Updated: 1/4/2019

Toxocariasis

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Snapshot
  • A 5-year-old boy presents to his pediatrician due to abdominal pain and a seizure. He has been complaining of abdominal pain and discomfort for approximately 10 days, which his parents attribute it to stress. The parents deny  any recent travel or sick contacts for the patient. He recently got a puppy about 1 month ago. Physical examination is remarkable for pain upon neck flexion and hepatomegaly. A complete blood cell count is notable for prominent eosinophilia.  
Introduction
  • Definition
    • human infection caused by the Toxocara nematode
  • Microbiology
    • caused by Toxocara canis (in dogs) and Toxocara cati (in cats)
      • roundworm nematodes
  • Epidemiology
    • incidence
      • more common in tropical regions and rural populations of the world
      • visceral larva migrans most commonly affects children
    • risk factors
      • contact with dogs or cats
      • exposure to infected eggs in
        • soil
        • vegetables and fruits
      • encapsulated larvae exposure in
        • undercooked meats (e.g., rabbit, chicken, cattle, and swine)
  • Pathophysiology
    • the adult nematode lives in the upper gastrointestinal tract of a dog or cat → the female nematode produces eggs that get excreted in feces → the excreted eggs become embryonated → ingestion of embryonated eggs lead to hatching of these eggs in the small intestines of the host → the larvae perforate the intestinal wall and enter the circulatory system
      • can migrate to the brain, causing neurotoxocariasis
      • can migrate to the lung and liver, causing visceral larva migrans
      • can migrate to the eye, causing ocular larva migrans
      • the fetus can also be infected transplacentally or through the breast milk in pregnant women 
  • Associated conditions
    • seizures
    • myocarditis
    • visual impairment and blindness
Presentation
  • Visceral larva migrans
    • symptoms
      • fever
      • abdominal pain
      • decreased appetite
      • chronic nonproductive cough
      • dyspnea
      • lymphadenopathy
    • physical exam
      • wheezes
      • hepatomegaly or nodularity
  • Ocular larva migrans
    • symptoms
      • visual impairment
    • physical exam
      • poor visual acuity and strabismus may be present
      • uveitis
      • retinal granulomatous lesions on fundoscopy
Studies
  • Labs
    • eosinophilia
  • Serology
    • enzyme-linked immunosorbent assay (ELISA) with larval antigens
Differential
  • Schistosomiasis
    • differentiating factors
      • no apparent signs of liver dysfunction
Treatment
  • Medical
    • albendazole
      • indication
        • treatment of choice since the drug effectively distributes throughout the body (including the eyes and brain)
Complications
  • Blindness
  • Neurodegenerative disorders (e.g., seizures and dementia)
 

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