointestinal tract. Symptoms of intestinal infection include vague abdominal pain, malabsorption, vomiting, and diarrhea. Larval migration from defecated stool can result in pruritic skin lesions in the perianal area, buttocks, and upper thighs, which may present as serpiginous, erythematous tracks called larva currens. Immunocompromised people, usually people receiving glucocorticoids for underlying malignancy or autoimmune disease and people with human T-lymphotropic virus (HTLV-1), are at risk of Strongyloides hyperinfection, which results from dissemination of larvae via the systemic circulation to a variety of tissues with subsequent abdominal pain, diffuse pulmonary infiltrates, and septicemia or meningitis from enteric gram-negative bacilli.