Helminth

Visceral Larva Migrans

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Visceral Larva Migrans, Toxocariasis, Visceral Toxocariasis

  • Epidemiology
  1. Incidence: 10,000 cases per year in United States
  2. Seroprevalance in United States: 13.9%
  • Pathophysiology
  1. Organism: Roundworms (Nematodes)
    1. Toxocara canis (dogs)
    2. Toxocara cati (cats)
  2. Transmission
    1. Dogs and cats ingest roundworm eggs in soil, feces
      1. Small mammals (rabbits) may act as intermediate hosts
      2. Female dogs or cats may transmit encysted larvae to puppies transplacentally or via Lactation
    2. Dog or cat feces contaminate soil
      1. Toxocara eggs incubate in feces for 2-4 weeks until larvae infectious
    3. Young children (age <3 years)
      1. Eat contaminated soil (Geophagia)
      2. Common in playgrounds and sandboxes (contamination rates are as high as 40%)
    4. Older children and adults
      1. Ingest undercooked meat or raw liver infected with Toxocara larvae
  3. Infection
    1. Infectious eggs ingested and hatch in Intestine
    2. Larvae trapped in liver or circulate and infect heart, lungs, brain, muscle, or eye
  4. Clinical manifestations are dependent on multiple factors
    1. Parasite load
    2. Host immune response
    3. Larvae migration path
  • Findings
  • Toxocariasis Presentations
  1. Visceral Toxocariasis (children ages 2-4 years old)
    1. Inflammatory response in liver, heart, lungs, brain, muscle
  2. Ocular Toxocariasis
    1. See Ocular Larva Migrans
  3. Covert Toxocariasis (most common)
    1. Asymptomatic or mild symptoms
  • Symptoms
  • Visceral Toxocariasis (children ages 2-4 years old)
  1. Constitutional
    1. Fever
    2. Myalgia
    3. Anorexia
    4. Fatigue
  2. Pulmonary
    1. Wheezing
    2. Cough
  3. Gastrointestinal
    1. Nausea
    2. Abdominal Pain
    3. Hepatomegaly
  4. Neurologic
    1. Meningoencephalitis
  5. Skin
    1. Edema
    2. Urticaria
  • Complications
  1. Epilepsy may develop in toddlers
  2. Ocular Larva Migrans (Endophthalmitis)
  • Differential Diagnosis
  1. Hepatitis
  2. Encephalitis
  3. Viral myalgia
  4. Epilepsy
  5. Pneumonia
  6. Trichinosis
  7. Eosinophilic Leukemia
  8. Periarteritis nodosa
  • Labs
  1. Complete Blood Count
    1. Anemia
    2. Leukocytosis with >20% Eosinophilia
  2. Serology for Toxocara Antibody
    1. Does not distinguish acute versus prior infection
  3. Other findings/tests
    1. Larval antigen ELISA Test
    2. Hypergammaglobulinemia
    3. Avoid stool testing (larva and eggs will not be found in the stool)
  • Course
  1. Typically a self limited course in most cases
  2. Generally benign
  • Management
  1. Indications
    1. Most cases are treated
    2. Severe cardiac or pulmonary disease
    3. Neurologic involvement
  2. Preparations
    1. Albendazole (Albenza)
      1. Dose: 7.5 mg/kg up to 400 mg orally twice daily for 5 days
      2. Preferred agent in United States
    2. Mebendazole (Vermox)
      1. Dose: 100-200 bid for 5 days
      2. Not available as of 2012 (use Albendazole instead)
    3. Diethylcarbamazine (Hetrazan)
      1. Dose: 6 mg/kg/day divided tid for 7-10 days
      2. Has been used outside U.S. to treat Visceral Larva Migrans
  3. Adjunctive
    1. Corticosteroids are indicated if inflammation present (especially with Ocular Larva Migrans)
  • Prevention
  1. Careful child supervision
    1. Prevent soil ingestion
    2. Encourage Hand Washing
  2. Regular worming of cats and dogs
  3. Clean up after pets
  4. Cover sandbox between use
  5. Cook liver and other organ meats well before eating
  • Resources