VISCERAL LARVA MIGRANS
 
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VISCERAL LARVA MIGRANS

 

DEFINITION:

A disorder caused by infection with larvae of Toxocara sp. resulting in gastrointestinal, respiratory, and ocular manifestations (also called Toxocariasis).

EPIDEMIOLOGY:

  • incidence: ?
  • age of onset:
    • occurs most frequently in children under the age of 10 years with a peak between 1-4 years
  • risk factors:
    • pica
    • close contact with dogs or cats

PATHOGENESIS:

  • adult worms of Toxocara sp. (T. canis, T. cati, T. leonina) reside in the GI tract of dogs and cats and excrete their eggs into the feces -> feces and/or contaminated soil is ingested by a child -> eggs travel to the gastrointestinal (GI) tract where the larvae penetrate the GI tract -> carried by the portal system to the liver where eosinophilic granu-lomas form -> spread to lungs and then to other organs -> eyes, central nervous system, kidney, heart

CLINICAL FEATURES:

1. Gastrointestinal Manifestations

  • abdominal pain
  • hepatomegaly

2. Respiratory Manifestations

  • cough with wheeze
  • crackles
  • respiratory distress

3. Ocular Toxocariasis

  • 3 different syndromes resulting in a posterior uveitis and leukocoria (involvement of the retina)

1. Chronic Endophthalmitis

  • usually occurs in those between 2-9 years of age
  • unilateral leukocoria
  • vitreous cavity filled with exudate
  • cyclitic membrane
  • pain, photophobia, increased lacrimation, decreased visual acuity, acutely inflammed globe
  • usually results in destruction of the globe

2. Localized Granuloma

  • usually occurs in those between 6-14 years of age
  • single localized granuloma
    • in macula or peripapillary region
    • white, elevated, and localized to the retina
  • asymptomatic -> decreased visual acuity, exotropia
  • inactive and nonprogressive

3. Peripheral Granuloma

  • usually occurs in those between 6-40 years of age
  • dense connective tissue in the vitreous cavity
  • heterotopia, decreased visual acuity
  • inactive and nonprogressive

4. Others

  • papular or urticarial skin lesions
  • lymph node enlargement
  • fever
  • seizures

INVESTIGATIONS:

1. Diagnosis

1. ELISA

  • positive in 78% of those with visceral larva migrans
  • positive in 45% of those with ocular toxocariasis

2. Serum

  • CBC - eosinophilia in nearly all cases of visceral larva migrans but less common in ocular toxocariasis
  • elevated gamma globulins, isohemagglutinins and IgE

3. Biopsy

  • in response to larval death, a granulomatous response is elicited with lesions characterized by large numbers of eosinophils, lymphocytes, mononuclear cells, fibrin, foreign body giant cells, and tissue necrosis

MANAGEMENT:

1. Supportive

  • therapy is not needed in a majority of cases as clinical symptoms are mild and resolve after weeks to months
  • prevention
    • wash hands after playing with pets
    • avoid infected areas
    • deworm dogs

2. Medical

1. Steroids

  • prednisone
    • po - treatment of choice (TOC) for active disease
    • periocular for acute ocular toxocariasis

2. Diethylcarbamazine

  • use for 3 wks
  • has larvicidal activity
  • however, may kill larvae and set up an even greater inflammatory response

 

 

 

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