Strongyloides

Aka: Strongyloides, Strongyloides Stercoralis, Strongyloidiasis, Threadworm, Larva currens

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II. Epidemiology

  1. Nematode: Roundworm
  2. Responsible for most U.S. cases fatal Helminth disease
  3. Found in regions of poor sanitation
  4. Endemic areas
    1. Tropical Asia
    2. Sub-Saharan Africa
    3. Latin America
    4. Pockets in Rural southeastern United States
    5. Pockets in Eastern Europe

III. Pathophysiology

  1. Soil transmitted Helminth
  2. On soil contact, filariform larvae penetrate skin (e.g. bare feet)
    1. Filariform larvae enter the venous system and are transported to the lungs
    2. Patient coughs, and worms are swallowed, resulting in intestinal infection
    3. Larvae develop into adult worms within the Small Intestine
  3. Adult Roundworms live in the Small Intestine, lay eggs which hatch, mature into filariform larvae and follow 3 routes
    1. Autoinfection
      1. Filariform larvae may penetrate the Small Intestine wall, and recirculate via veins and into the lung
    2. Direct Cycle (contamination of soil)
      1. Filariform larvae may be passed in the stool (not eggs) and infect soil
      2. Larvae then infect another person with exposed barefeet (or other exposed skin)
      3. Larvae may also infect perianal skin and follow the autoinfection route
    3. Indirect cycle (sexual reproduction)
      1. Filariform larvae are passed into soil and develop into male and female adult worms
      2. Worms mate in soil, producing fertilized eggs
      3. Eggs hatch in the soil, develop into filariform larvae which infect another human via bar skin

IV. Risk Factors: Hyperinfection (Immunocompromised)

  1. Chronic Corticosteroid use
  2. Chemotherapy
  3. Human Immunodeficiency Virus (HIV)

V. Differential Diagnosis

  1. Peptic Ulcer Disease

VI. Symptoms

  1. Often asymptomatic in immunocompetent patients
  2. Larva currens
    1. Recurrent serpiginous Urticaria and associated Pruritus
    2. Onset in perianal area
    3. Migratory rash to buttocks, groin, trunk
  3. Gastrointestinal side effects
    1. Abdominal Pain or Abdominal Bloating
    2. Diarrhea
    3. Vomiting
    4. Anorexia and weight loss
  4. Pulmonary involvement
    1. Cough
    2. Shortness of Breath
    3. Wheezing
    4. Dyspnea
    5. Hemoptysis

VII. Labs

  1. Eosinophilia (blood or stool)
    1. May be only finding in immunocompetent patients
  2. Guaiac-positive stools
  3. Strongyloides ELISA
  4. Microscopy
    1. Sample sources
      1. Stool sample
      2. Duodenal aspiration
      3. Enterotest (long nylon string end is swallowed and then retrieved from mouth)
    2. Findings
      1. Rhabditiform larvae present in sample (eggs will NOT be present)
    3. Efficacy
      1. False Negative test: 70% of cases

VIII. Management

  1. Precautions
    1. Avoid Corticosteroids (see hyperinfection as below)!
  2. Ivermectin (now preferred agent)
    1. Dose: 200 mcg/kg orally daily for 2 days
    2. Repeat every 15 days for disseminated infection until stool testing negative (and then one more treatment)
    3. Continuous dosing daily for hyperinfection (e.g. Sepsis, Meningitis) continued until stool and Sputum negative for 2 weeks
  3. Other agents
    1. Albendazole 400 mg orally twice daily for 7 days (for asymptomatic of intestinal infection)
    2. Thiabendazole (not available, poorly tolerated, less effective)

IX. Complications: Hyperinfection

  1. Background
    1. Provoked by Corticosteroids (often used empirically for reactive airway disease symptoms)
    2. Broad invasion of filariform larvae (multisystem ivolvement including Gastrointestinal Tract and lung)
  2. Findings
    1. Adult Respiratory Distress Syndrome (ARDS)
    2. Meningitis
    3. Septic Shock
  3. Prognosis
    1. Hyperinfection mortality rate in immunosuppressed: 87%

X. References

  1. Gilbert (2016) Sanford Guide, IOS version, accessed 9/12/2016
  2. Siddiqui (2001) Clin Infect Dis 33:1040-7 [PubMed]
  3. Schonau (2024) Am Fam Physician 109(6): 569-70 [PubMed]

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