Ascaris

Aka: Ascaris, Ascariasis

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II. Pathophysiology

  1. Nematode: Roundworm
  2. Infected patient with Ascariasis secretes eggs in stool
    1. Stool contaminates soil with Ascariasis eggs (and eggs may persist for up to 10 years in soil)
    2. Ascariasis eggs hatch into worms within 2-4 weeks at which point they are infective
  3. Ascariasis eggs are ingested by exposed persons
    1. Especially communities with open Defecation in fields or where animal feces are used to fertilize crops
    2. Ascariasis eggs that hatch after ingestion (typically by day 4) pass through the cecal mucosa
    3. Ascariasis worms enter lungs via circulatory system or Lymphatic System
  4. Ascariasis matures in lungs for 10-14 days
    1. Once mature, Ascariasis induces cough, and patient swallows coughed secretions, re-entering intestinal tract
  5. Ascariasis worms mature further in intestinal tract
    1. After 9-11 weeks from time of initial ingestion, Ascariasis starts to lay eggs
    2. Infected patients shed up to 200,000 Ascariasis eggs per day
    3. Worms live for 10 months to 2 years and do not reproduce within host patient

III. Epidemiology

  1. Prevalence
    1. Asia (75%)
    2. Africa (10%)
    3. Latin America (10%)
  2. Transmission
    1. Human feces contaminated fruits and vegetables
    2. Fomites
      1. Flies can deposit eggs on food

IV. Symptoms

  1. Often asymptomatic
  2. Intense lower Abdominal Pain for days

V. Signs

  1. Distinctive Ascariasis eggs in stool
  2. Roundworm passed in stool
    1. Length: 15-30 cm (6 to 12 inches)
    2. Color: creamy white

VI. Labs

  1. Stool Ova and Parasites
  2. Stool microscopy
  3. Worm if available

VII. Complications

  1. Bowel Obstruction
  2. Urticaria
  3. Asthma

VIII. Management

  1. May start empiric treatment with anti-Helminth agent if classic roundworm identified
    1. However, still send stool samples as above
    2. Concurrent infection with other Helminth (e.g. Strongyloides) requires additional management
  2. Anti-Helminth agents
    1. Albendazole 400 mg orally for one dose (pregnancy category C)
    2. Mebendazole (not available in U.S. as of 2012) 500 mg daily for one dose (or up to three days)
    3. Pyrantel Pamoate
      1. Indicated in pregnancy
  3. Patient Education
    1. Medication will result in passing very large numbers of worms in stool
    2. Close contacts are not empirically treated in most cases (unless unreliable for follow-up)
      1. Test suspected cases

IX. References

  1. Mason, Grock and Tenner in Herbert (2017) EM:Rap 17(11): 6

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